86 lines
2.7 KiB
Java
86 lines
2.7 KiB
Java
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/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.io;
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import static com.google.common.base.Preconditions.checkNotNull;
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import java.io.IOException;
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import java.io.Reader;
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import java.nio.CharBuffer;
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import java.util.LinkedList;
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import java.util.Queue;
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import com.google.common.annotations.Beta;
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/**
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* A class for reading lines of text. Provides the same functionality as
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* {@link java.io.BufferedReader#readLine()} but for all {@link Readable}
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* objects, not just instances of {@link Reader}.
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*
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* @author Chris Nokleberg
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* @since 1.0
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*/
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@Beta
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public final class LineReader {
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private final Readable readable;
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private final Reader reader;
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private final char[] buf = new char[0x1000]; // 4K
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private final CharBuffer cbuf = CharBuffer.wrap(buf);
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private final Queue<String> lines = new LinkedList<String>();
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private final LineBuffer lineBuf = new LineBuffer() {
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@Override
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protected void handleLine(String line, String end) {
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lines.add(line);
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}
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};
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/**
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* Creates a new instance that will read lines from the given {@code Readable}
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* object.
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*/
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public LineReader(Readable readable) {
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this.readable = checkNotNull(readable);
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this.reader = (readable instanceof Reader) ? (Reader) readable : null;
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}
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/**
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* Reads a line of text. A line is considered to be terminated by any one of a
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* line feed ({@code '\n'}), a carriage return ({@code '\r'}), or a carriage
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* return followed immediately by a linefeed ({@code "\r\n"}).
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*
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* @return a {@code String} containing the contents of the line, not including
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* any line-termination characters, or {@code null} if the end of the
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* stream has been reached.
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* @throws IOException if an I/O error occurs
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*/
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public String readLine() throws IOException {
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while (lines.peek() == null) {
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cbuf.clear();
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// The default implementation of Reader#read(CharBuffer) allocates a
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// temporary char[], so we call Reader#read(char[], int, int) instead.
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int read = (reader != null) ? reader.read(buf, 0, buf.length) : readable.read(cbuf);
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if (read == -1) {
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lineBuf.finish();
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break;
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}
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lineBuf.add(buf, 0, read);
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}
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return lines.poll();
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}
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}
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