Fossil

    for(j=0; j<m; j++){
      if( showLn ) appendDiffLineno(pOut, a+j+1, b+j+1, html);
      appendDiffLine(pOut, ' ', &B[b+j], html);
    }
  }
}

static int maxwidth;

/*
** Status of a single output line
*/
typedef struct SbsLine SbsLine;
struct SbsLine {
  char *zLine;             /* The output line under construction */
  int n;                   /* Index of next unused slot in the zLine[] */

  int i;   /* Number of input characters consumed */
  int j;   /* Number of output characters generated */
  int k;   /* Cursor position */
  int needEndSpan = 0;
  const char *zIn = pLine->z;
  char *z = &p->zLine[p->n];
  int w = p->width;

  if (n > maxwidth)
    maxwidth = n;

  for(i=j=k=0; k<w && i<n; i++, k++){
    char c = zIn[i];
    if( p->escHtml ){
      if( i==p->iStart ){
        int x = strlen(p->zStart);
        memcpy(z+j, p->zStart, x);
        j += x;

** in, compute a side-by-side diff into pOut.
*/
static void sbsDiff(
  DContext *p,       /* The computed diff */
  Blob *pOut,        /* Write the results here */
  int nContext,      /* Number of lines of context around each change */
  int width,         /* Width of each column of output */
  int escHtml       /* True to generate HTML output */
){
  DLine *A;     /* Left side of the diff */
  DLine *B;     /* Right side of the diff */  
  int a = 0;    /* Index of next line in A[] */
  int b = 0;    /* Index of next line in B[] */
  int *R;       /* Array of COPY/DELETE/INSERT triples */
  int r;        /* Index into R[] */

/*
** Extract the width of columns for side-by-side diff.  Supply an
** appropriate default if no width is given.
*/
int diff_width(int diffFlags){
  int w = (diffFlags & DIFF_WIDTH_MASK)/(DIFF_CONTEXT_MASK+1);

  return w;
}

/*
** Generate a report of the differences between files pA and pB.
** If pOut is not NULL then a unified diff is appended there.  It
** is assumed that pOut has already been initialized.  If pOut is

  if( (diffFlags & DIFF_NOOPT)==0 ) diff_optimize(&c);

  if( pOut ){
    /* Compute a context or side-by-side diff into pOut */
    int escHtml = (diffFlags & DIFF_HTML)!=0;
    if( diffFlags & DIFF_SIDEBYSIDE ){
      int width = diff_width(diffFlags);
      if (width == 0){ /* Autocalculate */
        Blob dump;
        /* Webserver */
        maxwidth = 0;
        blob_zero(&dump);
        sbsDiff(&c, &dump, nContext, width, escHtml);
        width = maxwidth;
      }
      sbsDiff(&c, pOut, nContext, width, escHtml);
    }else{
      int showLn = (diffFlags & DIFF_LINENO)!=0;
      contextDiff(&c, pOut, nContext, showLn, escHtml);
    }
    free(c.aFrom);
    free(c.aTo);

  char *z = 0;
  if( diffFlags & DIFF_BRIEF ){
    /* no-op */
  }else if( diffFlags & DIFF_SIDEBYSIDE ){
    int w = diff_width(diffFlags);
    int n1 = strlen(zLeft);
    int x;
    if (w > 0) {
        if( n1>w*2 ) n1 = w*2;
        x = w*2+17 - (n1+2);
    }else{
        /* Autocalculate width
         * We can't know the width in advance, so we'll make it
         * output three = around the name */
        x = 6;
    }
    z = mprintf("%.*c %.*s %.*c\n",
                x/2, '=', n1, zLeft, (x+1)/2, '=');
  }else{
    z = mprintf("--- %s\n+++ %s\n", zLeft, zRight);
  }
  fossil_print("%s", z);
  fossil_free(z);

  if( showDiff==0 ){
    diffFlags = 0;  /* Zero means do not show any diff */
  }else{
    int x;
    if( sideBySide ){
      diffFlags = DIFF_SIDEBYSIDE | DIFF_IGNORE_EOLWS;

      /* "dw" query parameter determines width of each column
       * 0 means autocalculate. */
      x = atoi(PD("dw","0"))*(DIFF_CONTEXT_MASK+1);
      if( x<0 || x>DIFF_WIDTH_MASK ) x = DIFF_WIDTH_MASK;
      diffFlags += x;
    }else{
      diffFlags = DIFF_INLINE | DIFF_IGNORE_EOLWS;
    }

    /* "dc" query parameter determines lines of context */