/* SPDX-License-Identifier: GPL-2.0 */

/** \file wma_common.c Functions used by both the WMA afh and decoder. */

#include <sys/types.h>

#include "para.h"
#include "error.h"
#include "afh.h"
#include "portable_io.h"
#include "imdct.h"
#include "wma.h"

/**
 * Find the first occurrence of the given pattern.
 *
 * \param pattern The pattern to search for.
 * \param pattern_len The length of the pattern in bytes.
 * \param buf The buffer to search for the pattern.
 * \param buf_size The number of bytes in \a buf.
 *
 * \return A pointer into \a buf or \p NULL if the pattern was not found.
 */
const char *search_pattern(const uint8_t *pattern, int pattern_len,
		const char *buf, int buf_size)
{
	const char *p, *end = buf + buf_size;

	/* TODO: Use suffix arrays to speed up the search. */
	for (p = buf; p + pattern_len < end; p++) {
		if (memcmp(p, pattern, pattern_len))
			continue;
		PARA_DEBUG_LOG("found %d byte pattern@%d\n",
			pattern_len, (int)(p - buf));
		return p;
	}
	PARA_NOTICE_LOG("%d byte pattern not found\n", pattern_len);
	return NULL;
}

static int find_file_properties(const char *buf, int len)
{
	const uint8_t pattern[] = {0xa1, 0xdc, 0xab, 0x8c};
	const char *p = search_pattern(pattern, sizeof(pattern), buf, len);

	if (!p)
		return -E_WMA_NO_GUID;
	PARA_DEBUG_LOG("found file property guid@%0x\n", (unsigned)(p - buf));
	return p - buf + 16;
}

/* 40 9e 69 f8 4d 5b cf 11  a8 fd 00 80 5f 5c 44 2b */
static int find_audio_stream_info(const char *buf, int len)
{
	const uint8_t pattern[] = {0x40, 0x9e, 0x69, 0xf8};
	const char *p = search_pattern(pattern, sizeof(pattern), buf, len);

	if (!p)
		return -E_WMA_NO_GUID;
	PARA_DEBUG_LOG("found audio stream guid@%0x\n", (unsigned)(p - buf));
	return p - buf + 16;
}

static int read_header_len(const char *buf, int len)
{
	uint16_t header_len;

	if (len < 18)
		return 0;
	header_len = read_u16(buf + 16) + 46;
	PARA_DEBUG_LOG("header_len: %d\n", header_len);
	return header_len;
}

/**
 * Read an asf audio file header.
 *
 * \param buf The input buffer.
 * \param loaded Number of bytes in \a buf.
 * \param ahi Result pointer.
 *
 * \return Negative on errors, zero if more data is needed in order to read the
 * full header, 1 on success.
 */
int read_asf_header(const char *buf, int loaded, struct asf_header_info *ahi)
{
	int ret;
	const char *start;

	ahi->header_len = read_header_len(buf, loaded);
	if (ahi->header_len == 0) /* too short to read header len */
		return 0;
	if (ahi->header_len > loaded) /* too short to read header */
		return 0;
	ret = find_audio_stream_info(buf, ahi->header_len);
	if (ret < 0)
		return ret;
	if (ret + 62 > loaded)
		return 0;
	ahi->audio_stream_info_start = ret;
	start = buf + ahi->audio_stream_info_start;
	ahi->channels = ((uint8_t *)start)[40];
	ahi->sample_rate = read_u16(start + 42);
	PARA_NOTICE_LOG("%d channels, sample rate: %d\n", ahi->channels,
		ahi->sample_rate);

	ahi->bit_rate = 8 * read_u16(start + 46);
	PARA_INFO_LOG("bit rate: %u\n", ahi->bit_rate);

	ahi->block_align = read_u16(start + 50);
	PARA_INFO_LOG("block_align: %d\n", ahi->block_align);

	ahi->flags1 = read_u32(start + 56);
	ahi->flags2 = read_u16(start + 60);
	PARA_INFO_LOG("read_asf_header: flags1: %u, flags2: %u\n",
		ahi->flags1, ahi->flags2);
	ahi->use_exp_vlc = ahi->flags2 & 0x0001;
	ahi->use_bit_reservoir = ahi->flags2 & 0x0002;
	ahi->use_variable_block_len = ahi->flags2 & 0x0004;

	ret = find_file_properties(buf, ahi->header_len);
	if (ret < 0)
		return ret;
	/* file property header is always 88 bytes (sans GUID) */
	if (ret + 88 > loaded)
		return 0;
	start = buf + ret;
	ahi->packet_size = read_u32(start + 76); /* min packet size */
	/* we only support fixed packet sizes */
	if (ahi->packet_size != read_u32(start + 80)) /* min != max */
		return -E_BAD_ASF_FILE_PROPS;
	if (ahi->packet_size <= ahi->block_align)
		return -E_BAD_ASF_FILE_PROPS;
	PARA_INFO_LOG("packet size: %u\n", ahi->packet_size);
	return 1;
}

static const uint8_t log2_tab[256] = {
	0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
	4, 4, 4, 4, 4, 4, 4, 4,
	5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
	5, 5, 5, 5, 5, 5, 5, 5,
	6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
	6, 6, 6, 6, 6, 6, 6, 6,
	6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
	6, 6, 6, 6, 6, 6, 6, 6,
	7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
	7, 7, 7, 7, 7, 7, 7, 7,
	7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
	7, 7, 7, 7, 7, 7, 7, 7,
	7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
	7, 7, 7, 7, 7, 7, 7, 7,
	7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
	7, 7, 7, 7, 7, 7, 7, 7
};

/**
 * Compute the base-2 logarithm.
 *
 * \param v The value to compute the logarithm of.
 *
 * \return An integer approximation of log2(v).
 */
__a_const int wma_log2(unsigned int v)
{
	int n = 0;
	if (v & 0xffff0000) {
		v >>= 16;
		n += 16;
	}
	if (v & 0xff00) {
		v >>= 8;
		n += 8;
	}
	return n + log2_tab[v];
}