mpd/src/decoder/plugins/OpusReader.hxx

/*
 * Copyright 2003-2020 The Music Player Daemon Project
 * http://www.musicpd.org
 *
 * This program 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 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifndef MPD_OPUS_READER_HXX
#define MPD_OPUS_READER_HXX

#include "util/StringView.hxx"

#include <algorithm>
#include <cstdint>

#include <string.h>

class OpusReader {
	const uint8_t *p, *const end;

public:
	OpusReader(const void *_p, size_t size)
		:p((const uint8_t *)_p), end(p + size) {}

	bool Skip(size_t length) {
		p += length;
		return p <= end;
	}

	const void *Read(size_t length) {
		const uint8_t *result = p;
		return Skip(length)
			? result
			: nullptr;
	}

	bool Expect(const void *value, size_t length) {
		const void *data = Read(length);
		return data != nullptr && memcmp(value, data, length) == 0;
	}

	bool ReadByte(uint8_t &value_r) {
		if (p >= end)
			return false;

		value_r = *p++;
		return true;
	}

	bool ReadShort(uint16_t &value_r) {
		const uint8_t *value = (const uint8_t *)Read(sizeof(value_r));
		if (value == nullptr)
			return false;

		value_r = value[0] | (value[1] << 8);
		return true;
	}

	bool ReadWord(uint32_t &value_r) {
		const uint8_t *value = (const uint8_t *)Read(sizeof(value_r));
		if (value == nullptr)
			return false;

		value_r = value[0] | (value[1] << 8)
			| (value[2] << 16) | (value[3] << 24);
		return true;
	}

	bool SkipString() {
		uint32_t length;
		return ReadWord(length) && Skip(length);
	}

	StringView ReadString() {
		uint32_t length;
		if (!ReadWord(length))
			return nullptr;

		const char *src = (const char *)Read(length);
		if (src == nullptr)
			return nullptr;

		return {src, length};
	}
};

#endif