FFmpeg 4.2.2
hash.h
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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_hash_generic
24 * Generic hashing API
25 */
26
27#ifndef AVUTIL_HASH_H
28#define AVUTIL_HASH_H
29
30#include <stdint.h>
31
32#include "version.h"
33
34/**
35 * @defgroup lavu_hash Hash Functions
36 * @ingroup lavu_crypto
37 * Hash functions useful in multimedia.
38 *
39 * Hash functions are widely used in multimedia, from error checking and
40 * concealment to internal regression testing. libavutil has efficient
41 * implementations of a variety of hash functions that may be useful for
42 * FFmpeg and other multimedia applications.
43 *
44 * @{
45 *
46 * @defgroup lavu_hash_generic Generic Hashing API
47 * An abstraction layer for all hash functions supported by libavutil.
48 *
49 * If your application needs to support a wide range of different hash
50 * functions, then the Generic Hashing API is for you. It provides a generic,
51 * reusable API for @ref lavu_hash "all hash functions" implemented in libavutil.
52 * If you just need to use one particular hash function, use the @ref lavu_hash
53 * "individual hash" directly.
54 *
55 * @section Sample Code
56 *
57 * A basic template for using the Generic Hashing API follows:
58 *
59 * @code
60 * struct AVHashContext *ctx = NULL;
61 * const char *hash_name = NULL;
62 * uint8_t *output_buf = NULL;
63 *
64 * // Select from a string returned by av_hash_names()
65 * hash_name = ...;
66 *
67 * // Allocate a hash context
68 * ret = av_hash_alloc(&ctx, hash_name);
69 * if (ret < 0)
70 * return ret;
71 *
72 * // Initialize the hash context
73 * av_hash_init(ctx);
74 *
75 * // Update the hash context with data
76 * while (data_left) {
77 * av_hash_update(ctx, data, size);
78 * }
79 *
80 * // Now we have no more data, so it is time to finalize the hash and get the
81 * // output. But we need to first allocate an output buffer. Note that you can
82 * // use any memory allocation function, including malloc(), not just
83 * // av_malloc().
84 * output_buf = av_malloc(av_hash_get_size(ctx));
85 * if (!output_buf)
86 * return AVERROR(ENOMEM);
87 *
88 * // Finalize the hash context.
89 * // You can use any of the av_hash_final*() functions provided, for other
90 * // output formats. If you do so, be sure to adjust the memory allocation
91 * // above. See the function documentation below for the exact amount of extra
92 * // memory needed.
93 * av_hash_final(ctx, output_buffer);
94 *
95 * // Free the context
96 * av_hash_freep(&ctx);
97 * @endcode
98 *
99 * @section Hash Function-Specific Information
100 * If the CRC32 hash is selected, the #AV_CRC_32_IEEE polynomial will be
101 * used.
102 *
103 * If the Murmur3 hash is selected, the default seed will be used. See @ref
104 * lavu_murmur3_seedinfo "Murmur3" for more information.
105 *
106 * @{
107 */
108
109/**
110 * @example ffhash.c
111 * This example is a simple command line application that takes one or more
112 * arguments. It demonstrates a typical use of the hashing API with allocation,
113 * initialization, updating, and finalizing.
114 */
115
116struct AVHashContext;
117
118/**
119 * Allocate a hash context for the algorithm specified by name.
120 *
121 * @return >= 0 for success, a negative error code for failure
122 *
123 * @note The context is not initialized after a call to this function; you must
124 * call av_hash_init() to do so.
125 */
126int av_hash_alloc(struct AVHashContext **ctx, const char *name);
127
128/**
129 * Get the names of available hash algorithms.
130 *
131 * This function can be used to enumerate the algorithms.
132 *
133 * @param[in] i Index of the hash algorithm, starting from 0
134 * @return Pointer to a static string or `NULL` if `i` is out of range
135 */
136const char *av_hash_names(int i);
137
138/**
139 * Get the name of the algorithm corresponding to the given hash context.
140 */
141const char *av_hash_get_name(const struct AVHashContext *ctx);
142
143/**
144 * Maximum value that av_hash_get_size() will currently return.
145 *
146 * You can use this if you absolutely want or need to use static allocation for
147 * the output buffer and are fine with not supporting hashes newly added to
148 * libavutil without recompilation.
149 *
150 * @warning
151 * Adding new hashes with larger sizes, and increasing the macro while doing
152 * so, will not be considered an ABI change. To prevent your code from
153 * overflowing a buffer, either dynamically allocate the output buffer with
154 * av_hash_get_size(), or limit your use of the Hashing API to hashes that are
155 * already in FFmpeg during the time of compilation.
156 */
157#define AV_HASH_MAX_SIZE 64
158
159/**
160 * Get the size of the resulting hash value in bytes.
161 *
162 * The maximum value this function will currently return is available as macro
163 * #AV_HASH_MAX_SIZE.
164 *
165 * @param[in] ctx Hash context
166 * @return Size of the hash value in bytes
167 */
168int av_hash_get_size(const struct AVHashContext *ctx);
169
170/**
171 * Initialize or reset a hash context.
172 *
173 * @param[in,out] ctx Hash context
174 */
175void av_hash_init(struct AVHashContext *ctx);
176
177/**
178 * Update a hash context with additional data.
179 *
180 * @param[in,out] ctx Hash context
181 * @param[in] src Data to be added to the hash context
182 * @param[in] len Size of the additional data
183 */
184#if FF_API_CRYPTO_SIZE_T
185void av_hash_update(struct AVHashContext *ctx, const uint8_t *src, int len);
186#else
187void av_hash_update(struct AVHashContext *ctx, const uint8_t *src, size_t len);
188#endif
189
190/**
191 * Finalize a hash context and compute the actual hash value.
192 *
193 * The minimum size of `dst` buffer is given by av_hash_get_size() or
194 * #AV_HASH_MAX_SIZE. The use of the latter macro is discouraged.
195 *
196 * It is not safe to update or finalize a hash context again, if it has already
197 * been finalized.
198 *
199 * @param[in,out] ctx Hash context
200 * @param[out] dst Where the final hash value will be stored
201 *
202 * @see av_hash_final_bin() provides an alternative API
203 */
204void av_hash_final(struct AVHashContext *ctx, uint8_t *dst);
205
206/**
207 * Finalize a hash context and store the actual hash value in a buffer.
208 *
209 * It is not safe to update or finalize a hash context again, if it has already
210 * been finalized.
211 *
212 * If `size` is smaller than the hash size (given by av_hash_get_size()), the
213 * hash is truncated; if size is larger, the buffer is padded with 0.
214 *
215 * @param[in,out] ctx Hash context
216 * @param[out] dst Where the final hash value will be stored
217 * @param[in] size Number of bytes to write to `dst`
218 */
219void av_hash_final_bin(struct AVHashContext *ctx, uint8_t *dst, int size);
220
221/**
222 * Finalize a hash context and store the hexadecimal representation of the
223 * actual hash value as a string.
224 *
225 * It is not safe to update or finalize a hash context again, if it has already
226 * been finalized.
227 *
228 * The string is always 0-terminated.
229 *
230 * If `size` is smaller than `2 * hash_size + 1`, where `hash_size` is the
231 * value returned by av_hash_get_size(), the string will be truncated.
232 *
233 * @param[in,out] ctx Hash context
234 * @param[out] dst Where the string will be stored
235 * @param[in] size Maximum number of bytes to write to `dst`
236 */
237void av_hash_final_hex(struct AVHashContext *ctx, uint8_t *dst, int size);
238
239/**
240 * Finalize a hash context and store the Base64 representation of the
241 * actual hash value as a string.
242 *
243 * It is not safe to update or finalize a hash context again, if it has already
244 * been finalized.
245 *
246 * The string is always 0-terminated.
247 *
248 * If `size` is smaller than AV_BASE64_SIZE(hash_size), where `hash_size` is
249 * the value returned by av_hash_get_size(), the string will be truncated.
250 *
251 * @param[in,out] ctx Hash context
252 * @param[out] dst Where the final hash value will be stored
253 * @param[in] size Maximum number of bytes to write to `dst`
254 */
255void av_hash_final_b64(struct AVHashContext *ctx, uint8_t *dst, int size);
256
257/**
258 * Free hash context and set hash context pointer to `NULL`.
259 *
260 * @param[in,out] ctx Pointer to hash context
261 */
262void av_hash_freep(struct AVHashContext **ctx);
263
264/**
265 * @}
266 * @}
267 */
268
269#endif /* AVUTIL_HASH_H */
void av_hash_freep(struct AVHashContext **ctx)
Free hash context and set hash context pointer to NULL.
void av_hash_final_b64(struct AVHashContext *ctx, uint8_t *dst, int size)
Finalize a hash context and store the Base64 representation of the actual hash value as a string.
const char * av_hash_get_name(const struct AVHashContext *ctx)
Get the name of the algorithm corresponding to the given hash context.
void av_hash_final_bin(struct AVHashContext *ctx, uint8_t *dst, int size)
Finalize a hash context and store the actual hash value in a buffer.
void av_hash_final_hex(struct AVHashContext *ctx, uint8_t *dst, int size)
Finalize a hash context and store the hexadecimal representation of the actual hash value as a string...
void av_hash_init(struct AVHashContext *ctx)
Initialize or reset a hash context.
int av_hash_get_size(const struct AVHashContext *ctx)
Get the size of the resulting hash value in bytes.
void av_hash_update(struct AVHashContext *ctx, const uint8_t *src, int len)
Update a hash context with additional data.
int av_hash_alloc(struct AVHashContext **ctx, const char *name)
Allocate a hash context for the algorithm specified by name.
const char * av_hash_names(int i)
Get the names of available hash algorithms.
void av_hash_final(struct AVHashContext *ctx, uint8_t *dst)
Finalize a hash context and compute the actual hash value.
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