FixedHash
FixedHash is a custom Grezzo format for serializing hash tables that map string keys to arbitrary binary blobs.
| File format | |
|---|---|
| Endianness | little |
| Version | 1 |
| This article is about the file format in general. For actual values, check the game RomFS. | |
Hash function
String keys are hashed using the following hash function:
u32 Hash(const char* key) {
u32 hash = 0;
while (*key) {
hash ^= *key++ + (h >> 2) + (h << 5);
}
return hash;
}
Format
| Offset | Type | Description |
|---|---|---|
| 0x0 | u8 | Magic (must be 0x3D) |
| 0x1 | u8 | Version (must be 1) |
| 0x2 | u16 | Number of hash table buckets (N) |
| 0x4 | u16 | Number of child FixedHash nodes |
| 0x6 | u16 | Padding? [check] |
| 0x8 | u32[N + 1] | Offsets to the first entry in each bucket (relative to the Entries section) 0xFFFFFFFF for empty buckets. |
| X = (0x8 + 4*(N+1) + 3) & -8 | u64 | Entries section size |
| X + 8 | Entry[...] | Entries |
| Y = align(X + entries section size, 8) | u64 | Entry offsets section size |
| Y + 8 | u32[...] | Entry offsets (relative to the Entries section) |
| Z = align(Y + entry offset section size, 8) | u64 | Data section size |
| Z + 8 | any | Data |
| A = align(Z + data section size, 4) | u32 | Names section size |
| A + 4 | C strings | Names |
Entry
| Offset | Type | Description |
|---|---|---|
| 0x0 | u16 | Node index if this describes a FixedHash child node (if so, it must be <= 0xFFED)
Otherwise, must be >= 0xFFF0 for non-node data. |
| 0x2 | u16 | Name offset (relative to the Name section) |
| 0x4 | u32 | Name hash |
| 0x8 | u32 | Next entry offset (relative to the Entries section) for hash table collision resolution. 0xFFFFFFFF if there is no other entry in the bucket. |
| 0xC | u32 | Data offset (relative to the Data section)
For non-node data, the data size is stored at offset+0 as a u64 and the actual data is at offset+8. |