369 lines
8.3 KiB
C
369 lines
8.3 KiB
C
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/*
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* Copyright (c) 2011 Apple Inc. All rights reserved.
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*
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* @APPLE_APACHE_LICENSE_HEADER_START@
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* @APPLE_APACHE_LICENSE_HEADER_END@
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*/
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/*
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File: ag_enc.c
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Contains: Adaptive Golomb encode routines.
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Copyright: (c) 2001-2011 Apple, Inc.
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*/
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#include "aglib.h"
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#include "ALACBitUtilities.h"
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#include "EndianPortable.h"
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#include "ALACAudioTypes.h"
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#include <math.h>
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#include <stdlib.h>
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#include <string.h>
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#define CODE_TO_LONG_MAXBITS 32
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#define N_MAX_MEAN_CLAMP 0xffff
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#define N_MEAN_CLAMP_VAL 0xffff
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#define REPORT_VAL 40
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#if __GNUC__
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#define ALWAYS_INLINE __attribute__((always_inline))
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#else
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#define ALWAYS_INLINE
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#endif
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/* And on the subject of the CodeWarrior x86 compiler and inlining, I reworked a lot of this
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to help the compiler out. In many cases this required manual inlining or a macro. Sorry
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if it is ugly but the performance gains are well worth it.
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- WSK 5/19/04
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*/
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// note: implementing this with some kind of "count leading zeros" assembly is a big performance win
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static inline int32_t lead( int32_t m )
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{
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long j;
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unsigned long c = (1ul << 31);
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for(j=0; j < 32; j++)
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{
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if((c & m) != 0)
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break;
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c >>= 1;
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}
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return (j);
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}
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#define arithmin(a, b) ((a) < (b) ? (a) : (b))
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static inline int32_t ALWAYS_INLINE lg3a( int32_t x)
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{
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int32_t result;
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x += 3;
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result = lead(x);
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return 31 - result;
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}
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static inline int32_t ALWAYS_INLINE abs_func( int32_t a )
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{
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// note: the CW PPC intrinsic __abs() turns into these instructions so no need to try and use it
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int32_t isneg = a >> 31;
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int32_t xorval = a ^ isneg;
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int32_t result = xorval-isneg;
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return result;
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}
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static inline uint32_t ALWAYS_INLINE unaligned_read32_be(const uint8_t *buffer)
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{
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// embedded CPUs typically can't read unaligned 32-bit words so just read the bytes
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uint32_t value;
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value = ((uint32_t)buffer[0] << 24) | ((uint32_t)buffer[1] << 16) |
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((uint32_t)buffer[2] << 8) | (uint32_t)buffer[3];
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return value;
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}
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static inline void ALWAYS_INLINE unaligned_write32_be(uint8_t *buffer, uint32_t value)
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{
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buffer[0] = value >> 24;
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buffer[1] = (value >> 16) & 0xff;
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buffer[2] = (value >> 8) & 0xff;
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buffer[3] = value & 0xff;
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}
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#if PRAGMA_MARK
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#pragma mark -
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#endif
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static inline int32_t dyn_code(int32_t m, int32_t k, int32_t n, uint32_t *outNumBits)
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{
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uint32_t div, mod, de;
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uint32_t numBits;
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uint32_t value;
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//Assert( n >= 0 );
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div = n/m;
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if(div >= MAX_PREFIX_16)
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{
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numBits = MAX_PREFIX_16 + MAX_DATATYPE_BITS_16;
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value = (((1<<MAX_PREFIX_16)-1)<<MAX_DATATYPE_BITS_16) + n;
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}
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else
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{
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mod = n%m;
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de = (mod == 0);
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numBits = div + k + 1 - de;
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value = (((1<<div)-1)<<(numBits-div)) + mod + 1 - de;
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// if coding this way is bigger than doing escape, then do escape
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if (numBits > MAX_PREFIX_16 + MAX_DATATYPE_BITS_16)
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{
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numBits = MAX_PREFIX_16 + MAX_DATATYPE_BITS_16;
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value = (((1<<MAX_PREFIX_16)-1)<<MAX_DATATYPE_BITS_16) + n;
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}
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}
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*outNumBits = numBits;
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return (int32_t) value;
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}
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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)
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{
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uint32_t div, mod, de;
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uint32_t numBits;
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uint32_t value;
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int32_t didOverflow = 0;
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div = n/m;
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if (div < MAX_PREFIX_32)
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{
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mod = n - (m * div);
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de = (mod == 0);
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numBits = div + k + 1 - de;
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value = (((1<<div)-1)<<(numBits-div)) + mod + 1 - de;
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if (numBits > 25)
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goto codeasescape;
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}
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else
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{
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codeasescape:
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numBits = MAX_PREFIX_32;
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value = (((1<<MAX_PREFIX_32)-1));
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*overflow = n;
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*overflowbits = maxbits;
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didOverflow = 1;
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}
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*outNumBits = numBits;
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*outValue = value;
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return didOverflow;
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}
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static inline void ALWAYS_INLINE dyn_jam_noDeref(unsigned char *out, uint32_t bitPos, uint32_t numBits, uint32_t value)
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{
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uint8_t *i = out + (bitPos >> 3);
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uint32_t mask;
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uint32_t curr;
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uint32_t shift;
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//Assert( numBits <= 32 );
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curr = unaligned_read32_be(i);
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shift = 32 - (bitPos & 7) - numBits;
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mask = ~0u >> (32 - numBits); // mask must be created in two steps to avoid compiler sequencing ambiguity
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mask <<= shift;
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value = (value << shift) & mask;
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value |= curr & ~mask;
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unaligned_write32_be(i, value);
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}
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static inline void ALWAYS_INLINE dyn_jam_noDeref_large(unsigned char *out, uint32_t bitPos, uint32_t numBits, uint32_t value)
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{
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uint8_t *i = out + (bitPos>>3);
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uint32_t w;
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uint32_t curr;
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uint32_t mask;
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int32_t shiftvalue = (32 - (bitPos&7) - numBits);
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//Assert(numBits <= 32);
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curr = unaligned_read32_be(i);
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if (shiftvalue < 0)
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{
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uint8_t tailbyte;
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uint8_t *tailptr;
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w = value >> -shiftvalue;
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mask = ~0u >> -shiftvalue;
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w |= (curr & ~mask);
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tailptr = i + 4;
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tailbyte = (value << ((8+shiftvalue))) & 0xff;
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*tailptr = (uint8_t)tailbyte;
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}
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else
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{
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mask = ~0u >> (32 - numBits);
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mask <<= shiftvalue; // mask must be created in two steps to avoid compiler sequencing ambiguity
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w = (value << shiftvalue) & mask;
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w |= curr & ~mask;
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}
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unaligned_write32_be(i, w);
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}
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int32_t dyn_comp( AGParamRecPtr params, int32_t * pc, BitBuffer * bitstream, int32_t numSamples, int32_t bitSize, uint32_t * outNumBits )
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{
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unsigned char * out;
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uint32_t bitPos, startPos;
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uint32_t m, k, n, c, mz, nz;
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uint32_t numBits;
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uint32_t value;
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int32_t del, zmode;
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uint32_t overflow, overflowbits;
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int32_t status;
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// shadow the variables in params so there's not the dereferencing overhead
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uint32_t mb, pb, kb, wb;
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int32_t rowPos = 0;
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int32_t rowSize = params->sw;
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int32_t rowJump = (params->fw) - rowSize;
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int32_t * inPtr = pc;
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*outNumBits = 0;
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RequireAction( (bitSize >= 1) && (bitSize <= 32), return kALAC_ParamError; );
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out = bitstream->cur;
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startPos = bitstream->bitIndex;
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bitPos = startPos;
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mb = params->mb = params->mb0;
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pb = params->pb;
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kb = params->kb;
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wb = params->wb;
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zmode = 0;
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c=0;
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status = ALAC_noErr;
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while (c < numSamples)
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{
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m = mb >> QBSHIFT;
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k = lg3a(m);
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if ( k > kb)
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{
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k = kb;
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}
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m = (1<<k)-1;
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del = *inPtr++;
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rowPos++;
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n = (abs_func(del) << 1) - ((del >> 31) & 1) - zmode;
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//Assert( 32-lead(n) <= bitSize );
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if ( dyn_code_32bit(bitSize, m, k, n, &numBits, &value, &overflow, &overflowbits) )
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{
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dyn_jam_noDeref(out, bitPos, numBits, value);
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bitPos += numBits;
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dyn_jam_noDeref_large(out, bitPos, overflowbits, overflow);
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bitPos += overflowbits;
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}
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else
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{
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dyn_jam_noDeref(out, bitPos, numBits, value);
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bitPos += numBits;
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}
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c++;
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if ( rowPos >= rowSize)
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{
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rowPos = 0;
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inPtr += rowJump;
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}
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mb = pb * (n + zmode) + mb - ((pb *mb)>>QBSHIFT);
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// update mean tracking if it's overflowed
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if (n > N_MAX_MEAN_CLAMP)
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mb = N_MEAN_CLAMP_VAL;
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zmode = 0;
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RequireAction(c <= numSamples, status = kALAC_ParamError; goto Exit; );
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if (((mb << MMULSHIFT) < QB) && (c < numSamples))
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{
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zmode = 1;
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nz = 0;
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while(c<numSamples && *inPtr == 0)
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{
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/* Take care of wrap-around globals. */
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++inPtr;
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++nz;
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++c;
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if ( ++rowPos >= rowSize)
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{
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rowPos = 0;
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inPtr += rowJump;
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}
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if(nz >= 65535)
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{
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zmode = 0;
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break;
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}
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}
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k = lead(mb) - BITOFF+((mb+MOFF)>>MDENSHIFT);
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mz = ((1<<k)-1) & wb;
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value = dyn_code(mz, k, nz, &numBits);
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dyn_jam_noDeref(out, bitPos, numBits, value);
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bitPos += numBits;
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mb = 0;
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}
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}
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*outNumBits = (bitPos - startPos);
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BitBufferAdvance( bitstream, *outNumBits );
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Exit:
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return status;
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}
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