workbench/classes/datatypes/wav/bitpack.c

   1 /*
   2  *      wave.datatype
   3  *      (c) Fredrik Wikstrom
   4  */
   5
   6 #include <exec/types.h>
   7 #include <dos/dos.h>
   8
   9 #include "endian.h"
  10 #include "bitpack.h"
  11
  12 // Generic BitPack stuff:
  13
  14 void bitpack_init (BitPack_buffer *b, void *ptr, LONG size) {
  15     b->buffer=b->ptr=ptr;
  16     b->size=size;
  17     b->endbyte=0;
  18     b->endbit=0;
  19 }
  20
  21 const ULONG bp_mask[33]={
  22         0x00000000,     0x00000001,     0x00000003,     0x00000007,
  23         0x0000000f,     0x0000001f,     0x0000003f,     0x0000007f,
  24         0x000000ff,     0x000001ff,     0x000003ff,     0x000007ff,
  25         0x00000fff,     0x00001fff,     0x00003fff,     0x00007fff,
  26         0x0000ffff,     0x0001ffff,     0x0003ffff,     0x0007ffff,
  27         0x000fffff,     0x001fffff,     0x003fffff,     0x007fffff,
  28         0x00ffffff,     0x01ffffff,     0x03ffffff,     0x07ffffff,
  29         0x0fffffff,     0x1fffffff,     0x3fffffff,     0x7fffffff,
  30         0xffffffff
  31 };
  32
  33 LONG bitpack_seek (BitPack_buffer *b, LONG offs, LONG type) {
  34         LONG oldoffset;
  35         oldoffset=(b->endbyte<<3)+b->endbit;
  36
  37     switch (type) {
  38
  39         case OFFSET_CURRENT:
  40             offs+=oldoffset;
  41             break;
  42
  43         case OFFSET_END:
  44             offs+=(b->size<<3);
  45             break;
  46
  47     }
  48
  49     b->endbyte=offs>>3;
  50     b->endbit=offs&7;
  51
  52     b->ptr=b->buffer+b->endbyte;
  53
  54     return (oldoffset);
  55 }
  56
  57 void * bitpack_align (BitPack_buffer *b) {
  58     if (b->endbit) {
  59         b->endbit=0;
  60         b->endbyte++;
  61         b->ptr++;
  62     }
  63     return (b->ptr);
  64 }
  65
  66 void * bitpack_align_even (BitPack_buffer *b) {
  67     bitpack_align_lsb(b);
  68     if (b->endbyte&1) {
  69         b->endbyte++;
  70         b->ptr++;
  71     }
  72     return (b->ptr);
  73 }