Fossil

** For any other binary type, return "unknown/unknown".
*/
const char *mimetype_from_content(Blob *pBlob){
  int i;
  int n;
  const unsigned char *x;

  static const char isBinary[256] = {
     1, 1, 1, 1,  1, 1, 1, 1,    1, 0, 0, 0,  0, 0, 1, 1,
     1, 1, 1, 1,  1, 1, 1, 1,    1, 1, 0, 0,  1, 1, 1, 1
  };

  /* A table of mimetypes based on file content prefixes
  */
  static const struct {
    const char *zPrefix;       /* The file prefix */
    int size;                  /* Length of the prefix */
    const char *zMimetype;     /* The corresponding mimetype */
  } aMime[] = {
    { "GIF87a",                  6, "image/gif"  },
    { "GIF89a",                  6, "image/gif"  },
    { "\211PNG\r\n\032\n",       8, "image/png"  },
    { "\377\332\377",            3, "image/jpeg" },
    { "\377\330\377",            3, "image/jpeg" },
  };

  x = (const unsigned char*)blob_buffer(pBlob);
  n = blob_size(pBlob);
  for(i=0; i<n; i++){
    unsigned char c = x[i];
    if( isBinary[c] ){
      break;
    }
  }
  if( i>=n ){
    return 0;   /* Plain text */
  }


  for(i=0; i<ArraySize(aMime); i++){
    if( n>=aMime[i].size && memcmp(x, aMime[i].zPrefix, aMime[i].size)==0 ){
      return aMime[i].zMimetype;
    }
  }
  return "unknown/unknown";
}