comparison: docs/Writerside/topics/hash_key.h.md
docs/Writerside/topics/hash_key.h.md
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| 5 | 5 |
| 6 ## Overview | 6 ## Overview |
| 7 ```C | 7 ```C |
| 8 #include <cx/hash_key.h> | 8 #include <cx/hash_key.h> |
| 9 | 9 |
| 10 void cx_hash_murmur(CxHashKey *key); | 10 void cx_hash_murmur(CxHashKey *key); |
| 11 | |
| 12 uint32_t cx_hash_u32(uint32_t x); | |
| 13 uint64_t cx_hash_u64(uint64_t x); | |
| 14 | |
| 11 CxHashKey cx_hash_key(const void *obj, size_t len); | 15 CxHashKey cx_hash_key(const void *obj, size_t len); |
| 12 CxHashKey cx_hash_key_str(const char *str); | 16 CxHashKey cx_hash_key_str(const char *str); |
| 13 CxHashKey cx_hash_key_bytes(const unsigned char *bytes, size_t len); | 17 CxHashKey cx_hash_key_bytes(const unsigned char *bytes, size_t len); |
| 14 CxHashKey cx_hash_key_cxstr(cxstring str); | 18 CxHashKey cx_hash_key_cxstr(cxstring str); |
| 19 CxHashKey cx_hash_key_u32(uint32_t x); | |
| 20 CxHashKey cx_hash_key_u64(uint64_t x); | |
| 21 | |
| 22 int cx_hash_key_cmp(const CxHashKey *left, const CxHashKey *right); | |
| 15 ``` | 23 ``` |
| 16 | 24 |
| 17 ## Description | 25 ## Description |
| 18 | 26 |
| 19 The primary function for creating a `CxHashKey` structure is `cx_hash_key()`. | 27 The primary function for creating a `CxHashKey` structure from non-integers is `cx_hash_key()`. |
| 20 The other functions do effectively the same, but | 28 The other functions effectively do the same, but |
| 21 | 29 |
| 22 * `cx_hash_key_bytes()` is strongly typed if you want to avoid passing `void*` | 30 * `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 | 31 * `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) | 32 * `cx_hash_key_cxstr()` conveniently takes a [UCX string](string.h.md) |
| 25 | 33 |
| 26 In all cases, the hash will be available in the `hash` field of the returned structure. | 34 In all cases, the hash will be available in the `hash` field of the returned structure. |
| 27 | |
| 28 | 35 |
| 29 > UCX assigns the hash value `1574210520` to the `NULL` pointer. | 36 > UCX assigns the hash value `1574210520` to the `NULL` pointer. |
| 30 > This is a careful choice which is not standard MurmurHash2 and an extension to support `NULL` pointers. | 37 > This is a careful choice which is not standard MurmurHash2 and an extension to support `NULL` pointers. |
| 31 | 38 |
| 32 If you want to create a hash completely manually, | 39 If you want to create a hash completely manually, |
| 40 key.data = mystring; | 47 key.data = mystring; |
| 41 key.len = strlen(mystring); | 48 key.len = strlen(mystring); |
| 42 cx_hash_murmur(&key); | 49 cx_hash_murmur(&key); |
| 43 ``` | 50 ``` |
| 44 | 51 |
| 52 Hashes from integers are created more efficiently by mixing up the bits to produce a good statistical distribution. | |
| 53 The function `cx_hash_u32()` and `cx_hash_u64()` are provided for this purpose and provide collision-free hashes. | |
| 54 The corresponding functions `cx_hash_key_u32()` and `cx_hash_key_u64()` can be used to create `CxHashKey` structures with those hashes. | |
| 55 | |
| 56 > Since integer hashes are collision-free, there is no need to store any `data` in the `CxHashKey` structure. | |
| 57 | |
| 58 Hash keys are compared with `cx_hash_key_cmp()`. | |
| 59 | |
| 45 <seealso> | 60 <seealso> |
| 46 <category ref="apidoc"> | 61 <category ref="apidoc"> |
| 47 <a href="https://ucx.sourceforge.io/api/hash__key_8h.html">hash_key.h</a> | 62 <a href="https://ucx.sourceforge.io/api/hash__key_8h.html">hash_key.h</a> |
| 48 </category> | 63 </category> |
| 49 </seealso> | 64 </seealso> |
