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/*
* Copyright (C) 2024 Mikhail Burakov. This file is part of receiver.
*
* receiver 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.
*
* receiver 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 receiver. If not, see <https://www.gnu.org/licenses/>.
*/
#include "bitstream.h"
#include <string.h>
static uint64_t BitstreamReadBit(struct Bitstream* bitstream) {
size_t shift = 7 - (bitstream->offset & 0x7);
if (shift == 7) {
size_t byte;
repeat:
byte = bitstream->offset >> 3;
if (byte >= bitstream->size) longjmp(bitstream->trap, 1);
bitstream->cache = (bitstream->cache << 8) | bitstream->data[byte];
if (bitstream->offset >= 24 && (bitstream->cache & 0xffffff) == 3) {
bitstream->offset += 8;
bitstream->epb_count++;
goto repeat;
}
}
bitstream->offset++;
return bitstream->cache >> shift & 0x1;
}
uint64_t BitstreamReadU(struct Bitstream* bitstream, size_t size) {
uint64_t result = 0;
for (; size; size--) {
result = (result << 1) | BitstreamReadBit(bitstream);
}
return result;
}
uint64_t BitstreamReadUE(struct Bitstream* bitstream) {
size_t size = 0;
while (!BitstreamReadBit(bitstream)) size++;
return (BitstreamReadU(bitstream, size) | (1 << size)) - 1;
}
int64_t BitstreamReadSE(struct Bitstream* bitstream) {
uint64_t result = BitstreamReadUE(bitstream);
int64_t sign = (int64_t)((result & 1) << 1) - 1;
return sign * (int64_t)((result + 1) >> 1);
}
void BitstreamByteAlign(struct Bitstream* bitstream) {
bitstream->offset = (bitstream->offset + 7) & ~(size_t)7;
}
bool BitstreamReadNalu(struct Bitstream* bitstream, struct Bitstream* output) {
if (bitstream->offset & 0x7) return false;
size_t byte_offset = bitstream->offset >> 3;
static const uint8_t kStartCodePrefix[] = {0, 0, 0, 1};
if (bitstream->size - byte_offset < sizeof(kStartCodePrefix)) {
return false;
}
const uint8_t* data = bitstream->data + byte_offset;
if (memcmp(bitstream->data + byte_offset, kStartCodePrefix,
sizeof(kStartCodePrefix))) {
return false;
}
data += sizeof(kStartCodePrefix);
byte_offset += sizeof(kStartCodePrefix);
size_t max_size = bitstream->size - byte_offset;
uint8_t* next =
memmem(data, max_size, kStartCodePrefix, sizeof(kStartCodePrefix));
size_t size = next ? (size_t)(next - data) : max_size;
bitstream->offset = (byte_offset + size) << 3;
*output = BitstreamCreate(data, size);
return true;
}
bool BitstreamAvail(const struct Bitstream* bitstream) {
return bitstream->offset < (bitstream->size << 3);
}
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