/*
 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * bitstream reader API header.
 */

#ifndef AVCODEC_GET_BITS_H
#define AVCODEC_GET_BITS_H

#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include "libavutil/bswap.h"
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "mathops.h"


typedef struct GetBitContext {
    uint8_t *rbsp;
    unsigned int rbsp_size;
    uint8_t *raw;
    const uint8_t *buffer, *buffer_end;
    unsigned int alloc_size;
    unsigned int buf_size;
    uint32_t *buffer_ptr;
    uint32_t cache0;
    uint32_t cache1;
    int bit_count;
    int size_in_bits;
} GetBitContext;

/* Bitstream reader API docs:
name
    arbitrary name which is used as prefix for the internal variables

gb
    getbitcontext

OPEN_READER(name, gb)
    loads gb into local variables

CLOSE_READER(name, gb)
    stores local vars in gb

UPDATE_CACHE(name, gb)
    refills the internal cache from the bitstream
    after this call at least MIN_CACHE_BITS will be available,

GET_CACHE(name, gb)
    will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)

SHOW_UBITS(name, gb, num)
    will return the next num bits

SHOW_SBITS(name, gb, num)
    will return the next num bits and do sign extension

SKIP_BITS(name, gb, num)
    will skip over the next num bits
    note, this is equivalent to SKIP_CACHE; SKIP_COUNTER

SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)

SKIP_COUNTER(name, gb, num)
    will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)

LAST_SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing

LAST_SKIP_BITS(name, gb, num)
    is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER

for examples see get_bits, show_bits, skip_bits, get_vlc
*/

#define MIN_CACHE_BITS 32

#define OPEN_READER(name, gb)\
	int name##_bit_count=(gb)->bit_count;\
	uint32_t name##_cache0= (gb)->cache0;\
	uint32_t name##_cache1= (gb)->cache1;\
	uint32_t * name##_buffer_ptr=(gb)->buffer_ptr;\

#define CLOSE_READER(name, gb)\
	(gb)->bit_count= name##_bit_count;\
	(gb)->cache0= name##_cache0;\
	(gb)->cache1= name##_cache1;\
	(gb)->buffer_ptr= name##_buffer_ptr;\

#define UPDATE_CACHE(name, gb)\
	if(name##_bit_count > 0){\
		const uint32_t next= be2me_32( *name##_buffer_ptr );\
		name##_cache0 |= NEG_USR32(next,name##_bit_count);\
		name##_cache1 |= next<<name##_bit_count;\
		name##_buffer_ptr++;\
		name##_bit_count-= 32;\
	}\

#if ARCH_X86
#   define SKIP_CACHE(name, gb, num)\
        __asm__(\
            "shldl %2, %1, %0          \n\t"\
            "shll %2, %1               \n\t"\
            : "+r" (name##_cache0), "+r" (name##_cache1)\
            : "Ic" ((uint8_t)(num))\
           );
#else
#   define SKIP_CACHE(name, gb, num)\
        name##_cache0 <<= (num);\
        name##_cache0 |= NEG_USR32(name##_cache1,num);\
        name##_cache1 <<= (num);
#endif

#define SKIP_COUNTER(name, gb, num)\
	name##_bit_count += (num);\

#define SKIP_BITS(name, gb, num)\
	{\
		SKIP_CACHE(name, gb, num)\
		SKIP_COUNTER(name, gb, num)\
	}\

#define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
#define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)

#define SHOW_UBITS(name, gb, num)\
	NEG_USR32(name##_cache0, num)

#define SHOW_SBITS(name, gb, num)\
        NEG_SSR32(name##_cache0, num)

#define GET_CACHE(name, gb)\
	(name##_cache0)

static inline int get_bits_count(const GetBitContext *s){
    return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
}

static inline void skip_bits_long(GetBitContext *s, int n){
    OPEN_READER(re, s)
    re_bit_count += n;
    re_buffer_ptr += re_bit_count>>5;
    re_bit_count &= 31;
    re_cache0 = be2me_32( re_buffer_ptr[-1] ) << re_bit_count;
    re_cache1 = 0;
    UPDATE_CACHE(re, s)
    CLOSE_READER(re, s)
}

/**
 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
 * if MSB not set it is negative
 * @param n length in bits
 * @author BERO
 */
static inline int get_xbits(GetBitContext *s, int n){
    register int sign;
    register int32_t cache;
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    cache = GET_CACHE(re,s);
    sign=(~cache)>>31;
    LAST_SKIP_BITS(re, s, n)
    CLOSE_READER(re, s)
    return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
}

static inline int get_sbits(GetBitContext *s, int n){
    register int tmp;
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    tmp= SHOW_SBITS(re, s, n);
    LAST_SKIP_BITS(re, s, n)
    CLOSE_READER(re, s)
    return tmp;
}

/**
 * reads 1-17 bits.
 * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
 */
static inline unsigned int get_bits(GetBitContext *s, int n){
    register int tmp;
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    tmp= SHOW_UBITS(re, s, n);
    LAST_SKIP_BITS(re, s, n)
    CLOSE_READER(re, s)
    return tmp;
}

/**
 * shows 1-17 bits.
 * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
 */
static inline unsigned int show_bits(GetBitContext *s, int n){
    register int tmp;
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    tmp= SHOW_UBITS(re, s, n);
//    CLOSE_READER(re, s)
    return tmp;
}

static inline void skip_bits(GetBitContext *s, int n){
 //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    LAST_SKIP_BITS(re, s, n)
    CLOSE_READER(re, s)
}

static inline unsigned int get_bits1(GetBitContext *s){
    return get_bits(s, 1);
}

static inline unsigned int show_bits1(GetBitContext *s){
    return show_bits(s, 1);
}

static inline void skip_bits1(GetBitContext *s){
    skip_bits(s, 1);
}

/**
 * reads 0-32 bits.
 */
static inline unsigned int get_bits_long(GetBitContext *s, int n){
    if(n<=MIN_CACHE_BITS) return get_bits(s, n);
    else{
        int ret= get_bits(s, 16) << (n-16);
        return ret | get_bits(s, n-16);
    }
}

/**
 * reads 0-32 bits as a signed integer.
 */
static inline int get_sbits_long(GetBitContext *s, int n) {
    return sign_extend(get_bits_long(s, n), n);
}

/**
 * shows 0-32 bits.
 */
static inline unsigned int show_bits_long(GetBitContext *s, int n){
    if(n<=MIN_CACHE_BITS) return show_bits(s, n);
    else{
        GetBitContext gb= *s;
        return get_bits_long(&gb, n);
    }
}

static inline int check_marker(GetBitContext *s, const char *msg)
{
    int bit= get_bits1(s);
    if(!bit)
        av_log(AV_LOG_INFO, "Marker bit missing %s\n", msg);

    return bit;
}

/**
 * init GetBitContext.
 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
 * @param bit_size the size of the buffer in bits
 *
 * While GetBitContext stores the buffer size, for performance reasons you are
 * responsible for checking for the buffer end yourself (take advantage of the padding)!
 */
static inline void init_get_bits(GetBitContext *s,
                   const uint8_t *buffer, int bit_size)
{
    int buffer_size= (bit_size+7)>>3;
    if(buffer_size < 0 || bit_size < 0) {
        buffer_size = bit_size = 0;
        buffer = NULL;
    }

    s->buffer= buffer;
    s->size_in_bits= bit_size;
    s->buffer_end= buffer + buffer_size;

    s->buffer_ptr = (uint32_t*)((intptr_t)buffer&(~3));
    s->bit_count = 32 + 8*((intptr_t)buffer&3);
    skip_bits_long(s, 0);
}

static inline void align_get_bits(GetBitContext *s)
{
    int n= (-get_bits_count(s)) & 7;
    if(n) skip_bits(s, n);
}

#define tprintf(p, ...) {}

static inline int get_bits_left(GetBitContext *gb)
{
    return gb->size_in_bits - get_bits_count(gb);
}

#endif /* AVCODEC_GET_BITS_H */