vio_example.go

package main

import "bytes"
import "io/ioutil"
import "fmt"
import "flag"

import "github.com/mkb218/gosndfile/sndfile"

type adapter struct {
	br    *bytes.Reader
	index int64
}

func main() {
	flag.Parse()
	fileBytes, err := ioutil.ReadFile(flag.Args()[0])
	if err != nil {
		fmt.Println(err)
		return
	}
	br := bytes.NewReader(fileBytes)
	var virtualIo sndfile.VirtualIo
	virtualIo.UserData = &adapter{br, 0}

	virtualIo.GetLength = func(userdata interface{}) int64 {
		a := userdata.(*adapter)
		return int64(a.br.Len())
	}

	virtualIo.Seek = func(offset int64, whence sndfile.Whence, userdata interface{}) int64 {
		a := userdata.(*adapter)
		var goWhence = int(whence)
		var err error
		a.index, err = a.br.Seek(offset, goWhence)
		if err != nil {
			panic(err)
		}
		return a.index
	}

	virtualIo.Read = func(output []byte, userdata interface{}) int64 {
		a := userdata.(*adapter)
		ret, err := a.br.Read(output)
		if err != nil {
			panic(err)
		}
		a.index += int64(ret)
		return int64(ret)
	}

	virtualIo.Write = func(output []byte, userdata interface{}) int64 {
		panic("read-only file")
	}

	virtualIo.Tell = func(userdata interface{}) int64 {
		return userdata.(*adapter).index
	}

	var info sndfile.Info
	_, err = sndfile.OpenVirtual(virtualIo, sndfile.Read, &info)
	if err != nil {
		panic(err)
	}

	fmt.Println(info)

}