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Diffstat (limited to 'venv/lib/python3.9/site-packages/gitdb/stream.py')
| -rw-r--r-- | venv/lib/python3.9/site-packages/gitdb/stream.py | 730 |
1 files changed, 730 insertions, 0 deletions
diff --git a/venv/lib/python3.9/site-packages/gitdb/stream.py b/venv/lib/python3.9/site-packages/gitdb/stream.py new file mode 100644 index 00000000..222b843e --- /dev/null +++ b/venv/lib/python3.9/site-packages/gitdb/stream.py @@ -0,0 +1,730 @@ +# Copyright (C) 2010, 2011 Sebastian Thiel (byronimo@gmail.com) and contributors +# +# This module is part of GitDB and is released under +# the New BSD License: http://www.opensource.org/licenses/bsd-license.php + +from io import BytesIO + +import mmap +import os +import sys +import zlib + +from gitdb.fun import ( + msb_size, + stream_copy, + apply_delta_data, + connect_deltas, + delta_types +) + +from gitdb.util import ( + allocate_memory, + LazyMixin, + make_sha, + write, + close, +) + +from gitdb.const import NULL_BYTE, BYTE_SPACE +from gitdb.utils.encoding import force_bytes + +has_perf_mod = False +try: + from gitdb_speedups._perf import apply_delta as c_apply_delta + has_perf_mod = True +except ImportError: + pass + +__all__ = ('DecompressMemMapReader', 'FDCompressedSha1Writer', 'DeltaApplyReader', + 'Sha1Writer', 'FlexibleSha1Writer', 'ZippedStoreShaWriter', 'FDCompressedSha1Writer', + 'FDStream', 'NullStream') + + +#{ RO Streams + +class DecompressMemMapReader(LazyMixin): + + """Reads data in chunks from a memory map and decompresses it. The client sees + only the uncompressed data, respective file-like read calls are handling on-demand + buffered decompression accordingly + + A constraint on the total size of bytes is activated, simulating + a logical file within a possibly larger physical memory area + + To read efficiently, you clearly don't want to read individual bytes, instead, + read a few kilobytes at least. + + **Note:** The chunk-size should be carefully selected as it will involve quite a bit + of string copying due to the way the zlib is implemented. Its very wasteful, + hence we try to find a good tradeoff between allocation time and number of + times we actually allocate. An own zlib implementation would be good here + to better support streamed reading - it would only need to keep the mmap + and decompress it into chunks, that's all ... """ + __slots__ = ('_m', '_zip', '_buf', '_buflen', '_br', '_cws', '_cwe', '_s', '_close', + '_cbr', '_phi') + + max_read_size = 512 * 1024 # currently unused + + def __init__(self, m, close_on_deletion, size=None): + """Initialize with mmap for stream reading + :param m: must be content data - use new if you have object data and no size""" + self._m = m + self._zip = zlib.decompressobj() + self._buf = None # buffer of decompressed bytes + self._buflen = 0 # length of bytes in buffer + if size is not None: + self._s = size # size of uncompressed data to read in total + self._br = 0 # num uncompressed bytes read + self._cws = 0 # start byte of compression window + self._cwe = 0 # end byte of compression window + self._cbr = 0 # number of compressed bytes read + self._phi = False # is True if we parsed the header info + self._close = close_on_deletion # close the memmap on deletion ? + + def _set_cache_(self, attr): + assert attr == '_s' + # only happens for size, which is a marker to indicate we still + # have to parse the header from the stream + self._parse_header_info() + + def __del__(self): + self.close() + + def _parse_header_info(self): + """If this stream contains object data, parse the header info and skip the + stream to a point where each read will yield object content + + :return: parsed type_string, size""" + # read header + # should really be enough, cgit uses 8192 I believe + # And for good reason !! This needs to be that high for the header to be read correctly in all cases + maxb = 8192 + self._s = maxb + hdr = self.read(maxb) + hdrend = hdr.find(NULL_BYTE) + typ, size = hdr[:hdrend].split(BYTE_SPACE) + size = int(size) + self._s = size + + # adjust internal state to match actual header length that we ignore + # The buffer will be depleted first on future reads + self._br = 0 + hdrend += 1 + self._buf = BytesIO(hdr[hdrend:]) + self._buflen = len(hdr) - hdrend + + self._phi = True + + return typ, size + + #{ Interface + + @classmethod + def new(self, m, close_on_deletion=False): + """Create a new DecompressMemMapReader instance for acting as a read-only stream + This method parses the object header from m and returns the parsed + type and size, as well as the created stream instance. + + :param m: memory map on which to operate. It must be object data ( header + contents ) + :param close_on_deletion: if True, the memory map will be closed once we are + being deleted""" + inst = DecompressMemMapReader(m, close_on_deletion, 0) + typ, size = inst._parse_header_info() + return typ, size, inst + + def data(self): + """:return: random access compatible data we are working on""" + return self._m + + def close(self): + """Close our underlying stream of compressed bytes if this was allowed during initialization + :return: True if we closed the underlying stream + :note: can be called safely + """ + if self._close: + if hasattr(self._m, 'close'): + self._m.close() + self._close = False + # END handle resource freeing + + def compressed_bytes_read(self): + """ + :return: number of compressed bytes read. This includes the bytes it + took to decompress the header ( if there was one )""" + # ABSTRACT: When decompressing a byte stream, it can be that the first + # x bytes which were requested match the first x bytes in the loosely + # compressed datastream. This is the worst-case assumption that the reader + # does, it assumes that it will get at least X bytes from X compressed bytes + # in call cases. + # The caveat is that the object, according to our known uncompressed size, + # is already complete, but there are still some bytes left in the compressed + # stream that contribute to the amount of compressed bytes. + # How can we know that we are truly done, and have read all bytes we need + # to read ? + # Without help, we cannot know, as we need to obtain the status of the + # decompression. If it is not finished, we need to decompress more data + # until it is finished, to yield the actual number of compressed bytes + # belonging to the decompressed object + # We are using a custom zlib module for this, if its not present, + # we try to put in additional bytes up for decompression if feasible + # and check for the unused_data. + + # Only scrub the stream forward if we are officially done with the + # bytes we were to have. + if self._br == self._s and not self._zip.unused_data: + # manipulate the bytes-read to allow our own read method to continue + # but keep the window at its current position + self._br = 0 + if hasattr(self._zip, 'status'): + while self._zip.status == zlib.Z_OK: + self.read(mmap.PAGESIZE) + # END scrub-loop custom zlib + else: + # pass in additional pages, until we have unused data + while not self._zip.unused_data and self._cbr != len(self._m): + self.read(mmap.PAGESIZE) + # END scrub-loop default zlib + # END handle stream scrubbing + + # reset bytes read, just to be sure + self._br = self._s + # END handle stream scrubbing + + # unused data ends up in the unconsumed tail, which was removed + # from the count already + return self._cbr + + #} END interface + + def seek(self, offset, whence=getattr(os, 'SEEK_SET', 0)): + """Allows to reset the stream to restart reading + :raise ValueError: If offset and whence are not 0""" + if offset != 0 or whence != getattr(os, 'SEEK_SET', 0): + raise ValueError("Can only seek to position 0") + # END handle offset + + self._zip = zlib.decompressobj() + self._br = self._cws = self._cwe = self._cbr = 0 + if self._phi: + self._phi = False + del(self._s) # trigger header parsing on first access + # END skip header + + def read(self, size=-1): + if size < 1: + size = self._s - self._br + else: + size = min(size, self._s - self._br) + # END clamp size + + if size == 0: + return b'' + # END handle depletion + + # deplete the buffer, then just continue using the decompress object + # which has an own buffer. We just need this to transparently parse the + # header from the zlib stream + dat = b'' + if self._buf: + if self._buflen >= size: + # have enough data + dat = self._buf.read(size) + self._buflen -= size + self._br += size + return dat + else: + dat = self._buf.read() # ouch, duplicates data + size -= self._buflen + self._br += self._buflen + + self._buflen = 0 + self._buf = None + # END handle buffer len + # END handle buffer + + # decompress some data + # Abstract: zlib needs to operate on chunks of our memory map ( which may + # be large ), as it will otherwise and always fill in the 'unconsumed_tail' + # attribute which possible reads our whole map to the end, forcing + # everything to be read from disk even though just a portion was requested. + # As this would be a nogo, we workaround it by passing only chunks of data, + # moving the window into the memory map along as we decompress, which keeps + # the tail smaller than our chunk-size. This causes 'only' the chunk to be + # copied once, and another copy of a part of it when it creates the unconsumed + # tail. We have to use it to hand in the appropriate amount of bytes during + # the next read. + tail = self._zip.unconsumed_tail + if tail: + # move the window, make it as large as size demands. For code-clarity, + # we just take the chunk from our map again instead of reusing the unconsumed + # tail. The latter one would safe some memory copying, but we could end up + # with not getting enough data uncompressed, so we had to sort that out as well. + # Now we just assume the worst case, hence the data is uncompressed and the window + # needs to be as large as the uncompressed bytes we want to read. + self._cws = self._cwe - len(tail) + self._cwe = self._cws + size + else: + cws = self._cws + self._cws = self._cwe + self._cwe = cws + size + # END handle tail + + # if window is too small, make it larger so zip can decompress something + if self._cwe - self._cws < 8: + self._cwe = self._cws + 8 + # END adjust winsize + + # takes a slice, but doesn't copy the data, it says ... + indata = self._m[self._cws:self._cwe] + + # get the actual window end to be sure we don't use it for computations + self._cwe = self._cws + len(indata) + dcompdat = self._zip.decompress(indata, size) + # update the amount of compressed bytes read + # We feed possibly overlapping chunks, which is why the unconsumed tail + # has to be taken into consideration, as well as the unused data + # if we hit the end of the stream + # NOTE: Behavior changed in PY2.7 onward, which requires special handling to make the tests work properly. + # They are thorough, and I assume it is truly working. + # Why is this logic as convoluted as it is ? Please look at the table in + # https://github.com/gitpython-developers/gitdb/issues/19 to learn about the test-results. + # Basically, on py2.6, you want to use branch 1, whereas on all other python version, the second branch + # will be the one that works. + # However, the zlib VERSIONs as well as the platform check is used to further match the entries in the + # table in the github issue. This is it ... it was the only way I could make this work everywhere. + # IT's CERTAINLY GOING TO BITE US IN THE FUTURE ... . + if zlib.ZLIB_VERSION in ('1.2.7', '1.2.5') and not sys.platform == 'darwin': + unused_datalen = len(self._zip.unconsumed_tail) + else: + unused_datalen = len(self._zip.unconsumed_tail) + len(self._zip.unused_data) + # # end handle very special case ... + + self._cbr += len(indata) - unused_datalen + self._br += len(dcompdat) + + if dat: + dcompdat = dat + dcompdat + # END prepend our cached data + + # it can happen, depending on the compression, that we get less bytes + # than ordered as it needs the final portion of the data as well. + # Recursively resolve that. + # Note: dcompdat can be empty even though we still appear to have bytes + # to read, if we are called by compressed_bytes_read - it manipulates + # us to empty the stream + if dcompdat and (len(dcompdat) - len(dat)) < size and self._br < self._s: + dcompdat += self.read(size - len(dcompdat)) + # END handle special case + return dcompdat + + +class DeltaApplyReader(LazyMixin): + + """A reader which dynamically applies pack deltas to a base object, keeping the + memory demands to a minimum. + + The size of the final object is only obtainable once all deltas have been + applied, unless it is retrieved from a pack index. + + The uncompressed Delta has the following layout (MSB being a most significant + bit encoded dynamic size): + + * MSB Source Size - the size of the base against which the delta was created + * MSB Target Size - the size of the resulting data after the delta was applied + * A list of one byte commands (cmd) which are followed by a specific protocol: + + * cmd & 0x80 - copy delta_data[offset:offset+size] + + * Followed by an encoded offset into the delta data + * Followed by an encoded size of the chunk to copy + + * cmd & 0x7f - insert + + * insert cmd bytes from the delta buffer into the output stream + + * cmd == 0 - invalid operation ( or error in delta stream ) + """ + __slots__ = ( + "_bstream", # base stream to which to apply the deltas + "_dstreams", # tuple of delta stream readers + "_mm_target", # memory map of the delta-applied data + "_size", # actual number of bytes in _mm_target + "_br" # number of bytes read + ) + + #{ Configuration + k_max_memory_move = 250 * 1000 * 1000 + #} END configuration + + def __init__(self, stream_list): + """Initialize this instance with a list of streams, the first stream being + the delta to apply on top of all following deltas, the last stream being the + base object onto which to apply the deltas""" + assert len(stream_list) > 1, "Need at least one delta and one base stream" + + self._bstream = stream_list[-1] + self._dstreams = tuple(stream_list[:-1]) + self._br = 0 + + def _set_cache_too_slow_without_c(self, attr): + # the direct algorithm is fastest and most direct if there is only one + # delta. Also, the extra overhead might not be worth it for items smaller + # than X - definitely the case in python, every function call costs + # huge amounts of time + # if len(self._dstreams) * self._bstream.size < self.k_max_memory_move: + if len(self._dstreams) == 1: + return self._set_cache_brute_(attr) + + # Aggregate all deltas into one delta in reverse order. Hence we take + # the last delta, and reverse-merge its ancestor delta, until we receive + # the final delta data stream. + dcl = connect_deltas(self._dstreams) + + # call len directly, as the (optional) c version doesn't implement the sequence + # protocol + if dcl.rbound() == 0: + self._size = 0 + self._mm_target = allocate_memory(0) + return + # END handle empty list + + self._size = dcl.rbound() + self._mm_target = allocate_memory(self._size) + + bbuf = allocate_memory(self._bstream.size) + stream_copy(self._bstream.read, bbuf.write, self._bstream.size, 256 * mmap.PAGESIZE) + + # APPLY CHUNKS + write = self._mm_target.write + dcl.apply(bbuf, write) + + self._mm_target.seek(0) + + def _set_cache_brute_(self, attr): + """If we are here, we apply the actual deltas""" + # TODO: There should be a special case if there is only one stream + # Then the default-git algorithm should perform a tad faster, as the + # delta is not peaked into, causing less overhead. + buffer_info_list = list() + max_target_size = 0 + for dstream in self._dstreams: + buf = dstream.read(512) # read the header information + X + offset, src_size = msb_size(buf) + offset, target_size = msb_size(buf, offset) + buffer_info_list.append((buf[offset:], offset, src_size, target_size)) + max_target_size = max(max_target_size, target_size) + # END for each delta stream + + # sanity check - the first delta to apply should have the same source + # size as our actual base stream + base_size = self._bstream.size + target_size = max_target_size + + # if we have more than 1 delta to apply, we will swap buffers, hence we must + # assure that all buffers we use are large enough to hold all the results + if len(self._dstreams) > 1: + base_size = target_size = max(base_size, max_target_size) + # END adjust buffer sizes + + # Allocate private memory map big enough to hold the first base buffer + # We need random access to it + bbuf = allocate_memory(base_size) + stream_copy(self._bstream.read, bbuf.write, base_size, 256 * mmap.PAGESIZE) + + # allocate memory map large enough for the largest (intermediate) target + # We will use it as scratch space for all delta ops. If the final + # target buffer is smaller than our allocated space, we just use parts + # of it upon return. + tbuf = allocate_memory(target_size) + + # for each delta to apply, memory map the decompressed delta and + # work on the op-codes to reconstruct everything. + # For the actual copying, we use a seek and write pattern of buffer + # slices. + final_target_size = None + for (dbuf, offset, src_size, target_size), dstream in zip(reversed(buffer_info_list), reversed(self._dstreams)): + # allocate a buffer to hold all delta data - fill in the data for + # fast access. We do this as we know that reading individual bytes + # from our stream would be slower than necessary ( although possible ) + # The dbuf buffer contains commands after the first two MSB sizes, the + # offset specifies the amount of bytes read to get the sizes. + ddata = allocate_memory(dstream.size - offset) + ddata.write(dbuf) + # read the rest from the stream. The size we give is larger than necessary + stream_copy(dstream.read, ddata.write, dstream.size, 256 * mmap.PAGESIZE) + + ####################################################################### + if 'c_apply_delta' in globals(): + c_apply_delta(bbuf, ddata, tbuf) + else: + apply_delta_data(bbuf, src_size, ddata, len(ddata), tbuf.write) + ####################################################################### + + # finally, swap out source and target buffers. The target is now the + # base for the next delta to apply + bbuf, tbuf = tbuf, bbuf + bbuf.seek(0) + tbuf.seek(0) + final_target_size = target_size + # END for each delta to apply + + # its already seeked to 0, constrain it to the actual size + # NOTE: in the end of the loop, it swaps buffers, hence our target buffer + # is not tbuf, but bbuf ! + self._mm_target = bbuf + self._size = final_target_size + + #{ Configuration + if not has_perf_mod: + _set_cache_ = _set_cache_brute_ + else: + _set_cache_ = _set_cache_too_slow_without_c + + #} END configuration + + def read(self, count=0): + bl = self._size - self._br # bytes left + if count < 1 or count > bl: + count = bl + # NOTE: we could check for certain size limits, and possibly + # return buffers instead of strings to prevent byte copying + data = self._mm_target.read(count) + self._br += len(data) + return data + + def seek(self, offset, whence=getattr(os, 'SEEK_SET', 0)): + """Allows to reset the stream to restart reading + + :raise ValueError: If offset and whence are not 0""" + if offset != 0 or whence != getattr(os, 'SEEK_SET', 0): + raise ValueError("Can only seek to position 0") + # END handle offset + self._br = 0 + self._mm_target.seek(0) + + #{ Interface + + @classmethod + def new(cls, stream_list): + """ + Convert the given list of streams into a stream which resolves deltas + when reading from it. + + :param stream_list: two or more stream objects, first stream is a Delta + to the object that you want to resolve, followed by N additional delta + streams. The list's last stream must be a non-delta stream. + + :return: Non-Delta OPackStream object whose stream can be used to obtain + the decompressed resolved data + :raise ValueError: if the stream list cannot be handled""" + if len(stream_list) < 2: + raise ValueError("Need at least two streams") + # END single object special handling + + if stream_list[-1].type_id in delta_types: + raise ValueError( + "Cannot resolve deltas if there is no base object stream, last one was type: %s" % stream_list[-1].type) + # END check stream + return cls(stream_list) + + #} END interface + + #{ OInfo like Interface + + @property + def type(self): + return self._bstream.type + + @property + def type_id(self): + return self._bstream.type_id + + @property + def size(self): + """:return: number of uncompressed bytes in the stream""" + return self._size + + #} END oinfo like interface + + +#} END RO streams + + +#{ W Streams + +class Sha1Writer: + + """Simple stream writer which produces a sha whenever you like as it degests + everything it is supposed to write""" + __slots__ = "sha1" + + def __init__(self): + self.sha1 = make_sha() + + #{ Stream Interface + + def write(self, data): + """:raise IOError: If not all bytes could be written + :param data: byte object + :return: length of incoming data""" + + self.sha1.update(data) + + return len(data) + + # END stream interface + + #{ Interface + + def sha(self, as_hex=False): + """:return: sha so far + :param as_hex: if True, sha will be hex-encoded, binary otherwise""" + if as_hex: + return self.sha1.hexdigest() + return self.sha1.digest() + + #} END interface + + +class FlexibleSha1Writer(Sha1Writer): + + """Writer producing a sha1 while passing on the written bytes to the given + write function""" + __slots__ = 'writer' + + def __init__(self, writer): + Sha1Writer.__init__(self) + self.writer = writer + + def write(self, data): + Sha1Writer.write(self, data) + self.writer(data) + + +class ZippedStoreShaWriter(Sha1Writer): + + """Remembers everything someone writes to it and generates a sha""" + __slots__ = ('buf', 'zip') + + def __init__(self): + Sha1Writer.__init__(self) + self.buf = BytesIO() + self.zip = zlib.compressobj(zlib.Z_BEST_SPEED) + + def __getattr__(self, attr): + return getattr(self.buf, attr) + + def write(self, data): + alen = Sha1Writer.write(self, data) + self.buf.write(self.zip.compress(data)) + + return alen + + def close(self): + self.buf.write(self.zip.flush()) + + def seek(self, offset, whence=getattr(os, 'SEEK_SET', 0)): + """Seeking currently only supports to rewind written data + Multiple writes are not supported""" + if offset != 0 or whence != getattr(os, 'SEEK_SET', 0): + raise ValueError("Can only seek to position 0") + # END handle offset + self.buf.seek(0) + + def getvalue(self): + """:return: string value from the current stream position to the end""" + return self.buf.getvalue() + + +class FDCompressedSha1Writer(Sha1Writer): + + """Digests data written to it, making the sha available, then compress the + data and write it to the file descriptor + + **Note:** operates on raw file descriptors + **Note:** for this to work, you have to use the close-method of this instance""" + __slots__ = ("fd", "sha1", "zip") + + # default exception + exc = IOError("Failed to write all bytes to filedescriptor") + + def __init__(self, fd): + super().__init__() + self.fd = fd + self.zip = zlib.compressobj(zlib.Z_BEST_SPEED) + + #{ Stream Interface + + def write(self, data): + """:raise IOError: If not all bytes could be written + :return: length of incoming data""" + self.sha1.update(data) + cdata = self.zip.compress(data) + bytes_written = write(self.fd, cdata) + + if bytes_written != len(cdata): + raise self.exc + + return len(data) + + def close(self): + remainder = self.zip.flush() + if write(self.fd, remainder) != len(remainder): + raise self.exc + return close(self.fd) + + #} END stream interface + + +class FDStream: + + """A simple wrapper providing the most basic functions on a file descriptor + with the fileobject interface. Cannot use os.fdopen as the resulting stream + takes ownership""" + __slots__ = ("_fd", '_pos') + + def __init__(self, fd): + self._fd = fd + self._pos = 0 + + def write(self, data): + self._pos += len(data) + os.write(self._fd, data) + + def read(self, count=0): + if count == 0: + count = os.path.getsize(self._filepath) + # END handle read everything + + bytes = os.read(self._fd, count) + self._pos += len(bytes) + return bytes + + def fileno(self): + return self._fd + + def tell(self): + return self._pos + + def close(self): + close(self._fd) + + +class NullStream: + + """A stream that does nothing but providing a stream interface. + Use it like /dev/null""" + __slots__ = tuple() + + def read(self, size=0): + return '' + + def close(self): + pass + + def write(self, data): + return len(data) + + +#} END W streams |