spx2wav/speex/speex_bits.h

/* Copyright (C) 2002 Jean-Marc Valin */
/**
   @file speex_bits.h
   @brief Handles bit packing/unpacking
*/
/*
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   are met:
   
   - Redistributions of source code must retain the above copyright
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   documentation and/or other materials provided with the distribution.
   
   - Neither the name of the Xiph.org Foundation nor the names of its
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   this software without specific prior written permission.
   
   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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   A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
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   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

#ifndef BITS_H
#define BITS_H
/** @defgroup SpeexBits SpeexBits: Bit-stream manipulations
 *  This is the structure that holds the bit-stream when encoding or decoding
 * with Speex. It allows some manipulations as well.
 *  @{
 */

#ifdef __cplusplus
extern "C" {
#endif

/** Bit-packing data structure representing (part of) a bit-stream. */
typedef struct SpeexBits {
   char *chars;   /**< "raw" data */
   int   nbBits;  /**< Total number of bits stored in the stream*/
   int   charPtr; /**< Position of the byte "cursor" */
   int   bitPtr;  /**< Position of the bit "cursor" within the current char */
   int   owner;   /**< Does the struct "own" the "raw" buffer (member "chars") */
   int   overflow;/**< Set to one if we try to read past the valid data */
   int   buf_size;/**< Allocated size for buffer */
   int   reserved1; /**< Reserved for future use */
   void *reserved2; /**< Reserved for future use */
} SpeexBits;

/** Initializes and allocates resources for a SpeexBits struct */
void speex_bits_init(SpeexBits *bits);

/** Initializes SpeexBits struct using a pre-allocated buffer*/
void speex_bits_init_buffer(SpeexBits *bits, void *buff, int buf_size);

/** Sets the bits in a SpeexBits struct to use data from an existing buffer (for decoding without copying data) */
void speex_bits_set_bit_buffer(SpeexBits *bits, void *buff, int buf_size);

/** Frees all resources associated to a SpeexBits struct. Right now this does nothing since no resources are allocated, but this could change in the future.*/
void speex_bits_destroy(SpeexBits *bits);

/** Resets bits to initial value (just after initialization, erasing content)*/
void speex_bits_reset(SpeexBits *bits);

/** Rewind the bit-stream to the beginning (ready for read) without erasing the content */
void speex_bits_rewind(SpeexBits *bits);

/** Initializes the bit-stream from the data in an area of memory */
void speex_bits_read_from(SpeexBits *bits, char *bytes, int len);

/** Append bytes to the bit-stream
 * 
 * @param bits Bit-stream to operate on
 * @param bytes pointer to the bytes what will be appended
 * @param len Number of bytes of append
 */
void speex_bits_read_whole_bytes(SpeexBits *bits, char *bytes, int len);

/** Write the content of a bit-stream to an area of memory
 * 
 * @param bits Bit-stream to operate on
 * @param bytes Memory location where to write the bits
 * @param max_len Maximum number of bytes to write (i.e. size of the "bytes" buffer)
 * @return Number of bytes written to the "bytes" buffer
*/
int speex_bits_write(SpeexBits *bits, char *bytes, int max_len);

/** Like speex_bits_write, but writes only the complete bytes in the stream. Also removes the written bytes from the stream */
int speex_bits_write_whole_bytes(SpeexBits *bits, char *bytes, int max_len);

/** Append bits to the bit-stream
 * @param bits Bit-stream to operate on
 * @param data Value to append as integer
 * @param nbBits number of bits to consider in "data"
 */
void speex_bits_pack(SpeexBits *bits, int data, int nbBits);

/** Interpret the next bits in the bit-stream as a signed integer
 *
 * @param bits Bit-stream to operate on
 * @param nbBits Number of bits to interpret
 * @return A signed integer represented by the bits read
 */
int speex_bits_unpack_signed(SpeexBits *bits, int nbBits);

/** Interpret the next bits in the bit-stream as an unsigned integer
 *
 * @param bits Bit-stream to operate on
 * @param nbBits Number of bits to interpret
 * @return An unsigned integer represented by the bits read
 */
unsigned int speex_bits_unpack_unsigned(SpeexBits *bits, int nbBits);

/** Returns the number of bytes in the bit-stream, including the last one even if it is not "full"
 *
 * @param bits Bit-stream to operate on
 * @return Number of bytes in the stream
 */
int speex_bits_nbytes(SpeexBits *bits);

/** Same as speex_bits_unpack_unsigned, but without modifying the cursor position 
 * 
 * @param bits Bit-stream to operate on
 * @param nbBits Number of bits to look for
 * @return Value of the bits peeked, interpreted as unsigned
 */
unsigned int speex_bits_peek_unsigned(SpeexBits *bits, int nbBits);

/** Get the value of the next bit in the stream, without modifying the
 * "cursor" position 
 * 
 * @param bits Bit-stream to operate on
 * @return Value of the bit peeked (one bit only)
 */
int speex_bits_peek(SpeexBits *bits);

/** Advances the position of the "bit cursor" in the stream 
 *
 * @param bits Bit-stream to operate on
 * @param n Number of bits to advance
 */
void speex_bits_advance(SpeexBits *bits, int n);

/** Returns the number of bits remaining to be read in a stream
 *
 * @param bits Bit-stream to operate on
 * @return Number of bits that can still be read from the stream
 */
int speex_bits_remaining(SpeexBits *bits);

/** Insert a terminator so that the data can be sent as a packet while auto-detecting 
 * the number of frames in each packet 
 *
 * @param bits Bit-stream to operate on
 */
void speex_bits_insert_terminator(SpeexBits *bits);

#ifdef __cplusplus
}
#endif

/* @} */
#endif