comparison: docs/Writerside/topics/hash_key.h.md
docs/Writerside/topics/hash_key.h.md
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| 1 # Hash Function | |
| 2 | |
| 3 UCX implements the MurmurHash2 algorithm for computing hashes that are primarily used for [CxMap](map.h.md). | |
| 4 But it can be used for arbitrary custom scenarios, too. | |
| 5 | |
| 6 ## Overview | |
| 7 ```C | |
| 8 #include <cx/hash_key.h> | |
| 9 | |
| 10 void cx_hash_murmur(CxHashKey *key); | |
| 11 CxHashKey cx_hash_key(const void *obj, size_t len); | |
| 12 CxHashKey cx_hash_key_str(const char *str); | |
| 13 CxHashKey cx_hash_key_bytes(const unsigned char *bytes, size_t len); | |
| 14 CxHashKey cx_hash_key_cxstr(cxstring str); | |
| 15 ``` | |
| 16 | |
| 17 ## Description | |
| 18 | |
| 19 The primary function for creating a `CxHashKey` structure is `cx_hash_key()`. | |
| 20 The other functions do effectively the same, but | |
| 21 | |
| 22 * `cx_hash_key_bytes()` is strongly typed if you want to avoid passing `void*` | |
| 23 * `cx_hash_key_str()` conveniently takes a C string and computes the length | |
| 24 * `cx_hash_key_cxstr()` conveniently takes a [UCX string](string.h.md) | |
| 25 | |
| 26 In all cases, the hash will be available in the `hash` field of the returned structure. | |
| 27 | |
| 28 <note> | |
| 29 UCX assigns the hash value <code>1574210520</code> to the <code>NULL</code> pointer. | |
| 30 This is a careful choice which is not standard MurmurHash2 and an extension to support <code>NULL</code> pointers. | |
| 31 </note> | |
| 32 | |
| 33 If you want to create a hash completely manually, | |
| 34 you can initialize the `data` and `len` members of `CxHashKey` | |
| 35 and call `cx_hash_murmur()`. | |
| 36 It is _not_ recommended to do so. | |
| 37 | |
| 38 Example that is equivalent to `CxHashKey key = cx_hash_str(mystring)` | |
| 39 ```C | |
| 40 CxHashKey key; | |
| 41 key.data = mystring; | |
| 42 key.len = strlen(mystring); | |
| 43 cx_hash_murmur(&key); | |
| 44 ``` | |
| 45 | |
| 46 <seealso> | |
| 47 <category ref="apidoc"> | |
| 48 <a href="https://ucx.sourceforge.io/api/hash__key_8h.html">hash_key.h</a> | |
| 49 </category> | |
| 50 </seealso> |
