Generic unicode textreader, which will use BOM mark to identify the encoding to be used. If BOM is not found then use a given default or system encoding.
//package org.zkoss.maven.yuicompressor.util;
/**
version: 1.1 / 2007-01-25
- changed BOM recognition ordering (longer boms first)
Original pseudocode : Thomas Weidenfeller
Implementation tweaked: Aki Nieminen
http://www.unicode.org/unicode/faq/utf_bom.html
BOMs:
00 00 FE FF = UTF-32, big-endian
FF FE 00 00 = UTF-32, little-endian
EF BB BF = UTF-8,
FE FF = UTF-16, big-endian
FF FE = UTF-16, little-endian
Win2k Notepad:
Unicode format = UTF-16LE
***/
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PushbackInputStream;
import java.nio.charset.Charset;
/**
* Generic unicode textreader, which will use BOM mark
* to identify the encoding to be used. If BOM is not found
* then use a given default or system encoding.
*/
public class UnicodeReader extends InputStreamReader {
PushbackInputStream internalIn;
InputStreamReader internalIn2 = null;
String defaultEnc;
private static final int BOM_SIZE = 4;
/**
*
* @param in inputstream to be read
* @param defaultEnc default encoding if stream does not have
* BOM marker. Give NULL to use system-level default.
*/
public UnicodeReader(InputStream in, String defaultEnc) {
super(in);
internalIn = new PushbackInputStream(in, BOM_SIZE);
this.defaultEnc = defaultEnc;
}
public UnicodeReader(InputStream in) {
this(in,Charset.defaultCharset().name());
}
public String getDefaultEncoding() {
return defaultEnc;
}
/**
* Get stream encoding or NULL if stream is uninitialized.
* Call init() or read() method to initialize it.
*/
public String getEncoding() {
if (internalIn2 == null) return null;
return internalIn2.getEncoding();
}
/**
* Read-ahead four bytes and check for BOM marks. Extra bytes are
* unread back to the stream, only BOM bytes are skipped.
*/
protected void init() throws IOException {
if (internalIn2 != null) return;
String encoding;
byte bom[] = new byte[BOM_SIZE];
int n, unread;
n = internalIn.read(bom, 0, bom.length);
if ( (bom[0] == (byte)0x00) && (bom[1] == (byte)0x00) &&
(bom[2] == (byte)0xFE) && (bom[3] == (byte)0xFF) ) {
encoding = "UTF-32BE";
unread = n - 4;
} else if ( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) &&
(bom[2] == (byte)0x00) && (bom[3] == (byte)0x00) ) {
encoding = "UTF-32LE";
unread = n - 4;
} else if ( (bom[0] == (byte)0xEF) && (bom[1] == (byte)0xBB) &&
(bom[2] == (byte)0xBF) ) {
encoding = "UTF-8";
unread = n - 3;
} else if ( (bom[0] == (byte)0xFE) && (bom[1] == (byte)0xFF) ) {
encoding = "UTF-16BE";
unread = n - 2;
} else if ( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) ) {
encoding = "UTF-16LE";
unread = n - 2;
} else {
// Unicode BOM mark not found, unread all bytes
encoding = defaultEnc;
unread = n;
}
//System.out.println("read=" + n + ", unread=" + unread);
if (unread > 0) internalIn.unread(bom, (n - unread), unread);
// Use given encoding
if (encoding == null) {
internalIn2 = new InputStreamReader(internalIn);
} else {
internalIn2 = new InputStreamReader(internalIn, encoding);
}
}
public void close() throws IOException {
init();
internalIn2.close();
}
public int read(char[] cbuf, int off, int len) throws IOException {
init();
return internalIn2.read(cbuf, off, len);
}
}
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