001// License: GPL. For details, see LICENSE file. 002package org.openstreetmap.josm.io; 003 004import java.io.IOException; 005import java.io.InputStream; 006import java.io.InputStreamReader; 007import java.io.PushbackInputStream; 008import java.io.UnsupportedEncodingException; 009 010/** 011 * Detects the different UTF encodings from byte order mark 012 */ 013public final class UTFInputStreamReader extends InputStreamReader { 014 015 /** 016 * Creates a new {@link InputStreamReader} from the {@link InputStream} with UTF-8 as default encoding. 017 * @param input input stream 018 * @return A reader with the correct encoding. Starts to read after the BOM. 019 * @throws IOException if any I/O error occurs 020 * @see #create(java.io.InputStream, String) 021 */ 022 public static UTFInputStreamReader create(InputStream input) throws IOException { 023 return create(input, "UTF-8"); 024 } 025 026 /** 027 * Creates a new {@link InputStreamReader} from the {@link InputStream}. 028 * @param input input stream 029 * @param defaultEncoding Used, when no BOM was recognized. Can be null. 030 * @return A reader with the correct encoding. Starts to read after the BOM. 031 * @throws IOException if any I/O error occurs 032 */ 033 public static UTFInputStreamReader create(InputStream input, String defaultEncoding) throws IOException { 034 byte[] bom = new byte[4]; 035 String encoding = defaultEncoding; 036 int unread; 037 PushbackInputStream pushbackStream = new PushbackInputStream(input, 4); 038 int n = pushbackStream.read(bom, 0, 4); 039 040 if ((bom[0] == (byte) 0xEF) && (bom[1] == (byte) 0xBB) && (bom[2] == (byte) 0xBF)) { 041 encoding = "UTF-8"; 042 unread = n - 3; 043 } else if ((bom[0] == (byte) 0x00) && (bom[1] == (byte) 0x00) && (bom[2] == (byte) 0xFE) && (bom[3] == (byte) 0xFF)) { 044 encoding = "UTF-32BE"; 045 unread = n - 4; 046 } else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE) && (bom[2] == (byte) 0x00) && (bom[3] == (byte) 0x00)) { 047 encoding = "UTF-32LE"; 048 unread = n - 4; 049 } else if ((bom[0] == (byte) 0xFE) && (bom[1] == (byte) 0xFF)) { 050 encoding = "UTF-16BE"; 051 unread = n - 2; 052 } else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE)) { 053 encoding = "UTF-16LE"; 054 unread = n - 2; 055 } else { 056 unread = n; 057 } 058 059 if (unread > 0) { 060 pushbackStream.unread(bom, n - unread, unread); 061 } else if (unread < -1) { 062 pushbackStream.unread(bom, 0, 0); 063 } 064 065 if (encoding == null) { 066 return new UTFInputStreamReader(pushbackStream); 067 } else { 068 return new UTFInputStreamReader(pushbackStream, encoding); 069 } 070 } 071 072 private UTFInputStreamReader(InputStream in) { 073 super(in); 074 } 075 076 private UTFInputStreamReader(InputStream in, String cs) throws UnsupportedEncodingException { 077 super(in, cs); 078 } 079}