org.beanio.stream.util.CommentReader Maven / Gradle / Ivy
/*
* Copyright 2011 Kevin Seim
*
* 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 org.beanio.stream.util;
import java.io.*;
/**
* Skips commented lines read from an input stream. The input stream must support marking (i.e.
* {@link Reader#markSupported()} must return true). A line is considered commented if it starts
* with one of the configured comment indicators.
*
* @author Kevin Seim
* @since 1.2
*/
public class CommentReader {
private Reader in;
private String[] comments;
private char[] commentBuffer;
private char recordTerminator = 0;
private boolean skipLF;
private boolean eof;
/**
* Constructs a new CommentReader.
* @param in the input stream to read
* @param comments an array of comment identifying strings
* @throws IllegalArgumentException if the configured comments are invalid or the reader does
* not support marking
*/
public CommentReader(Reader in, String [] comments) throws IllegalArgumentException {
this(in, comments, null);
}
/**
* Constructs a new CommentReader.
* @param in the input stream to read from
* @param comments an array of comment identifying strings
* @param recordTerminator the record terminating character
* @throws IllegalArgumentException if the configured comments are invalid or the reader does
* not support marking
*/
public CommentReader(Reader in, String [] comments, Character recordTerminator) throws IllegalArgumentException {
if (comments == null) {
throw new IllegalArgumentException("Comments not set");
}
if (!in.markSupported()) {
throw new IllegalArgumentException("Comments require reader.markSupported() to return true");
}
this.in = in;
this.comments = comments;
if (recordTerminator != null) {
this.recordTerminator = recordTerminator;
}
int maximumCommentLength = 0;
for (String s : comments) {
if (s == null || s.length() == 0) {
throw new IllegalArgumentException("Comment value cannot be null or empty string");
}
maximumCommentLength = Math.max(maximumCommentLength, s.length());
}
commentBuffer = new char[maximumCommentLength + 1];
}
/**
* Returns whether the next character should be ignored if its a line feed.
* @return true if the next line feed should be ignored
*/
public boolean isSkipLF() {
return skipLF;
}
/**
* Returns whether the end of the stream was reached reading a commented line.
* @return true if the end of the stream was reached reading a commented line.
*/
public boolean isEOF() {
return eof;
}
/**
* Skips comments in the input stream and returns the number of commented lines read.
* If no commented lines were read, the stream is positioned just as it had been before
* this method is called.
* @param initialSkipLF true if the first line feed character read should be ignored
* @return the number of skipped comment lines
* @throws IOException
*/
public int skipComments(boolean initialSkipLF) throws IOException {
skipLF = initialSkipLF;
int lines = 0;
while (true) {
// mark our current position in the stream
in.mark(commentBuffer.length);
// read the start of the line
int n = in.read(commentBuffer);
if (n <= 0) {
break;
}
String linePrefix;
if (skipLF && commentBuffer[0] == '\n') {
linePrefix = new String(commentBuffer, 1, n-1);
}
else {
linePrefix = new String(commentBuffer, 0, n);
}
// determine if the line prefix matches a configured comment
boolean commentFound = false;
for (String s : comments) {
if (linePrefix.startsWith(s)) {
commentFound = true;
++lines;
break;
}
}
// if no comment was found, break out
if (!commentFound) {
break;
}
// finish reading the entire line
in.reset();
while ((n = in.read()) != -1) {
char c = (char) n;
if (recordTerminator == 0) {
if (skipLF) {
skipLF = false;
if (c == '\n') {
continue;
}
}
if (c == '\n') {
break;
}
else if (c == '\r') {
skipLF = true;
break;
}
}
else if (c == recordTerminator) {
break;
}
}
if (n == -1) {
eof = true;
return lines;
}
}
in.reset();
return lines;
}
}