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sour.c

/*
 * Copyright 1996 by Jutta Degener and Carsten Bormann, Technische
 * Universitaet Berlin.  See the accompanying file "COPYRIGHT" for
 * details.  THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
 */

/*$Header*/

/* Generate code to pack a bit array from a name:#bits description,
 * WAV #49 style.
 */

#include    <stdio.h>
#include    "taste.h"
#include    "proto.h"
#include    <limits.h>

/* This module goes back to one Jeff Chilton used for his implementation
 * of the #49 WAV GSM format.  (In his original patch 8, it replaced
 * bitter.c.)
 *
 * In Microsoft's WAV #49 version of the GSM format, two 32 1/2
 * byte GSM frames are packed together to make one WAV frame, and
 * the GSM parameters are packed into bytes right-to-left rather
 * than left-to-right.
 *
 * That is, where toast's GSM format writes
 *
 *    aaaaaabb bbbbcccc cdddddee ...
 *    ___1____ ___2____ ___3____
 *
 *  for parameters a (6 bits), b (6 bits), c (5 bits), d (5 bits), e ..
 *  the WAV format has
 *
 *    bbaaaaaa ccccbbbb eedddddc ...
 *    ___1____ ___2____ ___3____
 *
 *  (This format looks a lot prettier if one pictures octets coming
 *  in through a fifo queue from the left, rather than waiting in the
 *  right-hand remainder of a C array.)
 */

#define WORD_BITS 16    /* sizeof(uword) * CHAR_BIT on the 
                         * target architecture---if this isn't 16,
                         * you're in trouble with this library anyway.
                         */

#define BYTE_BITS  8    /* CHAR_BIT on the target architecture---
                         * if this isn't 8, you're in *deep* trouble.
                         */

void write_code P2((s_spex, n_spex), struct spex * s_spex, int n_spex)
{
      struct spex * sp = s_spex;
      int           n_in = 0;

      printf("uword sr = 0;\n");

      for (; n_spex > 0; n_spex--, sp++) {

            /*    insert       old 
             *    new var          value     unused
             *    here  
             *
             *    [____________xxxxxx**********]
             *
             *    <----- n_in ------>
             */
            printf("sr = sr >> %d | %s << %d;\n",
                  sp->varsize,
                  sp->var, 
                  WORD_BITS - sp->varsize);

            n_in += sp->varsize;

            while (n_in >= BYTE_BITS) {
                  printf("*c++ = sr >> %d;\n",
                        WORD_BITS - n_in);
                  n_in -= BYTE_BITS;
            }
      }

      while (n_in >= BYTE_BITS) {
            printf("*c++ = sr >> %d;\n", WORD_BITS - n_in);
            n_in -= BYTE_BITS;
      }

      if (n_in > 0) {
            fprintf(stderr, "warning: %d bits left over\n", n_in);
      }
}

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