package ch.inftec.ju.util.io;
import java.io.IOException;
import java.io.Reader;
import java.util.LinkedList;
import java.util.Queue;
import org.apache.commons.io.LineIterator;
import org.apache.commons.lang3.StringUtils;
/**
* Reader that is aware of new line characters, i.e. that will try to auto detect what kind of NewLine
* the file uses (\r\n, \r or \n).
* <p>
* Initially, the newLine property will be set to null. If left to null, the Reader will set it to the
* value of the NewLine string as soon as it encounters the first new line. After that, all following
* lines are treated accordingly.
* <p>
* If set manually, the reader will treat the new lines accordingly to the value set. E.g. if the
* newLine string ist set manually to '\n' and the Reader encounters a '\r\n', the '\r' will be
* part of the string returned.
* @author Martin
*
*/
public class NewLineReader extends Reader {
public static String LF = "\n";
public static String CRLF = "\r\n";
/**
* Input new line String.
*/
private String inputNewLine = null;
/**
* Output new line String.
*/
private String outputNewLine = null;
/**
* Buffer for characters that have been read from the underlying reader.
* This will already contain the converted output NewLines (if different
* from the input NewLines).
*/
private Queue<Character> queue = new LinkedList<Character>();
/**
* Reader the NewLineReader works with.
*/
private Reader reader;
/**
* Creates a new NewLineReader, using the same input and output NewLine
* Strings as used in the character stream.
* @param reader Reader to read character stream from
*/
public NewLineReader(Reader reader) {
this(reader, null, null);
}
/**
* Creates a new NewLineReader using the specified input and output NewLine
* Strings.
* @param reader Reader to read character stream from
* @param inputNewLine Input NewLine String. If null, it is auto detected from the first
* occurrence of a newLine String in the stream. If not null, it must be either 1 or
* two characters.
* @param outputNewLine Output NewLine String. If null, the same NewLine String as
* the input NewLine String is used
*/
public NewLineReader(Reader reader, String inputNewLine, String outputNewLine) {
this.reader = reader;
if (StringUtils.length(inputNewLine) > 2 || StringUtils.length(outputNewLine) > 2) {
throw new IllegalArgumentException("Input and Output NewLine characters can not be longer than 2 characters.");
}
if (inputNewLine != null && inputNewLine.length() == 0) {
throw new IllegalArgumentException("Input NewLine may not be empty String");
}
this.inputNewLine = inputNewLine;
this.outputNewLine = outputNewLine;
}
/**
* Gets the Input NewLine character used or detected by this Reader. If none
* has been specified and the Reader hasn't encountered any, null is returned.
* @return Input NewLine String or null if not known
*/
public String getInputNewLine() {
return this.inputNewLine;
}
/**
* Gets the Output NewLine character used by this Reader. If none has been
* specified and the Reader hasn't encountered any, null is returned.
* @return Output NewLine String or null if not known
*/
public String getOutputNewLine() {
return this.outputNewLine;
}
@Override
public void close() throws IOException {
this.reader.close();
}
@Override
public int read(char[] cbuf, int off, int len) throws IOException {
this.doRead(len);
if (this.queue.size() == 0) return -1;
int i = off;
int lastIndex = off + len - 1;
while (i <= lastIndex && this.queue.size() > 0) {
cbuf[i] = this.queue.poll().charValue();
i++;
}
return i-off;
}
/**
* Makes sure the queue holds the the specified amount of characters. If the stream
* doesn't provide enough characters, as much as possible are read.
* @param len Characters to be read into the queue. If the stream ends
* before, we'll read as many characters as possible.
* @throws IOException If the next character cannot be read
*/
private void doRead(int len) throws IOException {
while (this.queue.size() < len) {
if (!this.readFirstChar()) return;
}
}
/**
* Reads a character from the underlying reader. If the character could be part
* of a two character new line sequence, another character will be read. The
* character(s) will be added to the reader's queue.
* @return False if the end of the reader was reached, true otherwise
* @throws IOException
*/
private boolean readFirstChar() throws IOException {
int nextChInt = this.reader.read();
if (nextChInt == -1) return false;
char nextCh = (char)nextChInt;
if (this.inputNewLine != null && this.inputNewLine.charAt(0) == nextCh) {
if (this.inputNewLine.length() == 1) {
this.addNewLine();
} else {
return this.readSecondChar(nextCh);
}
} else if (this.inputNewLine == null && nextCh == '\n') {
this.inputNewLine = "\n";
this.addNewLine();
} else if (this.inputNewLine == null && nextCh == '\r') {
return this.readSecondChar(nextCh);
} else {
this.queue.add(nextCh);
}
return true;
}
/**
* Reads the second character of a possible NewLine combination from the reader.
* The characters will be added to the reader's queue
* @param firstCh First character
* @return False if the end of the reader was reached, true otherwise
* @throws IOException If the character canot be read
*/
private boolean readSecondChar(char firstCh) throws IOException {
// Try to read second character.
int nextChInt = this.reader.read();
if (nextChInt == -1) {
if (this.inputNewLine == null && firstCh == '\r' || firstCh == '\n') {
// First char IS NewLine
this.inputNewLine = Character.toString(firstCh);
this.addNewLine();
} else {
// No NewLine found
this.queue.add(firstCh);
}
return false;
}
// Next character was not null
char nextCh = (char)nextChInt;
if (this.inputNewLine != null) {
if (this.inputNewLine.charAt(1) == nextCh) {
this.addNewLine();
} else {
this.queue.add(firstCh);
this.queue.add(nextCh);
}
} else {
// First character must have been '\r'
if (nextCh == '\n') {
this.inputNewLine = "\r\n";
this.addNewLine();
} else {
this.inputNewLine = "\r";
this.addNewLine();
this.queue.add(nextCh);
}
}
return true;
}
/**
* Adds a new (output) NewLine to the queue.
*/
private void addNewLine() {
if (this.outputNewLine == null) this.outputNewLine = this.inputNewLine;
for (int i = 0; i < this.outputNewLine.length(); i++) this.queue.add(this.outputNewLine.charAt(i));
}
@Override
public void reset() throws IOException {
this.reader.reset();
this.queue.clear();
}
/**
* Creates a new LineIterator instance on this reader.
* @return LineIterator
*/
public LineIterator iterateLines() {
return new LineIterator(this);
}
}