xferspdy

This library provides binary diff and patch API in golang.

Supported today:

Command line utilities to diff and patch binary files
Library for fingerprint generation, rolling hash and block matching
NEW : For large files, fingerprint generation automatically switches to parallel mode wherein multiple go routines are used concurrently. For files > 20 MB, there is an improvement of ~50% compared to sequential fingerprint generation.

Reference : [Rsync Algorithm] (https://rsync.samba.org/tech_report/node2.html)

Setup

Need to have go installed, [golang downloads] (https://golang.org/dl/)
Do go get
```
 `go get github.com/monmohan/xferspdy`
```
Install the command line utilities

Run go install ./... from the xferspdy directory

Using the API

See GoDoc. The docs also contain an example usage of the API.

Using the fpgen, diff and patch CLI utilities:

The library also provides CLI wrappers on API.

Example

You can see the usage of any of these commands using $ GOPATH/bin/<command> --help
Lets say you have a binary file (e.g. power point presentation MyPrezVersion1.pptx).
First generate a fingerprint of version 1

$ GOPATH/bin/fpgen -file <path>/MyPrezVersion1.pptx

This will generate the fingerprint file /MyPrezVersion1.pptx.fingerprint.
Lets say that the file was changed now (for example add a slide or image) and saved as MyPrezVersion2.pptx
Now Generate a diff (doesn't require original file)

$ GOPATH/bin/diff -fingerprint <path>/MyPrezVersion1.pptx.fingerprint -file <path>/MyPrezVersion2.pptx

It will create a patch file <path>/MyPrezVersion2.pptx.patch

Now patch the Version 1 file to get the Version 2

$ GOPATH/bin/patch -patch <path>/MyPrezVersion2.pptx.patch -base <path>/MyPrezVersion1.pptx
This will generate /Patched_MyPrezVersion1.pptx. This file would exactly be same as MyPrezVersion2.pptx.

NOTE: diff and patch are also common utilities present on most distributions so its better to give explicit path to these binaries. for example use $GOPATH/bin/diff and $GOPATH/bin/patch