com.google.common.io.LineBuffer Maven / Gradle / Ivy
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/*
* 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 {@link
* LineReader}. Line separators are per {@link java.io.BufferedReader}: line feed, carriage return,
* or carriage return followed immediately by a linefeed.
*
* 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. */
private StringBuilder line = new StringBuilder();
/** 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 {@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. */
@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 {@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 {@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;
}