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changed streamNb order to 1-4-4-4

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This commit is contained in:
Yann Collet 2016-07-22 17:30:52 +02:00
parent 772d912c2f
commit c2e1a68d81
3 changed files with 5 additions and 133 deletions
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132
lib/compress/zstd_compress.c
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@ -423,135 +423,7 @@ static void ZSTD_reduceIndex (ZSTD_CCtx* zc, const U32 reducerValue)
* Block entropic compression
*********************************************************/
/* Frame format description
Frame Header - [ Block Header - Block ] - Frame End
1) Frame Header
- 4 bytes : Magic Number : ZSTD_MAGICNUMBER (defined within zstd_static.h)
- 1 byte : Frame Header Descriptor
- 1-13 bytes : Optional fields
2) Block Header
- 3 bytes, starting with a 2-bits descriptor
Uncompressed, Compressed, Frame End, unused
3) Block
See Block Format Description
4) Frame End
- 3 bytes, compatible with Block Header
*/
/* Frame header :
1 byte - FrameHeaderDescription :
bit 0-1 : dictID (0, 1, 2 or 4 bytes)
bit 2-4 : reserved (must be zero)
bit 5 : SkippedWindowLog (if 1, WindowLog byte is not present)
bit 6-7 : FrameContentFieldsize (0, 2, 4, or 8)
if (SkippedWindowLog && !FrameContentFieldsize) FrameContentFieldsize=1;
Optional : WindowLog (0 or 1 byte)
bit 0-2 : octal Fractional (1/8th)
bit 3-7 : Power of 2, with 0 = 1 KB (up to 2 TB)
Optional : content size (0, 1, 2, 4 or 8 bytes)
0 : unknown
1 : 0-255 bytes
2 : 256 - 65535+256
8 : up to 16 exa
Optional : dictID (0, 1, 2 or 4 bytes)
Automatic adaptation
0 : no dictID
1 : 1 - 255
2 : 256 - 65535
4 : all other values
*/
/* Block format description
Block = Literals Section - Sequences Section
Prerequisite : size of (compressed) block, maximum size of regenerated data
1) Literal Section
1.1) Header : 1-5 bytes
flags: 2 bits
00 compressed by Huff0
01 repeat
10 is Raw (uncompressed)
11 is Rle
Note : using 01 => Huff0 with precomputed table ?
Note : delta map ? => compressed ?
1.1.1) Huff0-compressed literal block : 3-5 bytes
srcSize < 1 KB => 3 bytes (2-2-10-10) => single stream
srcSize < 1 KB => 3 bytes (2-2-10-10)
srcSize < 16KB => 4 bytes (2-2-14-14)
else => 5 bytes (2-2-18-18)
big endian convention
1.1.2) Raw (uncompressed) literal block header : 1-3 bytes
size : 5 bits: (IS_RAW<<6) + (0<<4) + size
12 bits: (IS_RAW<<6) + (2<<4) + (size>>8)
size&255
20 bits: (IS_RAW<<6) + (3<<4) + (size>>16)
size>>8&255
size&255
1.1.3) Rle (repeated single byte) literal block header : 1-3 bytes
size : 5 bits: (IS_RLE<<6) + (0<<4) + size
12 bits: (IS_RLE<<6) + (2<<4) + (size>>8)
size&255
20 bits: (IS_RLE<<6) + (3<<4) + (size>>16)
size>>8&255
size&255
1.1.4) Huff0-compressed literal block, using precomputed CTables : 3-5 bytes
srcSize < 1 KB => 3 bytes (2-2-10-10) => single stream
srcSize < 1 KB => 3 bytes (2-2-10-10)
srcSize < 16KB => 4 bytes (2-2-14-14)
else => 5 bytes (2-2-18-18)
big endian convention
1- CTable available (stored into workspace)
2- Small input (fast heuristic ? Full comparison ? depend on clevel ?)
1.2) Literal block content
1.2.1) Huff0 block, using sizes from header
See Huff0 format
1.2.2) Huff0 block, using prepared table
1.2.3) Raw content
1.2.4) single byte
2) Sequences section
- Nb Sequences : 2 bytes, little endian
- Control Token : 1 byte (see below)
- Dumps Length : 1 or 2 bytes (depending on control token)
- Dumps : as stated by dumps length
- Literal Lengths FSE table (as needed depending on encoding method)
- Offset Codes FSE table (as needed depending on encoding method)
- Match Lengths FSE table (as needed depending on encoding method)
2.1) Control Token
8 bits, divided as :
0-1 : dumpsLength
2-3 : MatchLength, FSE encoding method
4-5 : Offset Codes, FSE encoding method
6-7 : Literal Lengths, FSE encoding method
FSE encoding method :
FSE_ENCODING_RAW : uncompressed; no header
FSE_ENCODING_RLE : single repeated value; header 1 byte
FSE_ENCODING_STATIC : use prepared table; no header
FSE_ENCODING_DYNAMIC : read NCount
*/
/* See zstd_compression_format.md for detailed format description */
size_t ZSTD_noCompressBlock (void* dst, size_t dstCapacity, const void* src, size_t srcSize)
{
@ -652,7 +524,7 @@ static size_t ZSTD_compressLiterals (ZSTD_CCtx* zc,
switch(lhSize)
{
case 3: /* 2 - 2 - 10 - 10 */
{ U32 const lhc = hType + (singleStream << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<14);
{ U32 const lhc = hType + ((!singleStream) << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<14);
MEM_writeLE24(ostart, lhc);
break;
}

2
lib/decompress/zstd_decompress.c
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@ -480,7 +480,7 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
{
case 0: case 1: default: /* note : default is impossible, since lhlCode into [0..3] */
/* 2 - 2 - 10 - 10 */
{ singleStream = lhlCode;
{ singleStream = !lhlCode;
lhSize = 3;
litSize = (lhc >> 4) & 0x3FF;
litCSize = (lhc >> 14) & 0x3FF;

4
zstd_compression_format.md
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@ -488,10 +488,10 @@ using a long format, accepting the reduced compacity.
__Sizes format for Compressed literals block__ :
Note : also applicable to "repeat-stats" blocks.
- Value : 00 : 4 streams.
- Value : 00 : _Single stream_.
Compressed and regenerated sizes use 10 bits (0-1023).
Total literal header size is 3 bytes.
- Value : 01 : _Single stream_.
- Value : 01 : 4 streams.
Compressed and regenerated sizes use 10 bits (0-1023).
Total literal header size is 3 bytes.
- Value : 10 : 4 streams.