gecko-dev/config/MozZipFile.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

import os
import time
import zipfile

import six
from mozbuild.lock import lock_file


class ZipFile(zipfile.ZipFile):
    """Class with methods to open, read, write, close, list zip files.

    Subclassing zipfile.ZipFile to allow for overwriting of existing
    entries, though only for writestr, not for write.
    """

    def __init__(self, file, mode="r", compression=zipfile.ZIP_STORED, lock=False):
        if lock:
            assert isinstance(file, six.text_type)
            self.lockfile = lock_file(file + ".lck")
        else:
            self.lockfile = None

        if mode == "a" and lock:
            # appending to a file which doesn't exist fails, but we can't check
            # existence util we hold the lock
            if (not os.path.isfile(file)) or os.path.getsize(file) == 0:
                mode = "w"

        zipfile.ZipFile.__init__(self, file, mode, compression)
        self._remove = []
        self.end = self.fp.tell()
        self.debug = 0

    def writestr(self, zinfo_or_arcname, bytes):
        """Write contents into the archive.

        The contents is the argument 'bytes',  'zinfo_or_arcname' is either
        a ZipInfo instance or the name of the file in the archive.
        This method is overloaded to allow overwriting existing entries.
        """
        if not isinstance(zinfo_or_arcname, zipfile.ZipInfo):
            zinfo = zipfile.ZipInfo(
                filename=zinfo_or_arcname, date_time=time.localtime(time.time())
            )
            zinfo.compress_type = self.compression
            # Add some standard UNIX file access permissions (-rw-r--r--).
            zinfo.external_attr = (0x81A4 & 0xFFFF) << 16
        else:
            zinfo = zinfo_or_arcname

        # Now to the point why we overwrote this in the first place,
        # remember the entry numbers if we already had this entry.
        # Optimizations:
        # If the entry to overwrite is the last one, just reuse that.
        # If we store uncompressed and the new content has the same size
        # as the old, reuse the existing entry.

        doSeek = False  # store if we need to seek to the eof after overwriting
        if zinfo.filename in self.NameToInfo:
            # Find the last ZipInfo with our name.
            # Last, because that's catching multiple overwrites
            i = len(self.filelist)
            while i > 0:
                i -= 1
                if self.filelist[i].filename == zinfo.filename:
                    break
            zi = self.filelist[i]
            if (
                zinfo.compress_type == zipfile.ZIP_STORED
                and zi.compress_size == len(bytes)
            ) or (i + 1) == len(self.filelist):
                # make sure we're allowed to write, otherwise done by writestr below
                self._writecheck(zi)
                # overwrite existing entry
                self.fp.seek(zi.header_offset)
                if (i + 1) == len(self.filelist):
                    # this is the last item in the file, just truncate
                    self.fp.truncate()
                else:
                    # we need to move to the end of the file afterwards again
                    doSeek = True
                # unhook the current zipinfo, the writestr of our superclass
                # will add a new one
                self.filelist.pop(i)
                self.NameToInfo.pop(zinfo.filename)
            else:
                # Couldn't optimize, sadly, just remember the old entry for removal
                self._remove.append(self.filelist.pop(i))
        zipfile.ZipFile.writestr(self, zinfo, bytes)
        self.filelist.sort(key=lambda l: l.header_offset)
        if doSeek:
            self.fp.seek(self.end)
        self.end = self.fp.tell()

    def close(self):
        """Close the file, and for mode "w" and "a" write the ending
        records.

        Overwritten to compact overwritten entries.
        """
        if not self._remove:
            # we don't have anything special to do, let's just call base
            r = zipfile.ZipFile.close(self)
            self.lockfile = None
            return r

        if self.fp.mode != "r+b":
            # adjust file mode if we originally just wrote, now we rewrite
            self.fp.close()
            self.fp = open(self.filename, "r+b")
        all = map(lambda zi: (zi, True), self.filelist) + map(
            lambda zi: (zi, False), self._remove
        )
        all.sort(key=lambda l: l[0].header_offset)
        # empty _remove for multiple closes
        self._remove = []

        lengths = [
            all[i + 1][0].header_offset - all[i][0].header_offset
            for i in xrange(len(all) - 1)
        ]
        lengths.append(self.end - all[-1][0].header_offset)
        to_pos = 0
        for (zi, keep), length in zip(all, lengths):
            if not keep:
                continue
            oldoff = zi.header_offset
            # python <= 2.4 has file_offset
            if hasattr(zi, "file_offset"):
                zi.file_offset = zi.file_offset + to_pos - oldoff
            zi.header_offset = to_pos
            self.fp.seek(oldoff)
            content = self.fp.read(length)
            self.fp.seek(to_pos)
            self.fp.write(content)
            to_pos += length
        self.fp.truncate()
        zipfile.ZipFile.close(self)
        self.lockfile = None