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Diffstat (limited to 'objects/fun.py')
| -rw-r--r-- | objects/fun.py | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/objects/fun.py b/objects/fun.py new file mode 100644 index 00000000..9b0a377c --- /dev/null +++ b/objects/fun.py @@ -0,0 +1,199 @@ +"""Module with functions which are supposed to be as fast as possible""" +from stat import S_ISDIR + +__all__ = ('tree_to_stream', 'tree_entries_from_data', 'traverse_trees_recursive', + 'traverse_tree_recursive') + + + + +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 + + # here it comes: if the name is actually unicode, the replacement below + # will not work as the binsha is not part of the ascii unicode encoding - + # hence we must convert to an utf8 string for it to work properly. + # According to my tests, this is exactly what git does, that is it just + # takes the input literally, which appears to be utf8 on linux. + if isinstance(name, unicode): + name = name.encode("utf8") + 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 + + # default encoding for strings in git is utf8 + # Only use the respective unicode object if the byte stream was encoded + name = data[ns:i] + name_enc = name.decode("utf-8") + if len(name) > len(name_enc): + name = name_enc + # END handle encoding + + # 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 + + +def _find_by_name(tree_data, name, is_dir, start_at): + """return data entry matching the given name and tree mode + or None. + Before the item is returned, the respective data item is set + None in the tree_data list to mark it done""" + try: + item = tree_data[start_at] + if item and item[2] == name and S_ISDIR(item[1]) == is_dir: + tree_data[start_at] = None + return item + except IndexError: + pass + # END exception handling + for index, item in enumerate(tree_data): + if item and item[2] == name and S_ISDIR(item[1]) == is_dir: + tree_data[index] = None + return item + # END if item matches + # END for each item + return None + +def _to_full_path(item, path_prefix): + """Rebuild entry with given path prefix""" + if not item: + return item + return (item[0], item[1], path_prefix+item[2]) + +def traverse_trees_recursive(odb, tree_shas, path_prefix): + """ + :return: list with entries according to the given binary tree-shas. + The result is encoded in a list + of n tuple|None per blob/commit, (n == len(tree_shas)), where + * [0] == 20 byte sha + * [1] == mode as int + * [2] == path relative to working tree root + The entry tuple is None if the respective blob/commit did not + exist in the given tree. + :param tree_shas: iterable of shas pointing to trees. All trees must + be on the same level. A tree-sha may be None in which case None + :param path_prefix: a prefix to be added to the returned paths on this level, + set it '' for the first iteration + :note: The ordering of the returned items will be partially lost""" + trees_data = list() + nt = len(tree_shas) + for tree_sha in tree_shas: + if tree_sha is None: + data = list() + else: + data = tree_entries_from_data(odb.stream(tree_sha).read()) + # END handle muted trees + trees_data.append(data) + # END for each sha to get data for + + out = list() + out_append = out.append + + # find all matching entries and recursively process them together if the match + # is a tree. If the match is a non-tree item, put it into the result. + # Processed items will be set None + for ti, tree_data in enumerate(trees_data): + for ii, item in enumerate(tree_data): + if not item: + continue + # END skip already done items + entries = [ None for n in range(nt) ] + entries[ti] = item + sha, mode, name = item # its faster to unpack + is_dir = S_ISDIR(mode) # type mode bits + + # find this item in all other tree data items + # wrap around, but stop one before our current index, hence + # ti+nt, not ti+1+nt + for tio in range(ti+1, ti+nt): + tio = tio % nt + entries[tio] = _find_by_name(trees_data[tio], name, is_dir, ii) + # END for each other item data + + # if we are a directory, enter recursion + if is_dir: + out.extend(traverse_trees_recursive(odb, [((ei and ei[0]) or None) for ei in entries], path_prefix+name+'/')) + else: + out_append(tuple(_to_full_path(e, path_prefix) for e in entries)) + # END handle recursion + + # finally mark it done + tree_data[ii] = None + # END for each item + + # we are done with one tree, set all its data empty + del(tree_data[:]) + # END for each tree_data chunk + return out + +def traverse_tree_recursive(odb, tree_sha, path_prefix): + """ + :return: list of entries of the tree pointed to by the binary tree_sha. An entry + has the following format: + * [0] 20 byte sha + * [1] mode as int + * [2] path relative to the repository + :param path_prefix: prefix to prepend to the front of all returned paths""" + entries = list() + data = tree_entries_from_data(odb.stream(tree_sha).read()) + + # unpacking/packing is faster than accessing individual items + for sha, mode, name in data: + if S_ISDIR(mode): + entries.extend(traverse_tree_recursive(odb, sha, path_prefix+name+'/')) + else: + entries.append((sha, mode, path_prefix+name)) + # END for each item + + return entries |