buffers.c

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/**************************************************************************************
 * Fixed-point MP3 decoder
 * Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com)
 * June 2003
 *
 * buffers.c - allocation and freeing of internal MP3 decoder buffers
 *
 * All memory allocation for the codec is done in this file, so if you don't want 
 *  to use other the default system malloc() and free() for heap management this is 
 *  the only file you'll need to change.
 **************************************************************************************/
 
#include "mp3compat.h"    /* for malloc, free */ 
#include "coder.h"
 
/**************************************************************************************
 * Function:    ClearBuffer
 *
 * Description: fill buffer with 0's
 *
 * Inputs:      pointer to buffer
 *              number of bytes to fill with 0
 *
 * Outputs:     cleared buffer
 *
 * Return:      none
 *
 * Notes:       slow, platform-independent equivalent to memset(buf, 0, nBytes)
 **************************************************************************************/
static void ClearBuffer(void *buf, int nBytes)
{
  int i;
  unsigned char *cbuf = (unsigned char *)buf;
 
  for (i = 0; i < nBytes; i++)
    cbuf[i] = 0;
 
  return;
}
 
/**************************************************************************************
 * Function:    AllocateBuffers
 *
 * Description: allocate all the memory needed for the MP3 decoder
 *
 * Inputs:      none
 *
 * Outputs:     none
 *
 * Return:      pointer to MP3DecInfo structure (initialized with pointers to all 
 *                the internal buffers needed for decoding, all other members of 
 *                MP3DecInfo structure set to 0)
 *
 * Notes:       if one or more mallocs fail, function frees any buffers already
 *                allocated before returning
 **************************************************************************************/
MP3DecInfo *AllocateBuffers(void)
{
  MP3DecInfo *mp3DecInfo;
  FrameHeader *fh;
  SideInfo *si;
  ScaleFactorInfo *sfi;
  HuffmanInfo *hi;
  DequantInfo *di;
  IMDCTInfo *mi;
  SubbandInfo *sbi;
 
  mp3DecInfo = (MP3DecInfo *)malloc(sizeof(MP3DecInfo));
  if (!mp3DecInfo)
    return 0;
  ClearBuffer(mp3DecInfo, sizeof(MP3DecInfo));
  
  fh =  (FrameHeader *)     malloc(sizeof(FrameHeader));
  si =  (SideInfo *)        malloc(sizeof(SideInfo));
  sfi = (ScaleFactorInfo *) malloc(sizeof(ScaleFactorInfo));
  hi =  (HuffmanInfo *)     malloc(sizeof(HuffmanInfo));
  di =  (DequantInfo *)     malloc(sizeof(DequantInfo));
  mi =  (IMDCTInfo *)       malloc(sizeof(IMDCTInfo));
  sbi = (SubbandInfo *)     malloc(sizeof(SubbandInfo));
 
  mp3DecInfo->FrameHeaderPS =     (void *)fh;
  mp3DecInfo->SideInfoPS =        (void *)si;
  mp3DecInfo->ScaleFactorInfoPS = (void *)sfi;
  mp3DecInfo->HuffmanInfoPS =     (void *)hi;
  mp3DecInfo->DequantInfoPS =     (void *)di;
  mp3DecInfo->IMDCTInfoPS =       (void *)mi;
  mp3DecInfo->SubbandInfoPS =     (void *)sbi;
 
  if (!fh || !si || !sfi || !hi || !di || !mi || !sbi) {
    FreeBuffers(mp3DecInfo);  /* safe to call - only frees memory that was successfully allocated */
    return 0;
  }
 
  /* important to do this - DSP primitives assume a bunch of state variables are 0 on first use */
  ClearBuffer(fh,  sizeof(FrameHeader));
  ClearBuffer(si,  sizeof(SideInfo));
  ClearBuffer(sfi, sizeof(ScaleFactorInfo));
  ClearBuffer(hi,  sizeof(HuffmanInfo));
  ClearBuffer(di,  sizeof(DequantInfo));
  ClearBuffer(mi,  sizeof(IMDCTInfo));
  ClearBuffer(sbi, sizeof(SubbandInfo));
 
  return mp3DecInfo;
}
 
#define SAFE_FREE(x)  {if (x) free(x);  (x) = 0;} /* helper macro */
 
/**************************************************************************************
 * Function:    FreeBuffers
 *
 * Description: frees all the memory used by the MP3 decoder
 *
 * Inputs:      pointer to initialized MP3DecInfo structure
 *
 * Outputs:     none
 *
 * Return:      none
 *
 * Notes:       safe to call even if some buffers were not allocated (uses SAFE_FREE)
 **************************************************************************************/
void FreeBuffers(MP3DecInfo *mp3DecInfo)
{
  if (!mp3DecInfo)
    return;
 
  SAFE_FREE(mp3DecInfo->FrameHeaderPS);
  SAFE_FREE(mp3DecInfo->SideInfoPS);
  SAFE_FREE(mp3DecInfo->ScaleFactorInfoPS);
  SAFE_FREE(mp3DecInfo->HuffmanInfoPS);
  SAFE_FREE(mp3DecInfo->DequantInfoPS);
  SAFE_FREE(mp3DecInfo->IMDCTInfoPS);
  SAFE_FREE(mp3DecInfo->SubbandInfoPS);
 
  SAFE_FREE(mp3DecInfo);
}