README.md

go-bsdiff

Pure Go implementation of bsdiff 4.

bsdiff and bspatch are tools for building and applying patches to binary files. By using suffix sorting (specifically, Larsson and Sadakane's qsufsort) and taking advantage of how executable files change.

The package can be used as a library (pkg/bsdiff pkg/bspatch) or as a cli program (cmd/bsdiff cmd/bspatch).

As a library

Bsdiff Bytes

package main

import (
  "fmt"
  "bytes"

  "github.com/gabstv/go-bsdiff/pkg/bsdiff"
  "github.com/gabstv/go-bsdiff/pkg/bspatch"
)

func main(){
  // example files
  oldfile := []byte{0xfa, 0xdd, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff}
  newfile := []byte{0xfa, 0xdd, 0x00, 0x00, 0x00, 0xee, 0xee, 0x00, 0x00, 0xff, 0xfe, 0xfe}

  // generate a BSDIFF4 patch
  patch, err := bsdiff.Bytes(oldfile, newfile)
  if err != nil {
    panic(err)
  }
  fmt.Println(patch)

  // Apply a BSDIFF4 patch
  newfile2, err := bspatch.Bytes(oldfile, patch)
  if err != nil {
    panic(err)
  }
  if !bytes.Equal(newfile, newfile2) {
    panic()
  }
}

Bsdiff Reader

package main

import (
  "fmt"
  "bytes"

  "github.com/gabstv/go-bsdiff/pkg/bsdiff"
  "github.com/gabstv/go-bsdiff/pkg/bspatch"
)

func main(){
  oldrdr := bytes.NewReader([]byte{0xfa, 0xdd, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff})
  newrdr := bytes.NewReader([]byte{0xfa, 0xdd, 0x00, 0x00, 0x00, 0xee, 0xee, 0x00, 0x00, 0xff, 0xfe, 0xfe})
  patch := new(bytes.Buffer)

  // generate a BSDIFF4 patch
  if err := bsdiff.Reader(oldrdr, newrdr, patch); err != nil {
    panic(err)
  }

  newpatchedf := new(bytes.Buffer)
  oldrdr.Seek(0, 0)

  // Apply a BSDIFF4 patch
  if err := bspatch.Reader(oldrdr, newpatchedf, patch); err != nil {
    panic(err)
  }
  fmt.Println(newpatchedf.Bytes())
}

As a program (CLI)

go get -u -v github.com/gabstv/go-bsdiff/cmd/...

bsdiff oldfile newfile patch
bspatch oldfile newfile2 patch