net.paoding.analysis.knife.Beef Maven / Gradle / Ivy
/**
* Copyright 2007 The Apache Software Foundation
*
* 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.
*/
package net.paoding.analysis.knife;
/**
* {@link Beef}是要被庖丁“解”的“牛骨肉”，是对文本字符流的高效封装，可以从中读取指定位置的字符。
*
* {@link Beef}和{@link String}对象的不同之处在于：
* {@link Beef}共享输入的char数组，{@link String}的策略是对共享数组进行克隆，克隆损耗了性能。
* 同时，{@link Beef}在 {@link #charAt(int)}方法还进行对字符的预处理，使返回时符合规则:1)toLowerCase
* 2)全角转半角等
*
*
* @author Zhiliang Wang [[email protected]]
*
* @since 1.0
*
*/
public class Beef implements CharSequence {
// -------------------------------------------------
/**
* 文本字符数组
*/
private final char[] value;
/**
* 字符开始位置，即charAt(i)返回value[offset+i]字符
*/
private int offset;
/**
* 从offset位置开始的字符数
*/
private int count;
/** Cache the hash code for the beef */
private int hash; // Default to 0
// -------------------------------------------------
/**
* 构造函数
*
* @param body
* 被本对象中直接拥有的文本字符数组
* @param offset
* 字符开始位置，即get(i)返回body[offset+i]字符
* @param count
* 从offset位置开始的字符数
*/
public Beef(char[] value, int offset, int count) {
this.value = value;
set(offset, count);
}
// -------------------------------------------------
public void set(int offset, int count) {
if (offset < 0) {
throw new StringIndexOutOfBoundsException(offset);
}
if (count < 0) {
throw new StringIndexOutOfBoundsException(count);
}
if (offset > value.length - count) {
throw new StringIndexOutOfBoundsException(offset + count);
}
this.offset = offset;
this.count = count;
}
public char[] getValue() {
return value;
}
public int getCount() {
return count;
}
public int getOffset() {
return offset;
}
// -------------------------------------------------
/**
* 获取指定位置的字符。返回之前将被预处理：1)toLowerCase，2)全角转半角等
*/
public char charAt(int index) {
if (index >= 0 && index < count) {
char src = value[offset + index];
if (src > 65280 && src < 65375) {
src = (char) (src - 65248);
value[offset + index] = src;
}
if (src >= 'A' && src <= 'Z') {
src += 32;
value[offset + index] = src;
} else if (src == 12288) {
src = 32;
value[offset + index] = 32;
}
return src;
}
return (char) -1;
}
public int length() {
return count;
}
public CharSequence subSequence(int start, int end) {
return new String(value, offset + start, end - start);
}
// -------------------------------------------------
public String toString() {
return new String(value, offset, count);
}
public int hashCode() {
int h = hash;
if (h == 0) {
int off = offset;
char val[] = value;
int len = count;
for (int i = 0; i < len; i++) {
h = 31 * h + val[off++];
}
hash = h;
}
return h;
}
}