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 $ALPHANUMERIC_CHARS = [ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', ' ', '$', '%', '*', '+', '-', '.', '/', ':', ]; private static $GB2312_SUBSET = 1; public static function decode($bytes, $version, $ecLevel, $hints) { $bits = new BitSource($bytes); $result = '';//new StringBuilder(50); $byteSegments = []; $symbolSequence = -1; $parityData = -1; try { $currentCharacterSetECI = null; $fc1InEffect = false; $mode = ''; do { // While still another segment to read... if ($bits->available() < 4) { // OK, assume we're done. Really, a TERMINATOR mode should have been recorded here $mode = Mode::$TERMINATOR; } else { $mode = Mode::forBits($bits->readBits(4)); // mode is encoded by 4 bits } 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(); } // sequence number and parity is added later to the result metadata // Read next 8 bits (symbol sequence #) and 8 bits (parity data), then continue $symbolSequence = $bits->readBits(8); $parityData = $bits->readBits(8); } else if ($mode == Mode::$ECI) { // Count doesn't apply to ECI $value = self::parseECIValue($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 $subset = $bits->readBits(4); $countHanzi = $bits->readBits($mode->getCharacterCountBits($version)); if ($subset == self::$GB2312_SUBSET) { self::decodeHanziSegment($bits, $result, $countHanzi); } } else { // "Normal" QR code modes: // How many characters will follow, encoded in this mode? $count = $bits->readBits($mode->getCharacterCountBits($version)); if ($mode == Mode::$NUMERIC) { self::decodeNumericSegment($bits, $result, $count); } else if ($mode == Mode::$ALPHANUMERIC) { self::decodeAlphanumericSegment($bits, $result, $count, $fc1InEffect); } else if ($mode == Mode::$BYTE) { self::decodeByteSegment($bits, $result, $count, $currentCharacterSetECI, $byteSegments, $hints); } else if ($mode == Mode::$KANJI) { self::decodeKanjiSegment($bits, $result, $count); } else { throw FormatException::getFormatInstance(); } } } } } while ($mode != Mode::$TERMINATOR); } catch (\InvalidArgumentException $iae) { // from readBits() calls throw FormatException::getFormatInstance(); } return new DecoderResult($bytes, $result, empty($byteSegments) ? null : $byteSegments, $ecLevel == null ? null : 'L',//ErrorCorrectionLevel::toString($ecLevel), $symbolSequence, $parityData); } private static function parseECIValue($bits) { $firstByte = $bits->readBits(8); if (($firstByte & 0x80) == 0) { // just one byte return $firstByte & 0x7F; } if (($firstByte & 0xC0) == 0x80) { // two bytes $secondByte = $bits->readBits(8); return (($firstByte & 0x3F) << 8) | $secondByte; } if (($firstByte & 0xE0) == 0xC0) { // three bytes $secondThirdBytes = $bits->readBits(16); return (($firstByte & 0x1F) << 16) | $secondThirdBytes; } throw FormatException::getFormatInstance(); } /** * See specification GBT 18284-2000 */ private static function decodeHanziSegment($bits, &$result, $count) { // Don't crash trying to read more bits than we have available. if ($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 $buffer = fill_array(0, 2 * $count, 0); $offset = 0; while ($count > 0) { // Each 13 bits encodes a 2-byte character $twoBytes = $bits->readBits(13); $assembledTwoBytes = (($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] = (($assembledTwoBytes >> 8) & 0xFF);//(byte) $buffer[$offset + 1] = ($assembledTwoBytes & 0xFF);//(byte) $offset += 2; $count--; } $result .= iconv('GB2312', 'UTF-8', implode($buffer)); } private static function decodeNumericSegment($bits, &$result, $count) { // Read three digits at a time while ($count >= 3) { // Each 10 bits encodes three digits if ($bits->available() < 10) { throw FormatException::getFormatInstance(); } $threeDigitsBits = $bits->readBits(10); if ($threeDigitsBits >= 1000) { throw FormatException::getFormatInstance(); } $result .= (self::toAlphaNumericChar($threeDigitsBits / 100)); $result .= (self::toAlphaNumericChar(($threeDigitsBits / 10) % 10)); $result .= (self::toAlphaNumericChar($threeDigitsBits % 10)); $count -= 3; } if ($count == 2) { // Two digits left over to read, encoded in 7 bits if ($bits->available() < 7) { throw FormatException::getFormatInstance(); } $twoDigitsBits = $bits->readBits(7); if ($twoDigitsBits >= 100) { throw FormatException::getFormatInstance(); } $result .= (self::toAlphaNumericChar($twoDigitsBits / 10)); $result .= (self::toAlphaNumericChar($twoDigitsBits % 10)); } else if ($count == 1) { // One digit left over to read if ($bits->available() < 4) { throw FormatException::getFormatInstance(); } $digitBits = $bits->readBits(4); if ($digitBits >= 10) { throw FormatException::getFormatInstance(); } $result .= (self::toAlphaNumericChar($digitBits)); } } private static function toAlphaNumericChar($value) { if ($value >= count(self::$ALPHANUMERIC_CHARS)) { throw FormatException::getFormatInstance(); } return self::$ALPHANUMERIC_CHARS[$value]; } private static function decodeAlphanumericSegment($bits, &$result, $count, $fc1InEffect) { // Read two characters at a time $start = strlen($result); while ($count > 1) { if ($bits->available() < 11) { throw FormatException::getFormatInstance(); } $nextTwoCharsBits = $bits->readBits(11); $result .= (self::toAlphaNumericChar($nextTwoCharsBits / 45)); $result .= (self::toAlphaNumericChar($nextTwoCharsBits % 45)); $count -= 2; } if ($count == 1) { // special case: one character left if ($bits->available() < 6) { throw FormatException::getFormatInstance(); } $result .= self::toAlphaNumericChar($bits->readBits(6)); } // See section 6.4.8.1, 6.4.8.2 if ($fc1InEffect) { // We need to massage the result a bit if in an FNC1 mode: for ($i = $start; $i < strlen($result); $i++) { if ($result[$i] == '%') { if ($i < strlen($result) - 1 && $result[$i + 1] == '%') { // %% is rendered as % $result = substr_replace($result, '', $i + 1, 1);//deleteCharAt(i + 1); } else { // In alpha mode, % should be converted to FNC1 separator 0x1D $result . setCharAt($i, chr(0x1D)); } } } } } private static function decodeByteSegment($bits, &$result, $count, $currentCharacterSetECI, &$byteSegments, $hints) { // Don't crash trying to read more bits than we have available. if (8 * $count > $bits->available()) { throw FormatException::getFormatInstance(); } $readBytes = fill_array(0, $count, 0); for ($i = 0; $i < $count; $i++) { $readBytes[$i] = $bits->readBits(8);//(byte) } $text = implode(array_map('chr', $readBytes)); $encoding = ''; if ($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. $encoding = mb_detect_encoding($text, $hints); } else { $encoding = $currentCharacterSetECI->name(); } // $result.= mb_convert_encoding($text ,$encoding);//(new String(readBytes, encoding)); $result .= $text;//(new String(readBytes, encoding)); $byteSegments = array_merge($byteSegments, $readBytes); } private static function decodeKanjiSegment($bits, &$result, $count) { // Don't crash trying to read more bits than we have available. if ($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 $buffer = [0, 2 * $count, 0]; $offset = 0; while ($count > 0) { // Each 13 bits encodes a 2-byte character $twoBytes = $bits->readBits(13); $assembledTwoBytes = (($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] = ($assembledTwoBytes >> 8);//(byte) $buffer[$offset + 1] = $assembledTwoBytes; //(byte) $offset += 2; $count--; } // Shift_JIS may not be supported in some environments: $result .= iconv('shift-jis', 'utf-8', implode($buffer)); } private function DecodedBitStreamParser() { } }