Graphics directory

(Up to File formats)

A Worms directory (a DIR file) acts as a file archive, containing (usually graphics) files. Its built-in hash table allows fast access to files by the file name.

File Format

The format (as well as others) was first reverse-engineered by Jon Skeet, and implemented in Fudge Boy's sprite editor.

• A 12-byte header, consisting of:
  • A 4-byte signature, "DIR\x1A"
  • Complete file length, including header and table of contents (4 bytes)
  • Address (file offset) of the directory table of contents (4 bytes)
• The actual data of the files stored in the directory
• The table of contents, consisting of:
  • A signature (?) DWORD, 0x0000000A (4 bytes)
  • A 1024-entry DWORD hash table (4096 bytes). Each entry is an offset (relative to the start of the TOC) to the first file entry, whose file name matches this hash, or 0 for no matching file entries.
  • The list of files stored in the directory. Each list entry consists of:
    • Offset (relative to the start of the TOC) to the next entry for this hash value, or 0 for none (4 bytes)
    • Offset within DIR file of this file entry's data (4 bytes)
    • Length of file (4 bytes)
    • The file name, padded to a multiple of 4 characters (with at least one after trailing \0).

Hash Calculation

The hash function (with which the hashes to the file names are calculated) is as follows:

#define HASH_BITS 10
#define HASH_SIZE (1 << HASH_BITS)

static int hash(char *str)
{
    int sum = 0;
    while (*str)
    {
        sum = ((sum << 1) % HASH_SIZE) | (sum >> (HASH_BITS - 1) & 1);
        sum += (unsigned char)*str++;
        sum %= HASH_SIZE;
    }
    return sum;
}