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#!/usr/bin/python
# Copyright (c) 2011 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""A simple utility function to produce data pack files.
See base/pack_file* for details.
"""
import struct
FILE_FORMAT_VERSION = 3
HEADER_LENGTH = 2 * 4 # Two uint32s. (file version and number of entries)
class WrongFileVersion(Exception):
pass
def ReadDataPack(input_file):
"""Reads a data pack file and returns a dictionary."""
data = open(input_file, "rb").read()
original_data = data
# Read the header.
version, num_entries = struct.unpack("<II", data[:HEADER_LENGTH])
if version != FILE_FORMAT_VERSION:
raise WrongFileVersion
resources = {}
if num_entries == 0:
return resources
# Read the index and data.
data = data[HEADER_LENGTH:]
kIndexEntrySize = 2 + 4 # Each entry is a uint16 and a uint32.
for _ in range(num_entries):
id, offset = struct.unpack("<HI", data[:kIndexEntrySize])
data = data[kIndexEntrySize:]
next_id, next_offset = struct.unpack("<HI", data[:kIndexEntrySize])
resources[id] = original_data[offset:next_offset]
return resources
def WriteDataPack(resources, output_file):
"""Write a map of id=>data into output_file as a data pack."""
ids = sorted(resources.keys())
file = open(output_file, "wb")
# Write file header.
file.write(struct.pack("<II", FILE_FORMAT_VERSION, len(ids)))
# Each entry is a uint16 and a uint32. We have one extra entry for the last
# item.
index_length = (len(ids) + 1) * (2 + 4)
# Write index.
data_offset = HEADER_LENGTH + index_length
for id in ids:
file.write(struct.pack("<HI", id, data_offset))
data_offset += len(resources[id])
file.write(struct.pack("<HI", 0, data_offset))
# Write data.
for id in ids:
file.write(resources[id])
def main():
# Just write a simple file.
data = { 1: "", 4: "this is id 4", 6: "this is id 6", 10: "" }
WriteDataPack(data, "datapack1.pak")
data2 = { 1000: "test", 5: "five" }
WriteDataPack(data2, "datapack2.pak")
print "wrote datapack1 and datapack2 to current directory."
if __name__ == '__main__':
main()
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