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added comment addressing use of bits in frame header descriptor

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This commit is contained in:
Paul Cruz 2017-06-21 17:43:21 -07:00
parent acf0df678c
commit ccae9ec807
1 changed files with 7 additions and 0 deletions
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7
tests/decodecorpus.c
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@ -314,6 +314,13 @@ static void writeFrameHeader(U32* seed, frame_t* frame, dictInfo info)
pos += 4;
{
/*
* fcsCode: 2-bit flag specifying how many bytes used to represent Frame_Content_Size (bits 7-6)
* singleSegment: 1-bit flag describing if data must be regenerated within a single continuous memory segment. (bit 5)
* contentChecksumFlag: 1-bit flag that is set if frame includes checksum at the end -- set to 1 below (bit 2)
* dictBits: 2-bit flag describing how many bytes Dictionary_ID uses -- set to 3 (bits 1-0)
* For more information: https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#frame_header
*/
int const dictBits = info.useDict ? 3 : 0;
BYTE const frameHeaderDescriptor =
(BYTE) ((fcsCode << 6) | (singleSegment << 5) | (1 << 2) | dictBits);