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"""Module with functions which are supposed to be as fast as possible"""
__all__ = ('tree_to_stream', 'tree_entries_from_data')
def tree_to_stream(entries, write):
"""Write the give list of entries into a stream using its write method
:param entries: **sorted** list of tuples with (binsha, mode, name)
:param write: write method which takes a data string"""
ord_zero = ord('0')
bit_mask = 7 # 3 bits set
for binsha, mode, name in entries:
mode_str = ''
for i in xrange(6):
mode_str = chr(((mode >> (i*3)) & bit_mask) + ord_zero) + mode_str
# END for each 8 octal value
# git slices away the first octal if its zero
if mode_str[0] == '0':
mode_str = mode_str[1:]
# END save a byte
write("%s %s\0%s" % (mode_str, name, binsha))
# END for each item
def tree_entries_from_data(data):
"""Reads the binary representation of a tree and returns tuples of Tree items
:param data: data block with tree data
:return: list(tuple(binsha, mode, tree_relative_path), ...)"""
ord_zero = ord('0')
len_data = len(data)
i = 0
out = list()
while i < len_data:
mode = 0
# read mode
# Some git versions truncate the leading 0, some don't
# The type will be extracted from the mode later
while data[i] != ' ':
# move existing mode integer up one level being 3 bits
# and add the actual ordinal value of the character
mode = (mode << 3) + (ord(data[i]) - ord_zero)
i += 1
# END while reading mode
# byte is space now, skip it
i += 1
# parse name, it is NULL separated
ns = i
while data[i] != '\0':
i += 1
# END while not reached NULL
name = data[ns:i]
# byte is NULL, get next 20
i += 1
sha = data[i:i+20]
i = i + 20
out.append((sha, mode, name))
# END for each byte in data stream
return out
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