comparison: docs/Writerside/topics/hash_key.h.md
docs/Writerside/topics/hash_key.h.md
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- docs/3.1
- changeset 1144
- b23d07fff6ca
- parent 1143
- 0559812df10c
- child 1145
- 1a8fe7b7dd8a
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| 1143:0559812df10c | 1144:b23d07fff6ca |
|---|---|
| 1 # Hash Function | 1 # Hash Function |
| 2 | 2 |
| 3 ## Undocumented Symbols (TODO) | 3 UCX implements the MurmurHash2 algorithm for computing hashes that are primarily used for [CxMap](map.h.md). |
| 4 ### cx_hash_key | 4 But it can be used for arbitrary custom scenarios, too. |
| 5 ### cx_hash_key_bytes | 5 |
| 6 ### cx_hash_key_str | 6 There are four functions which all generate a `CxHashKey` structure for given data. |
| 7 ### cx_hash_murmur | 7 |
| 8 * `cx_hash_key()` takes an arbitrary pointer and a length | |
| 9 * `cx_hash_key_bytes()` takes an `unsigned char*` and a length | |
| 10 * `cx_hash_key_str()` takes a usual C string | |
| 11 * `cx_hash_key_cxstr()` takes a [UCX string](string.h.md) | |
| 12 | |
| 13 The hash is then available in the `hash` field of the returned structure. | |
| 14 | |
| 15 <note> | |
| 16 UCX assigns the hash value <code>1574210520</code> to the <code>NULL</code> pointer. | |
| 17 This is a careful choice which is not standard MurmurHash2 and an extension to support <code>NULL</code> pointers. | |
| 18 </note> | |
| 19 | |
| 20 If you want to create a hash completely manually, | |
| 21 you can initialize the `data` and `len` members of `CxHashKey` | |
| 22 and call `cx_hash_murmur()`. | |
| 23 It is _not_ recommended to do so. | |
| 24 | |
| 25 Example that is equivalent to `CxHashKey key = cx_hash_str(mystring)` | |
| 26 ```C | |
| 27 CxHashKey key; | |
| 28 key.data = mystring; | |
| 29 key.len = strlen(mystring); | |
| 30 cx_hash_murmur(&key); | |
| 31 ``` |
