notaz.gp2x.de / pcsx_rearmed.git / blame
| Commit | Line | Data |
|---|---|---|
| 3719602c PC |
1 | /* license:BSD-3-Clause |
| 2 | * copyright-holders:Aaron Giles | |
| 3 | *************************************************************************** | |
| 4 | ||
| 5 | bitstream.c | |
| 6 | ||
| 7 | Helper classes for reading/writing at the bit level. | |
| 8 | ||
| 9 | ***************************************************************************/ | |
| 10 | ||
| 11 | #include <stdlib.h> | |
| 12 | #include <libchdr/bitstream.h> | |
| 13 | ||
| 14 | /*************************************************************************** | |
| 15 | * INLINE FUNCTIONS | |
| 16 | *************************************************************************** | |
| 17 | */ | |
| 18 | ||
| 19 | int bitstream_overflow(struct bitstream* bitstream) { return ((bitstream->doffset - bitstream->bits / 8) > bitstream->dlength); } | |
| 20 | ||
| 21 | /*------------------------------------------------- | |
| 22 | * create_bitstream - constructor | |
| 23 | *------------------------------------------------- | |
| 24 | */ | |
| 25 | ||
| 26 | struct bitstream* create_bitstream(const void *src, uint32_t srclength) | |
| 27 | { | |
| 28 | struct bitstream* bitstream = (struct bitstream*)malloc(sizeof(struct bitstream)); | |
| 29 | bitstream->buffer = 0; | |
| 30 | bitstream->bits = 0; | |
| 31 | bitstream->read = (const uint8_t*)src; | |
| 32 | bitstream->doffset = 0; | |
| 33 | bitstream->dlength = srclength; | |
| 34 | return bitstream; | |
| 35 | } | |
| 36 | ||
| 37 | /*----------------------------------------------------- | |
| 38 | * bitstream_peek - fetch the requested number of bits | |
| 39 | * but don't advance the input pointer | |
| 40 | *----------------------------------------------------- | |
| 41 | */ | |
| 42 | ||
| 43 | uint32_t bitstream_peek(struct bitstream* bitstream, int numbits) | |
| 44 | { | |
| 45 | if (numbits == 0) | |
| 46 | return 0; | |
| 47 | ||
| 48 | /* fetch data if we need more */ | |
| 49 | if (numbits > bitstream->bits) | |
| 50 | { | |
| 51 | while (bitstream->bits <= 24) | |
| 52 | { | |
| 53 | if (bitstream->doffset < bitstream->dlength) | |
| 54 | bitstream->buffer |= bitstream->read[bitstream->doffset] << (24 - bitstream->bits); | |
| 55 | bitstream->doffset++; | |
| 56 | bitstream->bits += 8; | |
| 57 | } | |
| 58 | } | |
| 59 | ||
| 60 | /* return the data */ | |
| 61 | return bitstream->buffer >> (32 - numbits); | |
| 62 | } | |
| 63 | ||
| 64 | /*----------------------------------------------------- | |
| 65 | * bitstream_remove - advance the input pointer by the | |
| 66 | * specified number of bits | |
| 67 | *----------------------------------------------------- | |
| 68 | */ | |
| 69 | ||
| 70 | void bitstream_remove(struct bitstream* bitstream, int numbits) | |
| 71 | { | |
| 72 | bitstream->buffer <<= numbits; | |
| 73 | bitstream->bits -= numbits; | |
| 74 | } | |
| 75 | ||
| 76 | /*----------------------------------------------------- | |
| 77 | * bitstream_read - fetch the requested number of bits | |
| 78 | *----------------------------------------------------- | |
| 79 | */ | |
| 80 | ||
| 81 | uint32_t bitstream_read(struct bitstream* bitstream, int numbits) | |
| 82 | { | |
| 83 | uint32_t result = bitstream_peek(bitstream, numbits); | |
| 84 | bitstream_remove(bitstream, numbits); | |
| 85 | return result; | |
| 86 | } | |
| 87 | ||
| 88 | /*------------------------------------------------- | |
| 89 | * read_offset - return the current read offset | |
| 90 | *------------------------------------------------- | |
| 91 | */ | |
| 92 | ||
| 93 | uint32_t bitstream_read_offset(struct bitstream* bitstream) | |
| 94 | { | |
| 95 | uint32_t result = bitstream->doffset; | |
| 96 | int bits = bitstream->bits; | |
| 97 | while (bits >= 8) | |
| 98 | { | |
| 99 | result--; | |
| 100 | bits -= 8; | |
| 101 | } | |
| 102 | return result; | |
| 103 | } | |
| 104 | ||
| 105 | /*------------------------------------------------- | |
| 106 | * flush - flush to the nearest byte | |
| 107 | *------------------------------------------------- | |
| 108 | */ | |
| 109 | ||
| 110 | uint32_t bitstream_flush(struct bitstream* bitstream) | |
| 111 | { | |
| 112 | while (bitstream->bits >= 8) | |
| 113 | { | |
| 114 | bitstream->doffset--; | |
| 115 | bitstream->bits -= 8; | |
| 116 | } | |
| 117 | bitstream->bits = bitstream->buffer = 0; | |
| 118 | return bitstream->doffset; | |
| 119 | } |