/*
  * Copyright (C) 2013 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 

 /**
  * @file
  * @ingroup lavu_hash_generic
  * Generic hashing API
  */
 

 #ifndef AVUTIL_HASH_H
 #define AVUTIL_HASH_H
 
 #include <stdint.h>
 

 #include "version.h"
 

 /**
  * @defgroup lavu_hash Hash Functions
  * @ingroup lavu_crypto

  * Hash functions useful in multimedia.
  *
  * Hash functions are widely used in multimedia, from error checking and
  * concealment to internal regression testing. libavutil has efficient
  * implementations of a variety of hash functions that may be useful for
  * FFmpeg and other multimedia applications.

  *
  * @{
  *
  * @defgroup lavu_hash_generic Generic Hashing API

  * An abstraction layer for all hash functions supported by libavutil.
  *
  * If your application needs to support a wide range of different hash
  * functions, then the Generic Hashing API is for you. It provides a generic,
  * reusable API for @ref lavu_hash "all hash functions" implemented in libavutil.
  * If you just need to use one particular hash function, use the @ref lavu_hash
  * "individual hash" directly.
  *
  * @section Sample Code
  *
  * A basic template for using the Generic Hashing API follows:
  *
  * @code
  * struct AVHashContext *ctx = NULL;
  * const char *hash_name = NULL;
  * uint8_t *output_buf = NULL;
  *
  * // Select from a string returned by av_hash_names()
  * hash_name = ...;
  *
  * // Allocate a hash context
  * ret = av_hash_alloc(&ctx, hash_name);
  * if (ret < 0)
  *     return ret;
  *
  * // Initialize the hash context
  * av_hash_init(ctx);
  *
  * // Update the hash context with data
  * while (data_left) {
  *     av_hash_update(ctx, data, size);
  * }
  *
  * // Now we have no more data, so it is time to finalize the hash and get the
  * // output. But we need to first allocate an output buffer. Note that you can
  * // use any memory allocation function, including malloc(), not just
  * // av_malloc().
  * output_buf = av_malloc(av_hash_get_size(ctx));
  * if (!output_buf)
  *     return AVERROR(ENOMEM);
  *
  * // Finalize the hash context.
  * // You can use any of the av_hash_final*() functions provided, for other
  * // output formats. If you do so, be sure to adjust the memory allocation
  * // above. See the function documentation below for the exact amount of extra
  * // memory needed.
  * av_hash_final(ctx, output_buffer);
  *
  * // Free the context
  * av_hash_freep(&ctx);
  * @endcode
  *
  * @section Hash Function-Specific Information
  * If the CRC32 hash is selected, the #AV_CRC_32_IEEE polynomial will be
  * used.
  *
  * If the Murmur3 hash is selected, the default seed will be used. See @ref
  * lavu_murmur3_seedinfo "Murmur3" for more information.

  *
  * @{
  */
 

 /**
  * @example ffhash.c
  * This example is a simple command line application that takes one or more
  * arguments. It demonstrates a typical use of the hashing API with allocation,
  * initialization, updating, and finalizing.
  */
 

 struct AVHashContext;
 
 /**
  * Allocate a hash context for the algorithm specified by name.
  *
  * @return  >= 0 for success, a negative error code for failure

  *
  * @note The context is not initialized after a call to this function; you must
  * call av_hash_init() to do so.

  */
 int av_hash_alloc(struct AVHashContext **ctx, const char *name);
 
 /**
  * Get the names of available hash algorithms.
  *
  * This function can be used to enumerate the algorithms.
  *

  * @param[in] i  Index of the hash algorithm, starting from 0
  * @return       Pointer to a static string or `NULL` if `i` is out of range

  */
 const char *av_hash_names(int i);
 
 /**
  * Get the name of the algorithm corresponding to the given hash context.
  */
 const char *av_hash_get_name(const struct AVHashContext *ctx);
 
 /**

  * Maximum value that av_hash_get_size() will currently return.

  *

  * You can use this if you absolutely want or need to use static allocation for
  * the output buffer and are fine with not supporting hashes newly added to
  * libavutil without recompilation.
  *
  * @warning
  * Adding new hashes with larger sizes, and increasing the macro while doing
  * so, will not be considered an ABI change. To prevent your code from
  * overflowing a buffer, either dynamically allocate the output buffer with
  * av_hash_get_size(), or limit your use of the Hashing API to hashes that are
  * already in FFmpeg during the time of compilation.

  */

 #define AV_HASH_MAX_SIZE 64

 
 /**

  * Get the size of the resulting hash value in bytes.
  *

  * The maximum value this function will currently return is available as macro
  * #AV_HASH_MAX_SIZE.
  *
  * @param[in]     ctx Hash context
  * @return            Size of the hash value in bytes

  */
 int av_hash_get_size(const struct AVHashContext *ctx);
 
 /**
  * Initialize or reset a hash context.

  *
  * @param[in,out] ctx Hash context

  */
 void av_hash_init(struct AVHashContext *ctx);
 
 /**
  * Update a hash context with additional data.

  *
  * @param[in,out] ctx Hash context
  * @param[in]     src Data to be added to the hash context
  * @param[in]     len Size of the additional data

  */

 #if FF_API_CRYPTO_SIZE_T

 void av_hash_update(struct AVHashContext *ctx, const uint8_t *src, int len);

 #else
 void av_hash_update(struct AVHashContext *ctx, const uint8_t *src, size_t len);
 #endif

 
 /**
  * Finalize a hash context and compute the actual hash value.

  *
  * The minimum size of `dst` buffer is given by av_hash_get_size() or
  * #AV_HASH_MAX_SIZE. The use of the latter macro is discouraged.
  *
  * It is not safe to update or finalize a hash context again, if it has already
  * been finalized.
  *
  * @param[in,out] ctx Hash context
  * @param[out]    dst Where the final hash value will be stored
  *
  * @see av_hash_final_bin() provides an alternative API

  */
 void av_hash_final(struct AVHashContext *ctx, uint8_t *dst);
 
 /**

  * Finalize a hash context and store the actual hash value in a buffer.
  *
  * It is not safe to update or finalize a hash context again, if it has already
  * been finalized.
  *
  * If `size` is smaller than the hash size (given by av_hash_get_size()), the
  * hash is truncated; if size is larger, the buffer is padded with 0.
  *
  * @param[in,out] ctx  Hash context
  * @param[out]    dst  Where the final hash value will be stored
  * @param[in]     size Number of bytes to write to `dst`

  */
 void av_hash_final_bin(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.
  *
  * It is not safe to update or finalize a hash context again, if it has already
  * been finalized.
  *

  * The string is always 0-terminated.

  *
  * If `size` is smaller than `2 * hash_size + 1`, where `hash_size` is the
  * value returned by av_hash_get_size(), the string will be truncated.
  *
  * @param[in,out] ctx  Hash context
  * @param[out]    dst  Where the string will be stored
  * @param[in]     size Maximum number of bytes to write to `dst`

  */
 void av_hash_final_hex(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.
  *
  * It is not safe to update or finalize a hash context again, if it has already
  * been finalized.
  *

  * The string is always 0-terminated.

  *
  * If `size` is smaller than AV_BASE64_SIZE(hash_size), where `hash_size` is
  * the value returned by av_hash_get_size(), the string will be truncated.
  *
  * @param[in,out] ctx  Hash context
  * @param[out]    dst  Where the final hash value will be stored
  * @param[in]     size Maximum number of bytes to write to `dst`

  */
 void av_hash_final_b64(struct AVHashContext *ctx, uint8_t *dst, int size);
 
 /**

  * Free hash context and set hash context pointer to `NULL`.
  *
  * @param[in,out] ctx  Pointer to hash context

  */
 void av_hash_freep(struct AVHashContext **ctx);
 

 /**
  * @}
  * @}
  */
 

 #endif /* AVUTIL_HASH_H */