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README.chromium

      1 Name: BSDiff
      2 URL: http://www.daemonology.net/bsdiff/
      3 Source URL: http://www.daemonology.net/bsdiff/bsdiff-4.3.tar.gz
      4 Version: 4.3
      5 License: BSD
      6 License File: LICENSE
      7 
      8 Description:
      9 Binary diff/patch utility. There are other copies of BSDiff in the Chromium
     10 repository, but they're all different. The other copies are based on Mozilla's
     11 fork of BSDiff, which serves a different set of needs. Relative to upstream
     12 BSDiff, Mozilla's version removes all compression, adds a CRC-32 check of the
     13 original file, replaces the custom off_t encoding with signed 32-bit
     14 big-endian integers, and contains a total reorganization of the code. The
     15 version in this directory contains no Mozilla code and builds directly on the
     16 upstream version. It retains and enhances the compression, uses SHA1 to check
     17 both the original file and the patched file, uses a different off_t encoding
     18 more compatible with the original, and involves minimal changes to the
     19 original code.
     20 
     21 Theoretically, a hash of the original file should be enough to guarantee data
     22 integrity, but in the event of algorithmic or programming bugs or other
     23 unexpected conditions, a hash of the patched file provides a better guarantee.
     24 This implementation now checks the integrity of both the original and the
     25 patched files. SHA1, rather than CRC-32, is used to minimize the likelihood
     26 that an original file that has been intentionally tampered with will produce
     27 an altered patched file without being detected.
     28 
     29 Local Modifications:
     30  - Added LICENSE file by copying the license block from bsdiff.c and
     31    bspatch.c.
     32  - The following modifications are relative to the original unpatched version,
     33    checked in to the Chromium repository at r49280.
     34  - Created goobsdiff.gyp for GYP build system integration.
     35  - Renamed bsdiff.c to goobsdiff.c and bspatch.c to goobspatch.c.
     36  - Added sha1_adapter.cc, sha1_adapter.h, and empty.cc to facilitate hashing.
     37  - Added #include <sys/types.h> to goobspatch.c so that it compiles. (Oops!)
     38  - Changed the magic number in the header from BSDIFF40 to BSDIFF4G.
     39  - Expanded the header to include SHA1 hashes of the original and new files,
     40    and added hash checks to the patcher.
     41  - Expanded the header to include the lengths of the control, diff, and extra
     42    blocks in the patch file, and added patch file length validation to the
     43    patcher.
     44  - Replaced custom off_t encoding with signed 64-bit little-endian integers.
     45  - The control, diff, and extra blocks can be compressed with bzip2, gzip, or
     46    xz/lzma2, or left uncompressed, independently of one another, depending on
     47    which is smallest. This often results in a net reduction in patch size of
     48    about 3%-5%.
     49  - Error messages in the patcher are slightly more descriptive.
     50  - The patcher treats a few more unexpected read cases as errors than it did
     51    previously. This will theoretically cause it to exit with an error instead
     52    of sitting in a busy loop or crashing when certain malformatted patch files
     53    are provided.
     54