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Clarify what happens when Number_of_Sequences == 0

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Nick Terrell 2018-05-22 16:12:33 -07:00
parent 27af35c110
commit 73f4c890cd
1 changed files with 2 additions and 1 deletions
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doc/zstd_compression_format.md
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@ -603,6 +603,7 @@ Let's call its first byte `byte0`.
- `if (byte0 == 0)` : there are no sequences.
The sequence section stops there.
Decompressed content is defined entirely as Literals Section content.
The FSE tables used in `Repeat_Mode` aren't updated.
- `if (byte0 < 128)` : `Number_of_Sequences = byte0` . Uses 1 byte.
- `if (byte0 < 255)` : `Number_of_Sequences = ((byte0-128) << 8) + byte1` . Uses 2 bytes.
- `if (byte0 == 255)`: `Number_of_Sequences = byte1 + (byte2<<8) + 0x7F00` . Uses 3 bytes.
@ -631,7 +632,7 @@ They follow the same enumeration :
No distribution table will be present.
- `RLE_Mode` : The table description consists of a single byte.
This code will be repeated for all sequences.
- `Repeat_Mode` : The table used in the previous `Compressed_Block` will be used again,
- `Repeat_Mode` : The table used in the previous `Compressed_Block` with `Number_of_Sequences > 0` will be used again,
or if this is the first block, table in the dictionary will be used
No distribution table will be present.
Note that this includes `RLE_mode`, so if `Repeat_Mode` follows `RLE_Mode`, the same symbol will be repeated.