com.google.common.io.LineBuffer Maven / Gradle / Ivy
/*
* 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 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
*/
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;
}
}
line.append(cbuf, start, off + len - start);
}
/** Called when a line is complete. */
private boolean finishLine(boolean sawNewline) throws IOException {
handleLine(line.toString(), sawReturn
? (sawNewline ? "\r\n" : "\r")
: (sawNewline ? "\n" : ""));
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;
}