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Diffstat (limited to 'libraries/zxing/src/com/google/zxing/qrcode/decoder/DecodedBitStreamParser.java')
| -rw-r--r-- | libraries/zxing/src/com/google/zxing/qrcode/decoder/DecodedBitStreamParser.java | 322 |
1 files changed, 322 insertions, 0 deletions
diff --git a/libraries/zxing/src/com/google/zxing/qrcode/decoder/DecodedBitStreamParser.java b/libraries/zxing/src/com/google/zxing/qrcode/decoder/DecodedBitStreamParser.java new file mode 100644 index 000000000..ff374ac50 --- /dev/null +++ b/libraries/zxing/src/com/google/zxing/qrcode/decoder/DecodedBitStreamParser.java @@ -0,0 +1,322 @@ +/* + * 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 com.google.zxing.qrcode.decoder; + +import com.google.zxing.FormatException; +import com.google.zxing.common.BitSource; +import com.google.zxing.common.CharacterSetECI; +import com.google.zxing.common.DecoderResult; +import com.google.zxing.common.StringUtils; + +import java.io.UnsupportedEncodingException; +import java.util.Hashtable; +import java.util.Vector; + +/** + * <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 + */ +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 static final int GB2312_SUBSET = 1; + + 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 { + // First handle Hanzi mode which does not start with character count + if (mode.equals(Mode.HANZI)) { + //chinese mode contains a sub set indicator right after mode indicator + int subset = bits.readBits(4); + int countHanzi = bits.readBits(mode.getCharacterCountBits(version)); + if (subset == GB2312_SUBSET) { + decodeHanziSegment(bits, result, countHanzi); + } + } else { + // "Normal" QR code modes: + // 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 == null ? null : ecLevel.toString()); + } + + /** + * See specification GBT 18284-2000 + */ + private static void decodeHanziSegment(BitSource bits, + StringBuffer result, + int count) throws FormatException { + // Don't crash trying to read more bits than we have available. + if (count * 13 > bits.available()) { + throw FormatException.getFormatInstance(); + } + + // Each character will require 2 bytes. Read the characters as 2-byte pairs + // and decode as GB2312 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 / 0x060) << 8) | (twoBytes % 0x060); + if (assembledTwoBytes < 0x003BF) { + // In the 0xA1A1 to 0xAAFE range + assembledTwoBytes += 0x0A1A1; + } else { + // In the 0xB0A1 to 0xFAFE range + assembledTwoBytes += 0x0A6A1; + } + buffer[offset] = (byte) ((assembledTwoBytes >> 8) & 0xFF); + buffer[offset + 1] = (byte) (assembledTwoBytes & 0xFF); + offset += 2; + count--; + } + + try { + result.append(new String(buffer, StringUtils.GB2312)); + } catch (UnsupportedEncodingException uee) { + throw FormatException.getFormatInstance(); + } + } + + private static void decodeKanjiSegment(BitSource bits, + StringBuffer result, + int count) throws FormatException { + // Don't crash trying to read more bits than we have available. + if (count * 13 > bits.available()) { + throw FormatException.getFormatInstance(); + } + + // 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(); + } + } + + private static void decodeByteSegment(BitSource bits, + StringBuffer result, + int count, + CharacterSetECI currentCharacterSetECI, + Vector byteSegments, + Hashtable hints) throws FormatException { + // Don't crash trying to read more bits than we have available. + if (count << 3 > bits.available()) { + throw FormatException.getFormatInstance(); + } + + byte[] readBytes = new byte[count]; + 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(); + } + try { + result.append(new String(readBytes, encoding)); + } 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); + } + +} |