/*
 * 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 com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.IOException;

Package-protected abstract class that implements the line reading algorithm used by LineReader. Line separators are per BufferedReader: line feed, carriage return, or carriage return followed immediately by a linefeed.

Subclasses must implement handleLine, call add to pass character data, and call finish at the end of stream.

Author:Chris Nokleberg
Since:1.0
/** * Package-protected abstract class that implements the line reading algorithm used by {@link * LineReader}. Line separators are per {@link java.io.BufferedReader}: line feed, carriage return, * or carriage return followed immediately by a linefeed. * * <p>Subclasses must implement {@link #handleLine}, call {@link #add} to pass character data, and * call {@link #finish} at the end of stream. * * @author Chris Nokleberg * @since 1.0 */
@GwtIncompatible abstract class LineBuffer {
Holds partial line contents.
/** Holds partial line contents. */
private StringBuilder line = new StringBuilder();
Whether a line ending with a CR is pending processing.
/** Whether a line ending with a CR is pending processing. */
private boolean sawReturn;
Process additional characters from the stream. When a line separator is found the contents of the line and the line separator itself are passed to the abstract handleLine method.
Params:
  • cbuf – the character buffer to process
  • off – the offset into the buffer
  • len – the number of characters to process
Throws:
See Also:
/** * Process additional characters from the stream. When a line separator is found the contents of * the line and the line separator itself are passed to the abstract {@link #handleLine} method. * * @param cbuf the character buffer to process * @param off the offset into the buffer * @param len the number of characters to process * @throws IOException if an I/O error occurs * @see #finish */
protected void add(char[] cbuf, int off, int len) throws IOException { int pos = off; if (sawReturn && len > 0) { // Last call to add ended with a CR; we can handle the line now. if (finishLine(cbuf[pos] == '\n')) { pos++; } } int start = pos; for (int end = off + len; pos < end; pos++) { switch (cbuf[pos]) { case '\r': line.append(cbuf, start, pos - start); sawReturn = true; if (pos + 1 < end) { if (finishLine(cbuf[pos + 1] == '\n')) { pos++; } } start = pos + 1; break; case '\n': line.append(cbuf, start, pos - start); finishLine(true); start = pos + 1; break; default: // do nothing } } line.append(cbuf, start, off + len - start); }
Called when a line is complete.
/** Called when a line is complete. */
@CanIgnoreReturnValue private boolean finishLine(boolean sawNewline) throws IOException { String separator = sawReturn ? (sawNewline ? "\r\n" : "\r") : (sawNewline ? "\n" : ""); handleLine(line.toString(), separator); line = new StringBuilder(); sawReturn = false; return sawNewline; }
Subclasses must call this method after finishing character processing, in order to ensure that any unterminated line in the buffer is passed to handleLine.
Throws:
/** * Subclasses must call this method after finishing character processing, in order to ensure that * any unterminated line in the buffer is passed to {@link #handleLine}. * * @throws IOException if an I/O error occurs */
protected void finish() throws IOException { if (sawReturn || line.length() > 0) { finishLine(false); } }
Called for each line found in the character data passed to add.
Params:
  • line – a line of text (possibly empty), without any line separators
  • end – the line separator; one of "\r", "\n", "\r\n", or ""
Throws:
/** * Called for each line found in the character data passed to {@link #add}. * * @param line a line of text (possibly empty), without any line separators * @param end the line separator; one of {@code "\r"}, {@code "\n"}, {@code "\r\n"}, or {@code ""} * @throws IOException if an I/O error occurs */
protected abstract void handleLine(String line, String end) throws IOException; }