What causes "Invalid scan entry format in file %s " in DrKLO/Telegram?

Follow the exact format: component indices separated by spaces, then optional ': Ss Se Ah Al', terminated by ';'.

Invalid scan entry format in file %s

Error message

Invalid scan entry format in file %s

What it means

The scan definition parser expects each entry to follow the format: component indices (space-separated), optional ': Ss Se Ah Al' for progressive parameters, terminated by ';' or EOF. If the terminating character after parsing an entry is neither ';' nor EOF (or if read_scan_integer fails during progressive parameter parsing), execution jumps to the 'bogus' label and reports an invalid scan entry format.

Source

Thrown at TMessagesProj/jni/mozjpeg/rdswitch.c:245

      if (! read_scan_integer(fp, &val, &termchar) || termchar != ' ')
        goto bogus;
      scanptr->Se = (int) val;
      if (! read_scan_integer(fp, &val, &termchar) || termchar != ' ')
        goto bogus;
      scanptr->Ah = (int) val;
      if (! read_scan_integer(fp, &val, &termchar))
        goto bogus;
      scanptr->Al = (int) val;
    } else {
      /* set non-progressive parameters */
      scanptr->Ss = 0;
      scanptr->Se = DCTSIZE2-1;
      scanptr->Ah = 0;
      scanptr->Al = 0;
    }
    if (termchar != ';' && termchar != EOF) {
bogus:
      fprintf(stderr, "Invalid scan entry format in file %s\n", filename);
      fclose(fp);
      return FALSE;
    }
    scanptr++, scanno++;
  }

  if (termchar != EOF) {
    fprintf(stderr, "Non-numeric data in file %s\n", filename);
    fclose(fp);
    return FALSE;
  }

  if (scanno > 0) {
    /* Stash completed scan list in cinfo structure.
     * NOTE: for cjpeg's use, JPOOL_IMAGE is the right lifetime for this data,
     * but if you want to compress multiple images you'd want JPOOL_PERMANENT.
     */
    scanptr = (jpeg_scan_info *)

View on GitHub (pinned to 45ab8f4308)

Solutions

Follow the exact format: component indices separated by spaces, then optional ': Ss Se Ah Al', terminated by ';'.
Example valid entry: '0 1 2: 0 0 0 0;' (components 0,1,2, progressive params Ss=0 Se=0 Ah=0 Al=0).
Use a known-good scan script template and modify values carefully.
Validate the file for stray non-ASCII characters or incorrect separators.

Example fix

# before (invalid: missing semicolon, wrong separator)
0,1,2: 0 0 0 0
# after (valid)
0 1 2: 0 0 0 0;

Defensive patterns

Strategy: validation

Validate before calling

// Pre-validate scan entry syntax: components then optional ': Ss Se Ah Al' then ';'
static boolean validate_scan_syntax(const char *filename) {
  FILE *fp = fopen(filename, "r");
  if (!fp) return FALSE;
  int c;
  boolean ok = TRUE;
  while ((c = fgetc(fp)) != EOF) {
    if (c == ',') ok = FALSE; // commas are invalid separators
  }
  fclose(fp);
  return ok;
}

Prevention

Use a known-good scan script template and only modify numeric values.
Ensure component indices are space-separated, not comma-separated.
Verify each scan entry ends with ';' except possibly the last (which can end with EOF).
Test scan scripts on small images before using them in production pipelines.

When it happens

Trigger: A scan entry with incorrect syntax: wrong separator character (e.g., using ',' instead of ' '), missing semicolon between entries, or malformed progressive parameters after the colon. Also triggered when read_scan_integer fails during the Ss/Se/Ah/Al field parsing.

Common situations: Hand-written scan scripts with syntax errors; scan files copied from a different format; trailing characters after a valid scan entry; using a colon but not providing all four progressive parameters (Ss Se Ah Al); encoding issues introducing invisible characters.

Related errors

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/14e8406e710766f2. Report an issue: GitHub.