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BYAML File Format
These files are similar to regular YAML files, but are encoded in binary form. They usually have the file extension .byml or .byaml.
This page describes version 1 of the file format.
Offsets in the header are absolute.
| Offset | Size | Description |
|---|---|---|
| 0x0 | 2 | Magic number / BOM (BY: big endian, YB: little endian) |
| 0x2 | 2 | Version number |
| 0x4 | 4 | Offset to dictionary key table |
| 0x8 | 4 | Offset to string table |
| 0xC | 4 | Offset to binary data table |
| 0x10 | 4 | Offset to root node (array or dictionary) |
A node starts with a single byte that indicates its type.
| ID | Type |
|---|---|
| 0xA0 | String |
| 0xA1 | Binary data |
| 0xC0 | Array |
| 0xC1 | Dictionary |
| 0xC2 | String table |
| 0xC3 | Binary table |
| 0xD0 | Bool |
| 0xD1 | Integer |
| 0xD2 | Float |
For string and binary nodes, the value is simply an index into the string or binary table (see header).
The type table contains one byte per element that indicates its node type.
If the number of elements is not a multiple of 4, additional null bytes are inserted between the type table and the data table such that the data table is aligned to 4 bytes.
The data table contains either an absolute offset to the node (for container nodes), or simply the value of the array element (for primitive nodes).
| Offset | Size | Description |
|---|---|---|
| 0x0 | 1 | Node type (0xC0) |
| 0x1 | 3 | Number of elements (N) |
| 0x4 | N | Type table |
| 4 x N | Data table |
A dictionary contains key / value pairs. The pairs must be sorted by their keys, because a binary search algorithm is used to look them up.
| Offset | Size | Description |
|---|---|---|
| 0x0 | 1 | Node type (0xC1) |
| 0x1 | 3 | Number of pairs (N) |
| 0x4 | 8 x N | Pair table |
Every pair is stored as follows:
| Offset | Size | Description |
|---|---|---|
| 0x0 | 3 | Index into dictionary key table (see header) |
| 0x3 | 1 | Node type |
| 0x4 | 4 | Value |
Just like array elements, the value is either a primitive or an absolute offset to a container node.
A string table is a special kind of node.
The address table contains offsets to the strings, relative to the start of the string table node. It also contains an offset that points to the end of the string table (right behind the last string).
The address table and strings must both be sorted, because a binary search algorithm is used to find them.
| Offset | Size | Description |
|---|---|---|
| 0x0 | 1 | Node type (0xC2) |
| 0x1 | 3 | Number of strings (N) |
| 0x4 | 4 x (N + 1) | Address table |
| Null-terminated strings |
The address table contains offsets to the binary data, relative to the start of the binary table node. It also contains an offset that points to the end of the binary table (right behind the last binary blob).
The address table must be sorted, because the size of a binary blob is calculated from the difference between two offsets.
| Offset | Size | Description |
|---|---|---|
| 0x0 | 1 | Node type (0xC3) |
| 0x1 | 3 | Number of binary blobs (N) |
| 0x4 | 4 x N | Address table |
| Binary data |