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spec : clarify last literal copy command

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Yann Collet 2016-08-21 00:24:18 +02:00
parent 8baf78a291
commit 70c2326bf1
1 changed files with 13 additions and 8 deletions
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zstd_compression_format.md
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@ -443,7 +443,7 @@ using little-endian convention.
In this representation, bits on the left are smallest bits.
__`Literals_Block_Type`__
__`Literals_Block_Type`__
This field uses 2 lowest bits of first byte, describing 4 different block types :
@ -460,7 +460,7 @@ This field uses 2 lowest bits of first byte, describing 4 different block types
using Huffman tree _from previous Huffman-compressed literals block_.
Huffman tree description will be skipped.
__`Size_Format`__
__`Size_Format`__
`Size_Format` is divided into 2 families :
@ -697,8 +697,13 @@ A match copy command specifies an offset and a length.
The offset gives the position to copy from,
which can be within a previous block.
There are 3 symbol types, literals lengths, offsets and match lengths,
which are encoded together, interleaved in a single _bitstream_.
When all _sequences_ are decoded,
if there is any literal left in the _literal section_,
these bytes are added at the end of the block.
The _Sequences_Section_ regroup all symbols required to decode commands.
There are 3 symbol types : literals lengths, offsets and match lengths.
They are encoded together, interleaved, in a single _bitstream_.
Each symbol is a _code_ in its own context,
which specifies a baseline and a number of bits to add.
@ -905,8 +910,8 @@ since it will be discovered and reported by the decoding process.
The bitstream starts by reporting on which scale it operates.
`Accuracy_Log = low4bits + 5`.
Note that maximum `Accuracy_Log` for literal and match length is `9`,
and for offsets it is `8`. Higher values are considered errors.
Note that maximum `Accuracy_Log` for literal and match lengths is `9`,
and for offsets is `8`. Higher values are considered errors.
Then follow each symbol value, from `0` to last present one.
The number of bits used by each field is variable.
@ -1128,8 +1133,8 @@ _Reserved ranges :_
However, for public distribution of compressed frames,
the following ranges are reserved for future use and should not be used :
- low range : 1 - 32767
- high range : >= (2^31)
- low range : 1 - 32767
- high range : >= (2^31)
__`Entropy_Tables`__ : following the same format as a [compressed blocks].
They are stored in following order :