qrcodegen.h

/* 
 * QR Code generator library (C++)
 * 
 * Copyright (c) Project Nayuki. (MIT License)
 * https://www.nayuki.io/page/qr-code-generator-library
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * - The above copyright notice and this permission notice shall be included in
 *   all copies or substantial portions of the Software.
 * - The Software is provided "as is", without warranty of any kind, express or
 *   implied, including but not limited to the warranties of merchantability,
 *   fitness for a particular purpose and noninfringement. In no event shall the
 *   authors or copyright holders be liable for any claim, damages or other
 *   liability, whether in an action of contract, tort or otherwise, arising from,
 *   out of or in connection with the Software or the use or other dealings in the
 *   Software.
 */

#ifndef QRCODEGEN_H
#define QRCODEGEN_H

#include <array>
#include <cstdint>
#include <stdexcept>
#include <string>
#include <vector>


namespace qrcodegen {

/* 
 * A segment of character/binary/control data in a QR Code symbol.
 * Instances of this class are immutable.
 * The mid-level way to create a segment is to take the payload data
 * and call a static factory function such as QrSegment::makeNumeric().
 * The low-level way to create a segment is to custom-make the bit buffer
 * and call the QrSegment() constructor with appropriate values.
 * This segment class imposes no length restrictions, but QR Codes have restrictions.
 * Even in the most favorable conditions, a QR Code can only hold 7089 characters of data.
 * Any segment longer than this is meaningless for the purpose of generating QR Codes.
 */
class QrSegment final {
    
    /*---- Public helper enumeration ----*/
    
    /* 
     * Describes how a segment's data bits are interpreted. Immutable.
     */
    public: class Mode final {
        
        /*-- Constants --*/
        
        public: static const Mode NUMERIC;
        public: static const Mode ALPHANUMERIC;
        public: static const Mode BYTE;
        public: static const Mode KANJI;
        public: static const Mode ECI;
        
        
        /*-- Fields --*/
        
        // The mode indicator bits, which is a uint4 value (range 0 to 15).
        private: int modeBits;
        
        // Number of character count bits for three different version ranges.
        private: int numBitsCharCount[3];
        
        
        /*-- Constructor --*/
        
        private: Mode(int mode, int cc0, int cc1, int cc2);
        
        
        /*-- Methods --*/
        
        /* 
         * (Package-private) Returns the mode indicator bits, which is an unsigned 4-bit value (range 0 to 15).
         */
        public: int getModeBits() const;
        
        /* 
         * (Package-private) Returns the bit width of the character count field for a segment in
         * this mode in a QR Code at the given version number. The result is in the range [0, 16].
         */
        public: int numCharCountBits(int ver) const;
        
    };
    
    
    
    /*---- Static factory functions (mid level) ----*/
    
    /* 
     * Returns a segment representing the given binary data encoded in
     * byte mode. All input byte vectors are acceptable. Any text string
     * can be converted to UTF-8 bytes and encoded as a byte mode segment.
     */
    public: static QrSegment makeBytes(const std::vector<std::uint8_t> &data);
    
    
    /* 
     * Returns a segment representing the given string of decimal digits encoded in numeric mode.
     */
    public: static QrSegment makeNumeric(const char *digits);
    
    
    /* 
     * Returns a segment representing the given text string encoded in alphanumeric mode.
     * The characters allowed are: 0 to 9, A to Z (uppercase only), space,
     * dollar, percent, asterisk, plus, hyphen, period, slash, colon.
     */
    public: static QrSegment makeAlphanumeric(const char *text);
    
    
    /* 
     * Returns a list of zero or more segments to represent the given text string. The result
     * may use various segment modes and switch modes to optimize the length of the bit stream.
     */
    public: static std::vector<QrSegment> makeSegments(const char *text);
    
    
    /* 
     * Returns a segment representing an Extended Channel Interpretation
     * (ECI) designator with the given assignment value.
     */
    public: static QrSegment makeEci(long assignVal);
    
    
    /*---- Public static helper functions ----*/
    
    /* 
     * Tests whether the given string can be encoded as a segment in numeric mode.
     * A string is encodable iff each character is in the range 0 to 9.
     */
    public: static bool isNumeric(const char *text);
    
    
    /* 
     * Tests whether the given string can be encoded as a segment in alphanumeric mode.
     * A string is encodable iff each character is in the following set: 0 to 9, A to Z
     * (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
     */
    public: static bool isAlphanumeric(const char *text);
    
    
    
    /*---- Instance fields ----*/
    
    /* The mode indicator of this segment. Accessed through getMode(). */
    private: const Mode *mode;
    
    /* The length of this segment's unencoded data. Measured in characters for
     * numeric/alphanumeric/kanji mode, bytes for byte mode, and 0 for ECI mode.
     * Always zero or positive. Not the same as the data's bit length.
     * Accessed through getNumChars(). */
    private: int numChars;
    
    /* The data bits of this segment. Accessed through getData(). */
    private: std::vector<bool> data;
    
    
    /*---- Constructors (low level) ----*/
    
    /* 
     * Creates a new QR Code segment with the given attributes and data.
     * The character count (numCh) must agree with the mode and the bit buffer length,
     * but the constraint isn't checked. The given bit buffer is copied and stored.
     */
    public: QrSegment(const Mode &md, int numCh, const std::vector<bool> &dt);
    
    
    /* 
     * Creates a new QR Code segment with the given parameters and data.
     * The character count (numCh) must agree with the mode and the bit buffer length,
     * but the constraint isn't checked. The given bit buffer is moved and stored.
     */
    public: QrSegment(const Mode &md, int numCh, std::vector<bool> &&dt);
    
    
    /*---- Methods ----*/
    
    /* 
     * Returns the mode field of this segment.
     */
    public: const Mode &getMode() const;
    
    
    /* 
     * Returns the character count field of this segment.
     */
    public: int getNumChars() const;
    
    
    /* 
     * Returns the data bits of this segment.
     */
    public: const std::vector<bool> &getData() const;
    
    
    // (Package-private) Calculates the number of bits needed to encode the given segments at
    // the given version. Returns a non-negative number if successful. Otherwise returns -1 if a
    // segment has too many characters to fit its length field, or the total bits exceeds INT_MAX.
    public: static int getTotalBits(const std::vector<QrSegment> &segs, int version);
    
    
    /*---- Private constant ----*/
    
    /* The set of all legal characters in alphanumeric mode, where
     * each character value maps to the index in the string. */
    private: static const char *ALPHANUMERIC_CHARSET;
    
};



/* 
 * A QR Code symbol, which is a type of two-dimension barcode.
 * Invented by Denso Wave and described in the ISO/IEC 18004 standard.
 * Instances of this class represent an immutable square grid of dark and light cells.
 * The class provides static factory functions to create a QR Code from text or binary data.
 * The class covers the QR Code Model 2 specification, supporting all versions (sizes)
 * from 1 to 40, all 4 error correction levels, and 4 character encoding modes.
 * 
 * Ways to create a QR Code object:
 * - High level: Take the payload data and call QrCode::encodeText() or QrCode::encodeBinary().
 * - Mid level: Custom-make the list of segments and call QrCode::encodeSegments().
 * - Low level: Custom-make the array of data codeword bytes (including
 *   segment headers and final padding, excluding error correction codewords),
 *   supply the appropriate version number, and call the QrCode() constructor.
 * (Note that all ways require supplying the desired error correction level.)
 */
class QrCode final {
    
    /*---- Public helper enumeration ----*/
    
    /* 
     * The error correction level in a QR Code symbol.
     */
    public: enum Ecc {
        ECC_LOW = 0 ,  // The QR Code can tolerate about  7% erroneous codewords
        ECC_MEDIUM  ,  // The QR Code can tolerate about 15% erroneous codewords
        ECC_QUARTILE,  // The QR Code can tolerate about 25% erroneous codewords
        ECC_HIGH    ,  // The QR Code can tolerate about 30% erroneous codewords
    };
    
    
    // Returns a value in the range 0 to 3 (unsigned 2-bit integer).
    private: static int getFormatBits(Ecc ecl);
    
    
    
    /*---- Static factory functions (high level) ----*/
    
    /* 
     * Returns a QR Code representing the given Unicode text string at the given error correction level.
     * As a conservative upper bound, this function is guaranteed to succeed for strings that have 2953 or fewer
     * UTF-8 code units (not Unicode code points) if the low error correction level is used. The smallest possible
     * QR Code version is automatically chosen for the output. The ECC level of the result may be higher than
     * the ecl argument if it can be done without increasing the version.
     */
    public: static QrCode encodeText(const char *text, Ecc ecl);
    
    
    /* 
     * Returns a QR Code representing the given binary data at the given error correction level.
     * This function always encodes using the binary segment mode, not any text mode. The maximum number of
     * bytes allowed is 2953. The smallest possible QR Code version is automatically chosen for the output.
     * The ECC level of the result may be higher than the ecl argument if it can be done without increasing the version.
     */
    public: static QrCode encodeBinary(const std::vector<std::uint8_t> &data, Ecc ecl);
    
    
    /*---- Static factory functions (mid level) ----*/
    
    /* 
     * Returns a QR Code representing the given segments with the given encoding parameters.
     * The smallest possible QR Code version within the given range is automatically
     * chosen for the output. Iff boostEcl is true, then the ECC level of the result
     * may be higher than the ecl argument if it can be done without increasing the
     * version. The mask number is either between 0 to 7 (inclusive) to force that
     * mask, or -1 to automatically choose an appropriate mask (which may be slow).
     * This function allows the user to create a custom sequence of segments that switches
     * between modes (such as alphanumeric and byte) to encode text in less space.
     * This is a mid-level API; the high-level API is encodeText() and encodeBinary().
     */
    public: static QrCode encodeSegments(const std::vector<QrSegment> &segs, Ecc ecl,
        int minVersion=1, int maxVersion=40, int mask=-1, bool boostEcl=true);  // All optional parameters
    
    
    
    /*---- Instance fields ----*/
    
    // Immutable scalar parameters:
    
    /* The version number of this QR Code, which is between 1 and 40 (inclusive).
     * This determines the size of this barcode. */
    private: int version;
    
    /* The width and height of this QR Code, measured in modules, between
     * 21 and 177 (inclusive). This is equal to version * 4 + 17. */
    private: int size;
    
    /* The error correction level used in this QR Code. */
    private: Ecc errorCorrectionLevel;
    
    /* The index of the mask pattern used in this QR Code, which is between 0 and 7 (inclusive).
     * Even if a QR Code is created with automatic masking requested (mask = -1),
     * the resulting object still has a mask value between 0 and 7. */
    private: int mask;
    
    // Private grids of modules/pixels, with dimensions of size*size:
    
    // The modules of this QR Code (false = light, true = dark).
    // Immutable after constructor finishes. Accessed through getModule().
    private: std::vector<std::vector<bool> > modules;
    
    // Indicates function modules that are not subjected to masking. Discarded when constructor finishes.
    private: std::vector<std::vector<bool> > isFunction;
    
    
    
    /*---- Constructor (low level) ----*/
    
    /* 
     * Creates a new QR Code with the given version number,
     * error correction level, data codeword bytes, and mask number.
     * This is a low-level API that most users should not use directly.
     * A mid-level API is the encodeSegments() function.
     */
    public: QrCode(int ver, Ecc ecl, const std::vector<std::uint8_t> &dataCodewords, int msk);
    
    
    
    /*---- Public instance methods ----*/
    
    /* 
     * Returns this QR Code's version, in the range [1, 40].
     */
    public: int getVersion() const;
    
    
    /* 
     * Returns this QR Code's size, in the range [21, 177].
     */
    public: int getSize() const;
    
    
    /* 
     * Returns this QR Code's error correction level.
     */
    public: Ecc getErrorCorrectionLevel() const;
    
    
    /* 
     * Returns this QR Code's mask, in the range [0, 7].
     */
    public: int getMask() const;
    
    
    /* 
     * Returns the color of the module (pixel) at the given coordinates, which is false
     * for light or true for dark. The top left corner has the coordinates (x=0, y=0).
     * If the given coordinates are out of bounds, then false (light) is returned.
     */
    public: bool getModule(int x, int y) const;
    
    
    
    /*---- Private helper methods for constructor: Drawing function modules ----*/
    
    // Reads this object's version field, and draws and marks all function modules.
    private: void drawFunctionPatterns();
    
    
    // Draws two copies of the format bits (with its own error correction code)
    // based on the given mask and this object's error correction level field.
    private: void drawFormatBits(int msk);
    
    
    // Draws two copies of the version bits (with its own error correction code),
    // based on this object's version field, iff 7 <= version <= 40.
    private: void drawVersion();
    
    
    // Draws a 9*9 finder pattern including the border separator,
    // with the center module at (x, y). Modules can be out of bounds.
    private: void drawFinderPattern(int x, int y);
    
    
    // Draws a 5*5 alignment pattern, with the center module
    // at (x, y). All modules must be in bounds.
    private: void drawAlignmentPattern(int x, int y);
    
    
    // Sets the color of a module and marks it as a function module.
    // Only used by the constructor. Coordinates must be in bounds.
    private: void setFunctionModule(int x, int y, bool isDark);
    
    
    // Returns the color of the module at the given coordinates, which must be in range.
    private: bool module(int x, int y) const;
    
    
    /*---- Private helper methods for constructor: Codewords and masking ----*/
    
    // Returns a new byte string representing the given data with the appropriate error correction
    // codewords appended to it, based on this object's version and error correction level.
    private: std::vector<std::uint8_t> addEccAndInterleave(const std::vector<std::uint8_t> &data) const;
    
    
    // Draws the given sequence of 8-bit codewords (data and error correction) onto the entire
    // data area of this QR Code. Function modules need to be marked off before this is called.
    private: void drawCodewords(const std::vector<std::uint8_t> &data);
    
    
    // XORs the codeword modules in this QR Code with the given mask pattern.
    // The function modules must be marked and the codeword bits must be drawn
    // before masking. Due to the arithmetic of XOR, calling applyMask() with
    // the same mask value a second time will undo the mask. A final well-formed
    // QR Code needs exactly one (not zero, two, etc.) mask applied.
    private: void applyMask(int msk);
    
    
    // Calculates and returns the penalty score based on state of this QR Code's current modules.
    // This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
    private: long getPenaltyScore() const;
    
    
    
    /*---- Private helper functions ----*/
    
    // Returns an ascending list of positions of alignment patterns for this version number.
    // Each position is in the range [0,177), and are used on both the x and y axes.
    // This could be implemented as lookup table of 40 variable-length lists of unsigned bytes.
    private: std::vector<int> getAlignmentPatternPositions() const;
    
    
    // Returns the number of data bits that can be stored in a QR Code of the given version number, after
    // all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
    // The result is in the range [208, 29648]. This could be implemented as a 40-entry lookup table.
    private: static int getNumRawDataModules(int ver);
    
    
    // Returns the number of 8-bit data (i.e. not error correction) codewords contained in any
    // QR Code of the given version number and error correction level, with remainder bits discarded.
    // This stateless pure function could be implemented as a (40*4)-cell lookup table.
    private: static int getNumDataCodewords(int ver, Ecc ecl);
    
    
    // Returns a Reed-Solomon ECC generator polynomial for the given degree. This could be
    // implemented as a lookup table over all possible parameter values, instead of as an algorithm.
    private: static std::vector<std::uint8_t> reedSolomonComputeDivisor(int degree);
    
    
    // Returns the Reed-Solomon error correction codeword for the given data and divisor polynomials.
    private: static std::vector<std::uint8_t> reedSolomonComputeRemainder(const std::vector<std::uint8_t> &data, const std::vector<std::uint8_t> &divisor);
    
    
    // Returns the product of the two given field elements modulo GF(2^8/0x11D).
    // All inputs are valid. This could be implemented as a 256*256 lookup table.
    private: static std::uint8_t reedSolomonMultiply(std::uint8_t x, std::uint8_t y);
    
    
    // Can only be called immediately after a light run is added, and
    // returns either 0, 1, or 2. A helper function for getPenaltyScore().
    private: int finderPenaltyCountPatterns(const std::array<int,7> &runHistory) const;
    
    
    // Must be called at the end of a line (row or column) of modules. A helper function for getPenaltyScore().
    private: int finderPenaltyTerminateAndCount(bool currentRunColor, int currentRunLength, std::array<int,7> &runHistory) const;
    
    
    // Pushes the given value to the front and drops the last value. A helper function for getPenaltyScore().
    private: void finderPenaltyAddHistory(int currentRunLength, std::array<int,7> &runHistory) const;
    
    
    // Returns true iff the i'th bit of x is set to 1.
    private: static bool getBit(long x, int i);
    
    
    /*---- Constants and tables ----*/
    
    // The minimum version number supported in the QR Code Model 2 standard.
    public: static constexpr int MIN_VERSION =  1;
    
    // The maximum version number supported in the QR Code Model 2 standard.
    public: static constexpr int MAX_VERSION = 40;
    
    
    // For use in getPenaltyScore(), when evaluating which mask is best.
    private: static const int PENALTY_N1;
    private: static const int PENALTY_N2;
    private: static const int PENALTY_N3;
    private: static const int PENALTY_N4;
    
    
    private: static const std::int8_t ECC_CODEWORDS_PER_BLOCK[4][41];
    private: static const std::int8_t NUM_ERROR_CORRECTION_BLOCKS[4][41];
    
};



/*---- Public exception class ----*/

/* 
 * Thrown when the supplied data does not fit any QR Code version. Ways to handle this exception include:
 * - Decrease the error correction level if it was greater than Ecc::LOW.
 * - If the encodeSegments() function was called with a maxVersion argument, then increase
 *   it if it was less than QrCode::MAX_VERSION. (This advice does not apply to the other
 *   factory functions because they search all versions up to QrCode::MAX_VERSION.)
 * - Split the text data into better or optimal segments in order to reduce the number of bits required.
 * - Change the text or binary data to be shorter.
 * - Change the text to fit the character set of a particular segment mode (e.g. alphanumeric).
 * - Propagate the error upward to the caller/user.
 */
class data_too_long : public std::length_error {
    
    public: explicit data_too_long(const std::string &msg);
    
};



/* 
 * An appendable sequence of bits (0s and 1s). Mainly used by QrSegment.
 */
class BitBuffer final : public std::vector<bool> {
    
    /*---- Constructor ----*/
    
    // Creates an empty bit buffer (length 0).
    public: BitBuffer();
    
    
    
    /*---- Method ----*/
    
    // Appends the given number of low-order bits of the given value
    // to this buffer. Requires 0 <= len <= 31 and val < 2^len.
    public: void appendBits(std::uint32_t val, int len);
    
};

}

#endif // QRCODEGEN_H