This is the documentation for the latest (main) development branch of the Infuse-IoT platform. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

CPatch

Constrained Patch (CPatch) is a binary patching algorithm, designed to be as simple as possible to implement on the patch application side. It is optimised for patching embedded firmware applications.

Features

  • Small ROM footprint (~1200 bytes)

  • Constant size internal patch state

  • Configurable output buffer size

  • Linear patch read pattern

  • Linear output write pattern

  • Integrated input, patch & output data validation

  • No intermediate decompression step

  • Competitive compression ratio

Compression Tool Comparison

Using patch version increments of several applications as an example, we can compare the compression ratios of several binary diff tools.

nRF9151 TF-M application (528kB)

Algorithm

Patch Size (bytes)

Patch Ratio

CPatch

36836

6.81%

JojoDiff

49835

9.22%

bsdiff4

15317

2.83%

xdelta

82748

15.31%
nRF52840 application (320kB)

Algorithm

Patch Size (bytes)

Patch Ratio

CPatch

15252

4.66%

JojoDiff

21365

6.53%

bsdiff4

6994

2.14%

xdelta

41259

12.61%

Note

These comparisons can be generated on your own releases with the --tool-compare argument to west release-diff (The appropriate applications must be installed on PATH).

API Reference

cpatch patching APIs