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fix test 122

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it's an unsupported scenario.
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Yann Collet
2019-08-03 16:43:34 +02:00
parent efe8496755
commit 0b0b83e8f3
7 changed files with 45 additions and 33 deletions
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doc/zstd_manual.html
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@ -1557,7 +1557,7 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
<a name="Chapter23"></a><h2>Block level API</h2><pre></pre>
<pre><b></b><p> Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
User will have to take in charge required information to regenerate data, such as compressed and content sizes.
But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
A few rules to respect :
- Compressing and decompressing require a context structure
@ -1568,12 +1568,14 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
+ copyCCtx() and copyDCtx() can be used too
- Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
+ If input is larger than a block size, it's necessary to split input data into multiple blocks
+ For inputs larger than a single block, really consider using regular ZSTD_compress() instead.
Frame metadata is not that costly, and quickly becomes negligible as source size grows larger.
- When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
In which case, nothing is produced into `dst` !
+ User must test for such outcome and deal directly with uncompressed data
+ ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
+ For inputs larger than a single block, consider using regular ZSTD_compress() instead.
Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
- When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
===> In which case, nothing is produced into `dst` !
+ User __must__ test for such outcome and deal directly with uncompressed data
+ A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
Doing so would mess up with statistics history, leading to potential data corruption.
+ ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
+ In case of multiple successive blocks, should some of them be uncompressed,
decoder must be informed of their existence in order to follow proper history.
Use ZSTD_insertBlock() for such a case.