Shift-And和Shift-Or ByteBuffer匹配器
两个ByteBuffer的匹配算法java实现，原作者 庄大侠，这边收藏下
import java.nio.ByteBuffer;import java.util.ArrayList;import java.util.List;/** * @description * @author <a href="junyu@taobao.com">junyu</a> * @date 2012-9-7下午04:05:05 */public class ShiftAndByteBufferMatcher {private int[] b;private final int mask;private final int patternLimit;private final int patternPos;private final int patternLen;public ShiftAndByteBufferMatcher(final ByteBuffer pat) {if (pat == null || pat.remaining() == 0) {throw new IllegalArgumentException("blank buffer");}this.patternLimit = pat.limit();this.patternPos = pat.position();this.patternLen = pat.remaining();this.preprocess(pat);this.mask = 1 << this.patternLen - 1;}/** * 预处理 * * @param pat */private void preprocess(final ByteBuffer pat) {this.b = new int[256];for (int i = this.patternPos; i < this.patternLimit; i++) {final int p = (pat.get(i)) & 0xFF;this.b[p] = this.b[p] | 1 << i;}}public final List<Integer> matchAll(final ByteBuffer buffer) {final List<Integer> matches = new ArrayList<Integer>();final int bufferLimit = buffer.limit();int d = 0;for (int pos = buffer.position(); pos < bufferLimit; pos++) {d <<= 1;d |= 1;d &= this.b[(buffer.get(pos)) & 0xFF];if ((d & this.mask) != 0) {matches.add(pos - this.patternLen + 1);}}return matches;}public final int matchFirst(final ByteBuffer buffer) {if (buffer == null) {return -1;}final int bufferLimit = buffer.limit();int d = 0;for (int pos = buffer.position(); pos < bufferLimit; pos++) {d <<= 1;d |= 1;d &= this.b[(buffer.get(pos)) & 0xFF];if ((d & this.mask) != 0) {return pos - this.patternLen + 1;}}return -1;}}import java.nio.ByteBuffer;import java.util.ArrayList;import java.util.List;/** * @description * @author <a href="junyu@taobao.com">junyu</a> * @date 2012-9-7下午04:05:05 */public class ShiftOrByteBufferMatcher {private int[] b;private int lim;private final int patternLen;public ShiftOrByteBufferMatcher(final ByteBuffer pat) {if (pat == null || pat.remaining() == 0) {throw new IllegalArgumentException("blank buffer");}this.patternLen = pat.remaining();this.preprocess(pat);}/** * 预处理 * * @param pat */private void preprocess(final ByteBuffer pat) {this.b = new int[256];this.lim = 0;for (int i = 0; i < 256; i++) {this.b[i] = ~0;}for (int i = 0, j = 1; i < this.patternLen; i++, j <<= 1) {this.b[(pat.get(i)) & 0xFF] &= ~j;this.lim |= j;}this.lim = ~(this.lim >> 1);}public final List<Integer> matchAll(final ByteBuffer buffer) {final List<Integer> matches = new ArrayList<Integer>();final int bufferLimit = buffer.limit();int state = ~0;for (int pos = buffer.position(); pos < bufferLimit; pos++) {state <<= 1;state |= this.b[(buffer.get(pos)) & 0xFF];if (state < this.lim) {matches.add(pos - this.patternLen + 1);}}return matches;}public final int matchFirst(final ByteBuffer buffer) {if (buffer == null) {return -1;}final int bufferLimit = buffer.limit();int state = ~0;for (int pos = buffer.position(); pos < bufferLimit; pos++) {state = (state <<= 1) | this.b[(buffer.get(pos)) & 0xFF];if (state < this.lim) {return pos - this.patternLen + 1;}}return -1;}}