ungif

ungif.go

package main

import (
	"fmt"
	"os"
)

func main() {

	if len(os.Args) != 3 {
		fmt.Println("need 2 args (ex: gif input.gif output")
		os.Exit(-1)
	}

	inputFileInfo, err := os.Stat(os.Args[1])
	if err != nil {
		fmt.Println("input file not found")
		os.Exit(-1)
	}
	inputFile, err := os.Open(os.Args[1])
	defer inputFile.Close()
	if err != nil {
		fmt.Println("input file error")
		os.Exit(-1)
	}

	outputFile, err := os.Create(os.Args[2])
	defer outputFile.Close()
	if err != nil {
		fmt.Println("input file error")
		os.Exit(-1)
	}

	extractDataWrite(inputFile, inputFileInfo.Size(), outputFile)
}

func extractDataWrite(inputFile *os.File, inputFileSize int64, outputFile *os.File) {
	inputFile.Seek(24, 0)
	b255 := make([]byte, 256)
	for {
		inputFile.Read(b255)
		if b255[0] != uint8(255) {
			break
		}
		outputFile.Write(b255[1:])
	}
	outputFile.Write(b255[1 : (inputFileSize-26)%256])
}