Change summary:
+ There is now a `gzip.READ_BUFFER_SIZE` constant that is 128KB. Other programs that read in 128KB chunks: pigz and cat. So this seems best practice among good programs. Also it is faster than 8 kb chunks.
+ a zlib._ZlibDecompressor was added. This is the _bz2.BZ2Decompressor ported to zlib. Since the zlib.Decompress object is better for in-memory decompression, the _ZlibDecompressor is hidden. It only makes sense in file decompression, and that is already implemented now in the gzip library. No need to bother the users with this.
+ The ZlibDecompressor uses the older Cpython arrange_output_buffer functions, as those are faster and more appropriate for the use case.
+ GzipFile.read has been optimized. There is no longer a `unconsumed_tail` member to write back to padded file. This is instead handled by the ZlibDecompressor itself, which has an internal buffer. `_add_read_data` has been inlined, as it was just two calls.
EDIT: While I am adding improvements anyway, I figured I could add another one-liner optimization now to the python -m gzip application. That read chunks in io.DEFAULT_BUFFER_SIZE previously, but has been updated now to use READ_BUFFER_SIZE chunks.
When compiled with `USE_ZLIB_CRC32` defined (`configure` sets this on POSIX systems), `binascii.crc32(...)` failed to compute the correct value when the input data was >= 4GiB. Because the zlib crc32 API is limited to a 32-bit length.
This lines it up with the `zlib.crc32(...)` implementation that doesn't have that flaw.
**Performance:** This also adopts the same GIL releasing for larger inputs logic that `zlib.crc32` has, and causes the Windows build to always use zlib's crc32 instead of our slow C code as zlib is a required build dependency on Windows.
Clarifies a versionchanged note on crc32 & adler32 docs that the workaround is only needed for Python 2 and earlier.
Also cleans up an unnecessary intermediate variable in the implementation.
Authored-By: Ma Lin / animalize
Co-authored-by: Gregory P. Smith <greg@krypto.org>
* zlib uses an UINT32_MAX sliding window for the output buffer
These funtions have an initial output buffer size parameter:
- zlib.decompress(data, /, wbits=MAX_WBITS, bufsize=DEF_BUF_SIZE)
- zlib.Decompress.flush([length])
If the initial size > UINT32_MAX, use an UINT32_MAX sliding window, instead of clamping to UINT32_MAX.
Speed up when (the initial size == the actual size).
This fixes a memory consumption and copying performance regression in earlier 3.10 beta releases if someone used an output buffer larger than 4GiB with zlib.decompress.
Reviewed-by: Gregory P. Smith
* Fix initial buffer size can't > UINT32_MAX in zlib module
After commit f9bedb630e, in 64-bit build,
if the initial buffer size > UINT32_MAX, ValueError will be raised.
These two functions are affected:
1. zlib.decompress(data, /, wbits=MAX_WBITS, bufsize=DEF_BUF_SIZE)
2. zlib.Decompress.flush([length])
This commit re-allows the size > UINT32_MAX.
* adds curly braces per PEP 7.
* Renames `Buffer_*` to `OutputBuffer_*` for clarity
Faster bz2/lzma/zlib via new output buffering.
Also adds .readall() function to _compression.DecompressReader class
to take best advantage of this in the consume-all-output at once scenario.
Often a 5-20% speedup in common scenarios due to less data copying.
Contributed by Ma Lin.
No longer use deprecated aliases to functions:
* Replace PyObject_MALLOC() with PyObject_Malloc()
* Replace PyObject_REALLOC() with PyObject_Realloc()
* Replace PyObject_FREE() with PyObject_Free()
* Replace PyObject_Del() with PyObject_Free()
* Replace PyObject_DEL() with PyObject_Free()
* Fix potential division by zero in BZ2_Malloc()
* Avoid division by zero in PyLzma_Malloc()
* Avoid division by zero and integer overflow in PyZlib_Malloc()
Reported by Svace static analyzer.
When a single .c file contains several functions and/or methods with
the same name, a safety _METHODDEF #define statement is generated
only for one of them.
This fixes the bug by using the full name of the function to avoid
duplicates rather than just the name.
Ruben Vorderman
Victor Stinner
Eric Snow
Benjamin Peterson
Gregory P. Smith
Ma Lin
Christian Clauss
Mohamad Mansour
Erlend Egeberg Aasland
Mohamed Koubaa
Serhiy Storchaka
Hai Shi
Dino Viehland
Jeroen Demeyer
Alexey Izbyshev
Zackery Spytz
Xiang Zhang
Tal Einat
Antoine Pitrou
Segev Finer
Christian Heimes
Martin Panter