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Artifact 2552cac425404d15b72e545d39df784dcaab32c9:


/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 
/* vim: set ts=2 et sw=2 tw=80: */
#if !defined(NET_FOSSIL_SCM_FSL_UTIL_H_INCLUDED)
#define NET_FOSSIL_SCM_FSL_UTIL_H_INCLUDED
/*
** Copyright (c) 2013 D. Richard Hipp
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of the Simplified BSD License (also
** known as the "2-Clause License" or "FreeBSD License".)
**
** This program is distributed in the hope that it will be useful,
** but without any warranty; without even the implied warranty of
** merchantability or fitness for a particular purpose.
**
** Author contact information:
**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*******************************************************************************
*/

#include "fossil-config.h" /* MUST come first b/c of config macros */
#include <stdio.h> /* FILE type */
#include <stdarg.h> /* va_list */

#if defined(__cplusplus)
extern "C" {
#endif
  typedef struct fsl_allocator fsl_allocator;
  typedef struct fsl_buffer fsl_buffer;
  typedef struct fsl_error fsl_error;
  typedef struct fsl_finalizer fsl_finalizer;
  typedef struct fsl_fstat fsl_fstat;
  typedef struct fsl_list fsl_list;
  typedef struct fsl_outputer fsl_outputer;
  typedef struct fsl_state fsl_state;
  
  /**
   ** fsl_uuid_str and fsl_uuid_cstr are "for documentation and
   ** readability purposes" typedefs used to denote strings which the
   ** API requires to be in the form of Fossil UUID strings. Such
   ** strings are exactly FSL_UUID_STRLEN bytes long plus a
   ** terminating NUL byte and contain only lower-case hexadecimal
   ** bytes. Where this typedef is used, the library requires,
   ** enforces, and/or assumes (at different times) that fsl_is_uuid()
   ** returns true for such strings (if they are not NULL, though not
   ** all contexts allow a NULL UUID). These typedef are _not_ used to
   ** denote arguments which may refer to partial UUIDs or symbolic
   ** names, only 100% bonafide Fossil UUIDs (which are different from
   ** RFC4122 UUIDs).
   **
   ** The API guarantees that this typedef will always be (char *) and
   ** that fsl_uuid_cstr will always ben (char const *), and thus it
   ** is safe/portable to use those type instead of thse. These
   ** typedefs serve only to improve the readability of certain APIs
   ** by implying (through the use of this typedef) the preconditions
   ** defined for UUID strings.
   **
   ** @see fsl_is_uuid()
   */
  typedef char * fsl_uuid_str;

  /**
   ** The const counterpart of fsl_uuid_str.
   **
   ** @see fsl_is_uuid()
   */
  typedef char const * fsl_uuid_cstr;

  /**
   ** Returns true (non-0) if str is not NULL, is exactly
   ** FSL_UUID_STRLEN bytes long, and contains only lower-case
   ** hexadecimal characters, else returns false (0).
   **
   ** Note that Fossil UUIDs are not RFC4122 UUIDs, but are SHA1
   ** hash strings. Don't let that disturb you. As Tim Berners-Lee
   ** writes:
   **
   ** 'The assertion that the space of URIs is a universal space
   ** sometimes encounters opposition from those who feel there should
   ** not be one universal space. These people need not oppose the
   ** concept because it is not of a single universal space: Indeed,
   ** the fact that URIs form universal space does not prevent anyone
   ** else from forming their own universal space, which of course by
   ** definition would be able to envelop within it as a subset the
   ** universal URI space. Therefore the web meets the "independent
   ** design" test, that if a similar system had been concurrently and
   ** independently invented elsewhere, in such a way that the
   ** arbitrary design decisions were made differently, when they met
   ** later, the two systems could be made to interoperate.'
   **
   ** Source: http://www.w3.org/DesignIssues/Axioms.html
   **
   ** (Just mentally translate URI as UUID.)
   */
  char fsl_is_uuid(char const * str);
  
  /**
   ** Expects str to be a string containing an unsigned decimal
   ** value. Returns its decoded value, or -1 on error.
   */
  fsl_size_t fsl_str_to_size(char const * str);

  /**
   ** Expects str to be a string containing a decimal value,
   ** optionally with a leading sign. Returns its decoded value, or
   ** dflt if !str or on error.
   */
  fsl_int_t fsl_str_to_int(char const * str, fsl_int_t dflt);


  /**
   ** Generic list container type. This is used heavily by the Fossil
   ** API for storing arrays of dynamically-allocated objects. It is
   ** not useful as a non-pointer-array replacement.
   **
   ** It is up to the APIs using this type to manage the entry count
   ** member and use fsl_list_reserve() to manage the "capacity"
   ** member.
   **
   ** @see fsl_list_reserve()
   ** @see fsl_list_append()
   ** @see fsl_list_visit()
   */
  struct fsl_list {
    /**
     ** Array of entries. It contains this->capacity entries,
     ** this->count of which are "valid" (in use).
     */
    void ** list;
    /**
     ** Number of "used" entries in the list.
     */
    fsl_size_t used;
    /**
     ** Number of slots allocated in this->list. Use fsl_list_reserve()
     ** to modify this. Doing so might move the this->list pointer but
     ** the values it points to will stay stable.
     */
    fsl_size_t capacity;
  };

  /**
   ** Empty-initialized fsl_list structure, intended for const-copy
   ** initialization.
   */
#define fsl_list_empty_m { NULL, 0, 0 }
  /**
   ** Empty-initialized fsl_list structure, intended for copy
   ** initialization.
   */
  extern const fsl_list fsl_list_empty;


  /**
   ** Generic interface for finalizing/freeing memory. Intended
   ** primarily for use as a destructor/finalizer for high-level
   ** structs. Implementations must semantically behave like free(mem),
   ** regardless of whether or not they actually free the memory. At
   ** the very least, they generally should clean up any memory owned by
   ** mem (e.g. db resources or buffers), even if they do not free() mem.
   ** some implementations assume that mem is stack-allocated
   ** and they only clean up resources owned by mem.
   **
   ** The state parameter is any state needed by the finalizer
   ** (e.g. a memory allocation context) and mem is the memory which is
   ** being finalized. 
   **
   ** The exact interpretaion of the state and mem are of course
   ** implementation-specific.
   */
  typedef void (*fsl_finalizer_f)( void * state, void * mem );

  /**
   ** Generic interface for memory finalizers.
   */
  struct fsl_finalizer {
    /**
     ** State to be passed as the first argument to f().
     */
    void * state;
    /**
     ** Finalizer function. Should be called like this->f( this->state, ... ).
     */
    fsl_finalizer_f f;
  };

  /** Empty-initialized fsl_finalizer struct. */
#define fsl_finalizer_empty_m {NULL,NULL}

  /**
   ** fsl_finalizer_f() impl which requires that mem be-a
   ** (fsl_buffer*).  This function frees all memory associated with
   ** that buffer and zeroes out the structure, but does not free mem
   ** (because it is rare that fsl_buffers are created on the
   ** heap). The state parameter is ignored.
   */
  int fsl_finalizer_f_buffer( void * state, void * mem );

  
  /**
   ** Generic state-with-finalizer holder. Used for binding
   ** client-specified state to another other object, such that a
   ** client-specified finalizer is called with the other object is
   ** cleaned up.
   */
  struct fsl_state {
    /**
     ** Arbitrary context-dependent state.
     */
    void * state;
    /**
     ** Finalizer for this->state. If used, it should be called like:
     **
     ** @code
     ** this->finalize.f( this->finalize.state, this->state );
     ** @endcode
     **
     ** After which this->state must be treated as if it has been
     ** free(3)'d.
     */
    fsl_finalizer finalize;
  };

  /** Empty-initialized fsl_state struct. */
#define fsl_state_empty_m {NULL,fsl_finalizer_empty_m}

  /**
   ** Empty-initialized fsl_state struct, intended for
   ** copy-initializing.
   */
  extern const fsl_state fsl_state_empty;
  
  
  /**
   ** Generic interface for streaming out data. Implementations must
   ** write n bytes from s to their destination channel and return 0 on
   ** success, non-0 on error (assumed to be a value from the fsl_rc_t
   ** enum). The state parameter is the implementation-specified
   ** output channel.
   */
  typedef int (*fsl_output_f)( void * state,
                               void const * src, fsl_size_t n );


  /**
   ** Generic interface for flushing arbitrary output streams.  Must
   ** return 0 on success, non-0 on error, but the result code "should"
   ** (to avoid downstream confusion) be one of the fsl_rc_t
   ** values. When in doubt, return FSL_RC_IO on error.
   */
  typedef int (*fsl_flush_f)(void * state);

  /**
   ** Generic interface for streaming in data. Implementations must
   ** read (at most) *n bytes from their input, copy it to dest, assign
   ** *n to the number of bytes actually read, return 0 on success, and
   ** return non-0 on error (assumed to be a value from the fsl_rc_t
   ** enum). When called, *n is the max length to read. On return, *n
   ** is the actual amount read. The state parameter is the
   ** implementation-specified input file/buffer/whatever channel.
   */
  typedef int (*fsl_input_f)( void * state, void * dest, fsl_size_t * n );

  /**
   ** fsl_output_f() implementation which requires state to be
   ** a writeable (FILE*) handle.
   */
  int fsl_output_f_FILE( void * state, void const * src, fsl_size_t n );

  /**
   ** An interface which encapsulates data for managing an output
   ** destination, primarily intended for use with fsl_output(). Why
   ** abstract it to this level? So that we can do interesting things
   ** like output to buffers, files, sockets, etc., using the core
   ** output mechanism. e.g. so script bindings can send their output
   ** to the same channel used by the library and other library
   ** clients.
   */
  struct fsl_outputer {
    /**
     ** Output channel.
     */
    fsl_output_f out;
    /**
     ** flush() implementation.
     */
    fsl_flush_f flush;
    /**
     ** State to be used when calling this->out(), namely:
     ** this->out( this->state.state, ... ).
     */
    fsl_state state;
  };
  /** Empty-initialized fsl_outputer instance. */
#define fsl_outputer_empty_m {NULL,NULL,fsl_state_empty_m}
  /** Empty-initialized fsl_outputer instance, intended for
      copy-initializing.
  */
  extern const fsl_outputer fsl_outputer_empty;
  
  /**
   ** A fsl_outputer instance which is initialized to output to a
   ** (FILE*). To use it, this value then set the copy's state.state
   ** member to an opened-for-write (FILE*) handle. By default it will
   ** use stdout. Its finalizer (if called!) will fclose(3)
   ** self.state.state if self.state.state is not one of (stdout,
   ** stderr). To disable the closing behaviour (and not close the
   ** file), set self.state.finalize.f to NULL (but then be sure that
   ** the file handle outlives this object and to fclose(3) it when
   ** finished with it).
   */
  extern const fsl_outputer fsl_outputer_FILE;

  /**
   ** fsl_outputer initializer which uses fsl_flush_f_FILE(),
   ** fsl_output_f_FILE(), and fsl_finalizer_f_FILE().
   */
#define fsl_outputer_FILE_m {                   \
    fsl_output_f_FILE,                          \
      fsl_flush_f_FILE,                         \
      {/*state*/                                \
        NULL,                                   \
        {NULL,fsl_finalizer_f_FILE}             \
      }                                         \
  }
  /**
   ** Generic stateful alloc/free/realloc() interface.
   **
   ** Implementations must behave as follows:
   **
   ** - If 0==n then semantically behave like free(3) and return
   ** NULL.
   **
   ** - If 0!=n and !mem then semantically behave like malloc(3), returning
   ** newly-allocated memory on success and NULL on error.
   **
   ** - If 0!=n and NULL!=mem then semantically behave like
   ** realloc(3). Note that realloc specifies: "If n was equal to 0,
   ** either NULL or a pointer suitable to be passed to free() is
   ** returned." Which is kind of useless, and thus implementations
   ** MUST return NULL when n==0.
   */
  typedef void *(*fsl_realloc_f)(void * state, void * mem, fsl_size_t n);

  /**
   ** Holds an allocator function and its related state.
   */
  struct fsl_allocator {
    /**
     ** Base allocator function. It must be passed this->state
     ** as its first parameter.
     */
    fsl_realloc_f f;
    /**
     ** State intended to be passed as the first parameter to
     ** this->f().
     */
    void * state;
  };

  /** Empty-initialized fsl_allocator instance. */
#define fsl_allocator_empty_m {NULL,NULL}


  /**
   ** A fsl_realloc_f() implementation which uses the standard
   ** malloc()/free()/realloc(). The state parameter is ignored.
   */
  void * fsl_realloc_f_stdalloc(void * state, void * mem, fsl_size_t n);

  /**
   ** A fsl_flush_f() impl which expects _FILE to be-a (FILE*) opened
   ** for writing, which this function passes the call on to
   ** fflush(). If fflush() returns 0, so does this function, else it
   ** returns non-0.
   */
  int fsl_flush_f_FILE(void * _FILE);

  /**
   ** A fsl_finalizer_f() impl which requires that mem be-a (FILE*).
   ** This function passes that FILE to fsl_fclose(). The state
   ** parameter is ignored.
   */
  void fsl_finalizer_f_FILE( void * state, void * mem );

  /**
   ** A fsl_output_f() impl which requires state to be-a (FILE*), which
   ** this function passes the call on to fwrite(). Returns 0 on
   ** success, FSL_RC_IO on error.
   */
  int fsl_output_f_FILE( void * state, void const * src, fsl_size_t n );

  /**
   ** A fsl_output_f() impl which requires state to be-a (fsl_buffer*),
   ** which this function passes to fsl_buffer_append(). Returns 0 on
   ** success, FSL_RC_OOM (probably) on error.
   */
  int fsl_output_f_buffer( void * state, void const * src, fsl_size_t n );

  /**
   ** A fsl_input_f() implementation which requires that state be
   ** a readable (FILE*) handle.
   */
  int fsl_input_f_FILE( void * state, void * dest, fsl_size_t * n );

  /**
   ** A generic streaming routine which copies data from an
   ** fsl_input_f() to an fsl_outpuf_f().
   **
   ** Reads all data from inF() in chunks of an unspecified size and
   ** passes them on to outF(). It reads until inF() returns fewer
   ** bytes than requested. Returns the result of the last call to
   ** outF() or (only if reading fails) inF(). Returns FSL_RC_MISUSE
   ** if inF or ouF are NULL.
   **
   ** Here is an example which basically does the same thing as the
   ** cat(1) command on Unix systems:
   **
   ** @code
   ** fsl_stream( fsl_input_f_FILE, stdin, fsl_output_f_FILE, stdout );
   ** @endcode
   **
   ** Or copy a FILE to a buffer:
   **
   ** @code
   ** fsl_buffer myBuf = fsl_buffer_empty;
   ** rc = fsl_stream( fsl_input_f_FILE, stdin, fsl_output_f_buffer, &myBuf );
   ** // Note that on error myBuf might be partially populated.
   ** // Eventually clean up the buffer:
   ** fsl_buffer_clear(&myBuf);
   ** @endcode
   **
  */
  int fsl_stream( fsl_input_f inF, void * inState,
                  fsl_output_f outF, void * outState );

  /**
   **
   ** A general-purpose buffer class, analog to Fossil v1's Blob
   ** class. It is not called fsl_blob to avoid confusion with DB-side
   ** Blobs. Buffers are used extensively in fossil to do everything
   ** from reading files to compressing artifacts to creating
   ** dynamically-formatted strings. Because they are such a pervasive
   ** low-level type, and have such a simple structure, their members
   ** (unlike most other structs in this API) may be considered public
   ** and used directly by client code (as long as they do not mangle
   ** their state, e.g. by setting this->capacity smaller than
   ** this->used!).
   **
   ** @see fsl_buffer_reserve()
   ** @see fsl_buffer_append()
   ** @see fsl_buffer_appendf()
   ** @see fsl_buffer_cstr()
   ** @see fsl_buffer_size()
   ** @see fsl_buffer_capacity()
   ** @see fsl_buffer_clear()
   */
  struct fsl_buffer {
    /**
     ** The raw memory owned by this buffer. It is this->capacity bytes
     ** long, of which this->used are considered "used" by the client.
     ** The difference beween (this->capacity - this->used) represents
     ** space the buffer has available for use before it will require
     ** another expansion/reallocation.
     */
    unsigned char * mem;
    /**
     ** Number of bytes allocated for this buffer.
     */
    fsl_size_t capacity;
    /**
     ** Number of "used" bytes in the buffer. This is generally
     ** interpreted as the string length of this->mem, and the buffer
     ** APIs which add data to a buffer always ensure that
     ** this->capacity is large enough to account for a trailing NUL
     ** byte in this->mem.
     **
     ** Library routines which manipulate buffers must ensure that
     ** (this->used<=this->capacity) is always true, expanding the
     ** buffer if necessary. Much of the API assumes that precondition
     ** is always met, and any violation of it opens the code to
     ** undefined behaviour (which is okay, just don't ever break that
     ** precondition). Most APIs ensure that (used<capacity) is always
     ** true (as opposed to used<=capacity) because they add a
     ** trailing NUL byte which is not counted in the "used" length.
     */
    fsl_size_t used;
  };
  /** Empty-initialized fsl_buffer instance. */
#define fsl_buffer_empty_m {NULL,0U,0U}
  /** Empty-initialized fsl_buffer instance. */
  extern const fsl_buffer fsl_buffer_empty;
    
  /**
   ** A container for storing generic error state. It is used
   ** to propagate error state between layers of the API back
   ** to the client.
   **
   ** @see fsl_error_set()
   ** @see fsl_error_get()
   ** @see fsl_error_move()
   ** @see fsl_error_clear()
   */
  struct fsl_error {
    /**
     ** Error message text is stored in this->msg.mem. The usable text
     ** part is this->msg.used bytes long.
     */
    fsl_buffer msg;
    /**
     ** Error code, generally assumed to be a fsl_rc_t value.
     **
     ** Potential todo: change this to fsl_rc_t to help ensure that we
     ** don't get cross-API result code polution (e.g. from sqlite)?
     */
    int code;
  };
  /** Empty-initialized fsl_error instance. */
#define fsl_error_empty_m {fsl_buffer_empty_m,0}
  /** Empty-initialized fsl_error instance. */
  extern const fsl_error fsl_error_empty;

  /**
   ** Populates err with the given code and formatted string, replacing
   ** any existing state. If fmt==NULL then fsl_rc_cstr(rc) is used to
   ** get the error string.
   **
   ** Returns code on success, some other non-0 code on error.
   **
   ** As a special case, if 0==code then fmt is ignored and the error
   ** state is cleared. This will not free any memory held by err but
   ** will re-set its string to start with a NUL byte, ready for
   ** re-use later on.
   **
   ** As a special case, if code==FSL_RC_OOM then fmt is ignored
   ** to avoid a memory allocation (which would presumably fail).
   **
   ** @see fsl_error_get()
   ** @see fsl_error_clear()
   ** @see fsl_error_move()
   */
  int fsl_error_set( fsl_error * err, int code, char const * fmt,
                     ... );

  /**
   ** va_list counterpart to fsl_error_set().
   */
  int fsl_error_setv( fsl_error * err, int code, char const * fmt,
                      va_list args );

  /**
   ** Fetches the error state from err. If !err it returns
   ** FSL_RC_MISUSE without side-effects, else it returns err's current
   ** error code.
   **
   ** If str is not NULL then *str will be assigned to the raw
   ** (NUL-terminated) error string (which might be empty or even
   ** NULL). The memory for the string is owned by err and may be
   ** invalidated by any calls which take err as a non-const parameter
   ** OR which might modify it indirectly through its container, so
   ** the client is required to copy it if it is needed for later on.
   **
   ** If len is not NULL then *len will be assigned to the length of
   ** the returned string (in bytes).
   **
   ** @see fsl_error_set()
   ** @see fsl_error_clear()
   ** @see fsl_error_move()
   */
  int fsl_error_get( fsl_error const * err, char const ** str, fsl_size_t * len );

  /**
   ** Frees up any resources owned by err and sets its error code to 0,
   ** but does not free err. This is harmless no-op if !err or if err
   ** holds no dynamically allocated no memory.
   **
   ** @see fsl_error_set()
   ** @see fsl_error_get()
   ** @see fsl_error_move()
   */
  void fsl_error_clear( fsl_error * err );

  /**
   ** Swaps the error state of the two given error objects.
   **
   ** This "uplifts" an error from the 'from' object to the 'to'
   ** object. After this returns 'to' will contain the prior error
   ** state of 'from' and 'from' will contain the old error message
   ** memory of 'to' but will be re-set to the non-error state (we
   ** keep the buffer memory intact for later reuse, though).
   **
   ** Results are undefined if either parameter is NULL or either is
   ** not properly initialized. i.e. neither may refer to uninitialized
   ** memory. Copying fsl_error_empty at declaration-time is a simple
   ** way to ensure that instances are cleanly initialized.
   */
  void fsl_error_move( fsl_error * from, fsl_error * to );

  /**
   ** Returns the given Unix Epoch timestamp value as its approximate
   ** Julian Day value. Note that the calculation does not account for
   ** leap seconds.
   */
  fsl_double_t fsl_unix_to_julian( fsl_time_t unixEpoch );

  /**
   ** Returns the current Unix Epoch time converted to its approximate
   ** Julian form. Equivalent to fsl_unix_to_julian( time(0) );
   */
  fsl_double_t fsl_julian_now();

  /**
   ** Returns the given Unix Epoch time value formatted as an ISO8601
   ** string.  Returns NULL on allocation error, else a string 19
   ** bytes long plus a terminating NUL
   ** (e.g. "2013-08-19T20:35:49"). The returned memory must
   ** eventually be freed using fsl_free().
   */
  char * fsl_unix_to_iso8601( fsl_time_t j );

  /**
   ** Returns non-0 (true) if the first 10 digits of z _appear_ to
   ** form the start of an ISO date string (YYYY-MM-DD). Whether or
   ** not the string is really a valid date is left for downstream
   ** code to determine. Returns 0 (false) in all other cases,
   ** including if z is NULL.
   */
  char fsl_str_is_date(const char *z);


  /**
   ** Reserves at least n bytes of capacity in buf. Returns 0 on
   ** success, FSL_RC_OOM if allocation fails, FSL_RC_MISUSE if !buf.
   **
   ** This does not change buf->used, nor will it shrink the buffer
   ** (reduce buf->capacity) unless n is 0, in which case it
   ** immediately frees buf->mem and sets buf->capacity and buf->used
   ** to 0.
   **
   ** @see fsl_buffer_resize()
   ** @see fsl_buffer_clear()
   */
  int fsl_buffer_reserve( fsl_buffer * buf, fsl_size_t n );

  /**
   ** Convenience equivalent of fsl_buffer_reserve(buf,0).
   ** This a no-op if buf==NULL.
   */
  void fsl_buffer_clear( fsl_buffer * buf );

  /**
   ** Resets buf->used to 0 and sets buf->mem[0] (if buf->mem is not
   ** NULL) to 0. Does not (de)allocate memory, only changes the
   ** logical "used" size of the buffer. Returns 0 on success,
   ** FSL_RC_MISUSE if !buf.
   **
   ** Achtung for v1 porters: this function's semantics are much
   ** different from the v1 blob_reset(). To get those semantics, use
   ** fsl_buffer_reserve(buf, 0) or its convenience form
   ** fsl_buffer_clear().
   */
  int fsl_buffer_reset( fsl_buffer * buf );

  /**
   ** Similar to fsl_buffer_reserve() except that...
   **
   ** - It does not free all memory when n==0. Instead it essentially
   ** makes the memory a length-0, NUL-terminated string.
   **
   ** - It will try to shrink (realloc) buf's memory if (n<buf->capacity).
   **
   ** - It sets buf->capacity to (n+1) and buf->used to n. This routine
   ** allocates one extra byte to ensure that buf is always
   ** NUL-terminated.
   **
   ** - On success it always NUL-terminates the buffer at
   ** offset buf->used.
   **
   ** Returns 0 on success, FSL_RC_MISUSE if !buf, FSL_RC_OOM if
   ** (re)allocation fails.
   **
   ** @see fsl_buffer_reserve()
   ** @see fsl_buffer_clear()
   */
  int fsl_buffer_resize( fsl_buffer * buf, fsl_size_t n );

  /**
   ** Swaps the contents of the left and right arguments. Results are
   ** undefined if either argument is NULL or points to uninitialized
   ** memory.
   */
  void fsl_buffer_swap( fsl_buffer * left, fsl_buffer * right );

  /**
   ** Similar fsl_buffer_swap() but it also optionally frees one of
   ** the buffer's memories after swapping them. If clearWhich is
   ** negative then the left buffer (1st arg) is cleared _after_
   ** swapping (i.e., the NEW left hand side gets cleared). If
   ** clearWhich is greater than 0 then the right buffer (2nd arg) is
   ** cleared _after_ swapping (i.e. the NEW right hand side gets
   ** cleared). If clearWhich is 0, this function behaves identically
   ** to fsl_buffer_swap().
   */
  void fsl_buffer_swap_free( fsl_buffer * left, fsl_buffer * right, char clearWhich );  
  /**
   **
   ** Appends the first n bytes of src, plus a NUL byte, to b,
   ** expanding b as necessary and incrementing b->used by n. If n is
   ** less than 0 then the equivalent of fsl_strlen((char const*)src)
   ** is used to calculate the length.
   **
   ** If n is 0 (or negative and !*src), this function ensures that
   ** b->mem is at least 1 byte long and sets the first byte to 0
   ** (note that (b->used+n == b->used), so its effective length does
   ** not change in that case).
   **
   ** src may only be NULL if n==0. If passed (src==NULL, n!=0) then
   ** FSL_RC_RANGE is returned.
   **
   ** Returns 0 on success, FSL_RC_MISUSE if !f, !b, or !src,
   ** FSL_RC_OOM if allocation of memory fails.
   **
   ** If this function succeeds, it guarantees that it NUL-terminates
   ** the buffer (but that the NUL terminator is not counted in
   ** b->used). 
   */
  int fsl_buffer_append( fsl_buffer * b,
                         void const * src, fsl_int_t n );

  /**
   ** Uses fsl_appendf() to append formatted output to the given buffer.
   ** Returns 0 on success, FSL_RC_MISUSE if !f or !dest,
   */
  int fsl_buffer_appendf( fsl_buffer * dest,
                          char const * fmt, ... );

  /** va_list counterpart to fsl_buffer_appendfv(). */
  int fsl_buffer_appendfv( fsl_buffer * dest,
                           char const * fmt, va_list args );

  /**
   ** Compresses the first pIn->used bytes of pIn to pOut. It is ok for
   ** pIn and pOut to be the same blob.
   **
   ** pOut must either be the same as pIn or else cleanly
   ** initialized/empty.
   **
   ** Results are undefined if any argument is NULL.
   **
   ** Returns 0 on success, FSL_RC_OOM on allocation error, and FSL_RC_ERROR
   ** if the lower-level compression routines fail.
   **
   ** TODO: add a streaming variant which takes the input from a
   ** fsl_input_f() and pushes the output to a fsl_output_f(). The code
   ** exists in the libwhio source tree already.
   **
   ** TODO: if pOut!=pIn1 then re-use pOut's memory, if it has any.
   */
  int fsl_buffer_compress(fsl_buffer const *pIn, fsl_buffer *pOut);

  /**
   ** Compress the concatenation of a blobs pIn1 and pIn2 into pOut.
   **
   ** pOut must be either uninitialized or must be the same as either pIn1 or
   ** pIn2.
   **
   ** Results are undefined if any argument is NULL.
   **
   ** Returns 0 on success, FSL_RC_OOM on allocation error, and FSL_RC_ERROR
   ** if the lower-level compression routines fail.
   **
   ** TODO: if pOut!=(pIn1 or pIn2) then re-use its memory, if it has any.
   */
  int fsl_buffer_compress2(fsl_buffer const *pIn1,
                           fsl_buffer const *pIn2, fsl_buffer *pOut);

  /**
   ** Uncompress buffer pIn and store the result in pOut. It is ok for
   ** pIn and pOut to be the same buffer. Returns 0 on success. On
   ** error pOut is not modified.
   **
   ** pOut must be either cleanly initialized/empty or the same as pIn.
   **
   ** Results are undefined if any argument is NULL.
   **
   ** Returns 0 on success, FSL_RC_OOM on allocation error, and
   ** FSL_RC_ERROR if the lower-level decompression routines fail.
   **
   ** TODO: add a streaming variant which takes the input from a
   ** fsl_input_f() and pushes the output to a fsl_output_f(). The code
   ** exists in the libwhio source tree already.
   **
   ** TODO: if pOut!=(pIn1 or pIn2) then re-use its memory, if it has any.
   */
  int fsl_buffer_uncompress(fsl_buffer const *pIn, fsl_buffer *pOut);

  /**
   ** Returns true if this function believes that mem (which must be
   ** at least len bytes of valid memory long) appears to have been
   ** compressed by fsl_buffer_compress() or equivalent. This is not a
   ** 100% reliable check - it could potentially have false positives
   ** on certain inputs, but that is thought to be unlikely (at least
   ** for text data).
   **
   ** Returns 0 if mem is NULL.
   */
  char fsl_data_is_compressed(unsigned char const * mem, fsl_size_t len);

  /**
   ** Equivalent to fsl_data_is_compressed(buf->mem, buf->used).
   */
  char fsl_buffer_is_compressed(fsl_buffer const * buf);

  /**
   ** If fsl_data_is_compressed(mem,len) returns true then this function
   ** returns the uncompressed size of the data, else it returns a negative
   ** value.
   */
  fsl_int_t fsl_data_uncompressed_size(unsigned char const *mem, fsl_size_t len);

  /**
   ** The fsl_buffer counterpart of fsl_data_uncompressed_size().
   */
  fsl_int_t fsl_buffer_uncompressed_size(fsl_buffer const * b);
  

  
  /**
   ** Equivalent to ((char const *)b->mem), but returns NULL if !b. The
   ** returned memory is effectively b->used bytes long unless the user
   ** decides to apply his own conventions.
   **
   ** @see fsl_buffer_str()
   ** @see fsl_buffer_cstr2()
   */
  char const * fsl_buffer_cstr(fsl_buffer const *b);

  /**
   ** If buf is not NULL and has any memory allocated to it, that
   ** memory is returned. If both b and len are not NULL then *len is
   ** set to b->used. If b has no dynamic memory then NULL is returned
   ** and *len (if len is not NULL) is set to 0.
   **
   ** @see fsl_buffer_str()
   ** @see fsl_buffer_cstr()
   **/
  char const * fsl_buffer_cstr2(fsl_buffer const *b, fsl_size_t * len);

  /**
   ** Equivalent to ((char *)b->mem), but returns NULL if !b. The
   ** returned memory is effectively b->used bytes long unless the user
   ** decides to apply his own conventions.
   */
  char * fsl_buffer_str(fsl_buffer const *b);

  /**
   ** Returns the "used" size of b, or 0 if !b.
   */
  fsl_size_t fsl_buffer_size(fsl_buffer const * b);

  /**
   ** Returns the current capacity of b, or 0 if !b.
   */
  fsl_size_t fsl_buffer_capacity(fsl_buffer const * b);
  
  /**
   ** Compares the contents of buffers lhs and rhs using memcmp(3)
   ** semantics. Return negative, zero, or positive if the first
   ** buffer is less then, equal to, or greater than the second.
   ** Results are undefined if either argument is NULL.
   **
   ** When buffers of different length match on the first N bytes,
   ** where N is the shorter of the two buffers' lengths, it treats the
   ** shorter buffer as being "less than" the longer one.
   */
  int fsl_buffer_compare(fsl_buffer const * lhs, fsl_buffer const * rhs);

  /**
   ** Compare two buffers in constant (a.k.a. O(1)) time and return
   ** zero if they are equal.  Constant time comparison only applies
   ** for buffers of the same length.  If lengths are different,
   ** immediately returns 1.
   */
  int fsl_buffer_compare_O1(fsl_buffer const * lhs, fsl_buffer const * rhs);

  /**
   ** Overwrites dest's contents with those of src (reusing dest's memory
   ** if it has any). Results are undefined if either pointer is NULL
   ** or invalid. Returns 0 on success, FSL_RC_OOM on allocation error.
   */
  int fsl_buffer_copy( fsl_buffer const * src, fsl_buffer * dest );
  

  /**
   ** Apply the delta in pDelta to the original content pOriginal to
   ** generate the target content pTarget. All three pointers must point
   ** to properly initialized memory.
   **
   ** If pTarget==pOriginal then this is a destructive operation,
   ** replacing the original's content with its new form.
   **
   ** Return 0 on success.
   **
   ** @see fsl_buffer_delta_apply()
   ** @see fsl_delta_apply()
   ** @see fsl_delta_apply2()
   */
  int fsl_buffer_delta_apply( fsl_buffer const * pOriginal,
                              fsl_buffer const * pDelta,
                              fsl_buffer * pTarget);
  /**
   ** Identical to fsl_buffer_delta_apply() except that if
   ** delta application fails then any error messages/codes
   ** are written to pErr if it is not NULL.
   **
   ** @see fsl_buffer_delta_apply()
   ** @see fsl_delta_apply()
   ** @see fsl_delta_apply2()
   */
  int fsl_buffer_delta_apply2( fsl_buffer const * pOriginal,
                               fsl_buffer const * pDelta,
                               fsl_buffer * pTarget,
                               fsl_error * pErr);

  
  /**
   ** Uses a fsl_input_f() function to buffer input into a fsl_buffer.
   **
   ** dest must be a non-NULL, initialized (though possibly empty)
   ** fsl_buffer object. Its contents, if any, will be overwritten by
   ** this function, and any memory it holds might be re-used.
   **
   ** The src function is called, and passed the state parameter, to
   ** fetch the input. If it returns non-0, this function returns that
   ** error code. src() is called, possibly repeatedly, until it
   ** reports that there is no more data.
   **
   ** Whether or not this function succeeds, dest still owns any memory
   ** pointed to by dest->mem, and the client must eventually free it
   ** by calling fsl_buffer_reserve(dest,0).
   **
   ** dest->mem might (and possibly will) be (re)allocated by this
   ** function, so any pointers to it held from before this call might
   ** be invalidated by this call.
   **
   ** On error non-0 is returned and dest has almost certainly been
   ** modified but its state must be considered incomplete.
   **
   ** Errors include:
   **
   ** dest or src are NULL (FSL_RC_MISUSE)
   **
   ** Allocation error (FSL_RC_OOM)
   **
   ** src() returns an error code
   **
   ** Whether or not the state parameter may be NULL depends on the src
   ** implementation requirements.
   **
   ** On success dest will contain the contents read from the input
   ** source. dest->used will be the length of the read-in data, and
   ** dest->mem will point to the memory. dest->mem is automatically
   ** NUL-terminated if this function succeeds, but dest->used does not
   ** count that terminator. On error the state of dest->mem must be
   ** considered incomplete, and is not guaranteed to be
   ** NUL-terminated.
   **
   ** Example usage:
   **
   ** @code
   ** fsl_buffer buf = fsl_buffer_empty;
   ** int rc = fsl_buffer_fill_from( &buf,
   **                                fsl_input_f_FILE,
   **                                stdin );
   ** if( rc ){
   **   fprintf(stderr,"Error %d (%s) while filling buffer.\n",
   **   rc, fsl_rc_cstr(rc));
   **   fsl_buffer_reserve( &buf, 0 );
   **   return ...;
   ** }
   ** ... use the buf->mem ...
   ** ... clean up the buffer ...
   ** fsl_buffer_reserve( &buf, 0 );
   ** @endcode
   **
   ** To take over ownership of the buffer's memory, do:
   **
   ** @code
   ** void * mem = buf.mem;
   ** buf = fsl_buffer_empty;
   ** @endcode
   **
   ** In which case the memory must eventually be passed to fsl_free()
   ** to free it.
   */
  int fsl_buffer_fill_from( fsl_buffer * dest, fsl_input_f src, void * state );

  /**
   ** A fsl_buffer_fill_from() proxy which overwrite's dest->mem with
   ** the contents of the given FILE handler (which must be opened for
   ** read access).  Returns 0 on success, after which dest->mem
   ** contains dest->used bytes of content from the input source. On
   ** error dest may be partially filled.
  */
  int fsl_buffer_fill_from_FILE( fsl_buffer * dest, FILE * src );

  /**
   ** Wrapper for fsl_buffer_fill_from_FILE() which gets its input
   ** from the given file name.
   **
   ** Uses fsl_fopen() to open the file, so it supports the name '-'
   ** as an alias for stdin.
  */
  int fsl_buffer_fill_from_filename( fsl_buffer * dest, char const * filename );    

  /**
   ** Writes the given buffer to the given filename. Returns 0 on success,
   ** FSL_RC_MISUSE if !b or !fname, FSL_RC_IO if opening or writing fails.
   **
   ** Uses fsl_fopen() to open the file, so it supports the name '-'
   ** as an alias for stdout.
   */
  int fsl_buffer_to_filename( fsl_buffer * b, char const * fname );

  /**
   ** Works like fsl_appendfv(), but appends all output to a
   ** dynamically-allocated string, expanding the string as necessary
   ** to collect all formatted data. The returned NUL-terminated string
   ** is owned by the caller and it must be cleaned up using
   ** fsl_free(...). If !fmt, NULL is returned. It is conceivable that
   ** it returns NULL on a zero-length formatted string, e.g.  (%.*s)
   ** with (0,"...") as arguments, but it will only do that if the
   ** whole format string resolves to empty.
   */
  char * fsl_mprintf( char const * fmt, ... );

  /**
   ** va_list counterpart to fsl_mprintf().
   */
  char * fsl_mprintfv(char const * fmt, va_list vargs );

  /**
   ** An sprintf(3) clone which uses fsl_appendf() for the formatting.
   ** Outputs at most n bytes to dest and returns the number of bytes
   ** output. Returns a negative value if !dest or !fmt. Returns 0
   ** without side-effects if !n or !*fmt.
   **
   ** If the destination buffer is long enough (this function returns
   ** a non-negative value less than n), this function NUL-terminates it.
   ** If it returns n then there was no space for the terminator.
   ** 
   **/
  fsl_int_t fsl_snprintf( char * dest, fsl_size_t n, char const * fmt, ... );

  /** va_list counterpart to fsl_snprintf() */
  fsl_int_t fsl_snprintfv( char * dest, fsl_size_t n, char const * fmt, va_list args );
  
  /**
   ** Equivalent to fsl_strndup(src,-1).
   */
  char * fsl_strdup( char const * src );

  /**
   ** Similar to strndup(3) but returns NULL if !src.  The returned
   ** memory must eventually be passed to fsl_free(). Returns NULL on
   ** allocation error. If len is less than 0 and src is not NULL then
   ** fsl_strlen() is used to calculate its length.
   */
  char * fsl_strndup( char const * src, fsl_int_t len );
  
  /**
   ** Equivalent to strlen(3) but returns 0 if src is NULL.
   ** Note that it counts bytes, not UTF characters.
   */
  fsl_size_t fsl_strlen( char const * src );

  /**
   ** Like strcmp(3) except that it accepts NULL pointers.  NULL sorts
   ** before all non-NULL string pointers.  Also, this routine
   ** performs a binary comparison that does not consider locale.
   */
  int fsl_strcmp( char const * lhs, char const * rhs );

  /**
   ** Case-insensitive form of fsl_strcmp().
   */
  int fsl_stricmp(const char *zA, const char *zB);

  /**
   ** fsl_strcmp() variant which compares at most nByte bytes of the
   ** given strings, case-insensitively.  If nByte is less than 0 then
   ** fsl_strlen(zB) is used to obtain the length for comparision
   ** purposes.
   */
  int fsl_strnicmp(const char *zA, const char *zB, fsl_int_t nByte);

  /**
   ** fsl_strcmp() variant which compares at most nByte bytes of the
   ** given strings, case-sensitively. Returns 0 if nByte is 0.
   */
  int fsl_strncmp(const char *zA, const char *zB, fsl_size_t nByte);

  /**
   ** Equivalent to fsl_strncmp(lhs, rhs, FSL_UUID_STRLEN).
   */
  int fsl_uuidcmp( fsl_uuid_cstr lhs, fsl_uuid_cstr rhs );

  
  /**
   ** Returns false if s is NULL or starts with any of (0 (NUL), '0'
   ** (ASCII zero), 'f', 'n', "off"), case-insensitively, else it
   ** returns true.
   */
  char fsl_str_bool( char const * s );

  
  /**
   ** Flags for use with fsl_db_open() and friends.
   */
  enum fsl_open_flags {
  /**
   ** The "no flags" value.
   */
  FSL_OPEN_F_NONE = 0,
  /**
   ** Flag for fsl_db_open() specifying that the db should be opened
   ** in read-only mode.
   */
  FSL_OPEN_F_RO = 0x01,
  /**
   ** Flag for fsl_db_open() specifying that the db should be opened
   ** in read-write mode, but should not create the db if it does
   ** not already exist.
   */
  FSL_OPEN_F_RW = 0x02,
  /**
   ** Flag for fsl_db_open() specifying that the db should be opened in
   ** read-write mode, creating the db if it does not already exist.
   */
  FSL_OPEN_F_CREATE = 0x04,
  /**
   ** Shorthand for RW+CREATE flags.
   */
  FSL_OPEN_F_RWC = FSL_OPEN_F_RW | FSL_OPEN_F_CREATE,
  /**
   ** Tells fsl_repo_open_xxx() to confirm that the db
   ** is a repository.
   */
  FSL_OPEN_F_SCHEMA_VALIDATE = 0x20
  };
  
 
  /**
   ** _Almost_ equivalent to fopen(3) but:
   **
   ** - expects name to be UTF8-encoded.
   **
   ** - If name=="-", it returns one of stdin or stdout, depending on
   ** the mode string: stdout is returned if 'w' or '+' appear,
   ** otherwise stdin.
   **
   ** If at all possible, use fsl_close() to close these handles, as it
   ** has logic to skip closing the standard streams.
   **
   **
   ** Potential TODOs:
   **
   ** - extend mode string to support 'x', meaning "exclusive", analog
   ** to open(2)'s O_EXCL flag. Barring race conditions, we have
   ** enough infrastructure to implement that. (It turns out that
   ** glibc's fopen() supports an 'x' with exactly this meaning.)
   **
   ** - extend mode to support a 't', meaning "temporary". The idea
   ** would be that we delete the file from the FS right after
   ** opening, except that Windows can't do that.
   */
  FILE * fsl_fopen(char const * name, char const *mode);

  /**
   ** Passes f to fclose(3) unless f is NULL or one of (stdin, stdout,
   ** stderr).
   */
  void fsl_fclose(FILE * f);

  /**
   ** @typedef fsl_int_t (*fsl_appendf_f)( void * arg, char const * data, fsl_int_t n )
   **
   ** The fsl_appendf_f typedef is used to provide fsl_appendfv() with
   ** a flexible output routine, so that it can be easily send its
   ** output to arbitrary targets.
   **
   ** The policies which implementations need to follow are:
   **
   ** - arg is an implementation-specific pointer (may be 0) which is
   ** passed to fsl_appendf(). fsl_appendfv() doesn't know what this
   ** argument is but passes it to its fsl_appendf_f
   ** argument. Typically this pointer will be an object or resource
   ** handle to which string data is pushed.
   **
   ** - The 'data' parameter is the data to append. The API does not
   ** currently guaranty that data containing embeded NULs will
   ** survive the ride through fsl_appendf() and its delegates friends
   ** (but it "should work").
   **
   ** - n is the number of bytes to read from data. The fact that n is
   ** of a signed type is historical. It can be treated as an unsigned
   ** type for purposes of fsl_appendf().
   **
   ** - Returns, on success, the number of bytes appended (may be 0).
   **
   ** - Returns, on error, an implementation-specified negative
   ** number.  Returning a negative error code will cause
   ** fsl_appendfv() to stop processing and return. Note that 0 is a
   ** success value (some printf format specifiers do not add anything
   ** to the output).
   */
  typedef fsl_int_t (*fsl_appendf_f)( void * arg,
                                      char const * data,
                                      fsl_int_t n );

  /**
   ** This function works similarly to classical printf
   ** implementations, but instead of outputing somewhere specific, it
   ** uses a callback function to push its output somewhere. This
   ** allows it to be used for arbitrary external representations. It
   ** can be used, for example, to output to an external string, a UI
   ** widget, or file handle (it can also emulate printf by outputing
   ** to stdout this way).
   **
   ** INPUTS:
   **
   ** pfAppend: The is a fsl_appendf_f function which is responsible
   ** for accumulating the output. If pfAppend returns a negative
   ** value then processing stops immediately.
   **
   ** pfAppendArg: is ignored by this function but passed as the first
   ** argument to pfAppend. pfAppend will presumably use it as a data
   ** store for accumulating its string.
   **
   ** fmt: This is the format string, as in the usual printf(3), except
   ** that it supports more options (detailed below).
   **
   ** ap: This is a pointer to a list of arguments.  Same as in
   ** vprintf() and friends.
   **
   **
   ** OUTPUTS:
   **
   ** The return value is the total number of characters sent to the
   ** function "func", or a negative number on a pre-output error. If
   ** this function returns an integer greater than 1 it is in general
   ** impossible to know if all of the elements were output. As such
   ** failure can only happen if the callback function returns an
   ** error, and this type of error is very rare in a printf-like
   ** context, this is not considered to be a significant problem. (The
   ** same is true for any classical printf implementations.) Clients
   ** may use their own state objects which can propagate errors from
   ** their own internals back to the caller, but generically speaking
   ** it is difficult to trace errors back through this routine.  Then
   ** again, it only breaks when using using a broken output routine or
   ** bad output state.
   **
   ** Most printf-style specifiers work as they do in standard printf()
   ** implementations. There might be some very minor differences, but
   ** the more common format specifiers work as most developers expect
   ** them to. In addition...
   **
   ** Current (documented) printf extensions:
   **
   ** (If you are NOT reading this via doxygen-processed sources: the
   ** percent signs below are doubled for the sake of doxygen, and
   ** each pair refers to only a single percent sign in the format
   ** string.)
   **
   ** %%z works like %%s, but takes a non-const (char *) and deletes
   ** the string (using fsl_free()) after appending it to the output.
   **
   ** %%h (HTML) works like $%s but converts certain characters (namely
   ** '<' and '&') to their HTML escaped equivalents.
   **
   ** %%t (URL encode) works like %%s but converts certain characters
   ** into a representation suitable for use in an HTTP URL. (e.g. ' ' 
   ** gets converted to %%20)
   **
   ** %%T (URL decode) does the opposite of %t - it decodes URL-encoded
   ** strings and outputs their decoded form.
   **
   ** %%r requires an int and renders it in "ordinal form". That is,
   ** the number 1 converts to "1st" and 398 converts to "398th".
   **
   ** %%q quotes a string as required for SQL. That is, '\''
   ** characters get doubled. It does NOT included the outer quotes
   ** and NULL values get replaced by the string "(NULL) (without
   ** quotes). See %%Q...
   **
   ** %%Q works like %%q, but includes the outer '\'' characters and
   ** NULL pointers get output as the string literal "NULL" (without
   ** quotes), i.e. an SQL NULL.
   **
   ** %%/: works like %%s but normalizes path-like strings by
   ** replacing backslashes with the One True Slash.
   **
   ** %%b: works like %%s but takes its input from a (fsl_buffer*)
   ** argument.
   **
   ** %%B: works like %%Q but takes its input from a (fsl_buffer*)
   ** argument.
   **
   ** %%F: works like %%s but runs the output through
   ** fsl_bytes_fossilize(). This requires dynamic memory allocation,
   ** so is less efficient than re-using a client-provided buffer with
   ** fsl_bytes_fossilize() if the client needs to fossilize more than
   ** one element.
   **
   ** These extensions may be disabled by setting certain macros when
   ** compiling fsl_appendf.c (see that file for details).
   **
   **
   ** FIXME? fsl_appendf_f() is an artifact of older code from which
   ** this implementation derives. The first parameter should arguably
   ** be replaced with fsl_output_f(), which does the same thing _but_
   ** has different return semantics (more reliable, because the
   ** current semantics report partial success as success in some
   ** cases). Doing this would require us to change the return
   ** semantics of this function, but that wouldn't necessarily be a
   ** bad thing (we don't rely on sprintf()-like return semantics all
   ** that much, AFAIK?). Or we just add a proxy which forwards to a
   ** fsl_output_f(). Oh, hey, that's what fsl_outputf() does.
   */
  fsl_int_t fsl_appendfv(fsl_appendf_f pfAppend, void * pfAppendArg,
                         const char *fmt, va_list ap );

  /**
   ** Identical to fsl_appendfv() but takes a (...) ellipses list
   ** instead of a va_list.
   */
  fsl_int_t fsl_appendf(fsl_appendf_f pfAppend,
                        void * pfAppendArg,
                        const char *fmt,
                        ... );

  /**
   ** A fsl_appendf_f() impl which requires that state be an opened,
   ** writable (FILE*) handle.
   */
  fsl_int_t fsl_appendf_f_FILE( void * state,
                                char const * s, fsl_int_t n );

  
  /**
   ** Emulates fprintf() using fsl_appendf(). Returns the result of
   ** passing the data through fsl_appendf() to the given file handle.
   */
  fsl_int_t fsl_fprintf( FILE * fp, char const * fmt, ... );

  /**
   ** The va_list counterpart of fsl_fprintf().
   */
  fsl_int_t fsl_fprintfv( FILE * fp, char const * fmt, va_list args );


  /**
   ** Possibly reallocates self->list, changing its size. This function
   ** ensures that self->list has at least n entries. If n is 0 then
   ** the list is deallocated (but the self object is not), BUT THIS
   ** DOES NOT DO ANY TYPE-SPECIFIC CLEANUP of the items. If n is less
   ** than or equal to self->capacity then there are no side effects. If
   ** n is greater than self->capacity, self->list is reallocated and
   ** self->capacity is adjusted to be at least n (it might be bigger -
   ** this function may pre-allocate a larger value).
   **
   ** Passing an n of 0 when self->capacity is 0 is a no-op.
   **
   ** Newly-allocated slots will be initialized with NUL bytes.
   **
   ** Returns 0 on success, FSL_RC_MISUSE if !self, FSL_RC_OOM if
   ** reservation of new elements fails.
   **
   ** The return value should be used like this:
   **
   ** @code
   ** fsl_size_t const n = number of bytes to allocate;
   ** int const rc = fsl_list_reserve( myList, n );
   ** if( rc ) { ... error ... }
   ** @endcode
   */
  int fsl_list_reserve( fsl_list * self, fsl_size_t n );

  /**
   ** Appends a bitwise copy of cp to self->list, expanding the list as
   ** necessary and adjusting self->used.
   **
   ** Ownership of cp is unchanged by this call. cp may not be NULL.
   **
   ** Returns 0 on success, FSL_RC_MISUSE if any argument is NULL, or
   ** FSL_RC_OOM on allocation error.
   */
  int fsl_list_append( fsl_list * self, void * cp );

  /** @typedef typedef int (*fsl_list_visitor_f)(void * p, void * visitorState )
   **
   ** Generic visitor interface for fsl_list lists.  Used by
   ** fsl_list_visit(). p is the pointer held by that list entry and
   ** visitorState is the 4th argument passed to fsl_list_visit().
   **
   ** Implementations must return 0 on success. Any other value causes
   ** looping to stop and that value to be returned, but interpration
   ** of the value is up to the caller (it might or might not be an
   ** error, depending on the context). Note that client code may use
   ** custom values, and is not restricted to FSL_RC_xxx values.
   **
   */
  typedef int (*fsl_list_visitor_f)(void * obj, void * visitorState );

  /**
   ** A fsl_list_visitor_f() implementation which requires that obj be
   ** arbitrary memory which can legally be passed to fsl_free()
   ** (which this function does). The visitorState parameter is
   ** ignored.
   */
  int fsl_list_v_fsl_free(void * obj, void * visitorState );

  
  /**
   ** For each item in self->list, visitor(item,visitorState) is
   ** called.  The item is owned by self. The visitor function MUST
   ** NOT free the item (unless the visitor is a finalizer!), but may
   ** manipulate its contents if application rules do not specify
   ** otherwise.
   **
   ** If order is 0 or greater then the list is traversed from start
   ** to finish, else it is traverse from end to begin.
   **
   ** Returns 0 on success, non-0 on error.
   **
   ** If visitor() returns non-0 then looping stops and that code is
   ** returned.
   */
  int fsl_list_visit( fsl_list const * self, char order,
                      fsl_list_visitor_f visitor, void * visitorState );

  /**
   ** A list clean-up routine which takes a callback to clean up its
   ** contents.
   **
   ** Passes each element in the given list to
   ** childFinalizer(item,finalizerState). If that returns non-0,
   ** processing stops and that value is returned, otherwise
   ** fsl_list_reserve(list,0) is called and 0 is returned.
   **
   ** @see fsl_list_visit_free()
   **/
  int fsl_list_clear( fsl_list * list, fsl_list_visitor_f childFinalizer,
                      void * finalizerState );
  /**
   ** Similar to fsl_list_clear(list, fsl_list_v_fsl_free, NULL), but
   ** only clears the list itself if the second argument is true,
   ** otherwise it sets the list's length to 0 but keeps its memory
   ** intact for later use.
   **
   ** Be sure only to use this on lists of types for which fsl_free()
   ** is legal. i.e. don't use it on a list of fsl_deck objects or
   ** other types which have their own finalizers.
   **
   ** Results are undefined if list is NULL.
   **
   ** @see fsl_list_clear()
   */
  void fsl_list_visit_free( fsl_list * list, char freeListMem );
  
  /**
   **
   **
   ** Works similarly to the visit operation without the _p suffix
   ** except that the pointer the visitor function gets is a (**)
   ** pointing back to the entry within this list. That means that
   ** callers can assign the entry in the list to another value during
   ** the traversal process (e.g. set it to 0). If shiftIfNulled is
   ** true then if the callback sets the list's value to 0 then it is
   ** removed from the list and self->used is adjusted (self->capacity
   ** is not changed).
   */
  int fsl_list_visit_p( fsl_list * self, char order, char shiftIfNulled,
                        fsl_list_visitor_f visitor, void * visitorState );


  /**
   ** Sorts the given list using the given comparison function. Neither
   ** argument may be NULL. The arugments passed to the comparison function
   ** will be pointers to pointers to the original entries, and may (depending
   ** on how the list is used) point to NULL.
   */
  void fsl_list_sort( fsl_list * li, int (*cmp)( void const * lhs, void const * rhs ));
  
  /**
   ** Returns 0 if the given file is readable. Flags may be any values
   ** accepted by the accept(2) resp. _waccept() system calls.
   */
  int fsl_file_access(const char *zFilename, int flags);

  /**
   ** Compute a canonical pathname for a file or directory.
   ** Make the name absolute if it is relative.
   ** Remove redundant / characters.
   ** Remove all /./ path elements.
   ** Convert /A/../ to just /.
   ** If the slash parameter is non-zero, the trailing slash, if any,
   ** is retained.
   **
   ** Returns 0 on success, FSL_RC_MISUSE if !zOrigName or !pOut,
   ** FSL_RC_OOM if an allocation fails.
   **
   ** pOut is _appended_ to, so be sure to set pOut->used=0 (or pass it
   ** to fsl_buffer_reset()) before calling this if you want to start
   ** writing at the beginning.
   */
  int fsl_file_canonical_name(const char *zOrigName,
                              fsl_buffer *pOut, char slash);

  /**
   ** Writes the absolute path name of the current directory to zBuf,
   ** which must be at least nBuf bytes long (nBuf includes the space
   ** for a trailing NUL terminator).
   **
   ** Returns FSL_RC_RANGE if the name would be too long for nBuf,
   ** FSL_RC_IO if it cannot determine the current directory (e.g. a
   ** side effect of having removed the directory at runtime or similar
   ** things), and 0 on success.
   **
   ** On success, if outLen is not NULL then the length of the string
   ** written to zBuf is assigned to *outLen. The output string is
   ** always NUL-terminated.
   **
   ** On Windows, the name is converted from unicode to UTF8 and all '\\'
   ** characters are converted to '/'.  No conversions are needed on
   ** Unix.
   */
  int fsl_getcwd(char *zBuf, fsl_size_t nBuf, fsl_size_t * outLen);


  /**
   ** Return true if the filename given is a valid filename for
   ** a file in a repository.  Valid filenames follow all of the
   ** following rules:
   **
   **     *  Does not begin with "/"
   **     *  Does not contain any path element named "." or ".."
   **     *  Does not contain any of these characters in the path: "\"
   **     *  Does not end with "/".
   **     *  Does not contain two or more "/" characters in a row.
   **     *  Contains at least one character
   **
   ** Invalid UTF8 characters result in a false return if bStrictUtf8 is
   ** true.  If bStrictUtf8 is false, invalid UTF8 characters are silently
   ** ignored. See http://en.wikipedia.org/wiki/UTF-8#Invalid_byte_sequences
   ** and http://en.wikipedia.org/wiki/Unicode (for the noncharacters).
   **
   ** Fossil compatibility note: the bStrictUtf8 flag must be true
   ** when parsing new manifests but is false when parsing legacy
   ** manifests, for backwards compatibility.
   **
   ** z must be NUL terminated. Results are undefined if !z.
   */
  char fsl_is_simple_pathname(const char *z, char bStrictUtf8);

  /**
   ** Return the size of a file in bytes. Returns -1 if the file does
   ** not exist or is not stat(2)able.
   */
  fsl_size_t fsl_file_size(const char *zFilename);

  /**
   ** Return the modification time for a file.  Return -1 if the file
   ** does not exist or is not stat(2)able.
   */
  fsl_time_t fsl_file_mtime(const char *zFilename);

  /**
   ** Don't use this. The wd (working directory) family of functions
   ** might or might-not be necessary and in any case they require
   ** a fsl_cx context argument because they require repo-specific
   ** "allow-symlinks" setting.
   
   ** Return TRUE if the named file is an ordinary file or symlink
   ** and symlinks are allowed.
   **
   ** Return false for directories, devices, fifos, etc.
   */
  int fsl_file_wd_isfile_or_link(const char *zFilename);

  /**
   ** Return TRUE if the named file is an ordinary file.  Return false
   ** for directories, devices, fifos, symlinks, etc.
   */
  int fsl_file_isfile(const char *zFilename);

  /**
   ** Returns true if the given path appears to be absolute, else
   ** false. On Unix a path is absolute if it starts with a '/'.  On
   ** Windows a path is also absolute if it starts with a letter, a
   ** colon, and a backslash.
   */
  char fsl_file_is_absolute_path(const char *zPath);

  /**
   ** Simplify a filename by
   **
   **  * Convert all \ into / on windows and cygwin
   **  * removing any trailing and duplicate /
   **  * removing /./
   **  * removing /A/../
   **
   ** Changes are made in-place.  Return the new name length.  If the
   ** slash parameter is non-zero, the trailing slash, if any, is
   ** retained. If n is <0 then fsl_strlen(z) is used to calculate the
   ** length.
   */
  fsl_size_t fsl_file_simplify_name(char *z, fsl_int_t n_, char slash);

  
  /**
   ** Return non-zero if string z matches glob pattern zGlob and zero
   ** if the pattern does not match. Always returns 0 if either
   ** argument is NULL.
   **
   ** Globbing rules:
   **
   **      '*'       Matches any sequence of zero or more characters.
   **
   **      '?'       Matches exactly one character.
   **
   **     [...]      Matches one character from the enclosed list of
   **                characters.
   **
   **     [^...]     Matches one character not in the enclosed list.
   */
  char fsl_str_glob(const char *zGlob, const char *z);

  
  /**
   ** Returns true, else false if the given letter is an ASCII alphabet
   ** character.
   */
  char fsl_isalpha(int c);
  char fsl_islower(int c);
  char fsl_isspace(int c);
  char fsl_islower(int c);
  char fsl_isupper(int c);
  char fsl_isdigit(int c);
  char fsl_tolower(int c);
  char fsl_toupper(int c);
  char fsl_isalpha(int c);
  char fsl_isalnum(int c);

#ifdef _WIN32
  /**
   ** Translate MBCS to UTF-8.  Return a pointer to the translated
   ** text. ACHTUNG: Call fsl_mbcs_free() (not fsl_free()) to
   ** deallocate any memory used to store the returned pointer when
   ** done.
   */
  char * fsl_mbcs_to_utf8(char const * mbcs);

  /**
   ** Frees a string allocated from fsl_mbcs_to_utf8(). Results are undefined
   ** if mbcs was allocated using any other mechanism.
   */
  void fsl_mbcs_free(char * mbcs);
#endif
  /* _WIN32 */

  /**
   ** Deallocates the given memory, which must have been allocated
   ** from fsl_unicode_to_utf8(), fsl_utf8_to_unicode(), or any
   ** function which explicitly documents this function as being the
   ** proper finalizer for its returned memory.
   */
  void fsl_unicode_free(void *);


  /**
   ** Translate UTF-8 to Unicode for use in system calls. Returns a
   ** pointer to the translated text. The returned value must
   ** eventually be passed to fsl_unicode_free() to deallocate any
   ** memory used to store the returned pointer when done.
   **
   ** This function exists only for Windows. On other platforms
   ** it behaves like fsl_strdup().
   **
   ** The returned type is (wchar_t*) on Windows and (char*)
   ** everywhere else.
   */
  void *fsl_utf8_to_unicode(const char *zUtf8);

  /**
   ** Translates Unicode text into UTF-8.  Return a pointer to the
   ** translated text. Call fsl_unicode_free() to deallocate any
   ** memory used to store the returned pointer when done.
   **
   ** This function exists only for Windows. On other platforms it
   ** behaves like fsl_strdup().
   */
  char *fsl_unicode_to_utf8(const void *zUnicode);

  /**
   ** Translate text from the OS's character set into UTF-8. Return a
   ** pointer to the translated text. Call fsl_filename_free() to
   ** deallocate any memory used to store the returned pointer when
   ** done.
   **
   ** This function must not convert '\' to '/' on Windows/Cygwin, as
   ** it is used in places where we are not sure it's really filenames
   ** we are handling, e.g. fsl_getenv() or handling the argv
   ** arguments from main().
   **
   ** On Windows, translate some characters in the in the range
   ** U+F001 - U+F07F (private use area) to ASCII. Cygwin sometimes
   ** generates such filenames. See:
   ** <http://cygwin.com/cygwin-ug-net/using-specialnames.html>
   */
  char *fsl_filename_to_utf8(const void *zFilename);

  /**
   ** Translate text from UTF-8 to the OS's filename character set.
   ** Return a pointer to the translated text. Call
   ** fsl_filename_free() to deallocate any memory used to store the
   ** returned pointer when done.
   **
   ** On Windows, characters in the range U+0001 to U+0031 and the
   ** characters '"', '*', ':', '<', '>', '?' and '|' are invalid in
   ** filenames. Therefore, translate those to characters in the in the
   ** range U+F001 - U+F07F (private use area), so those characters
   ** never arrive in any Windows API. The filenames might look
   ** strange in Windows explorer, but in the cygwin shell everything
   ** looks as expected.
   **
   ** See: <http://cygwin.com/cygwin-ug-net/using-specialnames.html>
   **
   ** The returned type is (wchar_t*) on Windows and (char*)
   ** everywhere else.
   */
  void *fsl_utf8_to_filename(const char *zUtf8);

  
  /**
   ** Deallocate pOld, which must have been allocated by
   ** fsl_filename_to_utf8(), fsl_utf8_to_filename(), fsl_getenv(), or
   ** another routine which explicitly documents this function as
   ** being the proper finalizer for its returned memory.
   */
  void fsl_filename_free(void *pOld);

  /**
   ** Returns a (possible) copy of the environment variable with the
   ** given key, or NULL if no entry is found. The returned value must
   ** be passed to fsl_filename_free() to free it. ACHTUNG: DO NOT
   ** MODIFY the returned value - on Unix systems it is _not_ a
   ** copy. That interal API inconsistency "should" be resolved
   ** (==return a copy from here, but that means doing it everywhere)
   ** to avoid memory ownership problems later on.
   **
   ** Why return a copy? Because native strings from at least one of
   ** the more widespread OSes often have to be converted to something
   ** portable and this requires allocation on such platforms, but
   ** not on Unix. For API transparency, that means all platforms get
   ** the copy(-like) behaviour.
   **/
  char *fsl_getenv(const char *zName);

  /**
   ** Returns a positive value if zFilename is a directory, 0 if
   ** zFilename does not exist, or a negative value if zFilename
   ** exists but is something other than a directory. Results are
   ** undefined if zFilename is NULL.
   */
  char fsl_dir_check(const char *zFilename);

  /**
   ** Deletes the given file from the filesystem. Returns 0 on
   ** success.
   */
  int fsl_file_unlink(const char *zFilename);

  /**
   ** Create the directory with the given name if it does not already
   ** exist. If forceFlag is true, delete any prior non-directory
   ** object with the same name.
   **
   ** If the directory already exists, 0 is returned, not an error.
   **
   ** Return 0 on success, non-0 on error.
   */
  int fsl_mkdir(const char *zName, char forceFlag);
  
  /**
   ** Uses fsl_getenv() to look for the environment variables
   ** (FOSSIL_USER, (Windows: USERNAME), (Unix: USER, LOGNAME)).  If
   ** it finds one it returns a copy of that value, which must
   ** eventually be passed to fsl_free() to free it (NOT
   ** fsl_filename_free(), though fsl_getenv() requires that one). If
   ** it finds no match, or if copying the entry fails, it returns
   ** NULL.
   */
  char * fsl_guess_user_name();
  
  /**
   ** Tries to find the user's home directory. If found, 0 is
   ** returned, tgt's memory is _overwritten_ (not appended) with the
   ** path, and tgt->used is set to the path's string length.  (Design
   ** note: the overwrite behaviour is inconsistent with must of the
   ** API, but the implementation currently requires this.)
   **
   ** If requireWriteAccess is true then the directory is checked for
   ** write access, and FSL_RC_ACCESS is returned if that check
   ** fails. For historical (possibly techinical?) reasons, this check
   ** is only performed on Unix platforms. On others this argument is
   ** ignored. When writing code on Windows, it may be necessary to
   ** assume that write access is necessary on non-Windows platform,
   ** and to pass 1 for the second argument even though it is ignored
   ** on Windows.
   **
   ** On error non-0 is returned and tgt is updated with an error
   ** string OR (if the error was an allocation error while appending
   ** to the path or allocating MBCS strings for Windows), it returns
   ** FSL_RC_OOM and tgt "might" be updated with a partial path (up to
   ** the allocation error), and "might" be empty (if the allocation
   ** error happens early on).
   **
   ** This routine does not canonicalize/transform the home directory
   ** path provided by the environment, other than to convert the
   ** string byte encoding on some platforms. i.e. if the environment
   ** says that the home directory is "../" then this function will
   ** return that value, possibly to the eventual disappointment of
   ** the caller.
   **
   ** Result codes include:
   **
   ** - FSL_RC_OK (0) means a home directory was found and tgt is
   ** populated with its path.
   **
   ** - FSL_RC_NOT_FOUND means the home directory (platform-specific)
   ** could not be found.
   **
   ** - FSL_RC_ACCESS if the home directory is not writable and
   ** requireWriteAccess is true. Unix platforms only -
   ** requireWriteAccess is ignored on others.
   **
   ** - FSL_RC_TYPE if the home (as determined via inspection of the
   ** environment) is not a directory.
   **
   ** - FSL_RC_OOM if a memory (re)allocation fails.
   */
  int fsl_find_home_dir( fsl_buffer * tgt, char requireWriteAccess );

  /**
   ** Values for use with the fsl_fstat::mode field.
   */
  enum fsl_fstat_type_t {
  FSL_FSTAT_TYPE_UNKNOWN = 0,
  /** Indicates a directory filesystem entry. */
  FSL_FSTAT_TYPE_DIR,
  /** Indicates a non-directory, non-symlink filesystem entry. */
  FSL_FSTAT_TYPE_FILE,
  /** Indicates a symlink filesystem entry. */
  FSL_FSTAT_TYPE_LINK
  };
  typedef enum fsl_fstat_type_t fsl_fstat_type_t;

  /**
   ** Bitmask values for use with the fsl_fstat::perms field.
   */
  enum fsl_fstat_perm_t {
  /**
   ** Sentinel value.
   */
  FSL_FSTAT_PERM_UNKNOWN = 0,
  /**
   ** The executable bit, as understood by Fossil. Fossil does not
   ** differentiate between different +x values for user/group/other.
   */
  FSL_FSTAT_PERM_EXE = 0x01
  };
  typedef enum fsl_fstat_perm_t fsl_fstat_perm_t;
  
  /**
   ** A simple wrapper around the stat(2) structure resp. _stat/_wstat
   ** (on Windows). It exposes only the aspects of stat(2) info which
   ** Fossil works with, and not any platform-/filesystem-specific
   ** details except the executable bit for the permissions mode.
   **/
  struct fsl_fstat {
    /**
     ** Indicates the type of filesystem object.
     */
    fsl_fstat_type_t type;
    /**
     ** The creation time stat'd file, in... well, the man pages
     ** (neither for Linux nor Windows) do not specify exactly what
     ** unit this is. Let's assume seconds since the start of the Unix
     ** Epoch.
     */
    fsl_time_t ctime;
    /**
     ** Last modification time.
     */
    fsl_time_t mtime;
    /**
     ** The size of the stat'd file, in bytes.
     */
    fsl_size_t size;
    /**
     ** Not yet used.
     **
     ** TODO: decide whether we want to expose all OS/FS-level
     ** permissions or just the executable bit (as v1 does).
     ** fsl_fstat is intended to be used in more generic contexts than
     ** v1's fossil_stat(), so it "might" make sense to expose those
     ** here, even though fossil will only track the exec permission.
     */
    int perms;
  };
  /** Empty-initialized fsl_fstat structure. */
#define fsl_fstat_empty_m {FSL_FSTAT_TYPE_UNKNOWN,0,0,0,0}
  /** Empty-initialize fsl_fstat instance, intended for copy
      construction. */
  extern const fsl_fstat fsl_fstat_empty;

  /**
   ** Runs the OS's stat(2) equivalent to populate fst with
   ** information about the given file.
   **
   ** Returns 0 on success, FSL_RC_MISUSE if zFilename is NULL or
   ** starts with a NUL byte, or if fst is NULL. Returns
   ** FSL_RC_NOT_FOUND if no filesystem entry is found for the given
   ** name. Returns FSL_RC_IO if the underlying stat() (or equivalent)
   ** fails for other reasons (because MS apparently doesn't document
   ** the errno values which can be set by _wstati64()).
   **
   ** The derefSymlinks argument is ignored on non-Unix platforms.  On
   ** Unix platforms, if derefSymlinks is non-0 then stat(2) is used,
   ** else lstat(2) (if available on the platform) is used. For most
   ** cases clients should pass non-0. They should only pass 0 if they
   ** need to differentiate between symlinks and files.
   **
   ** The fsl_fstat_type_t family of flags can be used to determine
   ** the type of the filesystem object being stat()'d (file,
   ** directory, or symlink). It does apply any special logic for
   ** platform-specific oddities other than symlinks (e.g. character
   ** devices and such).
   **/
  int fsl_stat(const char *zFilename, fsl_fstat * fst,
               char derefSymlinks );

  /**
   ** Create a new delta between the memory zIn and zOut.
   **
   ** The delta is written into a preallocated buffer, zDelta, which
   ** must be at least 60 bytes longer than the target memory, zOut.
   ** The delta string will be NUL-terminated, but it might also
   ** contain embedded NUL characters if either the zSrc or zOut files
   ** are binary.
   **
   ** On success this function returns 0 and the length of the delta
   ** string, in bytes, excluding the final NUL terminator character,
   ** is written to *deltaSize.
   **
   ** Returns FSL_RC_MISUSE if any of the pointer arguments are NULL
   ** and FSL_RC_OOM if memory allocation fails during generation of
   ** the delta. Returns FSL_RC_RANGE if lenSrc or lenOut are "too
   ** big" (if they cause an overflow in the math).
   **
   ** Output Format:
   **
   ** The delta begins with a base64 number followed by a newline.
   ** This number is the number of bytes in the TARGET file.  Thus,
   ** given a delta file z, a program can compute the size of the
   ** output file simply by reading the first line and decoding the
   ** base-64 number found there.  The fsl_delta_applied_size()
   ** routine does exactly this.
   **
   ** After the initial size number, the delta consists of a series of
   ** literal text segments and commands to copy from the SOURCE file.
   ** A copy command looks like this:
   **
   ** (Achtung: extra backslashes are for Doxygen's benefit - not
   ** visible in the processsed docs.)
   **
   **     NNN\@MMM,
   **
   ** where NNN is the number of bytes to be copied and MMM is the
   ** offset into the source file of the first byte (both base-64).
   ** If NNN is 0 it means copy the rest of the input file.  Literal
   ** text is like this:
   **
   **     NNN:TTTTT
   **
   ** where NNN is the number of bytes of text (base-64) and TTTTT is
   ** the text.
   **
   ** The last term is of the form
   **
   **     NNN;
   **
   ** In this case, NNN is a 32-bit bigendian checksum of the output
   ** file that can be used to verify that the delta applied
   ** correctly.  All numbers are in base-64.
   **
   ** Pure text files generate a pure text delta.  Binary files
   ** generate a delta that may contain some binary data.
   **
   ** Algorithm:
   **
   ** The encoder first builds a hash table to help it find matching
   ** patterns in the source file.  16-byte chunks of the source file
   ** sampled at evenly spaced intervals are used to populate the hash
   ** table.
   **
   ** Next we begin scanning the target file using a sliding 16-byte
   ** window.  The hash of the 16-byte window in the target is used to
   ** search for a matching section in the source file.  When a match
   ** is found, a copy command is added to the delta.  An effort is
   ** made to extend the matching section to regions that come before
   ** and after the 16-byte hash window.  A copy command is only
   ** issued if the result would use less space that just quoting the
   ** text literally. Literal text is added to the delta for sections
   ** that do not match or which can not be encoded efficiently using
   ** copy commands.
   **
   ** @see fsl_delta_applied_size()
   ** @see fsl_delta_apply()
   */
  int fsl_delta_create( unsigned char const *zSrc, fsl_size_t lenSrc,
                        unsigned char const *zOut, fsl_size_t lenOut,
                        unsigned char *zDelta, fsl_size_t * deltaSize);

  /**
   ** Works identically to fsl_delta_create() but sends its output to
   ** the given output function. out(outState,...) may be called any
   ** number of times to emit delta output. Each time it is called it
   ** should append the new bytes to its output channel.
   **
   ** The semantics of the return value and the first four arguments
   ** are identical tofsl_delta_create(), with these ammendments
   ** regarding the return:
   **
   ** - Returns FSL_RC_MISUSE if any of (zSrc, zOut, out) are NULL.
   **
   ** - If out() returns non-0 at any time, delta generation is
   ** aborted and that code is returned.
   **
   ** Example usage:
   **
   ** @code
   ** int rc = fsl_delta_create( v1, v1len, v2, v2len,
   **                            fsl_output_f_FILE, stdout);
   ** @endcode
   */
  int fsl_delta_create2( unsigned char const *zSrc, fsl_size_t lenSrc,
                         unsigned char const *zOut, fsl_size_t lenOut,
                         fsl_output_f out, void * outState);

  /**
   ** A fsl_delta_create() wrapper which uses the first two arguments
   ** as the original and "new" content versions to delta, and outputs
   ** the delta to the 3rd argument (overwriting any existing contents
   ** and re-using any memory it had allocated).
   **
   ** Returns 0 on success.
   */
  int fsl_buffer_delta_create( fsl_buffer const * src,
                               fsl_buffer const * newVers,
                               fsl_buffer * delta);

  /**
   ** Apply a delta created using fsl_delta_create().
   **
   ** The output buffer must be big enough to hold the whole output
   ** file and a NUL terminator at the end. The
   ** fsl_delta_applied_size() routine can be used to determine that
   ** size.
   **
   ** zSrc represents the original sources to apply the delta to.
   ** It must be at least lenSrc bytes of valid memory.
   **
   ** zDelta holds the delta (created using fsl_delta_create()),
   ** and it must be lenDelta bytes long.
   **
   ** On success this function returns 0 and writes the applied delta
   ** to zOut.
   **
   ** Returns FSL_RC_MISUSE if any pointer argument is NULL. Returns
   ** FSL_RC_RANGE if lenSrc or lenDelta are "too big" (if they cause
   ** an overflow in the math). Invalid delta input can cause any of
   ** FSL_RC_RANGE, FSL_RC_DELTA_INVALID_TERMINATOR,
   ** FSL_RC_CHECKSUM_MISMATCH, FSL_RC_SIZE_MISMATCH, or
   ** FSL_RC_DELTA_INVALID_OPERATOR to be returned.
   **
   ** Refer to the fsl_delta_create() documentation above for a
   ** description of the delta file format.
   **
   ** @see fsl_delta_applied_size()
   ** @see fsl_delta_create()
   ** @see fsl_delta_apply2()
  */
  int fsl_delta_apply( unsigned char const *zSrc, fsl_size_t lenSrc,
                       unsigned char const *zDelta, fsl_size_t lenDelta,
                       unsigned char *zOut );

  /**
   ** Functionally identical to fsl_delta_apply() but any errors generated
   ** during application of the delta are described in more detail
   ** in pErr. If pErr is NULL this behaves exactly as documented for
   ** fsl_delta_apply().
   */
  int fsl_delta_apply2( unsigned char const *zSrc,
                        fsl_size_t lenSrc,
                        unsigned char const *zDelta,
                        fsl_size_t lenDelta,
                        unsigned char *zOut,
                        fsl_error * pErr);
  /*
  ** Calculates the size (in bytes) of the output from applying a the
  ** given delta. On success 0 is returned and *appliedSize will be
  ** updated with the amount of memory required for applying the
  ** delta. zDelta must point to lenDelta bytes of memory in the
  ** format emitted by fsl_delta_create(). It is legal for appliedSize
  ** to point to the same memory as the 2nd argument.
  **
  ** Returns FSL_RC_MISUSE if any pointer argument is NULL. Returns
  ** FSL_RC_RANGE if lenDelta is too short to be a delta. Returns
  ** FSL_RC_DELTA_INVALID_TERMINATOR if the delta's encoded length
  ** is not properly terminated.
  **
  ** This routine is provided so that an procedure that is able to
  ** call fsl_delta_apply() can learn how much space is required for
  ** the output and hence allocate nor more space that is really
  ** needed.
  **
  ** TODO?: consolidate 2nd and 3rd parameters into one i/o parameter?
  **
  ** @see fsl_delta_apply()
  ** @see fsl_delta_create()
  */
  int fsl_delta_applied_size(unsigned char const *zDelta,
                             fsl_size_t lenDelta,
                             fsl_size_t * appliedSize);

  /**
   ** "Fossilizes" the first len bytes of the given input string. If
   ** (len<0) then fsl_strlen(inp) is used to calculate its length.
   ** The output is appended to out, which is expanded as needed and
   ** out->used is updated accordingly.  Returns 0 on success,
   ** FSL_RC_MISUSE if !inp or !out. Returns 0 without side-effects if
   ** 0==len or (!*inp && len<0). Returns FSL_RC_OOM if reservation of
   ** the output buffer fails (it is expanded, at most, one time by
   ** this function).
   **
   ** Fossilization replaces the following bytes/sequences with the
   ** listed replacements:
   **
   ** (Achtung: usage of doubled backslashes here it just to please
   ** doxygen - they will show up as single slashes in the processed
   ** output.)
   **
   ** - Backslashes are doubled.
   **
   ** - (\\n, \\r, \\v, \\t, \\f) are replaced with \\\\X, where X is the
   ** conventional encoding letter for that escape sequence.
   **
   ** - Spaces are replaced with \\s.
   **
   ** - Embedded NULs are replaced by \\0 (numeric 0, not character
   ** '0').
   */
  int fsl_bytes_fossilize( unsigned char const * inp, fsl_int_t len,
                           fsl_buffer * out );
  /**
   ** "Defossilizes" bytes encoded by fsl_bytes_fossilize() in-place.
   ** inp must be a string encoded by fsl_bytes_fossilize(), and the
   ** decoding processes stops at the first unescaped NUL terminator.
   ** It has no error conditions except for !inp or if inp is not
   ** NUL-terminated, both of which invoke in undefined behaviour.
   **
   ** If resultLen is not NULL then *resultLen is set to the resulting string
   ** length.
   **
   */
  void fsl_bytes_defossilize( unsigned char * inp, fsl_size_t * resultLen );

  /**
   ** Defossilizes the contents of b. Equivalent to:
   ** fsl_bytes_defossilize( b->mem, &b->used );
   */
  void fsl_buffer_defossilize( fsl_buffer * b );
  
  /**
  ** Return true (non-0) if the input string contains only valid base-16
  ** digits. If any invalid characters appear in the string, return
  ** 0 (false).
  */
  char fsl_validate16(const char *zIn, fsl_size_t nIn);

  /**
  ** The input string is a base16 value.  Convert it into its canonical
  ** form.  This means that digits are all lower case and that conversions
  ** like "l"->"1" and "O"->"0" occur.
  */
  void fsl_canonical16(char *z, fsl_size_t n);

  /**
  ** Decode a N-character base-16 number into base-256.  N must be a 
  ** multiple of 2.  The output buffer must be at least N/2 characters
  ** in length. Returns 0 on success.
  */
  int fsl_decode16(const unsigned char *zIn, unsigned char *pOut, fsl_size_t N);

  /**
  ** Encode a N-digit base-256 in base-16. N is the byte length of pIn
  ** and zOut must be at least (N*2+1) bytes long (the extra is for a
  ** terminating NUL). Returns zero on success, FSL_RC_MISUSE if !pIn
  ** or !zOut.
  */
  int fsl_encode16(const unsigned char *pIn, unsigned char *zOut, fsl_size_t N);


  /**
   ** Tries to convert the value of errNo, which is assumed to come
   ** from the global errno, to a fsl_rc_t code. If it can, it returns
   ** something approximating the errno value, else it returns dflt.
   **
   ** Example usage:
   **
   ** @code
   ** FILE * f = fsl_fopen("...", "...");
   ** int rc = f ? 0 : fsl_errno_to_rc(errno, FSL_RC_IO);
   ** ...
   ** @endcode
   **
   ** Why require the caller to pass in errno, instead of accessing it
   ** directly from this function? To avoid the the off-chance that
   ** something changes errno between the call and the conversion
   ** (whether or not that's possible is as yet undetermined). It can
   ** also be used by clients to map to explicit errno values to
   ** fsl_rc_t values, e.g. fsl_errno_to_rc(EROFS,-1) returns
   ** FSL_RC_ACCESS.
   */
  int fsl_errno_to_rc(int errNo, int dflt);

  /**
   ** Make the given string safe for HTML by converting every "<" into
   ** "&lt;", every ">" into "&gt;", every "&" into "&amp;", and
   ** encode " as &quot; so that it can appear as an argument to
   ** markup.
   **
   ** The escaped output is send to out(oState,...).
   **
   ** Returns 0 on success or if there is nothing to do (input has a
   ** length of 0). Returns FSL_RC_MISUSE if !out or !zIn. If out()
   ** returns a non-0 code then that value is returned to the caller.
   **
   ** If n is negative, fsl_strlen() is used to calculate zIn's length.
   */
  int fsl_htmlize(fsl_output_f out, void * oState,
                  const char *zIn, fsl_int_t n);

  /**
   ** Functionally equivalent to fsl_htmlize() but optimized to perform
   ** only a single allocation.
   **
   ** Returns 0 on success or if there is nothing to do (input has a
   ** length of 0). Returns FSL_RC_MISUSE if !p or !zIn, and
   ** FSL_RC_OOM on allocation error.
   **
   ** If n is negative, fsl_strlen() is used to calculate zIn's length.
   */
  int fsl_htmlize_to_buffer(fsl_buffer *p, const char *zIn, fsl_int_t n);

  /**
   ** Equivalent to fsl_htmlize_to_buffer() but returns the result as a
   ** new string which must eventually be fsl_free()d by the caller.
   **
   ** Returns NULL for invalidate arguments or allocation error.
   */
  char *fsl_htmlize_str(const char *zIn, fsl_int_t n);


  /**
   ** If c is a character Fossil likes to HTML-escape, assigns *xlate
   ** to its transformed form, else set it to NULL. Returns 1 for
   ** untransformed characters and the strlen of *xlate for others.
   ** Bytes returned via xlate are static and immutable.
   **
   ** Results are undefined if xlate is NULL.
   */
  fsl_size_t fsl_htmlize_xlate(int c, char const ** xlate);

  /**
   ** Flags for use with text-diff generation APIs,
   ** e.g. fsl_diff_text().
   **
   ** Maintenance reminder: these values are holy and must not be
   ** changed without also changing the corresponding code in
   ** fsl_diff.c.
   */
  enum fsl_diff_flag_t {
  /** Inline (not side-by-side) diff */
  FSL_DIFF_INLINE =       0x00,
  /** Ignore end-of-line whitespace */
  FSL_DIFF_IGNORE_EOLWS = 0x01,
  /** Generate a side-by-side diff */
  FSL_DIFF_SIDEBYSIDE =   0x02,
  /** Missing shown as empty files */
  FSL_DIFF_VERBOSE =      0x04,
  /** Show filenames only */
  FSL_DIFF_BRIEF =        0x08,
  /** Render for HTML. */
  FSL_DIFF_HTML =         0x10,
  /** Show line numbers. */
  FSL_DIFF_LINENO =       0x20,
  /** Warn about whitespace. */
  FSL_DIFF_WS_WARNING =   0x40,
  /** Suppress optimizations (debug). */
  FSL_DIFF_NOOPT =        0x0100,
  /** Invert the diff (debug). */
  FSL_DIFF_INVERT =       0x0200,
  /** Use context even if zero. */
  FSL_DIFF_CONTEXT_EX =   0x0400,
  /** Only display if not "too big." */
  FSL_DIFF_NOTTOOBIG =    0x0800
  };  

  /**
   ** Generates a textual diff from two text inputs and writes
   ** it to the given output function.
   **
   ** pA and pB are the buffers to diff.
   **
   ** contextLines is the number of lines of context to output (or
   ** some default if <= 0). This parameter has a built-in limit
   ** of 2^16, and values larger than that get truncated.
   **
   ** sbsWidth specifies the width (in characters) of the side-by-side
   ** columns. If sbsWidth is not 0 then this function behaves as if
   ** diffFlags contains the FSL_DIFF_SIDEBYSIDE flag. If sbsWidth is
   ** negative, OR if diffFlags explicitly contains
   ** FSL_DIFF_SIDEBYSIDE and sbsWidth is 0, then some default width
   ** is used. This parameter has a built-in limit of 255, and values
   ** larger than that get truncated to 255.
   **
   ** diffFlags is a mask of fsl_diff_flag_t values. Not all of the
   ** fsl_diff_flag_t flags are yet [sup]ported.
   **
   ** The output is sent to out(outState,...). If out() returns non-0
   ** during processing, processing stops and that result is returned
   ** to the caller of this function.
   **
   ** Returns 0 on success, FSL_RC_OOM on allocation error,
   ** FSL_RC_MISUSE if any arguments are invalid, FSL_RC_TYPE if any
   ** of the content appears to be binary (contains embedded NUL
   ** bytes).
   **
   ** None of (pA, pB, out) may be NULL.
   **
   ** TODOs:
   **
   ** - Add a predicate function for outputing only matching
   ** differences, analog to fossil(1)'s regex support (but more
   ** flexible).
   **
   ** - Expose the raw diff-generation bits via the internal API
   ** to facilitate/enable the creation of custom diff formats.
   */
  int fsl_diff_text(fsl_buffer const *pA, fsl_buffer const *pB,
                    fsl_output_f out, void * outState,
                    short contextLines, short sbsWidth,
                    int diffFlags );

  /**
   ** Functionally equivalent to:
   **
   ** @code:
   ** fsl_diff_text(pA, pB, fsl_output_f_buffer, pOut,
   **               contextLines, sbsWidth, diffFlags);
   ** @endcode
   **
   ** Except that it returns FSL_RC_MISUSE if !pOut.
   */
  int fsl_diff_text_to_buffer(fsl_buffer const *pA, fsl_buffer const *pB,
                              fsl_buffer *pOut, short contextLines,
                              short sbsWidth, int diffFlags );

  
#if defined(__cplusplus)
} /*extern "C"*/
#endif
#endif
/* NET_FOSSIL_SCM_FSL_UTIL_H_INCLUDED */