String File Format


String Files (extension: .DAT) in Petroglyph's games hold <key, value> string pairs and allow the game to be easily ported across different languages by having a seperate String File for each language. In such a case, the sets of keys are typically identical for the different language string files while the sets of values differ for each language.

The keys are 8-bit ASCII strings and the values are 16-bit UTF-16LE strings.


Each string file begins with a header, followed by the string index table and finally the string data itself.

  +0000h  count      uint32      ; Number of records in the String Index Table

String Index Table record:
  +0000h  crc        uint32      ; CRC-32 of the key
  +0004h  nValChars  uint32      ; Length of the value string, in characters
  +0008h  nKeyChars  uint32      ; Length of the key string, in characters
String Data:
  +0000h  UNICHAR    String_Index_Table[0].nValChars
  +????h  UNICHAR    ...
  +????h  UNICHAR    String_Index_Table[count-1].nValChars
  +????h  CHAR       String_Index_Table[0].nKeyChars
  +????h  CHAR       ...
  +????h  CHAR       String_Index_Table[count-1].nKeyChars

Note that all string data is stored back-to-back, without zero-termination. All value strings are stored first, followed by all key strings.


The String Index table is not necessarily sorted on the CRC. Typically, there are two usages for String Files: game strings and credits. In the former case, language-dependent values are located by doing a lookup based on the language-independent key. For those files, the String Index Table is usually sorted. For the latter case, the strings are displayed one by one and, in fact, cannot be sorted by key.

A solution is, when reading the file, to keep track of the sortedness of the index (the CRC of the previously read entry should always be less than the CRC of the currently read entry), and when it turns out the file is sorted, O(log n) lookups can be performed instead of O(n).