/* * Copyright (C) 2010 ZXing authors * * Licensed 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 com.google.zxing.common; import java.nio.charset.Charset; import java.util.Map; import com.google.zxing.DecodeHintType; /** * Common string-related functions. * * @author Sean Owen * @author Alex Dupre */ public final class StringUtils { private static final String PLATFORM_DEFAULT_ENCODING = Charset.defaultCharset().name(); public static final String SHIFT_JIS = "SJIS"; public static final String GB2312 = "GB2312"; private static final String EUC_JP = "EUC_JP"; private static final String UTF8 = "UTF8"; private static final String ISO88591 = "ISO8859_1"; private static final boolean ASSUME_SHIFT_JIS = SHIFT_JIS.equalsIgnoreCase(PLATFORM_DEFAULT_ENCODING) || EUC_JP.equalsIgnoreCase(PLATFORM_DEFAULT_ENCODING); private StringUtils() { } /** * @param bytes bytes encoding a string, whose encoding should be guessed * @param hints decode hints if applicable * @return name of guessed encoding; at the moment will only guess one of: * {@link #SHIFT_JIS}, {@link #UTF8}, {@link #ISO88591}, or the platform * default encoding if none of these can possibly be correct */ public static String guessEncoding(byte[] bytes, Map hints) { if (hints != null && hints.containsKey(DecodeHintType.CHARACTER_SET)) { return hints.get(DecodeHintType.CHARACTER_SET).toString(); } // For now, merely tries to distinguish ISO-8859-1, UTF-8 and Shift_JIS, // which should be by far the most common encodings. int length = bytes.length; boolean canBeISO88591 = true; boolean canBeShiftJIS = true; boolean canBeUTF8 = true; int utf8BytesLeft = 0; int utf2BytesChars = 0; int utf3BytesChars = 0; int utf4BytesChars = 0; int sjisBytesLeft = 0; int sjisKatakanaChars = 0; int sjisCurKatakanaWordLength = 0; int sjisCurDoubleBytesWordLength = 0; int sjisMaxKatakanaWordLength = 0; int sjisMaxDoubleBytesWordLength = 0; int isoHighOther = 0; boolean utf8bom = bytes.length > 3 && bytes[0] == (byte) 0xEF && bytes[1] == (byte) 0xBB && bytes[2] == (byte) 0xBF; for (int i = 0; i < length && (canBeISO88591 || canBeShiftJIS || canBeUTF8); i++) { int value = bytes[i] & 0xFF; // UTF-8 stuff if (canBeUTF8) { if (utf8BytesLeft > 0) { if ((value & 0x80) == 0) { canBeUTF8 = false; } else { utf8BytesLeft--; } } else if ((value & 0x80) != 0) { if ((value & 0x40) == 0) { canBeUTF8 = false; } else { utf8BytesLeft++; if ((value & 0x20) == 0) { utf2BytesChars++; } else { utf8BytesLeft++; if ((value & 0x10) == 0) { utf3BytesChars++; } else { utf8BytesLeft++; if ((value & 0x08) == 0) { utf4BytesChars++; } else { canBeUTF8 = false; } } } } } } // ISO-8859-1 stuff if (canBeISO88591) { if (value > 0x7F && value < 0xA0) { canBeISO88591 = false; } else if (value > 0x9F && (value < 0xC0 || value == 0xD7 || value == 0xF7)) { isoHighOther++; } } // Shift_JIS stuff if (canBeShiftJIS) { if (sjisBytesLeft > 0) { if (value < 0x40 || value == 0x7F || value > 0xFC) { canBeShiftJIS = false; } else { sjisBytesLeft--; } } else if (value == 0x80 || value == 0xA0 || value > 0xEF) { canBeShiftJIS = false; } else if (value > 0xA0 && value < 0xE0) { sjisKatakanaChars++; sjisCurDoubleBytesWordLength = 0; sjisCurKatakanaWordLength++; if (sjisCurKatakanaWordLength > sjisMaxKatakanaWordLength) { sjisMaxKatakanaWordLength = sjisCurKatakanaWordLength; } } else if (value > 0x7F) { sjisBytesLeft++; //sjisDoubleBytesChars++; sjisCurKatakanaWordLength = 0; sjisCurDoubleBytesWordLength++; if (sjisCurDoubleBytesWordLength > sjisMaxDoubleBytesWordLength) { sjisMaxDoubleBytesWordLength = sjisCurDoubleBytesWordLength; } } else { //sjisLowChars++; sjisCurKatakanaWordLength = 0; sjisCurDoubleBytesWordLength = 0; } } } if (canBeUTF8 && utf8BytesLeft > 0) { canBeUTF8 = false; } if (canBeShiftJIS && sjisBytesLeft > 0) { canBeShiftJIS = false; } // Easy -- if there is BOM or at least 1 valid not-single byte character (and no evidence it can't be UTF-8), done if (canBeUTF8 && (utf8bom || utf2BytesChars + utf3BytesChars + utf4BytesChars > 0)) { return UTF8; } // Easy -- if assuming Shift_JIS or >= 3 valid consecutive not-ascii characters (and no evidence it can't be), done if (canBeShiftJIS && (ASSUME_SHIFT_JIS || sjisMaxKatakanaWordLength >= 3 || sjisMaxDoubleBytesWordLength >= 3)) { return SHIFT_JIS; } // Distinguishing Shift_JIS and ISO-8859-1 can be a little tough for short words. The crude heuristic is: // - If we saw // - only two consecutive katakana chars in the whole text, or // - at least 10% of bytes that could be "upper" not-alphanumeric Latin1, // - then we conclude Shift_JIS, else ISO-8859-1 if (canBeISO88591 && canBeShiftJIS) { return (sjisMaxKatakanaWordLength == 2 && sjisKatakanaChars == 2) || isoHighOther * 10 >= length ? SHIFT_JIS : ISO88591; } // Otherwise, try in order ISO-8859-1, Shift JIS, UTF-8 and fall back to default platform encoding if (canBeISO88591) { return ISO88591; } if (canBeShiftJIS) { return SHIFT_JIS; } if (canBeUTF8) { return UTF8; } // Otherwise, we take a wild guess with platform encoding return PLATFORM_DEFAULT_ENCODING; } }