Generate checksum for a file in Go
With billions of files being downloaded and transferred across Internet everyday. Generating checksum is important component in proramming today to ensure that the files are not being tempered with. In this tutorial, we will learn how to generate MD5 checksum for a sample file in Go
checksum.go
package main
import (
"fmt"
"io"
"os"
"math"
"crypto/md5"
)
const filechunk = 8192 // we settle for 8KB
func main() {
file, err := os.Open("utf8.txt")
if err != nil {
panic(err.Error())
}
defer file.Close()
// calculate the file size
info, _ := file.Stat()
filesize := info.Size()
blocks := uint64(math.Ceil(float64(filesize) / float64(filechunk)))
hash := md5.New()
for i := uint64(0); i < blocks; i++ {
blocksize := int(math.Min(filechunk, float64(filesize-int64(i*filechunk))))
buf := make([] byte, blocksize)
file.Read(buf)
io.WriteString(hash, string(buf)) // append into the hash
}
fmt.Printf("%s checksum is %x\n",file.Name(), hash.Sum(nil))
}
Output : >go run checksum.go
utf8.txt checksum is c3882b3e45e88ba87617f44ce1e7611d
This example uses the md5 crypto and of course you can just replace it with SHA1, SHA256 easily by changing the crypto package.
References :
By Adam Ng
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