poke/alac/codec/ag_dec.c

/*
 * Copyright (c) 2011 Apple Inc. All rights reserved.
 *
 * @APPLE_APACHE_LICENSE_HEADER_START@
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * @APPLE_APACHE_LICENSE_HEADER_END@
 */

/*
	File:		ag_dec.c
	
	Contains:   Adaptive Golomb decode routines.

	Copyright:	(c) 2001-2011 Apple, Inc.
*/

#include "aglib.h"
#include "ALACBitUtilities.h"
#include "ALACAudioTypes.h"

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#if __GNUC__ && TARGET_OS_MAC
	#if __POWERPC__
		#include <ppc_intrinsics.h>
	#else
		#include <libkern/OSByteOrder.h>
	#endif
#endif

#define CODE_TO_LONG_MAXBITS	32
#define N_MAX_MEAN_CLAMP		0xffff
#define N_MEAN_CLAMP_VAL		0xffff
#define REPORT_VAL  40

#if __GNUC__
#define ALWAYS_INLINE		__attribute__((always_inline))
#else
#define ALWAYS_INLINE
#endif

/*	And on the subject of the CodeWarrior x86 compiler and inlining, I reworked a lot of this
	to help the compiler out.   In many cases this required manual inlining or a macro.  Sorry
	if it is ugly but the performance gains are well worth it.
	- WSK 5/19/04
*/

void set_standard_ag_params(AGParamRecPtr params, uint32_t fullwidth, uint32_t sectorwidth)
{
	/* Use
		fullwidth = sectorwidth = numOfSamples, for analog 1-dimensional type-short data,
		but use
		fullwidth = full image width, sectorwidth = sector (patch) width
		for such as image (2-dim.) data.
	*/
	set_ag_params( params, MB0, PB0, KB0, fullwidth, sectorwidth, MAX_RUN_DEFAULT );
}

void set_ag_params(AGParamRecPtr params, uint32_t m, uint32_t p, uint32_t k, uint32_t f, uint32_t s, uint32_t maxrun)
{
	params->mb = params->mb0 = m;
	params->pb = p;
	params->kb = k;
	params->wb = (1u<<params->kb)-1;
	params->qb = QB-params->pb; 
	params->fw = f;
	params->sw = s;
	params->maxrun = maxrun;
}

#if PRAGMA_MARK
#pragma mark -
#endif


// note: implementing this with some kind of "count leading zeros" assembly is a big performance win
static inline int32_t lead( int32_t m )
{
	long j;
	unsigned long c = (1ul << 31);

	for(j=0; j < 32; j++)
	{
		if((c & m) != 0)
			break;
		c >>= 1;
	}
	return (j);
}

#define arithmin(a, b) ((a) < (b) ? (a) : (b))

static inline int32_t ALWAYS_INLINE lg3a( int32_t x)
{
    int32_t result;

    x += 3;
    result = lead(x);

    return 31 - result;
}

static inline uint32_t ALWAYS_INLINE read32bit( uint8_t * buffer )
{
	// embedded CPUs typically can't read unaligned 32-bit words so just read the bytes
	uint32_t		value;
	
	value = ((uint32_t)buffer[0] << 24) | ((uint32_t)buffer[1] << 16) |
			 ((uint32_t)buffer[2] << 8) | (uint32_t)buffer[3];
	return value;

}

#if PRAGMA_MARK
#pragma mark -
#endif

#define get_next_fromlong(inlong, suff)		((inlong) >> (32 - (suff)))


static inline uint32_t ALWAYS_INLINE
getstreambits( uint8_t *in, int32_t bitoffset, int32_t numbits )
{
	uint32_t	load1, load2;
	uint32_t	byteoffset = bitoffset / 8;
	uint32_t	result;
	
	//Assert( numbits <= 32 );

	load1 = read32bit( in + byteoffset );

	if ( (numbits + (bitoffset & 0x7)) > 32)
	{
		int32_t load2shift;

		result = load1 << (bitoffset & 0x7);
		load2 = (uint32_t) in[byteoffset+4];
		load2shift = (8-(numbits + (bitoffset & 0x7)-32));
		load2 >>= load2shift;
		result >>= (32-numbits);
		result |= load2;		
	}
	else
	{
		result = load1 >> (32-numbits-(bitoffset & 7));
	}

	// a shift of >= "the number of bits in the type of the value being shifted" results in undefined
	// behavior so don't try to shift by 32
	if ( numbits != (sizeof(result) * 8) )
		result &= ~(0xfffffffful << numbits);
	
	return result;
}


static inline int32_t dyn_get(unsigned char *in, uint32_t *bitPos, uint32_t m, uint32_t k)
{
    uint32_t	tempbits = *bitPos;
    uint32_t		result;
    uint32_t		pre = 0, v;
    uint32_t		streamlong;

	streamlong = read32bit( in + (tempbits >> 3) );
    streamlong <<= (tempbits & 7);

    /* find the number of bits in the prefix */ 
    {
        uint32_t	notI = ~streamlong;
    	pre = lead( notI);
    }

    if(pre >= MAX_PREFIX_16)
    {
        pre = MAX_PREFIX_16;
        tempbits += pre;
        streamlong <<= pre;
        result = get_next_fromlong(streamlong,MAX_DATATYPE_BITS_16);
        tempbits += MAX_DATATYPE_BITS_16;

    }
    else
    {
        // all of the bits must fit within the long we have loaded
        //Assert(pre+1+k <= 32);

        tempbits += pre;
        tempbits += 1;
        streamlong <<= pre+1;
        v = get_next_fromlong(streamlong, k);
        tempbits += k;
    
        result = pre*m + v-1;

        if(v<2) {
            result -= (v-1);
            tempbits -= 1;
        }
    }

    *bitPos = tempbits;
    return result;
}


static inline int32_t dyn_get_32bit( uint8_t * in, uint32_t * bitPos, int32_t m, int32_t k, int32_t maxbits )
{
	uint32_t	tempbits = *bitPos;
	uint32_t		v;
	uint32_t		streamlong;
	uint32_t		result;
	
	streamlong = read32bit( in + (tempbits >> 3) );
	streamlong <<= (tempbits & 7);

	/* find the number of bits in the prefix */ 
	{
		uint32_t notI = ~streamlong;
		result = lead( notI);
	}
	
	if(result >= MAX_PREFIX_32)
	{
		result = getstreambits(in, tempbits+MAX_PREFIX_32, maxbits);
		tempbits += MAX_PREFIX_32 + maxbits;
	}
	else
	{		
		/* all of the bits must fit within the long we have loaded*/
		//Assert(k<=14);
		//Assert(result<MAX_PREFIX_32);
		//Assert(result+1+k <= 32);
		
		tempbits += result;
		tempbits += 1;
		
		if (k != 1)
		{
			streamlong <<= result+1;
			v = get_next_fromlong(streamlong, k);
			tempbits += k;
			tempbits -= 1;
			result = result*m;
			
			if(v>=2)
			{
				result += (v-1);
				tempbits += 1;
			}
		}
	}

	*bitPos = tempbits;

	return result;
}

int32_t dyn_decomp( AGParamRecPtr params, BitBuffer * bitstream, int32_t * pc, int32_t numSamples, int32_t maxSize, uint32_t * outNumBits )
{
    uint8_t 		*in;
    int32_t			*outPtr = pc;
    uint32_t 	bitPos, startPos, maxPos;
    uint32_t		j, m, k, n, c, mz;
    int32_t			del, zmode;
    uint32_t 	mb;
    uint32_t	pb_local = params->pb;
    uint32_t	kb_local = params->kb;
    uint32_t	wb_local = params->wb;
    int32_t				status;

	RequireAction( (bitstream != nil) && (pc != nil) && (outNumBits != nil), return kALAC_ParamError; );
	*outNumBits = 0;

	in = bitstream->cur;
	startPos = bitstream->bitIndex;
	maxPos = bitstream->byteSize * 8;
	bitPos = startPos;

    mb = params->mb0;
    zmode = 0;

    c = 0;
	status = ALAC_noErr;

    while (c < numSamples)
    {
		// bail if we've run off the end of the buffer
    	RequireAction( bitPos < maxPos, status = kALAC_ParamError; goto Exit; );

        m = (mb)>>QBSHIFT;
        k = lg3a(m);

        k = arithmin(k, kb_local);
        m = (1<<k)-1;
        
		n = dyn_get_32bit( in, &bitPos, m, k, maxSize );

        // least significant bit is sign bit
        {
        	uint32_t	ndecode = n + zmode;
            int32_t		multiplier = (- (ndecode&1));

            multiplier |= 1;
            del = ((ndecode+1) >> 1) * (multiplier);
        }

        *outPtr++ = del;

        c++;

        mb = pb_local*(n+zmode) + mb - ((pb_local*mb)>>QBSHIFT);

		// update mean tracking
		if (n > N_MAX_MEAN_CLAMP)
			mb = N_MEAN_CLAMP_VAL;

        zmode = 0;

        if (((mb << MMULSHIFT) < QB) && (c < numSamples))
        {
            zmode = 1;
            k = lead(mb) - BITOFF+((mb+MOFF)>>MDENSHIFT);
            mz = ((1<<k)-1) & wb_local;

            n = dyn_get(in, &bitPos, mz, k);

            RequireAction(c+n <= numSamples, status = kALAC_ParamError; goto Exit; );

            for(j=0; j < n; j++)
            {
                *outPtr++ = 0;
                ++c;                    
            }

            if(n >= 65535)
            	zmode = 0;

            mb = 0;
        }
    }

Exit:
	*outNumBits = (bitPos - startPos);
	BitBufferAdvance( bitstream, *outNumBits );
	RequireAction( bitstream->cur <= bitstream->end, status = kALAC_ParamError; );

    return status;
}