ddidderr/zstd-rs
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update specification and comments

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This commit is contained in:
Yann Collet
2016-07-01 20:55:28 +02:00
parent 406dcca98a
commit 2fa9904844
4 changed files with 200 additions and 94 deletions
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lib/compress/zstd_compress.c
+10 -23
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@@ -427,21 +427,8 @@ static void ZSTD_reduceIndex (ZSTD_CCtx* zc, const U32 reducerValue)
*/
/* Frame descriptor
/* Frame header :
// old
1 byte - Alloc :
bit 0-3 : windowLog - ZSTD_WINDOWLOG_ABSOLUTEMIN (see zstd_internal.h)
bit 4 : reserved for windowLog (must be zero)
bit 5 : reserved (must be zero)
bit 6-7 : Frame content size : unknown, 1 byte, 2 bytes, 8 bytes
1 byte - checker :
bit 0-1 : dictID (0, 1, 2 or 4 bytes)
bit 2-7 : reserved (must be zero)
// new
1 byte - FrameHeaderDescription :
bit 0-1 : dictID (0, 1, 2 or 4 bytes)
bit 2-4 : reserved (must be zero)
@@ -453,24 +440,24 @@ static void ZSTD_reduceIndex (ZSTD_CCtx* zc, const U32 reducerValue)
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
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
*/
/* Block format description
Block = Literal Section - Sequences Section
Block = Literals Section - Sequences Section
Prerequisite : size of (compressed) block, maximum size of regenerated data
1) Literal Section
@@ -478,7 +465,7 @@ static void ZSTD_reduceIndex (ZSTD_CCtx* zc, const U32 reducerValue)
1.1) Header : 1-5 bytes
flags: 2 bits
00 compressed by Huff0
01 unused
01 repeat
10 is Raw (uncompressed)
11 is Rle
Note : using 01 => Huff0 with precomputed table ?
@@ -514,7 +501,7 @@ static void ZSTD_reduceIndex (ZSTD_CCtx* zc, const U32 reducerValue)
else => 5 bytes (2-2-18-18)
big endian convention
1- CTable available (stored into workspace ?)
1- CTable available (stored into workspace)
2- Small input (fast heuristic ? Full comparison ? depend on clevel ?)