/**
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 in byte length ordering:
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.*;
/**
* This inputstream will recognize unicode BOM marks and will skip bytes if
* getEncoding() method is called before any of the read(...) methods.
*
* Usage pattern: String enc = "ISO-8859-1"; // or NULL to use systemdefault
* FileInputStream fis = new FileInputStream(file); UnicodeInputStream uin = new
* UnicodeInputStream(fis, enc); enc = uin.getEncoding(); // check and skip
* possible BOM bytes InputStreamReader in; if (enc == null) in = new
* InputStreamReader(uin); else in = new InputStreamReader(uin, enc);
*/
public class UnicodeInputStream extends InputStream {
PushbackInputStream internalIn;
boolean isInited = false;
String defaultEnc;
String encoding;
private static final int BOM_SIZE = 4;
UnicodeInputStream(InputStream in, String defaultEnc) {
internalIn = new PushbackInputStream(in, BOM_SIZE);
this.defaultEnc = defaultEnc;
}
public String getDefaultEncoding() {
return defaultEnc;
}
public String getEncoding() {
if (!isInited) {
try {
init();
} catch (IOException ex) {
IllegalStateException ise = new IllegalStateException(
"Init method failed.");
ise.initCause(ise);
throw ise;
}
}
return encoding;
}
/**
* 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 (isInited)
return;
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);
isInited = true;
}
public void close() throws IOException {
// init();
isInited = true;
internalIn.close();
}
public int read() throws IOException {
// init();
isInited = true;
return internalIn.read();
}
}
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