/usr/lib/python2.7/dist-packages/subvertpy/delta.py is in python-subvertpy 0.9.3-3.
This file is owned by root:root, with mode 0o644.
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# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
"""Subversion delta operations."""
__author__ = "Jelmer Vernooij <jelmer@jelmer.uk>"
__docformat__ = "restructuredText"
from hashlib import (
md5,
)
TXDELTA_SOURCE = 0
TXDELTA_TARGET = 1
TXDELTA_NEW = 2
TXDELTA_INVALID = 3
MAX_ENCODED_INT_LEN = 10
DELTA_WINDOW_SIZE = 102400
def apply_txdelta_window(sbuf,
(sview_offset, sview_len, tview_len, src_ops, ops, new_data)):
"""Apply a txdelta window to a buffer.
:param sbuf: Source buffer (as bytestring)
:param sview_offset: Offset of the source view
:param sview_len: Length of the source view
:param tview_len: Target view length
:param src_ops: Operations to apply to sview
:param ops: Ops to apply
:param new_data: Buffer with possible new data
:return: Target buffer
"""
sview = sbuf[sview_offset:sview_offset+sview_len]
tview = txdelta_apply_ops(src_ops, ops, new_data, sview)
if len(tview) != tview_len:
raise AssertionError("%d != %d" % (len(tview), tview_len))
return tview
def apply_txdelta_handler_chunks(source_chunks, target_chunks):
"""Return a function that can be called repeatedly with txdelta windows.
:param sbuf: Source buffer
:param target_stream: Target stream
"""
sbuf = "".join(source_chunks)
def apply_window(window):
if window is None:
return # Last call
target_chunks.append(apply_txdelta_window(sbuf, window))
return apply_window
def apply_txdelta_handler(sbuf, target_stream):
"""Return a function that can be called repeatedly with txdelta windows.
:param sbuf: Source buffer
:param target_stream: Target stream
"""
def apply_window(window):
if window is None:
return # Last call
target_stream.write(apply_txdelta_window(sbuf, window))
return apply_window
def txdelta_apply_ops(src_ops, ops, new_data, sview):
"""Apply txdelta operations to a source view.
:param src_ops: Source operations, ignored.
:param ops: List of operations (action, offset, length).
:param new_data: Buffer to fetch fragments with new data from
:param sview: Source data
:return: Result data
"""
tview = ""
for (action, offset, length) in ops:
if action == TXDELTA_SOURCE:
# Copy from source area.
tview += sview[offset:offset+length]
elif action == TXDELTA_TARGET:
for i in xrange(length):
tview += tview[offset+i]
elif action == TXDELTA_NEW:
tview += new_data[offset:offset+length]
else:
raise Exception("Invalid delta instruction code")
return tview
def send_stream(stream, handler, block_size=DELTA_WINDOW_SIZE):
"""Send txdelta windows that create stream to handler
:param stream: file-like object to read the file from
:param handler: txdelta window handler function
:return: MD5 hash over the stream
"""
hash = md5()
text = stream.read(block_size)
while text != "":
hash.update(text)
window = (0, 0, len(text), 0, [(TXDELTA_NEW, 0, len(text))], text)
handler(window)
text = stream.read(block_size)
handler(None)
return hash.digest()
def encode_length(len):
"""Encode a length variable.
:param len: Length to encode
:return: String with encoded length
"""
# Based on encode_int() in subversion/libsvn_delta/svndiff.c
assert len >= 0
assert isinstance(len, int), "expected int, got %r" % (len,)
# Count number of required bytes
v = len >> 7
n = 1;
while v > 0:
v = v >> 7
n+=1
assert n <= MAX_ENCODED_INT_LEN
ret = ""
while n > 0:
n-=1
if n > 0:
cont = 1
else:
cont = 0
ret += chr(((len >> (n * 7)) & 0x7f) | (cont << 7))
return ret
def decode_length(text):
"""Decode a length variable.
:param text: Bytestring to decode
:return: Integer with actual length
"""
# Decode bytes until we're done. */
ret = 0
next = True
while next:
ret = ((ret << 7) | (ord(text[0]) & 0x7f))
next = ((ord(text[0]) >> 7) & 0x1)
text = text[1:]
return ret, text
def pack_svndiff_instruction((action, offset, length)):
"""Pack a SVN diff instruction
:param action: Action
:param offset: Offset
:param length: Length
:return: encoded text
"""
if length < 0x3f:
text = chr((action << 6) + length)
else:
text = chr((action << 6)) + encode_length(length)
if action != TXDELTA_NEW:
text += encode_length(offset)
return text
def unpack_svndiff_instruction(text):
"""Unpack a SVN diff instruction
:param text: Text to parse
:return: tuple with operation, remaining text
"""
action = (ord(text[0]) >> 6)
length = (ord(text[0]) & 0x3f)
text = text[1:]
assert action in (TXDELTA_NEW, TXDELTA_SOURCE, TXDELTA_TARGET)
if length == 0:
length, text = decode_length(text)
if action != TXDELTA_NEW:
offset, text = decode_length(text)
else:
offset = 0
return (action, offset, length), text
SVNDIFF0_HEADER = "SVN\0"
def pack_svndiff0_window(window):
"""Pack an individual window using svndiff0.
:param window: Window to pack
:return: Packed diff (as bytestring)
"""
(sview_offset, sview_len, tview_len, src_ops, ops, new_data) = window
ret = [encode_length(sview_offset) + \
encode_length(sview_len) + \
encode_length(tview_len)]
instrdata = ""
for op in ops:
instrdata += pack_svndiff_instruction(op)
ret.append(encode_length(len(instrdata)))
ret.append(encode_length(len(new_data)))
ret.append(instrdata)
ret.append(new_data)
return "".join(ret)
def pack_svndiff0(windows):
"""Pack a SVN diff file.
:param windows: Iterator over diff windows
:return: text
"""
ret = SVNDIFF0_HEADER
for window in windows:
ret += pack_svndiff0_window(window)
return ret
def unpack_svndiff0(text):
"""Unpack a version 0 svndiff text.
:param text: Text to unpack.
:return: yields tuples with sview_offset, sview_len, tview_len, ops_len,
ops, newdata
"""
assert text.startswith(SVNDIFF0_HEADER)
text = text[4:]
while text != "":
sview_offset, text = decode_length(text)
sview_len, text = decode_length(text)
tview_len, text = decode_length(text)
instr_len, text = decode_length(text)
newdata_len, text = decode_length(text)
instrdata = text[:instr_len]
text = text[instr_len:]
ops = []
while instrdata != "":
op, instrdata = unpack_svndiff_instruction(instrdata)
ops.append(op)
newdata = text[:newdata_len]
text = text[newdata_len:]
yield (sview_offset, sview_len, tview_len, len(ops), ops, newdata)
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