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doc/MST_format.md: Updated for recent changes.

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David Korth 2019-05-29 23:25:50 -04:00
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@ -74,37 +74,32 @@ The message table name offset points to the name of the message table,
encoded as Shift-JIS (code page 932). encoded as Shift-JIS (code page 932).
Following the WTXT header is an array of message table pointers. This Following the WTXT header is an array of message table pointers. This
table has the following general format for each entry: table has the following format for each entry:
```c ```c
typedef struct PACKED _WTXT_MsgPointer { typedef struct PACKED _WTXT_MsgPointer {
uint32_t msg_id_name_offset; // [0x000] Offset of message name. uint32_t name_offset; // [0x000] Offset of message name. (Shift-JIS)
uint32_t msg_offset; // [0x004] Offset of message. uint32_t text_offset; // [0x004] Offset of message text. (UTF-16)
uint32_t zero; // [0x008] Zero. (NOTE: May not be present!) uint32_t placeholder_offset; // [0x008] If non-zero, offset of placeholder icon name. (Shift-JIS)
} WTXT_MsgPointer; } WTXT_MsgPointer;
``` ```
* `msg_id_name_offset`: Offset of the message name. Encoded as Shift-JIS. * `name_offset`: Offset of the message name. Encoded as Shift-JIS.
* `msg_offset`: Offset of the message text. Encoded as UTF-16. * `text_offset`: Offset of the message text. Encoded as UTF-16.
Endianness depends on file endianness. Endianness depends on file endianness.
* `zero`: Unused. **HOWEVER**, this field may actually be missing entirely. * `placeholder_offset`: If non-zero, this indicates the offset of the
placeholder offset. Usually this is a button icon name, though sometimes
it can be an "rgb" string. Encoded as Shift-JIS.
`msg_tbl_count` is equal to the total number of strings in the offset table, `msg_tbl_count` is equal to the total number of strings in the offset table.
assuming each string entry is exactly 12 bytes. For an unknown reason, many
strings are missing the `zero` field, so this isn't entirely accurate. Also,
some strings might only have a name and no text. The easiest way to determine
this is by checking if `msg_offset >= msg_tbl_name_offset`. This works because
the message text is all stored in one block, and the message names are stored
in one block *after* the message text.
Due to the occasionally missing `msg_offset` and `zero` fields, it is
impossible to accurately determine which string is which by simply reading the
WTXT offsets. The differential offset table must be parsed first.
## Differential Offset Table ## Differential Offset Table
In Sonic '06 files, this usually looks like "ABABABABABABAB", though sometimes In Sonic '06 files, the differential offset table is present and allows for
there's strings of "AAAAAAAA". Here's how to decode it. parsing the main offset table while skipping zero offsets, e.g. for strings
that don't have placeholder names. This table usually looks like
"ABABABABABABAB", though in cases where a placeholder name is present, there
may be sections of "AAAAAAAA". Here's how to decode it.
Initial file position: 0x20 (32; size of header) Initial file position: 0x20 (32; size of header)
@ -125,19 +120,16 @@ For each non-zero byte in the offset table:
* Endianness depends on file endianness. * Endianness depends on file endianness.
* Repeat to determine all real offsets until the end of the offset table is reached. * Repeat to determine all real offsets until the end of the offset table is reached.
When parsing the offsets, some notes to keep in mind:
* The first offset is always the string table name, encoded in Shift-JIS.
* After the first offset, strings are stored using pairs of offsets:
* String name (encoded in Shift-JIS)
* String text (encoded in UTF-16)
* If the string text's offset is >= the offset of the string table name,
this string doesn't actually have text. The string text offset should
be considered the string name offset of the *next* message.
The end of the string table is aligned to a DWORD boundary, so extra `00` The end of the string table is aligned to a DWORD boundary, so extra `00`
bytes may be present. These can be ignored. (If writing an MST file, the bytes may be present. These can be ignored. (If writing an MST file, the
`00` bytes must be included for alignment, if necessary.) `00` bytes must be included for alignment, if necessary.)
This table is basically redundant, since you can just read the main offset
table to get the correct information. Sonic '06 **requires** this table to
be correct, though; otherwise, it will crash. `mst06` treats this table as
write-only; that is, it's not used when parsing MST files, but it *is* written
when converting XML to MST.
## References ## References
* HedgeLib BINA parser: https://github.com/Radfordhound/HedgeLib/blob/master/HedgeLib/Headers/BINAv1Header.cs * HedgeLib BINA parser: https://github.com/Radfordhound/HedgeLib/blob/master/HedgeLib/Headers/BINAv1Header.cs