thevar1able/ClickHouse
1
0
Fork 0
mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-09-20 00:30:49 +00:00
Code Issues Packages Projects Releases Wiki Activity

Merge pull request #37442 from kitaisreal/compressed-write-buffer-added-comment

Browse Source 
CompressedWriteBuffer added comment
This commit is contained in:
Maksim Kita 2022-05-23 23:44:33 +02:00 committed by GitHub
commit 168814ed78
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/Compression/CompressedWriteBuffer.cpp
View File

@ -22,15 +22,22 @@ void CompressedWriteBuffer::nextImpl()
if (!offset())
return;
UInt32 compressed_size = 0;
size_t decompressed_size = offset();
UInt32 compressed_reserve_size = codec->getCompressedReserveSize(decompressed_size);
if (out.available() > compressed_reserve_size + CHECKSUM_SIZE)
/** During compression we need buffer with capacity >= compressed_reserve_size + CHECKSUM_SIZE.
*
* If output buffer has necessary capacity, we can compress data directly in output buffer.
* Then we can write checksum at the output buffer begin.
*
* If output buffer does not have necessary capacity. Compress data in temporary buffer.
* Then we can write checksum and temporary buffer in output buffer.
*/
if (out.available() >= compressed_reserve_size + CHECKSUM_SIZE)
{
char * out_checksum_ptr = out.position();
char * out_compressed_ptr = out.position() + CHECKSUM_SIZE;
compressed_size = codec->compress(working_buffer.begin(), decompressed_size, out_compressed_ptr);
UInt32 compressed_size = codec->compress(working_buffer.begin(), decompressed_size, out_compressed_ptr);
CityHash_v1_0_2::uint128 checksum = CityHash_v1_0_2::CityHash128(out_compressed_ptr, compressed_size);
memcpy(out_checksum_ptr, reinterpret_cast<const char *>(&checksum), CHECKSUM_SIZE);
@ -39,7 +46,7 @@ void CompressedWriteBuffer::nextImpl()
else
{
compressed_buffer.resize(compressed_reserve_size);
compressed_size = codec->compress(working_buffer.begin(), decompressed_size, compressed_buffer.data());
UInt32 compressed_size = codec->compress(working_buffer.begin(), decompressed_size, compressed_buffer.data());
CityHash_v1_0_2::uint128 checksum = CityHash_v1_0_2::CityHash128(compressed_buffer.data(), compressed_size);
out.write(reinterpret_cast<const char *>(&checksum), CHECKSUM_SIZE);