SHA1 Hash Generator in Golang

sha1.go

package main

import (
	"crypto/sha1"
	"fmt"
	"io"
	"math"
	"os"
)

// 8KB
const filechunk = 8192

func main() {
	// Ensure the file argument is passed
	if len(os.Args) != 2 {
		fmt.Println("Please use this syntax: sha1.exe file.txt")
		return
	}

	// Open the file for reading
	file, err := os.Open(os.Args[1])
	if err != nil {
		fmt.Println("Cannot find file:", os.Args[1])
		return
	}

	defer file.Close()

	// Get file info
	info, err := file.Stat()
	if err != nil {
		fmt.Println("Cannot access file:", os.Args[1])
		return
	}

	// Get the filesize
	filesize := info.Size()

	// Calculate the number of blocks
	blocks := uint64(math.Ceil(float64(filesize) / float64(filechunk)))

	// Start hash
	//hash := md5.New()
	hash := sha1.New()

	// Check each block
	for i := uint64(0); i < blocks; i++ {
		// Calculate block size
		blocksize := int(math.Min(filechunk, float64(filesize-int64(i*filechunk))))

		// Make a buffer
		buf := make([]byte, blocksize)

		// Make a buffer
		file.Read(buf)

		// Write to the buffer
		io.WriteString(hash, string(buf))
	}

	// Output the results
	fmt.Printf("%x\n", hash.Sum(nil))
}

With that code (buffer+read+write):

(SHA1: 8b48ae8cc9e88214577f6e6de30bafd9756bdec8) = 6.035ms

Using only "io.Copy(hash, file)"...

(SHA1: 8b48ae8cc9e88214577f6e6de30bafd9756bdec8) = 3.0308ms