/*
* 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_enc.c
Contains: Adaptive Golomb encode routines.
Copyright: (c) 2001-2011 Apple, Inc.
*/
#include "aglib.h"
#include "ALACBitUtilities.h"
#include "EndianPortable.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
*/
// 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 int32_t ALWAYS_INLINE abs_func( int32_t a )
{
// note: the CW PPC intrinsic __abs() turns into these instructions so no need to try and use it
int32_t isneg = a >> 31;
int32_t xorval = a ^ isneg;
int32_t result = xorval-isneg;
return 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
static inline int32_t dyn_code(int32_t m, int32_t k, int32_t n, uint32_t *outNumBits)
{
uint32_t div, mod, de;
uint32_t numBits;
uint32_t value;
//Assert( n >= 0 );
div = n/m;
if(div >= MAX_PREFIX_16)
{
numBits = MAX_PREFIX_16 + MAX_DATATYPE_BITS_16;
value = (((1<<MAX_PREFIX_16)-1)<<MAX_DATATYPE_BITS_16) + n;
}
else
{
mod = n%m;
de = (mod == 0);
numBits = div + k + 1 - de;
value = (((1<<div)-1)<<(numBits-div)) + mod + 1 - de;
// if coding this way is bigger than doing escape, then do escape
if (numBits > MAX_PREFIX_16 + MAX_DATATYPE_BITS_16)
{
numBits = MAX_PREFIX_16 + MAX_DATATYPE_BITS_16;
value = (((1<<MAX_PREFIX_16)-1)<<MAX_DATATYPE_BITS_16) + n;
}
}
*outNumBits = numBits;
return (int32_t) value;
}
static inline int32_t dyn_code_32bit(int32_t maxbits, uint32_t m, uint32_t k, uint32_t n, uint32_t *outNumBits, uint32_t *outValue, uint32_t *overflow, uint32_t *overflowbits)
{
uint32_t div, mod, de;
uint32_t numBits;
uint32_t value;
int32_t didOverflow = 0;
div = n/m;
if (div < MAX_PREFIX_32)
{
mod = n - (m * div);
de = (mod == 0);
numBits = div + k + 1 - de;
value = (((1<<div)-1)<<(numBits-div)) + mod + 1 - de;
if (numBits > 25)
goto codeasescape;
}
else
{
codeasescape:
numBits = MAX_PREFIX_32;
value = (((1<<MAX_PREFIX_32)-1));
*overflow = n;
*overflowbits = maxbits;
didOverflow = 1;
}
*outNumBits = numBits;
*outValue = value;
return didOverflow;
}
static inline void ALWAYS_INLINE dyn_jam_noDeref(unsigned char *out, uint32_t bitPos, uint32_t numBits, uint32_t value)
{
uint32_t *i = (uint32_t *)(out + (bitPos >> 3));
uint32_t mask;
uint32_t curr;
uint32_t shift;
//Assert( numBits <= 32 );
curr = *i;
curr = Swap32NtoB( curr );
shift = 32 - (bitPos & 7) - numBits;
mask = ~0u >> (32 - numBits); // mask must be created in two steps to avoid compiler sequencing ambiguity
mask <<= shift;
value = (value << shift) & mask;
value |= curr & ~mask;
*i = Swap32BtoN( value );
}
static inline void ALWAYS_INLINE dyn_jam_noDeref_large(unsigned char *out, uint32_t bitPos, uint32_t numBits, uint32_t value)
{
uint32_t * i = (uint32_t *)(out + (bitPos>>3));
uint32_t w;
uint32_t curr;
uint32_t mask;
int32_t shiftvalue = (32 - (bitPos&7) - numBits);
//Assert(numBits <= 32);
curr = *i;
curr = Swap32NtoB( curr );
if (shiftvalue < 0)
{
uint8_t tailbyte;
uint8_t *tailptr;
w = value >> -shiftvalue;
mask = ~0u >> -shiftvalue;
w |= (curr & ~mask);
tailptr = ((uint8_t *)i) + 4;
tailbyte = (value << ((8+shiftvalue))) & 0xff;
*tailptr = (uint8_t)tailbyte;
}
else
{
mask = ~0u >> (32 - numBits);
mask <<= shiftvalue; // mask must be created in two steps to avoid compiler sequencing ambiguity
w = (value << shiftvalue) & mask;
w |= curr & ~mask;
}
*i = Swap32BtoN( w );
}
int32_t dyn_comp( AGParamRecPtr params, int32_t * pc, BitBuffer * bitstream, int32_t numSamples, int32_t bitSize, uint32_t * outNumBits )
{
unsigned char * out;
uint32_t bitPos, startPos;
uint32_t m, k, n, c, mz, nz;
uint32_t numBits;
uint32_t value;
int32_t del, zmode;
uint32_t overflow, overflowbits;
int32_t status;
// shadow the variables in params so there's not the dereferencing overhead
uint32_t mb, pb, kb, wb;
int32_t rowPos = 0;
int32_t rowSize = params->sw;
int32_t rowJump = (params->fw) - rowSize;
int32_t * inPtr = pc;
*outNumBits = 0;
RequireAction( (bitSize >= 1) && (bitSize <= 32), return kALAC_ParamError; );
out = bitstream->cur;
startPos = bitstream->bitIndex;
bitPos = startPos;
mb = params->mb = params->mb0;
pb = params->pb;
kb = params->kb;
wb = params->wb;
zmode = 0;
c=0;
status = ALAC_noErr;
while (c < numSamples)
{
m = mb >> QBSHIFT;
k = lg3a(m);
if ( k > kb)
{
k = kb;
}
m = (1<<k)-1;
del = *inPtr++;
rowPos++;
n = (abs_func(del) << 1) - ((del >> 31) & 1) - zmode;
//Assert( 32-lead(n) <= bitSize );
if ( dyn_code_32bit(bitSize, m, k, n, &numBits, &value, &overflow, &overflowbits) )
{
dyn_jam_noDeref(out, bitPos, numBits, value);
bitPos += numBits;
dyn_jam_noDeref_large(out, bitPos, overflowbits, overflow);
bitPos += overflowbits;
}
else
{
dyn_jam_noDeref(out, bitPos, numBits, value);
bitPos += numBits;
}
c++;
if ( rowPos >= rowSize)
{
rowPos = 0;
inPtr += rowJump;
}
mb = pb * (n + zmode) + mb - ((pb *mb)>>QBSHIFT);
// update mean tracking if it's overflowed
if (n > N_MAX_MEAN_CLAMP)
mb = N_MEAN_CLAMP_VAL;
zmode = 0;
RequireAction(c <= numSamples, status = kALAC_ParamError; goto Exit; );
if (((mb << MMULSHIFT) < QB) && (c < numSamples))
{
zmode = 1;
nz = 0;
while(c<numSamples && *inPtr == 0)
{
/* Take care of wrap-around globals. */
++inPtr;
++nz;
++c;
if ( ++rowPos >= rowSize)
{
rowPos = 0;
inPtr += rowJump;
}
if(nz >= 65535)
{
zmode = 0;
break;
}
}
k = lead(mb) - BITOFF+((mb+MOFF)>>MDENSHIFT);
mz = ((1<<k)-1) & wb;
value = dyn_code(mz, k, nz, &numBits);
dyn_jam_noDeref(out, bitPos, numBits, value);
bitPos += numBits;
mb = 0;
}
}
*outNumBits = (bitPos - startPos);
BitBufferAdvance( bitstream, *outNumBits );
Exit:
return status;
}