Checksum.groovy - Determine the MD5 or SHA1Sum of a file

import java.security.MessageDigest
import java.io.*

/**
 * Inspired in the original https://gist.github.com/marcelmaatkamp/347630/0d2b8a3b4e78c0be1cabf5a70c4784276d628d41
 * Determine the MD5 or SHA1Sum of a file:
 * 
 *   println Checksum.getMD5Sum(new File("file.bin"))
 *   println Checksum.getSHA1Sum(new File("file.bin"))
 *   println Checksum.getMD5Sum("Hello world")
 *   println Checksum.getSHA1Sum("Hello world")
 * 
 */
public class Checksum {
  
  static getSha1sum(File file) {
    return getChecksum(file, "SHA1")
  }

  static getSha1sum(String string) {
    return getChecksum(string, "SHA1")
  }

  static getMD5sum(File file) {
    return getChecksum(file, "MD5")
  }

  static getMD5sum(String string) {
    return getChecksum(string, "MD5")
  }

  static getChecksum(File file, type) {
    def digest = MessageDigest.getInstance(type)
    def inputstream = file.newInputStream()
    def buffer = new byte[16384]
    def len

    while((len=inputstream.read(buffer)) > 0) {
      digest.update(buffer, 0, len)
    }
    def sha1sum = digest.digest()

    def result = ""
    for(byte b : sha1sum) {
      result += toHex(b)
    }
    return result
  }

  static getChecksum(String string, type) {
    def digest = MessageDigest.getInstance(type)
    def inputstream = new ByteArrayInputStream( string.getBytes( 'UTF-8' ) )
    def buffer = new byte[16384]
    def len

    while((len=inputstream.read(buffer)) > 0) {
      digest.update(buffer, 0, len)
    }
    def sha1sum = digest.digest()

    def result = ""
    for(byte b : sha1sum) {
      result += toHex(b)
    }
    return result
  }
  
  private static hexChr(int b) {
    return Integer.toHexString(b & 0xF)
  }

  private static toHex(int b) {
    return hexChr((b & 0xF0) >> 4) + hexChr(b & 0x0F)
  }

  static def main(args) {
    def sha1sum = Checksum.getSha1sum(new File(args[0]))
    println "file($args[0]): sha1sum($sha1sum)"
  }

}