diff options
Diffstat (limited to 'lib/git/odb')
| -rw-r--r-- | lib/git/odb/db.py | 114 | ||||
| -rw-r--r-- | lib/git/odb/fun.py | 114 | ||||
| -rw-r--r-- | lib/git/odb/utils.py | 147 |
3 files changed, 322 insertions, 53 deletions
diff --git a/lib/git/odb/db.py b/lib/git/odb/db.py index 1248a3f4..5c50a512 100644 --- a/lib/git/odb/db.py +++ b/lib/git/odb/db.py @@ -1,17 +1,18 @@ """Contains implementations of database retrieveing objects""" -import os +from git.utils import IndexFileSHA1Writer from git.errors import ( InvalidDBRoot, - BadObject + BadObject, + BadObjectType ) -from git.utils import IndexFileSHA1Writer from utils import ( - getsize, + DecompressMemMapReader, + FDCompressedSha1Writer, + ENOENT, to_hex_sha, exists, hex_to_bin, - FDCompressedSha1Writer, isdir, mkdir, rename, @@ -19,8 +20,15 @@ from utils import ( join ) +from fun import ( + chunk_size, + loose_object_header_info, + write_object + ) + import tempfile import mmap +import os class iObjectDBR(object): @@ -36,7 +44,8 @@ class iObjectDBR(object): def has_object(self, sha): """ :return: True if the object identified by the given 40 byte hexsha or 20 bytes - binary sha is contained in the database""" + binary sha is contained in the database + :raise BadObject:""" raise NotImplementedError("To be implemented in subclass") def object(self, sha): @@ -44,14 +53,16 @@ class iObjectDBR(object): :return: tuple(type_string, size_in_bytes, stream) a tuple with object information including its type, its size as well as a stream from which its contents can be read - :param sha: 40 bytes hexsha or 20 bytes binary sha """ + :param sha: 40 bytes hexsha or 20 bytes binary sha + :raise BadObject:""" raise NotImplementedError("To be implemented in subclass") def object_info(self, sha): """ :return: tuple(type_string, size_in_bytes) tuple with the object's type string as well as its size in bytes - :param sha: 40 bytes hexsha or 20 bytes binary sha""" + :param sha: 40 bytes hexsha or 20 bytes binary sha + :raise BadObject:""" raise NotImplementedError("To be implemented in subclass") #} END query interface @@ -70,7 +81,8 @@ class iObjectDBW(object): :param stream: stream providing the data :param dry_run: if True, the object database will not actually be changed :param sha_as_hex: if True, the returned sha identifying the object will be - hex encoded, not binary""" + hex encoded, not binary + :raise IOError: if data could not be written""" raise NotImplementedError("To be implemented in subclass") def to_objects(self, iter_info, dry_run=False, sha_as_hex=True, max_threads=0): @@ -82,7 +94,8 @@ class iObjectDBW(object): :param dry_run: see ``to_obj`` :param sha_as_hex: see ``to_obj`` :param max_threads: if < 1, any number of threads may be started while processing - the request, otherwise the given number of threads will be started.""" + the request, otherwise the given number of threads will be started. + :raise IOError: if data could not be written""" # a trivial implementation, ignoring the threads for now # TODO: add configuration to the class to determine whether we may # actually use multiple threads, default False of course. If the add @@ -130,15 +143,19 @@ class FileDBBase(object): class LooseObjectDB(FileDBBase, iObjectDBR, iObjectDBW): """A database which operates on loose object files""" - __slots__ = ('_hexsha_to_file', ) - + __slots__ = ('_hexsha_to_file', '_fd_open_flags') # CONFIGURATION # chunks in which data will be copied between streams - stream_chunk_size = 1000*1000 + stream_chunk_size = chunk_size + def __init__(self, root_path): super(LooseObjectDB, self).__init__(root_path) self._hexsha_to_file = dict() + # Additional Flags - might be set to 0 after the first failure + # Depending on the root, this might work for some mounts, for others not, which + # is why it is per instance + self._fd_open_flags = os.O_NOATIME #{ Interface def object_path(self, hexsha): @@ -167,36 +184,46 @@ class LooseObjectDB(FileDBBase, iObjectDBR, iObjectDBW): #} END interface - def _object_header_info(self, mmap): - """:return: tuple(type_string, uncompressed_size_in_bytes - :param mmap: newly mapped memory map at position 0. It will be - seeked to the actual start of the object contents, which can be used - to initialize a zlib decompress object.""" - raise NotImplementedError("todo") - - def _map_object(self, sha): + def _map_loose_object(self, sha): """ - :return: tuple(file, mmap) tuple with an opened file for reading, and - a memory map of that file""" - db_path = self.readable_db_object_path(to_hex_sha(sha)) - f = open(db_path, 'rb') - m = mmap.mmap(f.fileno(), getsize(db_path), access=mmap.ACCESS_READ) - return (f, m) + :return: memory map of that file to allow random read access + :raise BadObject: if object could not be located""" + db_path = self.db_path(self.object_path(to_hex_sha(sha))) + try: + fd = os.open(db_path, os.O_RDONLY|self._fd_open_flags) + except OSError,e: + if e.errno != ENOENT: + # try again without noatime + try: + fd = os.open(db_path, os.O_RDONLY) + except OSError: + raise BadObject(to_hex_sha(sha)) + # didn't work because of our flag, don't try it again + self._fd_open_flags = 0 + else: + raise BadObject(to_hex_sha(sha)) + # END handle error + # END exception handling + try: + return mmap.mmap(fd, 0, access=mmap.ACCESS_READ) + finally: + os.close(fd) + # END assure file is closed def object_info(self, sha): - f, m = self._map_object(sha) + m = self._map_loose_object(sha) try: - type, size = self._object_header_info(m) + return loose_object_header_info(m) finally: - f.close() m.close() # END assure release of system resources def object(self, sha): - f, m = self._map_object(sha) - type, size = self._object_header_info(m) - # TODO: init a dynamic decompress stream from our memory map + m = self._map_loose_object(sha) + reader = DecompressMemMapReader(m, close_on_deletion = True) + type, size = reader.initialize() + return type, size, reader def has_object(self, sha): try: @@ -210,25 +237,10 @@ class LooseObjectDB(FileDBBase, iObjectDBR, iObjectDBW): # open a tmp file to write the data to fd, tmp_path = tempfile.mkstemp(prefix='obj', dir=self._root_path) writer = FDCompressedSha1Writer(fd) - - # WRITE HEADER: type SP size NULL - writer.write("%s %i%s" % (type, size, chr(0))) - - # WRITE ALL DATA - chunksize = self.stream_chunk_size + try: - try: - while True: - data_len = writer.write(stream.read(chunksize)) - if data_len < chunksize: - # WRITE FOOTER - writer.write('\n') - break - # END check for stream end - # END duplicate data - finally: - writer.close() - # END assure file was closed + write_object(type, size, stream, writer, + close_target_stream=True, chunk_size=self.stream_chunk_size) except: os.remove(tmp_path) raise diff --git a/lib/git/odb/fun.py b/lib/git/odb/fun.py new file mode 100644 index 00000000..ee7144dd --- /dev/null +++ b/lib/git/odb/fun.py @@ -0,0 +1,114 @@ +"""Contains basic c-functions which usually contain performance critical code +Keeping this code separate from the beginning makes it easier to out-source +it into c later, if required""" + +from git.errors import ( + BadObjectType + ) + +import zlib +decompressobj = zlib.decompressobj + + +# INVARIANTS +type_id_to_type_map = { + 1 : "commit", + 2 : "tree", + 3 : "blob", + 4 : "tag" + } + +# used when dealing with larger streams +chunk_size = 1000*1000 + + +#{ Routines + +def is_loose_object(m): + """:return: True the file contained in memory map m appears to be a loose object. + Only the first two bytes are needed""" + b0, b1 = map(ord, m[:2]) + word = (b0 << 8) + b1 + return b0 == 0x78 and (word % 31) == 0 + +def loose_object_header_info(m): + """:return: tuple(type_string, uncompressed_size_in_bytes) the type string of the + object as well as its uncompressed size in bytes. + :param m: memory map from which to read the compressed object data""" + decompress_size = 8192 # is used in cgit as well + hdr = decompressobj().decompress(m, decompress_size) + type_name, size = hdr[:hdr.find("\0")].split(" ") + return type_name, int(size) + +def object_header_info(m): + """:return: tuple(type_string, uncompressed_size_in_bytes + :param mmap: mapped memory map. It will be + seeked to the actual start of the object contents, which can be used + to initialize a zlib decompress object. + :note: This routine can only handle new-style objects which are assumably contained + in packs + """ + assert not is_loose_object(m), "Use loose_object_header_info instead" + + c = b0 # first byte + i = 1 # next char to read + type_id = (c >> 4) & 7 # numeric type + size = c & 15 # starting size + s = 4 # starting bit-shift size + while c & 0x80: + c = ord(m[i]) + i += 1 + size += (c & 0x7f) << s + s += 7 + # END character loop + + # finally seek the map to the start of the data stream + m.seek(i) + try: + return (type_id_to_type_map[type_id], size) + except KeyError: + # invalid object type - we could try to be smart now and decode part + # of the stream to get the info, problem is that we had trouble finding + # the exact start of the content stream + raise BadObjectType(type_id) + # END handle exceptions + +def write_object(type, size, source_stream, target_stream, close_target_stream=True, + chunk_size=chunk_size): + """Write the object as identified by type, size and source_stream into the + target_stream + + :param type: type string of the object + :param size: amount of bytes to write from source_stream + :param source_stream: stream as file-like object providing at least size bytes + :param target_stream: stream as file-like object to receive the data + :param close_target_stream: if True, the target stream will be closed when + the routine exits, even if an error is thrown + :param chunk_size: size of chunks to read from source. Larger values can be beneficial + for io performance, but cost more memory as well + :return: The actual amount of bytes written to stream, which includes the header and a trailing newline""" + tbw = 0 # total num bytes written + dbw = 0 # num data bytes written + try: + # WRITE HEADER: type SP size NULL + tbw += target_stream.write("%s %i\0" % (type, size)) + + # WRITE ALL DATA UP TO SIZE + while True: + cs = min(chunk_size, size-dbw) + data_len = target_stream.write(source_stream.read(cs)) + dbw += data_len + if data_len < cs or dbw == size: + tbw += dbw + break + # END check for stream end + # END duplicate data + return tbw + finally: + if close_target_stream: + target_stream.close() + # END handle stream closing + # END assure file was closed + + +#} END routines diff --git a/lib/git/odb/utils.py b/lib/git/odb/utils.py index d88dca1a..8a054201 100644 --- a/lib/git/odb/utils.py +++ b/lib/git/odb/utils.py @@ -1,7 +1,10 @@ import binascii import os import zlib +from cStringIO import StringIO from git.utils import make_sha +import errno +from fun import chunk_size __all__ = ('FDSha1Writer', ) @@ -21,8 +24,10 @@ def to_bin_sha(sha): return sha return hex_to_bin(sha) +# errors +ENOENT = errno.ENOENT + # os shortcuts -getsize = os.path.getsize exists = os.path.exists mkdir = os.mkdir isdir = os.path.isdir @@ -32,6 +37,11 @@ join = os.path.join read = os.read write = os.write close = os.close + +# ZLIB configuration +# used when compressing objects +Z_BEST_SPEED = 1 + #} END Routines @@ -50,7 +60,7 @@ class FDCompressedSha1Writer(object): def __init__(self, fd): self.fd = fd self.sha1 = make_sha("") - self.zip = zlib.compressobj() + self.zip = zlib.compressobj(Z_BEST_SPEED) def write(self, data): """:raise IOError: If not all bytes could be written @@ -76,4 +86,137 @@ class FDCompressedSha1Writer(object): return close(self.fd) +class DecompressMemMapReader(object): + """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, thats all ... """ + __slots__ = ('_m', '_zip', '_buf', '_buflen', '_br', '_cws', '_cwe', '_s', '_cs', '_close') + + def __init__(self, m, close_on_deletion, cs = 128*1024): + """Initialize with mmap and chunk_size for stream reading""" + self._m = m + self._zip = zlib.decompressobj() + self._buf = None # buffer of decompressed bytes + self._buflen = 0 # length of bytes in buffer + self._s = 0 # 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._cs = cs # chunk size (when reading from zip) + self._close = close_on_deletion # close the memmap on deletion ? + + def __del__(self): + if self._close: + self._m.close() + # END handle resource freeing + + def initialize(self, size=0): + """Initialize this instance for acting as a read-only stream for size bytes. + :param size: size in bytes to be decompresed before being depleted. + If 0, default object header information is parsed from the data, + returning a tuple of (type_string, uncompressed_size) + If not 0, the size will be used, and None is returned. + :note: must only be called exactly once""" + if size: + self._s = size + return + # END handle size + + # read header + maxb = 8192 + self._s = maxb + hdr = self.read(maxb) + hdrend = hdr.find("\0") + type, size = hdr[:hdrend].split(" ") + self._s = int(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 # count terminating \0 + self._buf = StringIO(hdr[hdrend:]) + self._buflen = len(hdr) - hdrend + + return type, size + + 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 str() + # 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 = str() + 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.getvalue() # 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 durin g + # the next read. + if self._zip.unconsumed_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(self._zip.unconsumed_tail) + self._cwe = self._cws + size + indata = self._m[self._cws:self._cwe] # another copy ... :( + else: + cws = self._cws + self._cws = self._cwe + self._cwe = cws + size + indata = self._m[self._cws:self._cwe] # ... copy it again :( + # END handle tail + + dcompdat = self._zip.decompress(indata, size) + self._br += len(dcompdat) + + if dat: + return dat + dcompdat + return dcompdat + #} END classes |