/*
 * Common bit I/O utils.
 *
 * Extracted 2009 from mplayer 2009-02-10 libavcodec/bitstream.c.
 *
 * Copyright (c) 2000, 2001 Fabrice Bellard
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
 * Copyright (C) 2009 Andre Noll <maan@tuebingen.mpg.de>
 *
 * Licensed under the GNU Lesser General Public License. see file COPYING.LIB.
 */

/** \file bitstream.c Bitstream API for the wma decoder. */

#include "para.h"
#include "error.h"
#include "string.h"
#include "wma.h"
#include "portable_io.h"
#include "bitstream.h"

static inline uint32_t get_data(const void *table, int i, int size)
{
	const uint8_t *ptr = (const uint8_t *)table + i * size;
	uint32_t v;

	switch (size) {
	case 1:
		v = *(const uint8_t *)ptr;
		break;
	case 2:
		v = *(const uint16_t *)ptr;
		break;
	default:
		v = *(const uint32_t *)ptr;
		break;
	}
	return v;
}

static void alloc_table(struct vlc *vlc, int size)
{
	vlc->table_size += size;
	if (vlc->table_size > vlc->table_allocated) {
		vlc->table_allocated += (1 << vlc->bits);
		vlc->table = arr_realloc(vlc->table, vlc->table_allocated,
			sizeof(int16_t) * 2);
	}
}

static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
		const void *bits, const void *codes, int codes_size,
		uint32_t code_prefix, int n_prefix)
{
	int i, j, k, n, table_size, table_index, nb, n1, idx;
	uint32_t code;
	int16_t (*table)[2];

	table_size = 1 << table_nb_bits;
	table_index = vlc->table_size;
	alloc_table(vlc, table_size);
	table = &vlc->table[table_index];

	for (i = 0; i < table_size; i++) {
		table[i][1] = 0; /* bits */
		table[i][0] = -1; /* codes */
	}

	/* map codes and compute auxiliary table sizes */
	for (i = 0; i < nb_codes; i++) {
		n = get_data(bits, i, 1);
		/* we accept tables with holes */
		n -= n_prefix;
		if (n <= 0)
			continue;
		code = get_data(codes, i, codes_size);
		/* if code matches the prefix, it is in the table */
		if ((code >> n) != code_prefix)
			continue;
		if (n <= table_nb_bits) {
			/* no need to add another table */
			j = (code << (table_nb_bits - n)) & (table_size - 1);
			nb = 1 << (table_nb_bits - n);
			for (k = 0; k < nb; k++) {
				assert(table[j][1] == 0); /* incorrect code */
				table[j][1] = n; /* bits */
				table[j][0] = i;
				j++;
			}
		} else {
			n -= table_nb_bits;
			j = (code >> n) & ((1 << table_nb_bits) - 1);
			/* compute table size */
			n1 = -table[j][1]; /* bits */
			if (n > n1)
				n1 = n;
			table[j][1] = -n1; /* bits */
		}
	}

	/* fill auxiliary tables recursively */
	for (i = 0; i < table_size; i++) {
		n = table[i][1]; /* bits */
		if (n < 0) {
			n = -n;
			if (n > table_nb_bits) {
				n = table_nb_bits;
				table[i][1] = -n; /* bits */
			}
			idx = build_table(vlc, n, nb_codes, bits, codes,
				codes_size, (code_prefix << table_nb_bits) | i,
				n_prefix + table_nb_bits);
			/* vlc->table might have changed */
			table = &vlc->table[table_index];
			table[i][0] = idx; /* code */
		}
	}
	return table_index;
}

/**
 * Build VLC decoding tables suitable for use with get_vlc().
 *
 * \param vlc The structure to be initialized.
 * \param nb_bits Set the decoding table size (2^nb_bits) entries.
 * \param nb_codes Number of vlc codes.
 * \param bits Table which gives the size (in bits) of each vlc code.
 * \param codes Table which gives the bit pattern of of each vlc code.
 * \param codes_size The number of bytes of each entry of the \a codes tables.
 *
 * The bigger \a nb_bits is, the faster is the decoding. But it should not be
 * too big to save memory and L1 cache. '9' is a good compromise.
 *
 * The wrap and size parameters allow to use any memory configuration and
 * types (byte/word/long) to store the bits and codes tables.
 */
void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
		const void *codes, int codes_size)
{
	PARA_INFO_LOG("nb_codes: %d\n", nb_codes);
	vlc->bits = nb_bits;
	vlc->table = NULL;
	vlc->table_allocated = 0;
	vlc->table_size = 0;
	build_table(vlc, nb_bits, nb_codes, bits, codes, codes_size, 0, 0);
}

/**
 * Deallocate all resources of a VLC table.
 *
 * \param vlc Pointer to an initialized vlc structure.
 *
 * The table given by \a vlc must have been initialized earlier via \ref
 * init_vlc().
 */
void free_vlc(struct vlc *vlc)
{
	freep(&vlc->table);
}

/**
 * Parse a vlc code.
 *
 * \param gbc The getbit context structure.
 * \param vlc The vlc tables to use.
 *
 * \return The vlc code.
 */
int get_vlc(struct getbit_context *gbc, const struct vlc *vlc)
{
	int n, idx, nb_bits, code;

	idx = show_bits(gbc, vlc->bits);
	code = vlc->table[idx][0];
	n = vlc->table[idx][1];
	if (n < 0) {
		skip_bits(gbc, vlc->bits);
		nb_bits = -n;
		idx = show_bits(gbc, nb_bits) + code;
		code = vlc->table[idx][0];
		n = vlc->table[idx][1];
		if (n < 0) {
			skip_bits(gbc, nb_bits);
			nb_bits = -n;
			idx = show_bits(gbc, nb_bits) + code;
			code = vlc->table[idx][0];
			n = vlc->table[idx][1];
		}
	}
	skip_bits(gbc, n);
	return code >= 0? code : -E_VLC;
}