hash.go

/*
 * Copyright (c) 2014 Jesse van den Kieboom. All rights reserved.
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *    * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following disclaimer
 *      in the documentation and/or other materials provided with the
 *      distribution.
 *    * Neither the name of Google Inc. nor the names of its
 *      contributors may be used to endorse or promote products derived from
 *      this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package main

import (
	"crypto/sha1"
)

type Hasher struct {
}

var hasher Hasher

func (h Hasher) shortHash(b []byte) string {
	const ValidChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

	ret := make([]byte, 10)

	for i, v := range b {
		ret[i%10] += v
	}

	bl := byte(len(ValidChars))

	for i, v := range ret {
		ret[i] = ValidChars[v%bl]
	}

	return string(ret)
}

func (h Hasher) Hash(data ...[]byte) string {
	s := sha1.New()

	for _, d := range data {
		s.Write(d)
	}

	ret := s.Sum(nil)
	return h.shortHash(ret)
}

func (h Hasher) ValidHash(s string) bool {
	for _, c := range s {
		switch {
		case c >= 'a' && c <= 'z':
		case c >= 'A' && c <= 'Z':
		case c >= '0' && c <= '9':
		default:
			return false
		}
	}

	return len(s) > 0
}