Here you can find the source of checksum(byte[] buf, int off, int len)
public final static int checksum(byte[] buf, int off, int len)
//package com.java2s; /******************************************************************************* * Copyright 2013 Zhang Zhuo(william@TinyGameX.com). * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License./*ww w . j a v a2s . co m*/ *******************************************************************************/ public class Main { private static int[] crc_t; public final static int checksum(byte[] buf, int off, int len) { return update(buf, off, len) ^ 0xFFFFFFFF; } private final static int update(byte[] buf, int off, int len) { int c = 0xFFFFFFFF; int n; if (crc_t == null) mk(); for (n = off; n < len + off; n++) { c = crc_t[(c ^ buf[n]) & 0xFF] ^ (c >>> 8); } return c; } private final static void mk() { int c, k; if (crc_t == null) crc_t = new int[256]; for (int n = 0; n < 256; n++) { c = n; for (k = 0; k < 8; k++) c = (c & 1) == 1 ? 0xEDB88320 ^ (c >>> 1) : c >>> 1; crc_t[n] = c; } } }