/* * 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 . */ #include "bitstream.h" #include 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); }