com.mayabot.nlp.common.FastCharReader Maven / Gradle / Ivy
/*
* Copyright 2018 mayabot.com authors. All rights reserved.
*
* 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 com.mayabot.nlp.common;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.nio.CharBuffer;
/**
* 没有实现标准接口。只是关注 read char. 该实现不支持多线程访问。所以没有锁，所以性能应该好一点。
* 不直接StringReader的原有是，它每次read都会 做锁同步。这个让人受不了
*
* @author jimichan
*/
public class FastCharReader {
private Reader reader;
private CharBuffer buffer;
private int capacity = 128;
private int offset = -1;
public FastCharReader(Reader reader) {
this.reader = reader;
}
public FastCharReader(String string) {
this.reader = new StringReader(string);
if (string.length() < 256) {
this.capacity = Math.max(string.length(), 4);
}
}
public FastCharReader(Reader reader, int capacity) {
this.reader = reader;
this.capacity = Math.max(capacity, 4);
}
public int offset() {
return offset;
}
public void reset(Reader reader) {
this.reader = reader;
this.buffer = null;
this.offset = -1;
}
// 返回-1就表示读完了
public int read() throws IOException {
// prepare buffer
if (buffer == null) { // first time
buffer = CharBuffer.allocate(capacity);
reader.read(buffer); // 写入字符
buffer.flip();// prepare read
} else {
if (buffer.hasRemaining()) {
} else {
buffer.clear();
reader.read(buffer); // 写入字符
buffer.flip();// prepare read
}
}
if (buffer.hasRemaining()) {
offset++;
return buffer.get();
} else {
return -1;
}
}
public static void main(String[] args) throws IOException {
String string = "";
FastCharReader r = new FastCharReader(new StringReader(string));
long t1 = System.currentTimeMillis();
for (int i = 0; i < 1; i++) {
//r = new FastCharReader(new StringReader(string));
r.reset(new StringReader(string));
int c = -1;
while ((c = r.read()) != -1) {
System.out.println(r.offset + " : " + (char) c);
}
}
long t2 = System.currentTimeMillis();
System.out.println(t2 - t1);
System.out.println("string length " + string.length());
}
public static void main2(String[] args) throws IOException {
String string = "\n"
+ "当读取数据时，也是从某个特定位置读。当将Buffer从写模式切换到读模式，position会被重置为0. 当从Buffer的position处读取数据时，position向前移动到下一个可读的位置。\n"
+ "limit\n"
+ "\n"
+ "在写模式下，Buffer的limit表示你最多能往Buffer里写多少数据。 写模式下，limit等于Buffer的capacity。\n"
+ "\n"
+ "当切换Buffer到读模式时， limit表示你最多能读到多少数据。因此，当切换Buffer到读模式时，limit会被设置成写模式下的position值。换句话说，你能读到之前写入的所有数据（limit被设置成已写数据的数量，这个值在写模式下就是position）";
FastCharReader r = new FastCharReader(new StringReader(string));
r.read();
r.read();
long t1 = System.currentTimeMillis();
for (int i = 0; i < 100000; i++) {
//r = new FastCharReader(new StringReader(string));
r.reset(new StringReader(string));
int c = -1;
while ((c = r.read()) != -1) {
// System.out.println(r.offset + " : " + (char) c);
}
}
long t2 = System.currentTimeMillis();
System.out.println(t2 - t1);
System.out.println("string length " + string.length());
}
}