com.google.zxing.qrcode.decoder.DecodedBitStreamParser Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of core Show documentation
Show all versions of core Show documentation
Core barcode encoding/decoding library
/*
* 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.DecodeHintType;
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.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
/**
* 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.
*
* See ISO 18004:2006, 6.4.3 - 6.4.7
*
* @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,
Map hints) throws FormatException {
BitSource bits = new BitSource(bytes);
StringBuilder result = new StringBuilder(50);
CharacterSetECI currentCharacterSetECI = null;
boolean fc1InEffect = false;
List byteSegments = new ArrayList(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 != Mode.TERMINATOR) {
if (mode == Mode.FNC1_FIRST_POSITION || mode == 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 == Mode.STRUCTURED_APPEND) {
if (bits.available() < 16) {
throw FormatException.getFormatInstance();
}
// 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 == 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 == 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 == Mode.NUMERIC) {
decodeNumericSegment(bits, result, count);
} else if (mode == Mode.ALPHANUMERIC) {
decodeAlphanumericSegment(bits, result, count, fc1InEffect);
} else if (mode == Mode.BYTE) {
decodeByteSegment(bits, result, count, currentCharacterSetECI, byteSegments, hints);
} else if (mode == Mode.KANJI) {
decodeKanjiSegment(bits, result, count);
} else {
throw FormatException.getFormatInstance();
}
}
}
}
} while (mode != 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,
StringBuilder 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,
StringBuilder 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,
StringBuilder result,
int count,
CharacterSetECI currentCharacterSetECI,
Collection byteSegments,
Map 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.name();
}
try {
result.append(new String(readBytes, encoding));
} catch (UnsupportedEncodingException uce) {
throw FormatException.getFormatInstance();
}
byteSegments.add(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,
StringBuilder result,
int count,
boolean fc1InEffect) throws FormatException {
// Read two characters at a time
int start = result.length();
while (count > 1) {
if (bits.available() < 11) {
throw FormatException.getFormatInstance();
}
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
if (bits.available() < 6) {
throw FormatException.getFormatInstance();
}
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,
StringBuilder result,
int count) throws FormatException {
// Read three digits at a time
while (count >= 3) {
// Each 10 bits encodes three digits
if (bits.available() < 10) {
throw FormatException.getFormatInstance();
}
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
if (bits.available() < 7) {
throw FormatException.getFormatInstance();
}
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
if (bits.available() < 4) {
throw FormatException.getFormatInstance();
}
int digitBits = bits.readBits(4);
if (digitBits >= 10) {
throw FormatException.getFormatInstance();
}
result.append(toAlphaNumericChar(digitBits));
}
}
private static int parseECIValue(BitSource bits) throws FormatException {
int firstByte = bits.readBits(8);
if ((firstByte & 0x80) == 0) {
// just one byte
return firstByte & 0x7F;
}
if ((firstByte & 0xC0) == 0x80) {
// two bytes
int secondByte = bits.readBits(8);
return ((firstByte & 0x3F) << 8) | secondByte;
}
if ((firstByte & 0xE0) == 0xC0) {
// three bytes
int secondThirdBytes = bits.readBits(16);
return ((firstByte & 0x1F) << 16) | secondThirdBytes;
}
throw FormatException.getFormatInstance();
}
}
© 2015 - 2024 Weber Informatics LLC | Privacy Policy