package com.java110.code.util;
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/**
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version: 1.1 / 2007-01-25
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- changed BOM recognition ordering (longer boms first)
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Original pseudocode : Thomas Weidenfeller
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Implementation tweaked: Aki Nieminen
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http://www.unicode.org/unicode/faq/utf_bom.html
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BOMs:
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00 00 FE FF = UTF-32, big-endian
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FF FE 00 00 = UTF-32, little-endian
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EF BB BF = UTF-8,
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FE FF = UTF-16, big-endian
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FF FE = UTF-16, little-endian
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Win2k Notepad:
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Unicode format = UTF-16LE
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***/
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import java.io.*;
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/**
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* Generic unicode textreader, which will use BOM mark
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* to identify the encoding to be used. If BOM is not found
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* then use a given default or system encoding.
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*/
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public class UnicodeReader extends Reader {
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PushbackInputStream internalIn;
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InputStreamReader internalIn2 = null;
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String defaultEnc;
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private static final int BOM_SIZE = 4;
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/**
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*
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* @param in inputstream to be read
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* @param defaultEnc default encoding if stream does not have
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* BOM marker. Give NULL to use system-level default.
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*/
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public UnicodeReader(InputStream in, String defaultEnc) {
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internalIn = new PushbackInputStream(in, BOM_SIZE);
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this.defaultEnc = defaultEnc;
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}
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public String getDefaultEncoding() {
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return defaultEnc;
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}
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/**
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* Get stream encoding or NULL if stream is uninitialized.
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* Call init() or read() method to initialize it.
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*/
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public String getEncoding() {
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if (internalIn2 == null) return null;
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return internalIn2.getEncoding();
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}
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/**
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* Read-ahead four bytes and check for BOM marks. Extra bytes are
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* unread back to the stream, only BOM bytes are skipped.
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*/
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protected void init() throws IOException {
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if (internalIn2 != null) return;
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String encoding;
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byte bom[] = new byte[BOM_SIZE];
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int n, unread;
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n = internalIn.read(bom, 0, bom.length);
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if ( (bom[0] == (byte)0x00) && (bom[1] == (byte)0x00) &&
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(bom[2] == (byte)0xFE) && (bom[3] == (byte)0xFF) ) {
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encoding = "UTF-32BE";
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unread = n - 4;
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} else if ( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) &&
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(bom[2] == (byte)0x00) && (bom[3] == (byte)0x00) ) {
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encoding = "UTF-32LE";
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unread = n - 4;
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} else if ( (bom[0] == (byte)0xEF) && (bom[1] == (byte)0xBB) &&
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(bom[2] == (byte)0xBF) ) {
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encoding = "UTF-8";
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unread = n - 3;
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} else if ( (bom[0] == (byte)0xFE) && (bom[1] == (byte)0xFF) ) {
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encoding = "UTF-16BE";
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unread = n - 2;
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} else if ( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) ) {
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encoding = "UTF-16LE";
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unread = n - 2;
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} else {
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// Unicode BOM mark not found, unread all bytes
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encoding = defaultEnc;
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unread = n;
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}
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//System.out.println("read=" + n + ", unread=" + unread);
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if (unread > 0) internalIn.unread(bom, (n - unread), unread);
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// Use given encoding
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if (encoding == null) {
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internalIn2 = new InputStreamReader(internalIn);
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} else {
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internalIn2 = new InputStreamReader(internalIn, encoding);
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}
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}
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public void close() throws IOException {
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init();
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internalIn2.close();
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}
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public int read(char[] cbuf, int off, int len) throws IOException {
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init();
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return internalIn2.read(cbuf, off, len);
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}
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}
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