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The Apache Commons CSV library provides a simple interface for reading and writing CSV files of various types.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.csv;
import static org.apache.commons.csv.Constants.CR;
import static org.apache.commons.csv.Constants.END_OF_STREAM;
import static org.apache.commons.csv.Constants.LF;
import static org.apache.commons.csv.Constants.UNDEFINED;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
/**
* A special buffered reader which supports sophisticated read access.
*
* In particular the reader supports a look-ahead option, which allows you to see the next char returned by
* {@link #read()}. This reader also tracks how many characters have been read with {@link #getPosition()}.
*
*/
final class ExtendedBufferedReader extends BufferedReader {
/** The last char returned */
private int lastChar = UNDEFINED;
/** The count of EOLs (CR/LF/CRLF) seen so far */
private long eolCounter;
/** The position, which is number of characters read so far */
private long position;
private boolean closed;
/**
* Created extended buffered reader using default buffer-size
*/
ExtendedBufferedReader(final Reader reader) {
super(reader);
}
/**
* Closes the stream.
*
* @throws IOException
* If an I/O error occurs
*/
@Override
public void close() throws IOException {
// Set ivars before calling super close() in case close() throws an IOException.
closed = true;
lastChar = END_OF_STREAM;
super.close();
}
/**
* Returns the current line number
*
* @return the current line number
*/
long getCurrentLineNumber() {
// Check if we are at EOL or EOF or just starting
if (lastChar == CR || lastChar == LF || lastChar == UNDEFINED || lastChar == END_OF_STREAM) {
return eolCounter; // counter is accurate
}
return eolCounter + 1; // Allow for counter being incremented only at EOL
}
/**
* Returns the last character that was read as an integer (0 to 65535). This will be the last character returned by
* any of the read methods. This will not include a character read using the {@link #lookAhead()} method. If no
* character has been read then this will return {@link Constants#UNDEFINED}. If the end of the stream was reached
* on the last read then this will return {@link Constants#END_OF_STREAM}.
*
* @return the last character that was read
*/
int getLastChar() {
return lastChar;
}
/**
* Gets the character position in the reader.
*
* @return the current position in the reader (counting characters, not bytes since this is a Reader)
*/
long getPosition() {
return this.position;
}
public boolean isClosed() {
return closed;
}
/**
* Returns the next character in the current reader without consuming it. So the next call to {@link #read()} will
* still return this value. Does not affect line number or last character.
*
* @return the next character
*
* @throws IOException
* If an I/O error occurs
*/
int lookAhead() throws IOException {
super.mark(1);
final int c = super.read();
super.reset();
return c;
}
/**
* Populates the buffer with the next {@code buf.length} characters in the
* current reader without consuming them. The next call to {@link #read()} will
* still return the next value. This doesn't affect line number or last
* character.
*
* @param buf the buffer to fill for the look ahead.
* @return the buffer itself
* @throws IOException If an I/O error occurs
*/
char[] lookAhead(final char[] buf) throws IOException {
final int n = buf.length;
super.mark(n);
super.read(buf, 0, n);
super.reset();
return buf;
}
/**
* Returns the next n characters in the current reader without consuming them. The next call to {@link #read()} will still return the next value. This
* doesn't affect line number or last character.
*
* @param n the number characters look ahead.
* @return the next n characters.
* @throws IOException If an I/O error occurs
*/
char[] lookAhead(final int n) throws IOException {
final char[] buf = new char[n];
return lookAhead(buf);
}
@Override
public int read() throws IOException {
final int current = super.read();
if (current == CR || current == LF && lastChar != CR ||
current == END_OF_STREAM && lastChar != CR && lastChar != LF && lastChar != END_OF_STREAM) {
eolCounter++;
}
lastChar = current;
position++;
return lastChar;
}
@Override
public int read(final char[] buf, final int offset, final int length) throws IOException {
if (length == 0) {
return 0;
}
final int len = super.read(buf, offset, length);
if (len > 0) {
for (int i = offset; i < offset + len; i++) {
final char ch = buf[i];
if (ch == LF) {
if (CR != (i > offset ? buf[i - 1] : lastChar)) {
eolCounter++;
}
} else if (ch == CR) {
eolCounter++;
}
}
lastChar = buf[offset + len - 1];
} else if (len == -1) {
lastChar = END_OF_STREAM;
}
position += len;
return len;
}
/**
* Gets the next line, dropping the line terminator(s). This method should only be called when processing a
* comment, otherwise information can be lost.
*
* Increments {@link #eolCounter} and updates {@link #position}.
*
*
* Sets {@link #lastChar} to {@link Constants#END_OF_STREAM} at EOF, otherwise the last EOL character.
*
*
* @return the line that was read, or null if reached EOF.
*/
@Override
public String readLine() throws IOException {
if (lookAhead() == END_OF_STREAM) {
return null;
}
final StringBuilder buffer = new StringBuilder();
while (true) {
final int current = read();
if (current == CR) {
final int next = lookAhead();
if (next == LF) {
read();
}
}
if (current == END_OF_STREAM || current == LF || current == CR) {
break;
}
buffer.append((char) current);
}
return buffer.toString();
}
}