example.go

package main

import (
	"bytes"
	"encoding/binary"
	"flag"
	"fmt"
	"github.com/Cryptkeeper/go-fseq"
	"github.com/Cryptkeeper/go-fseq/pkg/v1"
	"github.com/Cryptkeeper/go-fseq/pkg/v2"
	"io"
	"io/ioutil"
	"log"
	"os"
)

func main() {
	var path = flag.String("path", "in.fseq", "input file to read")
	flag.Parse()

	b, err := ioutil.ReadFile(*path)
	if err != nil {
		log.Fatal(err)
	}

	_, majorVersion := fseq.ReadVersion(b) // discard minorVersion return
	switch majorVersion {
	case v1.MajorVersion:
		// go-fseq supports the v1 format, this is simply an example usage of version matching
		log.Fatal("outdated format version, v1!")

	case v2.MajorVersion:
		var r = bytes.NewReader(b)

		// fseq files are encoded as little-endian
		var h v2.Header
		if err := binary.Read(r, binary.LittleEndian, &h); err != nil {
			log.Fatal(err)
		}

		// If the file is compressed, dump the Compression Blocks into files
		// These will not be decompressed, simply read and separated
		if h.Compression != v2.None {
			var blocks = make([]v2.CompressionBlock, h.CompressionBlockCount)

			for i := 0; i < int(h.CompressionBlockCount); i++ {
				if err := binary.Read(r, binary.LittleEndian, &blocks[i]); err != nil {
					log.Fatal(err)
				}

				// fpp source code ignores 0 length Compression Blocks (no idea why they're encoded, alignment?)
				if blocks[i].Length == 0 {
					// Trim array since it isn't full
					blocks = blocks[:i]

					break
				}
			}

			log.Printf("%+v\n", blocks)

			// Compression Block offsets are relative to Channel Data Start Offset
			if _, err := r.Seek(int64(h.ChannelDataStartOffset), io.SeekStart); err != nil {
				log.Fatal(err)
			}

			for _, block := range blocks {
				var b = make([]uint8, block.Length)

				if n, err := r.Read(b); err != nil {
					log.Fatal(err)
				} else if n != int(block.Length) {
					log.Fatalf("n = %d, expected %d", n, block.Length)
				}

				var out = fmt.Sprintf("frame_%d.bin", block.FrameNumber)

				log.Println("writing:", out)

				// Write the Compression Block out to a file
				if err := ioutil.WriteFile(out, b, os.ModePerm); err != nil {
					log.Fatal(err)
				}
			}

			// Ensure the full file has been read
			if r.Len() != 0 {
				log.Fatalf("%d bytes remaining, should be empty!", r.Len())
			}
		}

	default:
		log.Fatal("unknown format version!")
	}
}