pack

Go Pack

Lightweight dependency-free embedding of static files into Go executables.

There are other "embedding" type modules, namely:

• statik

However, those implementation did not fit the use case I was targeting.

NOTE: Go Pack currently breaks is using code signing on macOS, there is a fix possible but it will break the existing steps.

Implementation

The implementation assumes the following binary file structure

executable + zip contents + zip size

offset 0
Executable Data
offset x - y
Zip Data
offset x - 10
Zip Size (y)
offset x

The logic attempts to find a string represented size marker (10 bytes) at the end of the Go executable. This marker is used to calculate the offset of the zip contents from the end of the executable. The zip contents are optionally buffered and used to access the static files in the zip contents or extracted to the directory containing the executable.

Usage

For the demo, the following steps were used to generate the expected executable file format:

    zip pack cmd/index.html
    printf "%010d" `stat -f%z pack.zip` >> pack.zip
    mv TheExecutable main.pack; cat main.pack pack.zip > TheExecutable
    chmod +x TheExecutable

The API is simply:

package main

import "github.com/mlavergn/gopack/src/pack"

func main() {
    pack := gopack.NewPack()
    // A) extract to working directory
    pack.Extract()
    // -or-
    // B) read from memory buffer
    pack.Load()
    // b1) string value
    stringValue := pack.String("cmd/index.html")
    // b2) []byte value
    byteValue := pack.Bytes("cmd/index.html")
    // b3) pipe value (eg. http.resp)
    reader := pack.Pipe("cmd/index.html")
    ioutil.Copy(resp, reader)
}