/*
* 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.io.input;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.List;
import org.apache.commons.io.ByteOrderMark;
/**
* This class is used to wrap a stream that includes an encoded
* {@link ByteOrderMark} as its first bytes.
*
* This class detects these bytes and, if required, can automatically skip them
* and return the subsequent byte as the first byte in the stream.
*
* The {@link ByteOrderMark} implementation has the following pre-defined BOMs:
* <ul>
* <li>UTF-8 - {@link ByteOrderMark#UTF_8}</li>
* <li>UTF-16BE - {@link ByteOrderMark#UTF_16LE}</li>
* <li>UTF-16LE - {@link ByteOrderMark#UTF_16BE}</li>
* </ul>
*
*
* <h3>Example 1 - Detect and exclude a UTF-8 BOM</h3>
* <pre>
* BOMInputStream bomIn = new BOMInputStream(in);
* if (bomIn.hasBOM()) {
* // has a UTF-8 BOM
* }
* </pre>
*
* <h3>Example 2 - Detect a UTF-8 BOM (but don't exclude it)</h3>
* <pre>
* boolean include = true;
* BOMInputStream bomIn = new BOMInputStream(in, include);
* if (bomIn.hasBOM()) {
* // has a UTF-8 BOM
* }
* </pre>
*
* <h3>Example 3 - Detect Multiple BOMs</h3>
* <pre>
* BOMInputStream bomIn = new BOMInputStream(in, ByteOrderMark.UTF_16LE, ByteOrderMark.UTF_16BE);
* if (bomIn.hasBOM() == false) {
* // No BOM found
* } else if (bomIn.hasBOM(ByteOrderMark.UTF_16LE)) {
* // has a UTF-16LE BOM
* } else if (bomIn.hasBOM(ByteOrderMark.UTF_16BE)) {
* // has a UTF-16BE BOM
* }
* </pre>
*
* @see org.apache.commons.io.ByteOrderMark
* @see <a href="http://en.wikipedia.org/wiki/Byte_order_mark">Wikipedia - Byte Order Mark</a>
* @version $Revision: 1052095 $ $Date: 2010-12-22 18:03:20 -0500 (Wed, 22 Dec 2010) $
* @since Commons IO 2.0
*/
public class BOMInputStream extends ProxyInputStream {
private final boolean include;
private final List<ByteOrderMark> boms;
private ByteOrderMark byteOrderMark;
private int[] firstBytes;
private int fbLength;
private int fbIndex;
private int markFbIndex;
private boolean markedAtStart;
/**
* Constructs a new BOM InputStream that excludes
* a {@link ByteOrderMark#UTF_8} BOM.
* @param delegate the InputStream to delegate to
*/
public BOMInputStream(InputStream delegate) {
this(delegate, false, ByteOrderMark.UTF_8);
}
/**
* Constructs a new BOM InputStream that detects a
* a {@link ByteOrderMark#UTF_8} and optionally includes it.
* @param delegate the InputStream to delegate to
* @param include true to include the UTF-8 BOM or
* false to exclude it
*/
public BOMInputStream(InputStream delegate, boolean include) {
this(delegate, include, ByteOrderMark.UTF_8);
}
/**
* Constructs a new BOM InputStream that excludes
* the specified BOMs.
* @param delegate the InputStream to delegate to
* @param boms The BOMs to detect and exclude
*/
public BOMInputStream(InputStream delegate, ByteOrderMark... boms) {
this(delegate, false, boms);
}
/**
* Constructs a new BOM InputStream that detects the
* specified BOMs and optionally includes them.
* @param delegate the InputStream to delegate to
* @param include true to include the specified BOMs or
* false to exclude them
* @param boms The BOMs to detect and optionally exclude
*/
public BOMInputStream(InputStream delegate, boolean include, ByteOrderMark... boms) {
super(delegate);
if (boms == null || boms.length == 0) {
throw new IllegalArgumentException("No BOMs specified");
}
this.include = include;
this.boms = Arrays.asList(boms);
}
/**
* Indicates whether the stream contains one of the specified BOMs.
*
* @return true if the stream has one of the specified BOMs, otherwise false
* if it does not
* @throws IOException if an error reading the first bytes of the stream occurs
*/
public boolean hasBOM() throws IOException {
return (getBOM() != null);
}
/**
* Indicates whether the stream contains the specified BOM.
*
* @param bom The BOM to check for
* @return true if the stream has the specified BOM, otherwise false
* if it does not
* @throws IllegalArgumentException if the BOM is not one the stream
* is configured to detect
* @throws IOException if an error reading the first bytes of the stream occurs
*/
public boolean hasBOM(ByteOrderMark bom) throws IOException {
if (!boms.contains(bom)) {
throw new IllegalArgumentException("Stream not configure to detect " + bom);
}
return (byteOrderMark != null && getBOM().equals(bom));
}
/**
* Return the BOM (Byte Order Mark).
*
* @return The BOM or null if none
* @throws IOException if an error reading the first bytes of the stream occurs
*/
public ByteOrderMark getBOM() throws IOException {
if (firstBytes == null) {
int max = 0;
for (ByteOrderMark bom : boms) {
max = Math.max(max, bom.length());
}
firstBytes = new int[max];
for (int i = 0; i < firstBytes.length; i++) {
firstBytes[i] = in.read();
fbLength++;
if (firstBytes[i] < 0) {
break;
}
byteOrderMark = find();
if (byteOrderMark != null) {
if (!include) {
fbLength = 0;
}
break;
}
}
}
return byteOrderMark;
}
/**
* Return the BOM charset Name - {@link ByteOrderMark#getCharsetName()}.
*
* @return The BOM charset Name or null if no BOM found
* @throws IOException if an error reading the first bytes of the stream occurs
*
*/
public String getBOMCharsetName() throws IOException {
getBOM();
return (byteOrderMark == null ? null : byteOrderMark.getCharsetName());
}
/**
* This method reads and either preserves or skips the first bytes in the
* stream. It behaves like the single-byte <code>read()</code> method,
* either returning a valid byte or -1 to indicate that the initial bytes
* have been processed already.
* @return the byte read (excluding BOM) or -1 if the end of stream
* @throws IOException if an I/O error occurs
*/
private int readFirstBytes() throws IOException {
getBOM();
return (fbIndex < fbLength) ? firstBytes[fbIndex++] : -1;
}
/**
* Find a BOM with the specified bytes.
*
* @return The matched BOM or null if none matched
*/
private ByteOrderMark find() {
for (ByteOrderMark bom : boms) {
if (matches(bom)) {
return bom;
}
}
return null;
}
/**
* Check if the bytes match a BOM.
*
* @param bom The BOM
* @return true if the bytes match the bom, otherwise false
*/
private boolean matches(ByteOrderMark bom) {
if (bom.length() != fbLength) {
return false;
}
for (int i = 0; i < bom.length(); i++) {
if (bom.get(i) != firstBytes[i]) {
return false;
}
}
return true;
}
//----------------------------------------------------------------------------
// Implementation of InputStream
//----------------------------------------------------------------------------
/**
* Invokes the delegate's <code>read()</code> method, detecting and
* optionally skipping BOM.
* @return the byte read (excluding BOM) or -1 if the end of stream
* @throws IOException if an I/O error occurs
*/
@Override
public int read() throws IOException {
int b = readFirstBytes();
return (b >= 0) ? b : in.read();
}
/**
* Invokes the delegate's <code>read(byte[], int, int)</code> method, detecting
* and optionally skipping BOM.
* @param buf the buffer to read the bytes into
* @param off The start offset
* @param len The number of bytes to read (excluding BOM)
* @return the number of bytes read or -1 if the end of stream
* @throws IOException if an I/O error occurs
*/
@Override
public int read(byte[] buf, int off, int len) throws IOException {
int firstCount = 0;
int b = 0;
while ((len > 0) && (b >= 0)) {
b = readFirstBytes();
if (b >= 0) {
buf[off++] = (byte) (b & 0xFF);
len--;
firstCount++;
}
}
int secondCount = in.read(buf, off, len);
return (secondCount < 0) ? (firstCount > 0 ? firstCount : -1) : firstCount + secondCount;
}
/**
* Invokes the delegate's <code>read(byte[])</code> method, detecting and
* optionally skipping BOM.
* @param buf the buffer to read the bytes into
* @return the number of bytes read (excluding BOM)
* or -1 if the end of stream
* @throws IOException if an I/O error occurs
*/
@Override
public int read(byte[] buf) throws IOException {
return read(buf, 0, buf.length);
}
/**
* Invokes the delegate's <code>mark(int)</code> method.
* @param readlimit read ahead limit
*/
@Override
public synchronized void mark(int readlimit) {
markFbIndex = fbIndex;
markedAtStart = (firstBytes == null);
in.mark(readlimit);
}
/**
* Invokes the delegate's <code>reset()</code> method.
* @throws IOException if an I/O error occurs
*/
@Override
public synchronized void reset() throws IOException {
fbIndex = markFbIndex;
if (markedAtStart) {
firstBytes = null;
}
in.reset();
}
/**
* Invokes the delegate's <code>skip(long)</code> method, detecting
* and optionallyskipping BOM.
* @param n the number of bytes to skip
* @return the number of bytes to skipped or -1 if the end of stream
* @throws IOException if an I/O error occurs
*/
@Override
public long skip(long n) throws IOException {
while ((n > 0) && (readFirstBytes() >= 0)) {
n--;
}
return in.skip(n);
}
}
|