*/
#define DIFF_CANNOT_COMPUTE_BINARY \
    "cannot compute difference between binary files\n"

#define DIFF_CANNOT_COMPUTE_SYMLINK \
    "cannot compute difference between symlink and regular file\n"

#define looks_like_binary(blob) (looks_like_text((blob)) == 0)
#endif /* INTERFACE */

/*
** Maximum length of a line in a text file.  (8192)
*/
#define LENGTH_MASK_SZ  13
#define LENGTH_MASK     ((1<<LENGTH_MASK_SZ)-1)

** contains a line that is too long
** Returns -1, if the file appears text, but it contains CrLf
*/
int looks_like_text(const Blob *pContent){
  const char *z = blob_buffer(pContent);
  unsigned int n = blob_size(pContent);
  int j, c;
  int result = 1;  /* Assume text with no CrLf */

  /* Check individual lines.
  */
  if( n==0 ) return result;  /* Empty file -> text */
  c = *z;
  if( c==0 ) return 0;  /* \000 byte in a file -> binary */
  j = (c!='\n');
  while( --n>0 ){
    c = *++z; ++j;
    if( c==0 ) return 0;  /* \000 byte in a file -> binary */
    if( c=='\n' ){
      if( z[-1]=='\r' ){
        result = -1;  /* Contains CrLf, continue */
      }
      if( j>LENGTH_MASK ){
        return 0;  /* Very long line -> binary */
      }
      j = 0;
    }
  }
  if( j>LENGTH_MASK ){
    return 0;  /* Very long line -> binary */
  }
  return result;  /* No problems seen -> not binary */
}

/*
** Return true if two DLine elements are identical.
*/
static int same_dline(DLine *pA, DLine *pB){
  return pA->h==pB->h && memcmp(pA->z,pB->z,pA->h & LENGTH_MASK)==0;