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Binary delta encoding tools.

Project description

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Binary delta encoding in Python 3 and C.

Based on, with the following differences:

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

  • Linear patch file access pattern to allow streaming and less RAM usage.

  • SA-IS instead of qsufsort.

  • Variable length size fields.

  • Incremental apply patch implemented in C, suitable for memory constrained embedded devices.

  • Normal or in-place (resumable) updates.

  • 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 Anyway, this patent expires in August 2019 as I understand it.

    Supported data formats:

    • ARM Cortex-M4
    • AArch64

Project homepage:



pip install detools


“LZMA ref.” is the target binary compressed with lzma --best.

The percentages are calculated as “patch size” / “to size”. Lower is better.

Update To size LZMA ref. LZMA heatshrink CRLE
upy v1.9.4 -> v1.10 615388 59.8 % 11.7 % 15.7 % 26.2 %
python 3.5 -> 3.6 4568920 30.7 % 31.8 % - -
foo old -> new 2780 69.5 % 4.5 % 4.5 % 6.8 %

Example usage

Examples in C are found in src/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 patch 'foo.patch'!
$ ls -l foo.patch
-rw-rw-r-- 1 erik erik 127 Mar  1 19:18 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 patch 'foo-no-compression.patch'!
$ ls -l foo-no-compression.patch
-rw-rw-r-- 1 erik erik 2792 Mar  1 19:18 foo-no-compression.patch

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

$ detools create_patch --type in-place --memory-size 3000 --segment-size 500 \
      tests/files/foo/old tests/files/foo/new foo-in-place.patch
Successfully created patch 'foo-in-place.patch'!
$ ls -l foo-in-place.patch
-rw-rw-r-- 1 erik erik 672 Mar 16 08:49 foo-in-place.patch

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

$ detools create_patch --type bsdiff \
      tests/files/foo/old tests/files/foo/new foo-bsdiff.patch
Successfully created patch 'foo-bsdiff.patch'!
$ ls -l foo-bsdiff.patch
-rw-rw-r-- 1 erik erik 261 Apr 22 18:20 foo-bsdiff.patch

The apply patch subcommand

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

$ detools apply_patch tests/files/foo/old foo.patch
$ ls -l
-rw-rw-r-- 1 erik erik 2780 Mar  1 19:18

The in-place apply patch subcommand

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

$ cp tests/files/foo/old foo.mem
$ detools apply_patch_in_place foo.mem foo-in-place.patch
$ ls -l foo.mem
-rwxrwxr-x 1 erik erik 2780 Mar 16 08:51 foo.mem

The bsdiff apply patch subcommand

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

$ detools apply_patch_bsdiff tests/files/foo/old foo-bsdiff.patch
$ ls -l
-rw-rw-r-- 1 erik erik 2780 Mar  1 19:18

The patch info subcommand

Print information about the patch foo.patch.

$ detools patch_info foo.patch
Type:               normal
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


  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.

Project details

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