HuaHuaY commented on code in PR #48865:
URL: https://github.com/apache/arrow/pull/48865#discussion_r2695189171
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cpp/src/arrow/util/compression_zstd.cc:
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@@ -207,24 +198,24 @@ class ZSTDCodec : public Codec {
Result<int64_t> Compress(int64_t input_len, const uint8_t* input,
int64_t output_buffer_len, uint8_t* output_buffer)
override {
- size_t ret = ZSTD_compress(output_buffer,
static_cast<size_t>(output_buffer_len),
- input, static_cast<size_t>(input_len),
compression_level_);
+ ARROW_ASSIGN_OR_RAISE(auto cctx, CreateCCtx());
+ size_t ret = ZSTD_compressCCtx(cctx.get(), output_buffer,
+ static_cast<size_t>(output_buffer_len),
input,
+ static_cast<size_t>(input_len),
compression_level_);
Review Comment:
After I read the Zstd's document again, I think there is a mistake here. We
need to use `ZSTD_compress2` instead of `ZSTD_compressCCtx` because
`ZSTD_compressCCtx` will reset other parameters. Thank for your good attention!
```cpp
/*! ZSTD_compressCCtx() :
* Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
* Important : in order to mirror `ZSTD_compress()` behavior,
* this function compresses at the requested compression level,
* __ignoring any other advanced parameter__ .
* If any advanced parameter was set using the advanced API,
* they will all be reset. Only @compressionLevel remains.
*/
ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
int compressionLevel);
/*! ZSTD_compress2() :
* Behave the same as ZSTD_compressCCtx(), but compression parameters are
set using the advanced API.
* (note that this entry point doesn't even expose a compression level
parameter).
* ZSTD_compress2() always starts a new frame.
* Should cctx hold data from a previously unfinished frame, everything
about it is forgotten.
* - Compression parameters are pushed into CCtx before starting
compression, using ZSTD_CCtx_set*()
* - The function is always blocking, returns when compression is completed.
* NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees
that zstd will have
* enough space to successfully compress the data, though it is
possible it fails for other reasons.
* @return : compressed size written into `dst` (<= `dstCapacity),
* or an error code if it fails (which can be tested using
ZSTD_isError()).
*/
ZSTDLIB_API size_t ZSTD_compress2( ZSTD_CCtx* cctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize);
```
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