ffmpeg.libavutil.murmur3 source code

1 /*
2  * Copyright (C) 2013 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * @ingroup lavu_murmur3
24  * Public header for MurmurHash3 hash function implementation.
25  */
26 module ffmpeg.libavutil.murmur3;
27 extern (C) @nogc nothrow:
28 
29 /**
30  * @defgroup lavu_murmur3 Murmur3
31  * @ingroup lavu_hash
32  * MurmurHash3 hash function implementation.
33  *
34  * MurmurHash3 is a non-cryptographic hash function, of which three
35  * incompatible versions were created by its inventor Austin Appleby:
36  *
37  * - 32-bit output
38  * - 128-bit output for 32-bit platforms
39  * - 128-bit output for 64-bit platforms
40  *
41  * FFmpeg only implements the last variant: 128-bit output designed for 64-bit
42  * platforms. Even though the hash function was designed for 64-bit platforms,
43  * the function in reality works on 32-bit systems too, only with reduced
44  * performance.
45  *
46  * @anchor lavu_murmur3_seedinfo
47  * By design, MurmurHash3 requires a seed to operate. In response to this,
48  * libavutil provides two functions for hash initiation, one that requires a
49  * seed (av_murmur3_init_seeded()) and one that uses a fixed arbitrary integer
50  * as the seed, and therefore does not (av_murmur3_init()).
51  *
52  * To make hashes comparable, you should provide the same seed for all calls to
53  * this hash function -- if you are supplying one yourself, that is.
54  *
55  * @{
56  */
57 
58 /**
59  * Allocate an AVMurMur3 hash context.
60  *
61  * @return Uninitialized hash context or `NULL` in case of error
62  */
63 struct AVMurMur3;
64 AVMurMur3* av_murmur3_alloc ();
65 
66 /**
67  * Initialize or reinitialize an AVMurMur3 hash context with a seed.
68  *
69  * @param[out] c    Hash context
70  * @param[in]  seed Random seed
71  *
72  * @see av_murmur3_init()
73  * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
74  * seeds for MurmurHash3.
75  */
76 void av_murmur3_init_seeded (AVMurMur3* c, ulong seed);
77 
78 /**
79  * Initialize or reinitialize an AVMurMur3 hash context.
80  *
81  * Equivalent to av_murmur3_init_seeded() with a built-in seed.
82  *
83  * @param[out] c    Hash context
84  *
85  * @see av_murmur3_init_seeded()
86  * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
87  * seeds for MurmurHash3.
88  */
89 void av_murmur3_init (AVMurMur3* c);
90 
91 /**
92  * Update hash context with new data.
93  *
94  * @param[out] c    Hash context
95  * @param[in]  src  Input data to update hash with
96  * @param[in]  len  Number of bytes to read from `src`
97  */
98 void av_murmur3_update (AVMurMur3* c, const(ubyte)* src, int len);
99 
100 /**
101  * Finish hashing and output digest value.
102  *
103  * @param[in,out] c    Hash context
104  * @param[out]    dst  Buffer where output digest value is stored
105  */
106 void av_murmur3_final (AVMurMur3* c, ref ubyte[16] dst);
107 
108 /**
109  * @}
110  */
111 
112 /* AVUTIL_MURMUR3_H */