** 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 width;               /* Maximum width of a column in the output */
  unsigned char escHtml;   /* True to escape html characters */
  int iStart;              /* Write zStart prior to character iStart */
  const char *zStart;      /* A <span> tag */
  int iEnd;                /* Write </span> prior to character iEnd */
};

/*
** Flags for sbsWriteText()
*/
#define SBS_NEWLINE      0x0001   /* End with \n\000 */
#define SBS_PAD          0x0002   /* Pad output to width spaces */


/*
** Write up to width characters of pLine into z[].  Translate tabs into
** spaces.  Add a newline if SBS_NEWLINE is set.  Translate HTML characters
** if SBS_HTML is set.  Pad the rendering out width bytes if SBS_PAD is set.
*/
static void sbsWriteText(SbsLine *p, DLine *pLine, unsigned flags){
  int n = pLine->h & LENGTH_MASK;
  int i;   /* Number of input characters consumed */
  int j;   /* Number of output characters generated */
  int k;   /* Cursor position */
  const char *zIn = pLine->z;
  char *z = &p->zLine[p->n];
  int w = p->width;
  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;
      }else if( i==p->iEnd ){
        memcpy(z+j, "</span>", 7);
        j += 7;
      }
    }
    if( c=='\t' ){
      z[j++] = ' ';
      while( (k&7)!=7 && k<w ){ z[j++] = ' '; k++; }
    }else if( c=='\r' || c=='\f' ){
      z[j++] = ' ';
    }else if( c=='<' && p->escHtml ){
      memcpy(&z[j], "&lt;", 4);
      j += 4;
    }else if( c=='&' && p->escHtml ){
      memcpy(&z[j], "&amp;", 5);
      j += 5;
    }else if( c=='>' && p->escHtml ){
      memcpy(&z[j], "&gt;", 4);
      j += 4;
    }else{
      z[j++] = c;
    }
  }
  if( p->escHtml && i<=p->iEnd ){
    memcpy(&z[j], "</span>", 7);
    j += 7;
  }
  if( (flags & SBS_PAD)!=0 ){
    while( k<w ){ k++;  z[j++] = ' '; }
  }
  if( flags & SBS_NEWLINE ){

  sbsWriteHtml(p, "<span class=\"diffln\">");
  sqlite3_snprintf(7, &p->zLine[p->n], "%5d ", ln+1);
  p->n += 6;
  sbsWriteHtml(p, "</span>");
  p->zLine[p->n++] = ' ';
}

/*
** Write out lines that have been edited.  Adjust the highlight to cover
** only those parts of the line that actually changed.
*/
static void sbsWriteLineChange(
  SbsLine *p,          /* The SBS output line */
  DLine *pLeft,        /* Left line of the change */
  int lnLeft,          /* Line number for the left line */
  DLine *pRight,       /* Right line of the change */
  int lnRight          /* Line number of the right line */
){
  int nLeft;           /* Length of left line in bytes */
  int nRight;          /* Length of right line in bytes */
  int nPrefix;         /* Length of common prefix */
  int nSuffix;         /* Length of common suffix */
  int width;           /* Total column width */
  const char *zLeft;   /* Text of the left line */
  const char *zRight;  /* Text of the right line */

  nLeft = pLeft->h & LENGTH_MASK;
  zLeft = pLeft->z;
  nRight = pRight->h & LENGTH_MASK;
  zRight = pRight->z;

  nPrefix = 0;
  while( nPrefix<nLeft && nPrefix<nRight && zLeft[nPrefix]==zRight[nPrefix] ){
    nPrefix++;
  }
  nSuffix = 0;
  if( nPrefix<nLeft && nPrefix<nRight ){
    while( nSuffix<nLeft && nSuffix<nRight
           && zLeft[nLeft-nSuffix-1]==zRight[nRight-nSuffix-1] ){
      nSuffix++;
    }
    if( nSuffix==nLeft || nSuffix==nRight ) nPrefix = 0;
  }
  if( nPrefix+nSuffix > nLeft ) nSuffix = nLeft - nPrefix;
  if( nPrefix+nSuffix > nRight ) nSuffix = nRight - nPrefix;
  if( nPrefix+nSuffix==nLeft ){
    /* Text inserted on the right */
    sbsWriteLineno(p, lnLeft);
    p->iStart = p->iEnd = -1;
    sbsWriteText(p, pLeft, SBS_PAD);
    sbsWrite(p, " | ", 3);
    sbsWriteLineno(p, lnRight);
    p->iStart = nPrefix;
    p->iEnd = nRight - nSuffix;
    p->zStart = "<span class=\"diffadd\">";
    sbsWriteText(p, pRight, SBS_NEWLINE);
  }else if( nPrefix+nSuffix==nRight ){
    /* Text deleted from the left */
    sbsWriteLineno(p, lnLeft);
    p->iStart = nPrefix;
    p->iEnd = nLeft - nSuffix;
    p->zStart = "<span class=\"diffrm\">";
    sbsWriteText(p, pLeft, SBS_PAD);
    sbsWrite(p, " | ", 3);
    sbsWriteLineno(p, lnRight);
    p->iStart = p->iEnd = -1;
    sbsWriteText(p, pRight, SBS_NEWLINE);
  }else{
    /* Text modified between left and right */
    sbsWriteLineno(p, lnLeft);
    p->iStart = nPrefix;
    p->iEnd = nLeft - nSuffix;
    p->zStart = "<span class=\"diffchng\">";
    sbsWriteText(p, pLeft, SBS_PAD);
    sbsWrite(p, " | ", 3);
    sbsWriteLineno(p, lnRight);
    p->iEnd = nRight - nSuffix;
    sbsWriteText(p, pRight, SBS_NEWLINE);
  }
}


/*
** Given a diff context in which the aEdit[] array has been filled
** in, compute a side-by-side diff into pOut.
*/
static void sbsDiff(
  DContext *p,       /* The computed diff */

  int skip;     /* Number of lines to skip */
  SbsLine s;    /* Output line buffer */

  s.zLine = fossil_malloc( 10*width + 100 );
  if( s.zLine==0 ) return;
  s.width = width;
  s.escHtml = escHtml;
  s.iStart = -1;
  s.iEnd = -1;
  A = p->aFrom;
  B = p->aTo;
  R = p->aEdit;
  mxr = p->nEdit;
  while( mxr>2 && R[mxr-1]==0 && R[mxr-2]==0 ){ mxr -= 3; }
  for(r=0; r<mxr; r += 3*nr){
    /* Figure out how many triples to show in a single block */

    /* Show the initial common area */
    a += skip;
    b += skip;
    m = R[r] - skip;
    for(j=0; j<m; j++){
      s.n = 0;
      sbsWriteLineno(&s, a+j);
      s.iStart = s.iEnd = -1;
      sbsWriteText(&s, &A[a+j], SBS_PAD);
      sbsWrite(&s, "   ", 3);
      sbsWriteLineno(&s, b+j);
      sbsWriteText(&s, &B[b+j], SBS_NEWLINE);
      blob_append(pOut, s.zLine, s.n);
    }
    a += m;
    b += m;

    /* Show the differences */
    for(i=0; i<nr; i++){
      ma = R[r+i*3+1];   /* Lines on left but not on right */
      mb = R[r+i*3+2];   /* Lines on right but not on left */
      while( ma+mb>0 ){
        if( ma<mb && (ma==0 ||
                match_dline(&A[a],&B[b]) < match_dline(&A[a],&B[b+1]) ) ){
          s.n = 0;
          sbsWriteSpace(&s, width + 7);
          sbsWrite(&s, " > ", 3);
          sbsWriteLineno(&s, b);
          s.iStart = 0;
          s.zStart = "<span class=\"diffadd\">";
          s.iEnd = s.width;
          sbsWriteText(&s, &B[b], SBS_NEWLINE);
          blob_append(pOut, s.zLine, s.n);
          mb--;
          b++;
        }else if( ma>mb && (mb==0 ||
                  match_dline(&A[a],&B[b]) < match_dline(&A[a+1],&B[b])) ){
          s.n = 0;
          sbsWriteLineno(&s, a);
          s.iStart = 0;
          s.zStart = "<span class=\"diffrm\">";
          s.iEnd = s.width;
          sbsWriteText(&s, &A[a], SBS_PAD);
          sbsWrite(&s, " <\n", 3);
          blob_append(pOut, s.zLine, s.n);
          ma--;
          a++;
        }else{
          s.n = 0;
          sbsWriteLineChange(&s, &A[a], a, &B[b], b);






          blob_append(pOut, s.zLine, s.n);
          ma--;
          mb--;
          a++;
          b++;
        }
      }
      if( i<nr-1 ){
        m = R[r+i*3+3];
        for(j=0; j<m; j++){
          s.n = 0;
          sbsWriteLineno(&s, a+j);
          s.iStart = s.iEnd = -1;
          sbsWriteText(&s, &A[a+j], SBS_PAD);
          sbsWrite(&s, "   ", 3);
          sbsWriteLineno(&s, b+j);
          sbsWriteText(&s, &B[b+j], SBS_NEWLINE);
          blob_append(pOut, s.zLine, s.n);
        }
        b += m;
        a += m;
      }
    }

    /* Show the final common area */
    assert( nr==i );
    m = R[r+nr*3];
    if( m>nContext ) m = nContext;
    for(j=0; j<m; j++){
      s.n = 0;
      sbsWriteLineno(&s, a+j);
      s.iStart = s.iEnd = -1;
      sbsWriteText(&s, &A[a+j], SBS_PAD);
      sbsWrite(&s, "   ", 3);
      sbsWriteLineno(&s, b+j);
      sbsWriteText(&s, &B[b+j], SBS_NEWLINE);
      blob_append(pOut, s.zLine, s.n);
    }
  }

  { "div.udiff",
    "context diff display",
    @   font-family: monospace;
    @   white-space: pre;
  },
  { "span.diffchng",
    "changes in a diff",
    @   background-color: #e0e0ff;
  },
  { "span.diffadd",
    "added code in a diff",
    @   background-color: #e0ffe0;
  },
  { "span.diffrm",
    "deleted in a diff",