Java tutorial
/* * Copyright 2007 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 org.zywx.wbpalmstar.plugin.uexzxing.qrcode.decoder; import java.io.UnsupportedEncodingException; import java.util.Hashtable; import java.util.Vector; import org.apache.http.util.ByteArrayBuffer; import org.zywx.wbpalmstar.plugin.uexzxing.FormatException; import org.zywx.wbpalmstar.plugin.uexzxing.common.BitSource; import org.zywx.wbpalmstar.plugin.uexzxing.common.CharacterSetECI; import org.zywx.wbpalmstar.plugin.uexzxing.common.DecoderResult; import org.zywx.wbpalmstar.plugin.uexzxing.common.StringUtils; /** * <p>QR Codes can encode text as bits in one of several modes, and can use multiple modes * in one QR Code. This class decodes the bits back into text.</p> * * <p>See ISO 18004:2006, 6.4.3 - 6.4.7</p> * * @author Sean Owen */ @SuppressWarnings("rawtypes") final class DecodedBitStreamParser { /** * See ISO 18004:2006, 6.4.4 Table 5 */ private static final char[] ALPHANUMERIC_CHARS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', ' ', '$', '%', '*', '+', '-', '.', '/', ':' }; private DecodedBitStreamParser() { } static DecoderResult decode(byte[] bytes, Version version, ErrorCorrectionLevel ecLevel, Hashtable hints) throws FormatException { BitSource bits = new BitSource(bytes); StringBuffer result = new StringBuffer(50); CharacterSetECI currentCharacterSetECI = null; boolean fc1InEffect = false; Vector byteSegments = new Vector(1); Mode mode; do { // While still another segment to read... if (bits.available() < 4) { // OK, assume we're done. Really, a TERMINATOR mode should have been recorded here mode = Mode.TERMINATOR; } else { try { mode = Mode.forBits(bits.readBits(4)); // mode is encoded by 4 bits } catch (IllegalArgumentException iae) { throw FormatException.getFormatInstance(); } } if (!mode.equals(Mode.TERMINATOR)) { if (mode.equals(Mode.FNC1_FIRST_POSITION) || mode.equals(Mode.FNC1_SECOND_POSITION)) { // We do little with FNC1 except alter the parsed result a bit according to the spec fc1InEffect = true; } else if (mode.equals(Mode.STRUCTURED_APPEND)) { // not really supported; all we do is ignore it // Read next 8 bits (symbol sequence #) and 8 bits (parity data), then continue bits.readBits(16); } else if (mode.equals(Mode.ECI)) { // Count doesn't apply to ECI int value = parseECIValue(bits); currentCharacterSetECI = CharacterSetECI.getCharacterSetECIByValue(value); if (currentCharacterSetECI == null) { throw FormatException.getFormatInstance(); } } else { // How many characters will follow, encoded in this mode? int count = bits.readBits(mode.getCharacterCountBits(version)); if (mode.equals(Mode.NUMERIC)) { decodeNumericSegment(bits, result, count); } else if (mode.equals(Mode.ALPHANUMERIC)) { decodeAlphanumericSegment(bits, result, count, fc1InEffect); } else if (mode.equals(Mode.BYTE)) { decodeByteSegment(bits, result, count, currentCharacterSetECI, byteSegments, hints); } else if (mode.equals(Mode.KANJI)) { decodeKanjiSegment(bits, result, count); } else { throw FormatException.getFormatInstance(); } } } } while (!mode.equals(Mode.TERMINATOR)); return new DecoderResult(bytes, result.toString(), byteSegments.isEmpty() ? null : byteSegments, ecLevel); } private static void decodeKanjiSegment(BitSource bits, StringBuffer result, int count) throws FormatException { // Each character will require 2 bytes. Read the characters as 2-byte pairs // and decode as Shift_JIS afterwards byte[] buffer = new byte[2 * count]; int offset = 0; while (count > 0) { // Each 13 bits encodes a 2-byte character int twoBytes = bits.readBits(13); int assembledTwoBytes = ((twoBytes / 0x0C0) << 8) | (twoBytes % 0x0C0); if (assembledTwoBytes < 0x01F00) { // In the 0x8140 to 0x9FFC range assembledTwoBytes += 0x08140; } else { // In the 0xE040 to 0xEBBF range assembledTwoBytes += 0x0C140; } buffer[offset] = (byte) (assembledTwoBytes >> 8); buffer[offset + 1] = (byte) assembledTwoBytes; offset += 2; count--; } // Shift_JIS may not be supported in some environments: try { result.append(new String(buffer, StringUtils.SHIFT_JIS)); } catch (UnsupportedEncodingException uee) { throw FormatException.getFormatInstance(); } } @SuppressWarnings("unchecked") private static void decodeByteSegment(BitSource bits, StringBuffer result, int count, CharacterSetECI currentCharacterSetECI, Vector byteSegments, Hashtable hints) throws FormatException { byte[] readBytes = new byte[count]; if (count << 3 > bits.available()) { throw FormatException.getFormatInstance(); } for (int i = 0; i < count; i++) { readBytes[i] = (byte) bits.readBits(8); } String encoding; if (currentCharacterSetECI == null) { // The spec isn't clear on this mode; see // section 6.4.5: t does not say which encoding to assuming // upon decoding. I have seen ISO-8859-1 used as well as // Shift_JIS -- without anything like an ECI designator to // give a hint. encoding = StringUtils.guessEncoding(readBytes, hints); } else { encoding = currentCharacterSetECI.getEncodingName(); } if (null != encoding && !encoding.equals("UTF8")) { encoding = StringUtils.GBK; } try { int len = readBytes.length; ByteArrayBuffer buffer = new ByteArrayBuffer(len + 20); for (int i = 0; i < len; ++i) { int c = readBytes[i]; if (c == 34 || c == 39 || c == 92 || c == 10 || c == 13 || c == 38) { buffer.append('\\'); } buffer.append(c); } readBytes = buffer.toByteArray(); result.append(new String(readBytes, encoding)); // result.append(new String(readBytes, encoding).replaceAll("\\s*|\t|\r|\n", "\\n")); } catch (UnsupportedEncodingException uce) { throw FormatException.getFormatInstance(); } byteSegments.addElement(readBytes); } private static char toAlphaNumericChar(int value) throws FormatException { if (value >= ALPHANUMERIC_CHARS.length) { throw FormatException.getFormatInstance(); } return ALPHANUMERIC_CHARS[value]; } private static void decodeAlphanumericSegment(BitSource bits, StringBuffer result, int count, boolean fc1InEffect) throws FormatException { // Read two characters at a time int start = result.length(); while (count > 1) { int nextTwoCharsBits = bits.readBits(11); result.append(toAlphaNumericChar(nextTwoCharsBits / 45)); result.append(toAlphaNumericChar(nextTwoCharsBits % 45)); count -= 2; } if (count == 1) { // special case: one character left result.append(toAlphaNumericChar(bits.readBits(6))); } // See section 6.4.8.1, 6.4.8.2 if (fc1InEffect) { // We need to massage the result a bit if in an FNC1 mode: for (int i = start; i < result.length(); i++) { if (result.charAt(i) == '%') { if (i < result.length() - 1 && result.charAt(i + 1) == '%') { // %% is rendered as % result.deleteCharAt(i + 1); } else { // In alpha mode, % should be converted to FNC1 separator 0x1D result.setCharAt(i, (char) 0x1D); } } } } } private static void decodeNumericSegment(BitSource bits, StringBuffer result, int count) throws FormatException { // Read three digits at a time while (count >= 3) { // Each 10 bits encodes three digits int threeDigitsBits = bits.readBits(10); if (threeDigitsBits >= 1000) { throw FormatException.getFormatInstance(); } result.append(toAlphaNumericChar(threeDigitsBits / 100)); result.append(toAlphaNumericChar((threeDigitsBits / 10) % 10)); result.append(toAlphaNumericChar(threeDigitsBits % 10)); count -= 3; } if (count == 2) { // Two digits left over to read, encoded in 7 bits int twoDigitsBits = bits.readBits(7); if (twoDigitsBits >= 100) { throw FormatException.getFormatInstance(); } result.append(toAlphaNumericChar(twoDigitsBits / 10)); result.append(toAlphaNumericChar(twoDigitsBits % 10)); } else if (count == 1) { // One digit left over to read int digitBits = bits.readBits(4); if (digitBits >= 10) { throw FormatException.getFormatInstance(); } result.append(toAlphaNumericChar(digitBits)); } } private static int parseECIValue(BitSource bits) { int firstByte = bits.readBits(8); if ((firstByte & 0x80) == 0) { // just one byte return firstByte & 0x7F; } else if ((firstByte & 0xC0) == 0x80) { // two bytes int secondByte = bits.readBits(8); return ((firstByte & 0x3F) << 8) | secondByte; } else if ((firstByte & 0xE0) == 0xC0) { // three bytes int secondThirdBytes = bits.readBits(16); return ((firstByte & 0x1F) << 16) | secondThirdBytes; } throw new IllegalArgumentException("Bad ECI bits starting with byte " + firstByte); } }