Merge branch 'odb'

Conflicts:
	lib/git/cmd.py

1 files changed, 446 insertions, 0 deletions

diff --git a/lib/git/odb/stream.py b/lib/git/odb/stream.py
new file mode 100644
index 00000000..d1181382
--- /dev/null
+++ b/lib/git/odb/stream.py
@@ -0,0 +1,446 @@
+import zlib
+from cStringIO import StringIO
+from git.utils import make_sha
+import errno
+
+from utils import (
+		to_hex_sha,
+		to_bin_sha, 
+		write, 
+		close
+	)
+
+__all__ = ('OInfo', 'OStream', 'IStream', 'InvalidOInfo', 'InvalidOStream', 
+			'DecompressMemMapReader', 'FDCompressedSha1Writer')
+
+
+# ZLIB configuration
+# used when compressing objects - 1 to 9 ( slowest )
+Z_BEST_SPEED = 1
+
+
+#{ ODB Bases
+
+class OInfo(tuple):
+	"""Carries information about an object in an ODB, provdiing information 
+	about the sha of the object, the type_string as well as the uncompressed size
+	in bytes.
+	
+	It can be accessed using tuple notation and using attribute access notation::
+	
+		assert dbi[0] == dbi.sha
+		assert dbi[1] == dbi.type
+		assert dbi[2] == dbi.size
+	
+	The type is designed to be as lighteight as possible."""
+	__slots__ = tuple()
+	
+	def __new__(cls, sha, type, size):
+		return tuple.__new__(cls, (sha, type, size))
+	
+	def __init__(self, *args):
+		tuple.__init__(self)
+	
+	#{ Interface 
+	@property
+	def sha(self):
+		return self[0]
+		
+	@property
+	def type(self):
+		return self[1]
+		
+	@property
+	def size(self):
+		return self[2]
+	#} END interface
+
+
+class OStream(OInfo):
+	"""Base for object streams retrieved from the database, providing additional 
+	information about the stream.
+	Generally, ODB streams are read-only as objects are immutable"""
+	__slots__ = tuple()
+	
+	def __new__(cls, sha, type, size, stream, *args, **kwargs):
+		"""Helps with the initialization of subclasses"""
+		return tuple.__new__(cls, (sha, type, size, stream))
+	
+	
+	def __init__(self, *args, **kwargs):
+		tuple.__init__(self)
+	#{ Interface 
+	
+	def is_compressed(self):
+		""":return: True if reads of this stream yield zlib compressed data. Default False
+		:note: this does not imply anything about the actual internal storage.
+			Hence the data could be uncompressed, but read compressed, or vice versa"""
+		raise False
+		
+	#} END interface
+	
+	#{ Stream Reader Interface 
+	
+	def read(self, size=-1):
+		return self[3].read(size)
+		
+	#} END stream reader interface
+
+
+class IStream(list):
+	"""Represents an input content stream to be fed into the ODB. It is mutable to allow 
+	the ODB to record information about the operations outcome right in this instance.
+	
+	It provides interfaces for the OStream and a StreamReader to allow the instance
+	to blend in without prior conversion.
+	
+	The only method your content stream must support is 'read'"""
+	__slots__ = tuple()
+	
+	def __new__(cls, type, size, stream, sha=None, compressed=False):
+		return list.__new__(cls, (sha, type, size, stream, compressed, None))
+		
+	def __init__(self, type, size, stream, sha=None, compressed=None):
+		list.__init__(self, (sha, type, size, stream, compressed, None))
+	
+	#{ Interface 
+	
+	def hexsha(self):
+		""":return: our sha, hex encoded, 40 bytes"""
+		return to_hex_sha(self[0])
+	
+	def binsha(self):
+		""":return: our sha as binary, 20 bytes"""
+		return to_bin_sha(self[0])
+		
+	def _error(self):
+		""":return: the error that occurred when processing the stream, or None"""
+		return self[5]
+		
+	def _set_error(self, exc):
+		"""Set this input stream to the given exc, may be None to reset the error"""
+		self[5] = exc
+			
+	error = property(_error, _set_error)
+	
+	#} END interface
+	
+	#{ Stream Reader Interface
+	
+	def read(self, size=-1):
+		"""Implements a simple stream reader interface, passing the read call on 
+			to our internal stream"""
+		return self[3].read(size)
+		
+	#} END stream reader interface 
+	
+	#{  interface
+	
+	def _set_sha(self, sha):
+		self[0] = sha
+		
+	def _sha(self):
+		return self[0]
+		
+	sha = property(_sha, _set_sha)
+	
+	
+	def _type(self):
+		return self[1]
+	
+	def _set_type(self, type):
+		self[1] = type
+		
+	type = property(_type, _set_type)
+	
+	def _size(self):
+		return self[2]
+		
+	def _set_size(self, size):
+		self[2] = size
+	
+	size = property(_size, _set_size)
+	
+	def _stream(self):
+		return self[3]
+		
+	def _set_stream(self, stream):
+		self[3] = stream
+	
+	stream = property(_stream, _set_stream)
+	
+	#} END odb info interface 
+	
+	#{ OStream interface 
+	
+	def is_compressed(self):
+		return self[4]
+		
+	#} END OStream interface
+		
+
+class InvalidOInfo(tuple):
+	"""Carries information about a sha identifying an object which is invalid in 
+	the queried database. The exception attribute provides more information about
+	the cause of the issue"""
+	__slots__ = tuple()
+	
+	def __new__(cls, sha, exc):
+		return tuple.__new__(cls, (sha, exc))
+		
+	def __init__(self, sha, exc):
+		tuple.__init__(self, (sha, exc))
+	
+	@property
+	def sha(self):
+		return self[0]
+		
+	@property
+	def error(self):
+		""":return: exception instance explaining the failure"""
+		return self[1]
+
+
+class InvalidOStream(InvalidOInfo):
+	"""Carries information about an invalid ODB stream"""
+	__slots__ = tuple()
+	
+#} END ODB Bases
+
+
+#{ RO Streams
+
+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', '_close')
+	
+	max_read_size = 512*1024
+	
+	def __init__(self, m, close_on_deletion, size):
+		"""Initialize with mmap 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 = 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._close = close_on_deletion			# close the memmap on deletion ?
+		
+	def __del__(self):
+		if self._close:
+			self._m.close()
+		# END handle resource freeing
+		
+	@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 oparate
+		:param close_on_deletion: if True, the memory map will be closed once we are 
+			being deleted"""
+		inst = DecompressMemMapReader(m, close_on_deletion, 0)
+		
+		# read header
+		maxb = 512				# should really be enough, cgit uses 8192 I believe
+		inst._s = maxb
+		hdr = inst.read(maxb)
+		hdrend = hdr.find("\0")
+		type, size = hdr[:hdrend].split(" ")
+		size = int(size)
+		inst._s = size
+		
+		# adjust internal state to match actual header length that we ignore
+		# The buffer will be depleted first on future reads
+		inst._br = 0
+		hdrend += 1									# count terminating \0
+		inst._buf = StringIO(hdr[hdrend:])
+		inst._buflen = len(hdr) - hdrend
+		
+		return type, size, inst
+		
+	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
+		
+		# protect from memory peaks
+		# If he tries to read large chunks, our memory patterns get really bad
+		# as we end up copying a possibly huge chunk from our memory map right into
+		# memory. This might not even be possible. Nonetheless, try to dampen the 
+		# effect a bit by reading in chunks, returning a huge string in the end.
+		# Our performance now depends on StringIO. This way we don't need two large
+		# buffers in peak times, but only one large one in the end which is 
+		# the return buffer
+		# NO: We don't do it - if the user thinks its best, he is right. If he 
+		# has trouble, he will start reading in chunks. According to our tests
+		# its still faster if we read 10 Mb at once instead of chunking it.
+		
+		# if size > self.max_read_size:
+			# sio = StringIO()
+			# while size:
+				# read_size = min(self.max_read_size, size)
+				# data = self.read(read_size)
+				# sio.write(data)
+				# size -= len(data)
+				# if len(data) < read_size:
+					# break
+			# # END data loop
+			# sio.seek(0)
+			# return sio.getvalue()
+		# # END handle maxread
+		# 
+		# 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.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 durin g
+		# 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
+			
+			
+			indata = self._m[self._cws:self._cwe]		# another copy ... :(
+			# get the actual window end to be sure we don't use it for computations
+			self._cwe = self._cws + len(indata) 
+		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:
+			dcompdat = dat + dcompdat
+			
+		return dcompdat
+		
+#} END RO streams
+
+
+#{ W Streams
+
+class Sha1Writer(object):
+	"""Simple stream writer which produces a sha whenever you like as it degests
+	everything it is supposed to write"""
+	
+	def __init__(self):
+		self.sha1 = make_sha("")
+
+	#{ Stream Interface
+
+	def write(self, data):
+		""":raise IOError: If not all bytes could be written
+		:return: lenght 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 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(FDCompressedSha1Writer, self).__init__()
+		self.fd = fd
+		self.zip = zlib.compressobj(Z_BEST_SPEED)
+
+	#{ Stream Interface
+
+	def write(self, data):
+		""":raise IOError: If not all bytes could be written
+		:return: lenght 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
+
+#} END W streams