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| author | Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> | 2020-03-04 07:06:19 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-03-04 07:06:19 (GMT) |
| commit | 12c45efe828a90a2f2f58a1f95c85d792a0d9c0a (patch) | |
| tree | 54b7db6cfae96c80d144e0666cebfa5e6271bab2 /Lib/gzip.py | |
| parent | 3eff46fc7d2e3c80c4dedba4177782f1fc8ad89b (diff) | |
| download | cpython-12c45efe828a90a2f2f58a1f95c85d792a0d9c0a.zip cpython-12c45efe828a90a2f2f58a1f95c85d792a0d9c0a.tar.gz cpython-12c45efe828a90a2f2f58a1f95c85d792a0d9c0a.tar.bz2 | |
[3.7] bpo-39389: gzip: fix compression level metadata (GH-18077) (GH-18101)
* bpo-39389: gzip: fix compression level metadata (GH-18077)
As described in RFC 1952, section 2.3.1, the XFL (eXtra FLags) byte of a
gzip member header should indicate whether the DEFLATE algorithm was
tuned for speed or compression ratio. Prior to this patch, archives
emitted by the `gzip` module always indicated maximum compression.
(cherry picked from commit eab3b3f1c60afecfb4db3c3619109684cb04bd60)
Co-authored-by: William Chargin <wchargin@gmail.com>
Diffstat (limited to 'Lib/gzip.py')
| -rw-r--r-- | Lib/gzip.py | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/Lib/gzip.py b/Lib/gzip.py index ddc7bda..e59b454 100644 --- a/Lib/gzip.py +++ b/Lib/gzip.py @@ -17,6 +17,11 @@ FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16 READ, WRITE = 1, 2 +_COMPRESS_LEVEL_FAST = 1 +_COMPRESS_LEVEL_TRADEOFF = 6 +_COMPRESS_LEVEL_BEST = 9 + + def open(filename, mode="rb", compresslevel=9, encoding=None, errors=None, newline=None): """Open a gzip-compressed file in binary or text mode. @@ -191,7 +196,7 @@ class GzipFile(_compression.BaseStream): self.fileobj = fileobj if self.mode == WRITE: - self._write_gzip_header() + self._write_gzip_header(compresslevel) @property def filename(self): @@ -218,7 +223,7 @@ class GzipFile(_compression.BaseStream): self.bufsize = 0 self.offset = 0 # Current file offset for seek(), tell(), etc - def _write_gzip_header(self): + def _write_gzip_header(self, compresslevel): self.fileobj.write(b'\037\213') # magic header self.fileobj.write(b'\010') # compression method try: @@ -239,7 +244,13 @@ class GzipFile(_compression.BaseStream): if mtime is None: mtime = time.time() write32u(self.fileobj, int(mtime)) - self.fileobj.write(b'\002') + if compresslevel == _COMPRESS_LEVEL_BEST: + xfl = b'\002' + elif compresslevel == _COMPRESS_LEVEL_FAST: + xfl = b'\004' + else: + xfl = b'\000' + self.fileobj.write(xfl) self.fileobj.write(b'\377') if fname: self.fileobj.write(fname + b'\000') |