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(
(buffer(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 reversed(
zip(buffer_info_list, 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
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((buffer(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 reversed(zip(buffer_info_list, 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