About

Binary delta encoding in Python 3.6+ and C.

Based on http://www.daemonology.net/bsdiff/ and HDiffPatch, with the following features:

• bsdiff, hdiffpatch and match-blocks algorithms.

• sequential, hdiffpatch or in-place (resumable) patch types.

• BZ2, LZ4, LZMA, Zstandard, heatshrink or CRLE compression.

• Sequential patches allow streaming.

• Maximum file size is 2 GB for the bsdiff algorithm. There is practically no limit for the hdiffpatch and match-blocks algorithms.

• Incremental apply patch implemented in C, suitable for memory constrained embedded devices. Only the sequential patch type is supported.

• SA-IS or divsufsort instead of qsufsort for bsdiff.

• Optional experimental data format aware algorithm for potentially smaller patches. I don't recommend anyone to use this functionality as the gain is small in relation to memory usage and code complexity!

  There is a risk this functionality uses patent https://patents.google.com/patent/EP1988455B1/en. Anyway, this patent expires in August 2019 as I understand it.

  Supported data formats:

  • ARM Cortex-M4
  • AArch64

Project homepage: https://github.com/eerimoq/detools

Documentation: http://detools.readthedocs.org/en/latest

Installation

pip install detools

Statistics

Patch sizes, memory usage (RSS) and elapsed times when creating a patch from Python-3.7.3.tar (79M) to Python-3.8.1.tar (84M) for various algorithm, patch type and compression combinations.

See tests/benchmark.sh for details on how the data was collected.

Algorithm	Patch type	Compr.	Patch size	RSS	Time
bsdiff	sequential	lzma	3,5M	662M	0:24.29
bsdiff	sequential	none	86M	646M	0:15.20
hdiffpatch	hdiffpatch	lzma	2,4M	523M	0:13.74
hdiffpatch	hdiffpatch	none	7,2M	523M	0:10.24
match-blocks	sequential	lzma	2,9M	273M	0:08.57
match-blocks	sequential	none	84M	273M	0:01.72
match-blocks	hdiffpatch	lzma	2,6M	212M	0:06.07
match-blocks	hdiffpatch	none	9,7M	212M	0:01.30

Same as above, but for MicroPython ESP8266 binary releases (from 604k to 615k).

Algorithm	Patch type	Compr.	Patch size	RSS	Time
bsdiff	sequential	lzma	71K	46M	0:00.64
bsdiff	sequential	none	609K	27M	0:00.33
hdiffpatch	hdiffpatch	lzma	65K	42M	0:00.37
hdiffpatch	hdiffpatch	none	123K	25M	0:00.32
match-blocks	sequential	lzma	194K	46M	0:00.44
match-blocks	sequential	none	606K	25M	0:00.22
match-blocks	hdiffpatch	lzma	189K	43M	0:00.38
match-blocks	hdiffpatch	none	313K	24M	0:00.19

Example usage

Examples in C are found in c.

Command line tool

The create patch subcommand

Create a patch foo.patch from tests/files/foo/old to tests/files/foo/new.

$ detools create_patch tests/files/foo/old tests/files/foo/new foo.patch
Successfully created 'foo.patch' in 0.01 seconds!
$ ls -l foo.patch
-rw-rw-r-- 1 erik erik 127 feb  2 10:35 foo.patch

Create the same patch as above, but without compression.

$ detools create_patch --compression none \
      tests/files/foo/old tests/files/foo/new foo-no-compression.patch
Successfully created 'foo-no-compression.patch' in 0 seconds!
$ ls -l foo-no-compression.patch
-rw-rw-r-- 1 erik erik 2792 feb  2 10:35 foo-no-compression.patch

Create a hdiffpatch patch foo-hdiffpatch.patch.

$ detools create_patch --algorithm hdiffpatch --patch-type hdiffpatch \
      tests/files/foo/old tests/files/foo/new foo-hdiffpatch.patch
Successfully created patch 'foo-hdiffpatch.patch' in 0.01 seconds!
$ ls -l foo-hdiffpatch.patch
-rw-rw-r-- 1 erik erik 146 feb  2 10:37 foo-hdiffpatch.patch

Lower memory usage with --algorithm match-blocks algorithm. Mainly useful for big files. Creates slightly bigger patches than bsdiff and hdiffpatch.

$ detools create_patch --algorithm match-blocks \
      tests/files/foo/old tests/files/foo/new foo-hdiffpatch-64.patch
Successfully created patch 'foo-hdiffpatch-64.patch' in 0.01 seconds!
$ ls -l foo-hdiffpatch-64.patch
-rw-rw-r-- 1 erik erik 404 feb  8 11:03 foo-hdiffpatch-64.patch

Non-sequential but smaller patch with --patch-type hdiffpatch.

$ detools create_patch \
      --algorithm match-blocks --patch-type hdiffpatch \
      tests/files/foo/old tests/files/foo/new foo-hdiffpatch-sequential.patch
Successfully created 'foo-hdiffpatch-sequential.patch' in 0.01 seconds!
$ ls -l foo-hdiffpatch-sequential.patch
-rw-rw-r-- 1 erik erik 389 feb  8 11:05 foo-hdiffpatch-sequential.patch

The create in-place patch subcommand

Create an in-place patch foo-in-place.patch.

$ detools create_patch_in_place --memory-size 3000 --segment-size 500 \
      tests/files/foo/old tests/files/foo/new foo-in-place.patch
Successfully created 'foo-in-place.patch' in 0.01 seconds!
$ ls -l foo-in-place.patch
-rw-rw-r-- 1 erik erik 672 feb  2 10:36 foo-in-place.patch

The create bsdiff patch subcommand

Create a bsdiff patch foo-bsdiff.patch, compatible with the original bsdiff program.

$ detools create_patch_bsdiff \
      tests/files/foo/old tests/files/foo/new foo-bsdiff.patch
Successfully created 'foo-bsdiff.patch' in 0 seconds!
$ ls -l foo-bsdiff.patch
-rw-rw-r-- 1 erik erik 261 feb  2 10:36 foo-bsdiff.patch

The apply patch subcommand

Apply the patch foo.patch to tests/files/foo/old to create foo.new.

$ detools apply_patch tests/files/foo/old foo.patch foo.new
Successfully created 'foo.new' in 0 seconds!
$ ls -l foo.new
-rw-rw-r-- 1 erik erik 2780 feb  2 10:38 foo.new

The in-place apply patch subcommand

Apply the in-place patch foo-in-place.patch to foo.mem.

$ cp tests/files/foo/in-place-3000-500.mem foo.mem
$ detools apply_patch_in_place foo.mem foo-in-place.patch
Successfully created 'foo.mem' in 0 seconds!
$ ls -l foo.mem
-rw-rw-r-- 1 erik erik 3000 feb  2 10:40 foo.mem

The bsdiff apply patch subcommand

Apply the patch foo-bsdiff.patch to tests/files/foo/old to create foo.new.

$ detools apply_patch_bsdiff tests/files/foo/old foo-bsdiff.patch foo.new
Successfully created 'foo.new' in 0 seconds!
$ ls -l foo.new
-rw-rw-r-- 1 erik erik 2780 feb  2 10:41 foo.new

The patch info subcommand

Print information about the patch foo.patch.

$ detools patch_info foo.patch
Type:               sequential
Patch size:         127 bytes
To size:            2.71 KiB
Patch/to ratio:     4.6 % (lower is better)
Diff/extra ratio:   9828.6 % (higher is better)
Size/data ratio:    0.3 % (lower is better)
Compression:        lzma

Number of diffs:    2
Total diff size:    2.69 KiB
Average diff size:  1.34 KiB
Median diff size:   1.34 KiB

Number of extras:   2
Total extra size:   28 bytes
Average extra size: 14 bytes
Median extra size:  14 bytes

Contributing

1. Fork the repository.

2. Install prerequisites.

   pip install -r requirements.txt
   

3. Implement the new feature or bug fix.

4. Implement test case(s) to ensure that future changes do not break legacy.

5. Run the tests.

   make test
   

6. Create a pull request.