diff options
| author | Mikhail Burakov <mburakov@mailbox.org> | 2023-05-01 17:43:43 +0200 |
|---|---|---|
| committer | Mikhail Burakov <mburakov@mailbox.org> | 2023-05-01 17:43:43 +0200 |
| commit | 9546ab4acf17ea6a81f058eb28b8a72e1174a671 (patch) | |
| tree | be80fc2aa4d8c857a64c6cb3bbb9ee35470a38aa | |
| parent | 68fbbd6e8a10bc034dbc003392e536cd898806bc (diff) | |
Add simplistic bitstream writer implementation
| -rw-r--r-- | bitstream.c | 59 | ||||
| -rw-r--r-- | bitstream.h | 34 |
2 files changed, 93 insertions, 0 deletions
diff --git a/bitstream.c b/bitstream.c new file mode 100644 index 0000000..1f3242e --- /dev/null +++ b/bitstream.c @@ -0,0 +1,59 @@ +/* + * Copyright (C) 2023 Mikhail Burakov. This file is part of streamer. + * + * streamer is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * streamer is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with streamer. If not, see <https://www.gnu.org/licenses/>. + */ + +#include "bitstream.h" + +void BitstreamAppend(struct Bitstream* bitstream, size_t size, uint32_t bits) { + uint8_t* ptr = (uint8_t*)bitstream->data + bitstream->size / 8; + size_t vacant_bits = 8 - bitstream->size % 8; + *ptr &= ~0 << vacant_bits; + + if (vacant_bits >= size) { + *ptr |= bits << (vacant_bits - size); + bitstream->size += size; + return; + } + + *ptr |= bits >> (size - vacant_bits); + bitstream->size += vacant_bits; + BitstreamAppend(bitstream, size - vacant_bits, bits); +} + +void BitstreamAppendUE(struct Bitstream* bitstream, uint32_t bits) { + size_t size = 0; + uint32_t dummy = ++bits; + while (dummy) { + dummy >>= 1; + size++; + } + BitstreamAppend(bitstream, size - 1, 0); + BitstreamAppend(bitstream, size, bits); +} + +void BitstreamAppendSE(struct Bitstream* bitstream, int32_t bits) { + BitstreamAppendUE( + bitstream, bits <= 0 ? (uint32_t)(-2 * bits) : (uint32_t)(2 * bits - 1)); +} + +void BitstreamByteAlign(struct Bitstream* bitstream) { + uint8_t* ptr = (uint8_t*)bitstream->data + bitstream->size / 8; + size_t vacant_bits = 8 - bitstream->size % 8; + if (vacant_bits == 8) return; + + *ptr &= ~0 << vacant_bits; + bitstream->size += vacant_bits; +} diff --git a/bitstream.h b/bitstream.h new file mode 100644 index 0000000..87edec3 --- /dev/null +++ b/bitstream.h @@ -0,0 +1,34 @@ +/* + * Copyright (C) 2023 Mikhail Burakov. This file is part of streamer. + * + * streamer is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * streamer is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with streamer. If not, see <https://www.gnu.org/licenses/>. + */ + +#ifndef STREAMER_BITSTREAM_H_ +#define STREAMER_BITSTREAM_H_ + +#include <stddef.h> +#include <stdint.h> + +struct Bitstream { + void* data; + size_t size; +}; + +void BitstreamAppend(struct Bitstream* bitstream, size_t size, uint32_t bits); +void BitstreamAppendUE(struct Bitstream* bitstream, uint32_t bits); +void BitstreamAppendSE(struct Bitstream* bitstream, int32_t bits); +void BitstreamByteAlign(struct Bitstream* bitstream); + +#endif // STREAMER_BITSTREAM_H_ |