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Add read support for all missing variants of the GNU sparse

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extensions. Thus, in addition to GNUTYPE_SPARSE headers, sparse
information in pax headers created by GNU tar can now be decoded.
All three formats 0.0, 0.1 and 1.0 are supported.
On filesystems that support this, holes in files are now restored
whenever a sparse member is extracted.
This commit is contained in:
Lars Gustäbel 2010-10-29 09:08:19 +00:00
parent 3122ce3e5d
commit 9cbdd75ec5
5 changed files with 180 additions and 127 deletions
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3
Doc/library/tarfile.rst
View file

@ -20,7 +20,8 @@ Some facts and figures:
* read/write support for the POSIX.1-1988 (ustar) format.
* read/write support for the GNU tar format including *longname* and *longlink*
extensions, read-only support for the *sparse* extension.
extensions, read-only support for all variants of the *sparse* extension
including restoration of sparse files.
* read/write support for the POSIX.1-2001 (pax) format.

231
Lib/tarfile.py
View file

@ -701,13 +701,29 @@ class _FileInFile(object):
object.
"""
def __init__(self, fileobj, offset, size, sparse=None):
def __init__(self, fileobj, offset, size, blockinfo=None):
self.fileobj = fileobj
self.offset = offset
self.size = size
self.sparse = sparse
self.position = 0
if blockinfo is None:
blockinfo = [(0, size)]
# Construct a map with data and zero blocks.
self.map_index = 0
self.map = []
lastpos = 0
realpos = self.offset
for offset, size in blockinfo:
if offset > lastpos:
self.map.append((False, lastpos, offset, None))
self.map.append((True, offset, offset + size, realpos))
realpos += size
lastpos = offset + size
if lastpos < self.size:
self.map.append((False, lastpos, self.size, None))
def seekable(self):
if not hasattr(self.fileobj, "seekable"):
# XXX gzip.GzipFile and bz2.BZ2File
@ -732,48 +748,26 @@ def read(self, size=None):
else:
size = min(size, self.size - self.position)
if self.sparse is None:
return self.readnormal(size)
else:
return self.readsparse(size)
def readnormal(self, size):
"""Read operation for regular files.
"""
self.fileobj.seek(self.offset + self.position)
self.position += size
return self.fileobj.read(size)
def readsparse(self, size):
"""Read operation for sparse files.
"""
data = b""
buf = b""
while size > 0:
buf = self.readsparsesection(size)
if not buf:
break
size -= len(buf)
data += buf
return data
def readsparsesection(self, size):
"""Read a single section of a sparse file.
"""
section = self.sparse.find(self.position)
if section is None:
return b""
size = min(size, section.offset + section.size - self.position)
if isinstance(section, _data):
realpos = section.realpos + self.position - section.offset
self.fileobj.seek(self.offset + realpos)
self.position += size
return self.fileobj.read(size)
else:
self.position += size
return NUL * size
while True:
data, start, stop, offset = self.map[self.map_index]
if start <= self.position < stop:
break
else:
self.map_index += 1
if self.map_index == len(self.map):
self.map_index = 0
length = min(size, stop - self.position)
if data:
self.fileobj.seek(offset)
block = self.fileobj.read(stop - start)
buf += block[self.position - start:self.position + length]
else:
buf += NUL * length
size -= length
self.position += length
return buf
#class _FileInFile
@ -1367,28 +1361,15 @@ def _proc_sparse(self, tarfile):
numbytes = nti(buf[pos + 12:pos + 24])
except ValueError:
break
structs.append((offset, numbytes))
if offset and numbytes:
structs.append((offset, numbytes))
pos += 24
isextended = bool(buf[504])
# Transform the sparse structures to something we can use
# in ExFileObject.
self.sparse = _ringbuffer()
lastpos = 0
realpos = 0
for offset, numbytes in structs:
if offset > lastpos:
self.sparse.append(_hole(lastpos, offset - lastpos))
self.sparse.append(_data(offset, numbytes, realpos))
realpos += numbytes
lastpos = offset + numbytes
if lastpos < origsize:
self.sparse.append(_hole(lastpos, origsize - lastpos))
self.sparse = structs
self.offset_data = tarfile.fileobj.tell()
tarfile.offset = self.offset_data + self._block(self.size)
self.size = origsize
return self
def _proc_pax(self, tarfile):
@ -1464,6 +1445,19 @@ def _proc_pax(self, tarfile):
except HeaderError:
raise SubsequentHeaderError("missing or bad subsequent header")
# Process GNU sparse information.
if "GNU.sparse.map" in pax_headers:
# GNU extended sparse format version 0.1.
self._proc_gnusparse_01(next, pax_headers)
elif "GNU.sparse.size" in pax_headers:
# GNU extended sparse format version 0.0.
self._proc_gnusparse_00(next, pax_headers, buf)
elif pax_headers.get("GNU.sparse.major") == "1" and pax_headers.get("GNU.sparse.minor") == "0":
# GNU extended sparse format version 1.0.
self._proc_gnusparse_10(next, pax_headers, tarfile)
if self.type in (XHDTYPE, SOLARIS_XHDTYPE):
# Patch the TarInfo object with the extended header info.
next._apply_pax_info(pax_headers, tarfile.encoding, tarfile.errors)
@ -1480,24 +1474,59 @@ def _proc_pax(self, tarfile):
return next
def _proc_gnusparse_00(self, next, pax_headers, buf):
"""Process a GNU tar extended sparse header, version 0.0.
"""
offsets = []
for match in re.finditer(br"\d+ GNU.sparse.offset=(\d+)\n", buf):
offsets.append(int(match.group(1)))
numbytes = []
for match in re.finditer(br"\d+ GNU.sparse.numbytes=(\d+)\n", buf):
numbytes.append(int(match.group(1)))
next.sparse = list(zip(offsets, numbytes))
def _proc_gnusparse_01(self, next, pax_headers):
"""Process a GNU tar extended sparse header, version 0.1.
"""
sparse = [int(x) for x in pax_headers["GNU.sparse.map"].split(",")]
next.sparse = list(zip(sparse[::2], sparse[1::2]))
def _proc_gnusparse_10(self, next, pax_headers, tarfile):
"""Process a GNU tar extended sparse header, version 1.0.
"""
fields = None
sparse = []
buf = tarfile.fileobj.read(BLOCKSIZE)
fields, buf = buf.split(b"\n", 1)
fields = int(fields)
while len(sparse) < fields * 2:
if b"\n" not in buf:
buf += tarfile.fileobj.read(BLOCKSIZE)
number, buf = buf.split(b"\n", 1)
sparse.append(int(number))
next.offset_data = tarfile.fileobj.tell()
next.sparse = list(zip(sparse[::2], sparse[1::2]))
def _apply_pax_info(self, pax_headers, encoding, errors):
"""Replace fields with supplemental information from a previous
pax extended or global header.
"""
for keyword, value in pax_headers.items():
if keyword not in PAX_FIELDS:
continue
if keyword == "path":
value = value.rstrip("/")
if keyword in PAX_NUMBER_FIELDS:
try:
value = PAX_NUMBER_FIELDS[keyword](value)
except ValueError:
value = 0
setattr(self, keyword, value)
if keyword == "GNU.sparse.name":
setattr(self, "path", value)
elif keyword == "GNU.sparse.size":
setattr(self, "size", int(value))
elif keyword == "GNU.sparse.realsize":
setattr(self, "size", int(value))
elif keyword in PAX_FIELDS:
if keyword in PAX_NUMBER_FIELDS:
try:
value = PAX_NUMBER_FIELDS[keyword](value)
except ValueError:
value = 0
if keyword == "path":
value = value.rstrip("/")
setattr(self, keyword, value)
self.pax_headers = pax_headers.copy()
@ -1535,7 +1564,7 @@ def isblk(self):
def isfifo(self):
return self.type == FIFOTYPE
def issparse(self):
return self.type == GNUTYPE_SPARSE
return self.sparse is not None
def isdev(self):
return self.type in (CHRTYPE, BLKTYPE, FIFOTYPE)
# class TarInfo
@ -2255,10 +2284,17 @@ def makedir(self, tarinfo, targetpath):
def makefile(self, tarinfo, targetpath):
"""Make a file called targetpath.
"""
source = self.extractfile(tarinfo)
source = self.fileobj
source.seek(tarinfo.offset_data)
target = bltn_open(targetpath, "wb")
copyfileobj(source, target)
source.close()
if tarinfo.sparse is not None:
for offset, size in tarinfo.sparse:
target.seek(offset)
copyfileobj(source, target, size)
else:
copyfileobj(source, target, tarinfo.size)
target.seek(tarinfo.size)
target.truncate()
target.close()
def makeunknown(self, tarinfo, targetpath):
@ -2544,49 +2580,6 @@ def __next__(self):
self.index += 1
return tarinfo
# Helper classes for sparse file support
class _section:
"""Base class for _data and _hole.
"""
def __init__(self, offset, size):
self.offset = offset
self.size = size
def __contains__(self, offset):
return self.offset <= offset < self.offset + self.size
class _data(_section):
"""Represent a data section in a sparse file.
"""
def __init__(self, offset, size, realpos):
_section.__init__(self, offset, size)
self.realpos = realpos
class _hole(_section):
"""Represent a hole section in a sparse file.
"""
pass
class _ringbuffer(list):
"""Ringbuffer class which increases performance
over a regular list.
"""
def __init__(self):
self.idx = 0
def find(self, offset):
idx = self.idx
while True:
item = self[idx]
if offset in item:
break
idx += 1
if idx == len(self):
idx = 0
if idx == self.idx:
# End of File
return None
self.idx = idx
return item
#--------------------
# exported functions
#--------------------

70
Lib/test/test_tarfile.py
View file

@ -526,6 +526,22 @@ def test_find_sparse(self):
tarinfo = self.tar.getmember("ustar/sparse")
self._test_member(tarinfo, size=86016, chksum=md5_sparse)
def test_find_gnusparse(self):
tarinfo = self.tar.getmember("gnu/sparse")
self._test_member(tarinfo, size=86016, chksum=md5_sparse)
def test_find_gnusparse_00(self):
tarinfo = self.tar.getmember("gnu/sparse-0.0")
self._test_member(tarinfo, size=86016, chksum=md5_sparse)
def test_find_gnusparse_01(self):
tarinfo = self.tar.getmember("gnu/sparse-0.1")
self._test_member(tarinfo, size=86016, chksum=md5_sparse)
def test_find_gnusparse_10(self):
tarinfo = self.tar.getmember("gnu/sparse-1.0")
self._test_member(tarinfo, size=86016, chksum=md5_sparse)
def test_find_umlauts(self):
tarinfo = self.tar.getmember("ustar/umlauts-\xc4\xd6\xdc\xe4\xf6\xfc\xdf")
self._test_member(tarinfo, size=7011, chksum=md5_regtype)
@ -589,13 +605,53 @@ class GNUReadTest(LongnameTest):
subdir = "gnu"
longnametype = tarfile.GNUTYPE_LONGNAME
def test_sparse_file(self):
tarinfo1 = self.tar.getmember("ustar/sparse")
fobj1 = self.tar.extractfile(tarinfo1)
tarinfo2 = self.tar.getmember("gnu/sparse")
fobj2 = self.tar.extractfile(tarinfo2)
self.assertEqual(fobj1.read(), fobj2.read(),
"sparse file extraction failed")
# Since 3.2 tarfile is supposed to accurately restore sparse members and
# produce files with holes. This is what we actually want to test here.
# Unfortunately, not all platforms/filesystems support sparse files, and
# even on platforms that do it is non-trivial to make reliable assertions
# about holes in files. Therefore, we first do one basic test which works
# an all platforms, and after that a test that will work only on
# platforms/filesystems that prove to support sparse files.
def _test_sparse_file(self, name):
self.tar.extract(name, TEMPDIR)
filename = os.path.join(TEMPDIR, name)
with open(filename, "rb") as fobj:
data = fobj.read()
self.assertEqual(md5sum(data), md5_sparse,
"wrong md5sum for %s" % name)
if self._fs_supports_holes():
s = os.stat(filename)
self.assertTrue(s.st_blocks * 512 < s.st_size)
def test_sparse_file_old(self):
self._test_sparse_file("gnu/sparse")
def test_sparse_file_00(self):
self._test_sparse_file("gnu/sparse-0.0")
def test_sparse_file_01(self):
self._test_sparse_file("gnu/sparse-0.1")
def test_sparse_file_10(self):
self._test_sparse_file("gnu/sparse-1.0")
@staticmethod
def _fs_supports_holes():
# Return True if the platform knows the st_blocks stat attribute and
# uses st_blocks units of 512 bytes, and if the filesystem is able to
# store holes in files.
if sys.platform == "linux2":
# Linux evidentially has 512 byte st_blocks units.
name = os.path.join(TEMPDIR, "sparse-test")
with open(name, "wb") as fobj:
fobj.seek(4096)
fobj.truncate()
s = os.stat(name)
os.remove(name)
return s.st_blocks == 0
else:
return False
class PaxReadTest(LongnameTest):

BIN
Lib/test/testtar.tar
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Binary file not shown.

3
Misc/NEWS
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@ -54,6 +54,9 @@ Core and Builtins
Library
-------
- tarfile.py: Add support for all missing variants of the GNU sparse
extensions and create files with holes when extracting sparse members.
- Issue #10218: Return timeout status from ``Condition.wait`` in threading.
- Issue #7351: Add ``zipfile.BadZipFile`` spelling of the exception name