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lzav.h
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lzav.h
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/**
* @file lzav.h
*
* @version 4.1
*
* @brief The inclusion file for the "LZAV" in-memory data compression and
* decompression algorithms.
*
* Description is available at https://github.com/avaneev/lzav
*
* E-mail: aleksey.vaneev@gmail.com or info@voxengo.com
*
* LICENSE:
*
* Copyright (c) 2023-2024 Aleksey Vaneev
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef LZAV_INCLUDED
#define LZAV_INCLUDED
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#define LZAV_API_VER 0x105 ///< API version, unrelated to code's version.
#define LZAV_VER_STR "4.1" ///< LZAV source code version string.
#if !defined( LZAV_FMT_MIN )
#define LZAV_FMT_MIN 1 ///< Minimal stream format id supported by the
///< decompressor. You may set here (or define via compile options) a
///< value of 2, to reduce decompressor's code size.
#endif // !defined( LZAV_FMT_MIN )
// Decompression error codes:
#define LZAV_E_PARAMS -1 ///< Incorrect function parameters.
#define LZAV_E_SRCOOB -2 ///< Source buffer OOB.
#define LZAV_E_DSTOOB -3 ///< Destination buffer OOB.
#define LZAV_E_REFOOB -4 ///< Back-reference OOB.
#define LZAV_E_DSTLEN -5 ///< Decompressed length mismatch.
#define LZAV_E_UNKFMT -6 ///< Unknown stream format.
// NOTE: all macros defined below are for internal use, do not change.
#define LZAV_WIN_LEN ( 1 << 23 ) ///< LZ77 window length, in bytes.
#define LZAV_REF_MIN 6 ///< Min reference length, in bytes.
#define LZAV_REF_LEN ( LZAV_REF_MIN + 15 + 255 + 254 ) ///< Max ref length.
#define LZAV_LIT_FIN 6 ///< The number of literals required at finish.
#define LZAV_FMT_CUR 2 ///< Stream format identifier used by the compressor.
/**
* @def LZAV_LITTLE_ENDIAN
* @brief Endianness definition macro, can be used as a logical constant.
*/
#if defined( __LITTLE_ENDIAN__ ) || defined( __LITTLE_ENDIAN ) || \
defined( _LITTLE_ENDIAN ) || defined( _WIN32 ) || defined( i386 ) || \
defined( __i386 ) || defined( __i386__ ) || defined( __x86_64__ ) || \
( defined( __BYTE_ORDER__ ) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ )
#define LZAV_LITTLE_ENDIAN 1
#elif defined( __BIG_ENDIAN__ ) || defined( __BIG_ENDIAN ) || \
defined( _BIG_ENDIAN ) || defined( __SYSC_ZARCH__ ) || \
defined( __zarch__ ) || defined( __s390x__ ) || defined( __sparc ) || \
defined( __sparc__ ) || \
( defined( __BYTE_ORDER__ ) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ )
#define LZAV_LITTLE_ENDIAN 0
#else // defined( __BIG_ENDIAN__ )
#warning LZAV: cannot determine endianness, assuming little-endian.
#define LZAV_LITTLE_ENDIAN 1
#endif // defined( __BIG_ENDIAN__ )
/**
* @def LZAV_ARCH64
* @brief Macro that denotes availability of 64-bit instructions.
*/
#if defined( _WIN64 ) || defined( __x86_64__ ) || defined( __ia64__ ) || \
defined( __aarch64__ ) || defined( __arm64 ) || defined( __PPC64__ ) || \
defined( __powerpc64__ ) || defined( __LP64__ ) || defined( _LP64 )
#define LZAV_ARCH64
#endif // 64-bit availability check
/**
* @def LZAV_GCC_BUILTINS
* @brief Macro that denotes availability of GCC-style built-in functions.
*/
#if defined( __GNUC__ ) || defined( __clang__ ) || \
defined( __IBMC__ ) || defined( __IBMCPP__ ) || defined( __COMPCERT__ )
#define LZAV_GCC_BUILTINS
#endif // GCC built-ins check
/**
* @def LZAV_IEC16( x )
* @brief In-place endianness-correction macro, for singular 16-bit variables.
* @param x Value to correct in-place.
*/
/**
* @def LZAV_IEC32( x )
* @brief In-place endianness-correction macro, for singular 32-bit variables.
* @param x Value to correct in-place.
*/
/**
* @def LZAV_IEC64( x )
* @brief In-place endianness-correction macro, for singular 64-bit variables.
* @param x Value to correct in-place.
*/
#if LZAV_LITTLE_ENDIAN
#define LZAV_IEC16( x )
#define LZAV_IEC32( x )
#define LZAV_IEC64( x )
#else // LZAV_LITTLE_ENDIAN
#if defined( LZAV_GCC_BUILTINS )
#define LZAV_IEC16( x ) x = __builtin_bswap16( x )
#define LZAV_IEC32( x ) x = __builtin_bswap32( x )
#elif defined( _MSC_VER )
#define LZAV_IEC16( x ) x = _byteswap_ushort( x )
#define LZAV_IEC32( x ) x = _byteswap_ulong( x )
#else // defined( _MSC_VER )
#define LZAV_IEC16( x ) x = (uint16_t) ( x >> 8 | x << 8 )
#define LZAV_IEC32( x ) x = (uint32_t) ( \
x >> 24 | \
( x & 0x00FF0000 ) >> 8 | \
( x & 0x0000FF00 ) << 8 | \
x << 24 )
#endif // defined( _MSC_VER )
#define LZAV_IEC64( x ) { \
const uint64_t sw = x >> 32 | ( x & 0xFFFFFFFF ) << 32; \
const uint64_t sw2 = ( sw & 0xFFFF0000FFFF0000 ) >> 16 | \
( sw & 0x0000FFFF0000FFFF ) << 16; \
x = ( sw2 & 0xFF00FF00FF00FF00 ) >> 8 | \
( sw2 & 0x00FF00FF00FF00FF ) << 8; }
#endif // LZAV_LITTLE_ENDIAN
/**
* @def LZAV_LIKELY( x )
* @brief Likelihood macro that is used for manually-guided
* micro-optimization.
* @param x Expression that is likely to be evaluated to 1.
*/
/**
* @def LZAV_UNLIKELY( x )
* @brief Unlikelihood macro that is used for manually-guided
* micro-optimization.
* @param x Expression that is unlikely to be evaluated to 1.
*/
#if defined( LZAV_GCC_BUILTINS ) && \
!( defined( __aarch64__ ) && defined( __APPLE__ ))
#define LZAV_LIKELY( x ) __builtin_expect( x, 1 )
#define LZAV_UNLIKELY( x ) __builtin_expect( x, 0 )
#else // Likelihood macros
#define LZAV_LIKELY( x ) ( x )
#define LZAV_UNLIKELY( x ) ( x )
#endif // Likelihood macros
#if defined( _MSC_VER ) && !defined( LZAV_GCC_BUILTINS )
#include <intrin.h> // For _BitScanForwardX and _byteswap_X.
#endif // defined( _MSC_VER ) && !defined( LZAV_GCC_BUILTINS )
/**
* @brief Data match length finding function.
*
* Function finds the number of continuously-matching leading bytes between
* two buffers. This function is well-optimized for a wide variety of
* compilers and platforms.
*
* @param p1 Pointer to buffer 1.
* @param p2 Pointer to buffer 2.
* @param ml Maximal number of bytes to match.
* @return The number of matching leading bytes.
*/
static inline size_t lzav_match_len( const uint8_t* p1, const uint8_t* p2,
const size_t ml )
{
const uint8_t* const p1s = p1;
const uint8_t* const p1e = p1 + ml;
#if defined( LZAV_ARCH64 )
while( LZAV_LIKELY( p1 + 7 < p1e ))
{
uint64_t v1, v2, vd;
memcpy( &v1, p1, 8 );
memcpy( &v2, p2, 8 );
vd = v1 ^ v2;
if( vd != 0 )
{
#if defined( LZAV_GCC_BUILTINS )
#if LZAV_LITTLE_ENDIAN
return( p1 - p1s + ( __builtin_ctzll( vd ) >> 3 ));
#else // LZAV_LITTLE_ENDIAN
return( p1 - p1s + ( __builtin_clzll( vd ) >> 3 ));
#endif // LZAV_LITTLE_ENDIAN
#else // defined( LZAV_GCC_BUILTINS )
#if defined( _MSC_VER )
unsigned long i;
_BitScanForward64( &i, (unsigned __int64) vd );
return( p1 - p1s + ( i >> 3 ));
#else // defined( _MSC_VER )
LZAV_IEC64( vd );
const uint64_t m = 0x0101010101010101;
return( p1 - p1s +
(((( vd ^ ( vd - 1 )) & ( m - 1 )) * m ) >> 56 ));
#endif // defined( _MSC_VER )
#endif // defined( LZAV_GCC_BUILTINS )
}
p1 += 8;
p2 += 8;
}
// At most 7 bytes left.
if( LZAV_LIKELY( p1 + 3 < p1e ))
{
#else // defined( LZAV_ARCH64 )
while( LZAV_LIKELY( p1 + 3 < p1e ))
{
#endif // defined( LZAV_ARCH64 )
uint32_t v1, v2, vd;
memcpy( &v1, p1, 4 );
memcpy( &v2, p2, 4 );
vd = v1 ^ v2;
if( vd != 0 )
{
#if defined( LZAV_GCC_BUILTINS )
#if LZAV_LITTLE_ENDIAN
return( p1 - p1s + ( __builtin_ctz( vd ) >> 3 ));
#else // LZAV_LITTLE_ENDIAN
return( p1 - p1s + ( __builtin_clz( vd ) >> 3 ));
#endif // LZAV_LITTLE_ENDIAN
#else // defined( LZAV_GCC_BUILTINS )
#if defined( _MSC_VER )
unsigned long i;
_BitScanForward( &i, (unsigned long) vd );
return( p1 - p1s + ( i >> 3 ));
#else // defined( _MSC_VER )
LZAV_IEC32( vd );
const uint32_t m = 0x01010101;
return( p1 - p1s +
(((( vd ^ ( vd - 1 )) & ( m - 1 )) * m ) >> 24 ));
#endif // defined( _MSC_VER )
#endif // defined( LZAV_GCC_BUILTINS )
}
p1 += 4;
p2 += 4;
}
// At most 3 bytes left.
if( p1 < p1e )
{
if( *p1 != p2[ 0 ])
{
return( p1 - p1s );
}
if( ++p1 < p1e )
{
if( *p1 != p2[ 1 ])
{
return( p1 - p1s );
}
if( ++p1 < p1e )
{
if( *p1 != p2[ 2 ])
{
return( p1 - p1s );
}
}
}
}
return( ml );
}
/**
* @brief Data match length finding function, reverse direction.
*
* @param p1 Origin pointer to buffer 1.
* @param p2 Origin pointer to buffer 2.
* @param ml Maximal number of bytes to back-match.
* @return The number of matching prior bytes, not including origin position.
*/
static inline size_t lzav_match_len_r( const uint8_t* p1, const uint8_t* p2,
const size_t ml )
{
if( LZAV_UNLIKELY( ml == 0 ))
{
return( 0 );
}
if( p1[ -1 ] != p2[ -1 ])
{
return( 0 );
}
if( LZAV_UNLIKELY( ml != 1 ))
{
const uint8_t* const p1s = p1;
const uint8_t* p1e = p1 - ml + 1;
p1--;
p2--;
while( LZAV_UNLIKELY( p1 > p1e ))
{
uint16_t v1, v2;
memcpy( &v1, p1 - 2, 2 );
memcpy( &v2, p2 - 2, 2 );
const uint32_t vd = v1 ^ v2;
if( vd != 0 )
{
#if LZAV_LITTLE_ENDIAN
return( p1s - p1 + (( vd & 0xFF00 ) == 0 ));
#else // LZAV_LITTLE_ENDIAN
return( p1s - p1 + (( vd & 0x00FF ) == 0 ));
#endif // LZAV_LITTLE_ENDIAN
}
p1 -= 2;
p2 -= 2;
}
p1e--;
if( p1 > p1e && p1[ -1 ] != p2[ -1 ])
{
return( p1s - p1 );
}
}
return( ml );
}
/**
* @brief Internal LZAV block header writing function (stream format 2).
*
* Internal function writes a block to the output buffer. This function can be
* used in custom compression algorithms.
*
* Stream format 2.
*
* "Raw" compressed stream consists of any quantity of unnumerated "blocks".
* A block starts with a header byte, followed by several optional bytes.
* Bits 4-5 of the header specify block's type.
*
* CC00LLLL: literal block (1-6 bytes). `LLLL` is literal length.
* OO01RRRR: 10-bit offset block (2-4 bytes). `RRRR` is reference length.
* OO10RRRR: 18-bit offset block (3-5 bytes).
* OO11RRRR: 23-bit offset block (4-6 bytes).
*
* If `LLLL` or `RRRR` equals 0, a value of 16 is assumed, and an additional
* length byte follows. If in a literal block this additional byte's highest
* bit is 1, one more length byte follows that defines higher bits of length
* (up to 4 bytes). In a reference block, additional 1-2 length bytes follow
* the offset bytes. `CC` is a reference offset carry value (additional 2
* lowest bits of offset of the next reference block). Block type 3 includes 3
* carry bits (highest bits of 4th byte).
*
* The overall compressed data is prefixed with a byte whose lower 4 bits
* contain minimal reference length (mref), and the highest 4 bits contain
* stream format identifier. Compressed data always finishes with
* `LZAV_LIT_FIN` literals. The lzav_write_fin_2() function should be used to
* finalize compression.
*
* Except the block previous to the last block, a literal block is always
* followed by a reference block.
*
* @param op Output buffer pointer.
* @param lc Literal length, in bytes.
* @param rc Reference length, in bytes, not lesser than mref.
* @param d Reference offset, in bytes. Should be lesser than `LZAV_WIN_LEN`,
* and not lesser than `rc` since fast copy on decompression cannot provide
* consistency of copying of data that is not in the output yet.
* @param ipa Literals anchor pointer.
* @param cbpp Pointer to the pointer to the latest offset carry block header.
* Cannot be 0, but the contained pointer can be 0 (initial value).
* @param mref Minimal reference length, in bytes, used by the compression
* algorithm.
* @return Incremented output buffer pointer.
*/
static inline uint8_t* lzav_write_blk_2( uint8_t* op, size_t lc, size_t rc,
size_t d, const uint8_t* ipa, uint8_t** const cbpp, const size_t mref )
{
rc = rc + 1 - mref;
uint8_t* const cbp = *cbpp;
if( LZAV_UNLIKELY( lc != 0 ))
{
// Write a literal block.
size_t cv; // Offset carry value in literal block.
if( LZAV_UNLIKELY( cbp != 0 ))
{
// Perform offset carry to a previous block type 3.
*cbp |= (uint8_t) ( d << 5 );
cv = ( d & 0x18 ) << 3;
*cbpp = 0;
d >>= 5;
}
else
{
cv = ( d & 3 ) << 6;
d >>= 2;
}
if( LZAV_LIKELY( lc < 9 ))
{
*op = (uint8_t) ( cv | lc );
op++;
memcpy( op, ipa, 8 );
op += lc;
}
else
if( LZAV_LIKELY( lc < 16 ))
{
*op = (uint8_t) ( cv | lc );
op++;
memcpy( op, ipa, 16 );
op += lc;
}
else
if( LZAV_LIKELY( lc < 16 + 128 ))
{
#if LZAV_LITTLE_ENDIAN
uint16_t ov = (uint16_t) (( lc - 16 ) << 8 | cv );
#else // LZAV_LITTLE_ENDIAN
uint16_t ov = (uint16_t) ( cv << 8 | ( lc - 16 ));
#endif // LZAV_LITTLE_ENDIAN
memcpy( op, &ov, 2 );
op += 2;
memcpy( op, ipa, 16 );
memcpy( op + 16, ipa + 16, 16 );
if( lc < 33 )
{
op += lc;
}
else
{
ipa += 32;
op += 32;
lc -= 32;
do
{
*op = *ipa;
ipa++;
op++;
} while( --lc != 0 );
}
}
else
{
*op = (uint8_t) cv;
op++;
size_t lcw = lc - 16;
while( lcw > 127 )
{
*op = (uint8_t) ( 0x80 | lcw );
lcw >>= 7;
op++;
}
*op = (uint8_t) lcw;
op++;
memcpy( op, ipa, lc );
op += lc;
}
}
else
{
if( LZAV_UNLIKELY( cbp != 0 ))
{
// Perform offset carry to a previous block type 3.
*cbp |= (uint8_t) ( d << 5 );
*cbpp = 0;
d >>= 3;
}
}
// Write a reference block.
if( LZAV_LIKELY( rc < 16 ))
{
rc |= d << 6;
if( d < ( 1 << 18 ))
{
if( d < ( 1 << 10 ))
{
uint16_t ov = (uint16_t) ( 1 << 4 | rc );
LZAV_IEC16( ov );
memcpy( op, &ov, 2 );
return( op + 2 );
}
*op = (uint8_t) ( 2 << 4 | rc );
uint16_t ov = (uint16_t) ( d >> 2 );
LZAV_IEC16( ov );
memcpy( op + 1, &ov, 2 );
return( op + 3 );
}
*cbpp = op + 3;
uint32_t ov = (uint32_t) ( 3 << 4 | rc );
LZAV_IEC32( ov );
memcpy( op, &ov, 4 );
return( op + 4 );
}
if( LZAV_LIKELY( rc < 16 + 255 ))
{
rc -= 16;
if( LZAV_UNLIKELY( d < ( 1 << 10 )))
{
*op = (uint8_t) ( d << 6 | 1 << 4 );
#if LZAV_LITTLE_ENDIAN
uint16_t ov = (uint16_t) ( rc << 8 | d >> 2 );
#else // LZAV_LITTLE_ENDIAN
uint16_t ov = (uint16_t) (( d & ~3 ) << 6 | rc );
#endif // LZAV_LITTLE_ENDIAN
memcpy( op + 1, &ov, 2 );
return( op + 3 );
}
if( LZAV_LIKELY( d < ( 1 << 18 )))
{
uint32_t ov = (uint32_t) ( rc << 24 | d << 6 | 2 << 4 );
LZAV_IEC32( ov );
memcpy( op, &ov, 4 );
return( op + 4 );
}
*cbpp = op + 3;
*op = (uint8_t) ( d << 6 | 3 << 4 );
uint32_t ov = (uint32_t) ( rc << 24 | d >> 2 );
LZAV_IEC32( ov );
memcpy( op + 1, &ov, 4 );
return( op + 5 );
}
rc -= 16 + 255;
if( LZAV_UNLIKELY( d < ( 1 << 10 )))
{
*op = (uint8_t) ( d << 6 | 1 << 4 );
#if LZAV_LITTLE_ENDIAN
uint16_t ov = (uint16_t) ( 255 << 8 | d >> 2 );
#else // LZAV_LITTLE_ENDIAN
uint16_t ov = (uint16_t) (( d & ~3 ) << 6 | 255 );
#endif // LZAV_LITTLE_ENDIAN
memcpy( op + 1, &ov, 2 );
op[ 3 ] = (uint8_t) rc;
return( op + 4 );
}
if( LZAV_LIKELY( d < ( 1 << 18 )))
{
uint32_t ov = (uint32_t) ( (uint32_t) 255 << 24 | d << 6 | 2 << 4 );
LZAV_IEC32( ov );
memcpy( op, &ov, 4 );
op[ 4 ] = (uint8_t) rc;
return( op + 5 );
}
*cbpp = op + 3;
*op = (uint8_t) ( d << 6 | 3 << 4 );
uint32_t ov = (uint32_t) ( (uint32_t) 255 << 24 | d >> 2 );
LZAV_IEC32( ov );
memcpy( op + 1, &ov, 4 );
op[ 5 ] = (uint8_t) rc;
return( op + 6 );
}
/**
* @brief Internal LZAV finishing function (stream format 2).
*
* Internal function writes finishing literal block(s) to the output buffer.
* This function can be used in custom compression algorithms.
*
* Stream format 2.
*
* @param op Output buffer pointer.
* @param lc Literal length, in bytes. Not less than `LZAV_LIT_FIN`.
* @param ipa Literals anchor pointer.
* @return Incremented output buffer pointer.
*/
static inline uint8_t* lzav_write_fin_2( uint8_t* op, size_t lc,
const uint8_t* ipa )
{
if( lc > 15 )
{
size_t wc = lc - LZAV_LIT_FIN; // Leave literals for the final block.
if( wc < 16 )
{
*op = (uint8_t) wc;
op++;
}
else
{
*op = 0;
op++;
size_t lcw = wc - 16;
while( lcw > 127 )
{
*op = (uint8_t) ( 0x80 | lcw );
lcw >>= 7;
op++;
}
*op = (uint8_t) lcw;
op++;
}
memcpy( op, ipa, wc );
op += wc;
ipa += wc;
lc -= wc;
}
*op = (uint8_t) lc;
op++;
memcpy( op, ipa, lc );
return( op + lc );
}
/**
* @brief Function returns buffer size required for LZAV compression.
*
* @param srcl The length of the source data to be compressed.
* @return The required allocation size for destination compression buffer.
* Always a positive value.
*/
static inline int lzav_compress_bound( const int srcl )
{
if( srcl <= 0 )
{
return( 16 );
}
const int k = 16 + 127 + 1;
const int l2 = srcl / ( k + 6 );
return(( srcl - l2 * 6 + k - 1 ) / k * 2 - l2 + srcl + 16 );
}
/**
* @brief Function returns buffer size required for the higher-ratio LZAV
* compression.
*
* @param srcl The length of the source data to be compressed.
* @return The required allocation size for destination compression buffer.
* Always a positive value.
*/
static inline int lzav_compress_bound_hi( const int srcl )
{
if( srcl <= 0 )
{
return( 16 );
}
const int l2 = srcl / ( 16 + 5 );
return(( srcl - l2 * 5 + 15 ) / 16 * 2 - l2 + srcl + 16 );
}
/**
* @brief LZAV compression function, with external buffer option.
*
* Function performs in-memory data compression using the LZAV compression
* algorithm and stream format. The function produces a "raw" compressed data,
* without a header containing data length nor identifier nor checksum.
*
* Note that compression algorithm and its output on the same source data may
* differ between LZAV versions, and may differ between big- and little-endian
* systems. However, the decompression of a compressed data produced by any
* prior compressor version will remain possible.
*
* @param[in] src Source (uncompressed) data pointer, can be 0 if `srcl`
* equals 0. Address alignment is unimportant.
* @param[out] dst Destination (compressed data) buffer pointer. The allocated
* size should be at least lzav_compress_bound() bytes large. Address
* alignment is unimportant. Should be different to `src`.
* @param srcl Source data length, in bytes, can be 0: in this case the
* compressed length is assumed to be 0 as well.
* @param dstl Destination buffer's capacity, in bytes.
* @param ext_buf External buffer to use for hash-table, set to 0 for the
* function to manage memory itself (via standard `malloc`). Supplying a
* pre-allocated buffer is useful if compression is performed during
* application's operation often: this reduces memory allocation overhead and
* fragmentation. Note that the access to the supplied buffer is not
* implicitly thread-safe. Buffer's address must be aligned to 32 bits.
* @param ext_bufl The capacity of the `ext_buf`, in bytes, should be a
* power-of-2 value. Set to 0 if `ext_buf` is 0. The capacity should not be
* lesser than 4 x `srcl`, and not greater than 1 MiB. Same `ext_bufl` value
* can be used for any smaller source data. The `ext_bufl` value does not
* affect the compression algorithm: the `ext_buf` simply will not be used, if
* it is too small.
* @return The length of compressed data, in bytes. Returns 0 if `srcl` is
* lesser or equal to 0, or if `dstl` is too small, or if not enough memory.
*/
static inline int lzav_compress( const void* const src, void* const dst,
const int srcl, const int dstl, void* const ext_buf, const int ext_bufl )
{
if(( srcl <= 0 ) | ( src == 0 ) | ( dst == 0 ) | ( src == dst ) |
( dstl < lzav_compress_bound( srcl )))
{
return( 0 );
}
if( srcl <= LZAV_LIT_FIN )
{
// Handle a very short source data.
*(uint8_t*) dst = LZAV_FMT_CUR << 4 | LZAV_REF_MIN;
*( (uint8_t*) dst + 1 ) = (uint8_t) srcl;
memcpy( (uint8_t*) dst + 2, src, srcl );
memset( (uint8_t*) dst + 2 + srcl, 0, LZAV_LIT_FIN - srcl );
return( 2 + LZAV_LIT_FIN );
}
uint32_t stack_buf[ 4096 ]; // On-stack hash-table.
void* alloc_buf = 0; // Hash-table allocated on heap.
uint8_t* ht = (uint8_t*) stack_buf; // The actual hash-table pointer.
int htcap = 1 << 7; // Hash-table's capacity (power-of-2).
while( htcap != ( 1 << 16 ) && htcap * 4 < srcl )
{
htcap <<= 1;
}
const size_t htsize = htcap * sizeof( uint32_t ) * 4;
if( htsize > sizeof( stack_buf ))
{
if( ext_buf != 0 && ext_bufl >= (int) htsize )
{
ht = (uint8_t*) ext_buf;
}
else
{
alloc_buf = malloc( htsize );
if( alloc_buf == 0 )
{
return( 0 );
}
ht = (uint8_t*) alloc_buf;
}
}
const uint32_t hmask = (uint32_t) (( htsize - 1 ) ^ 15 ); // Hash mask.
const uint8_t* ip = (const uint8_t*) src; // Source data pointer.
const uint8_t* const ipe = ip + srcl - LZAV_LIT_FIN; // End pointer.
const uint8_t* const ipet = ipe - 9; // Hashing threshold, avoids I/O OOB.
const uint8_t* ipa = ip; // Literals anchor pointer.
uint8_t* op = (uint8_t*) dst; // Destination (compressed data) pointer.
uint8_t* cbp = 0; // Pointer to the latest offset carry block header.
intptr_t mavg = 100 << 21; // Running average of hash match rate (*2^15).
// Two-factor average: success (0-64) by average reference length.
uint32_t rndb = 0; // PRNG bit derived from the non-matching offset.
ip += 16; // Skip source bytes, to avoid OOB in back-match.
*op = LZAV_FMT_CUR << 4 | LZAV_REF_MIN; // Write prefix byte.
op++;
// Initialize the hash-table. Each hash-table item consists of 2 tuples
// (4 initial match bytes; 32-bit source data offset). Set source data
// offset to avoid OOB in back-match.
uint32_t initv[ 2 ] = { 0, 16 };
if( LZAV_LIKELY( ip < ipet ))
{
memcpy( initv, ip, 4 );
}
uint32_t* ht32 = (uint32_t*) ht;
int i;
for( i = 0; i < htcap * 2; i++ )
{
ht32[ 0 ] = initv[ 0 ];
ht32[ 1 ] = initv[ 1 ];
ht32 += 2;
}
while( LZAV_LIKELY( ip < ipet ))
{
// Hash source data (endianness is unimportant for compression
// efficiency). Hash is based on the "komihash" math construct, see
// https://github.com/avaneev/komihash for details.
uint32_t iw1;
uint16_t iw2, ww2;
memcpy( &iw1, ip, 4 );
const uint32_t Seed1 = 0x243F6A88 ^ iw1;
memcpy( &iw2, ip + 4, 2 );
const uint64_t hm = (uint64_t) Seed1 * (uint32_t) ( 0x85A308D3 ^ iw2 );
const uint32_t hval = (uint32_t) hm ^ (uint32_t) ( hm >> 32 );
// Hash-table access.
uint32_t* const hp = (uint32_t*) ( ht + ( hval & hmask ));
const uint32_t ipo = (uint32_t) ( ip - (const uint8_t*) src );
const uint32_t hw1 = hp[ 0 ]; // Tuple 1's match word.
const uint8_t* wp; // At window pointer.
size_t d, ml, rc, lc;
// Find source data in hash-table tuples.
if( LZAV_LIKELY( iw1 != hw1 ))
{
if( LZAV_LIKELY( iw1 != hp[ 2 ]))
{
goto _no_match;
}
wp = (const uint8_t*) src + hp[ 3 ];
memcpy( &ww2, wp + 4, 2 );
if( LZAV_UNLIKELY( iw2 != ww2 ))
{
goto _no_match;
}
}
else
{
wp = (const uint8_t*) src + hp[ 1 ];
memcpy( &ww2, wp + 4, 2 );
if( LZAV_UNLIKELY( iw2 != ww2 ))
{
if( LZAV_LIKELY( iw1 != hp[ 2 ]))
{
goto _no_match;
}
wp = (const uint8_t*) src + hp[ 3 ];
memcpy( &ww2, wp + 4, 2 );
if( LZAV_UNLIKELY( iw2 != ww2 ))
{
goto _no_match;
}
}
}
d = ip - wp; // Reference offset (distance).
if( LZAV_UNLIKELY(( d < 8 ) | ( d > LZAV_WIN_LEN - 1 )))
{
// Small offsets may be inefficient.
ip++;
if( LZAV_LIKELY( d < LZAV_WIN_LEN ))
{
continue;
}
hp[ 1 + ( iw1 != hw1 ) * 2 ] = ipo;
continue;
}
// Source data and hash-table entry match.
// Disallow reference copy overlap by using `d` as max match length.
ml = ( d > LZAV_REF_LEN ? LZAV_REF_LEN : d );
if( LZAV_UNLIKELY( ip + ml > ipe ))
{
// Make sure `LZAV_LIT_FIN` literals remain on finish.
ml = ipe - ip;
}
if( LZAV_LIKELY( d > 273 ))
{
// Update a matching entry which is not inside max reference
// length's range. Otherwise, source data consisting of same-byte
// runs won't compress well.
if( LZAV_LIKELY( iw1 == hw1 )) // Replace tuple, or insert.
{
hp[ 1 ] = ipo;
}
else
{