| /* |
| * Copyright (C) 2007 The Guava Authors |
| * |
| * 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.google.common.io; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| import static com.google.common.io.CharStreams.createBuffer; |
| |
| import com.google.common.annotations.Beta; |
| import com.google.common.annotations.GwtIncompatible; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import java.io.IOException; |
| import java.io.Reader; |
| import java.nio.CharBuffer; |
| import java.util.LinkedList; |
| import java.util.Queue; |
| import org.checkerframework.checker.nullness.compatqual.NullableDecl; |
| |
| /** |
| * A class for reading lines of text. Provides the same functionality as {@link |
| * java.io.BufferedReader#readLine()} but for all {@link Readable} objects, not just instances of |
| * {@link Reader}. |
| * |
| * @author Chris Nokleberg |
| * @since 1.0 |
| */ |
| @Beta |
| @GwtIncompatible |
| public final class LineReader { |
| private final Readable readable; |
| @NullableDecl private final Reader reader; |
| private final CharBuffer cbuf = createBuffer(); |
| private final char[] buf = cbuf.array(); |
| |
| private final Queue<String> lines = new LinkedList<>(); |
| private final LineBuffer lineBuf = |
| new LineBuffer() { |
| @Override |
| protected void handleLine(String line, String end) { |
| lines.add(line); |
| } |
| }; |
| |
| /** Creates a new instance that will read lines from the given {@code Readable} object. */ |
| public LineReader(Readable readable) { |
| this.readable = checkNotNull(readable); |
| this.reader = (readable instanceof Reader) ? (Reader) readable : null; |
| } |
| |
| /** |
| * Reads a line of text. A line is considered to be terminated by any one of a line feed ({@code |
| * '\n'}), a carriage return ({@code '\r'}), or a carriage return followed immediately by a |
| * linefeed ({@code "\r\n"}). |
| * |
| * @return a {@code String} containing the contents of the line, not including any |
| * line-termination characters, or {@code null} if the end of the stream has been reached. |
| * @throws IOException if an I/O error occurs |
| */ |
| @CanIgnoreReturnValue // to skip a line |
| public String readLine() throws IOException { |
| while (lines.peek() == null) { |
| Java8Compatibility.clear(cbuf); |
| // The default implementation of Reader#read(CharBuffer) allocates a |
| // temporary char[], so we call Reader#read(char[], int, int) instead. |
| int read = (reader != null) ? reader.read(buf, 0, buf.length) : readable.read(cbuf); |
| if (read == -1) { |
| lineBuf.finish(); |
| break; |
| } |
| lineBuf.add(buf, 0, read); |
| } |
| return lines.poll(); |
| } |
| } |