318 lines
12 KiB
C++
318 lines
12 KiB
C++
/*
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* QR Code generator library (C++)
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*
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* Copyright (c) Project Nayuki. (MIT License)
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* https://www.nayuki.io/page/qr-code-generator-library
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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* - The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* - The Software is provided "as is", without warranty of any kind, express or
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* implied, including but not limited to the warranties of merchantability,
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* fitness for a particular purpose and noninfringement. In no event shall the
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* authors or copyright holders be liable for any claim, damages or other
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* liability, whether in an action of contract, tort or otherwise, arising from,
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* out of or in connection with the Software or the use or other dealings in the
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* Software.
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*/
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#pragma once
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#include <cstdint>
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#include <string>
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#include <vector>
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#include "QrSegment.hpp"
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namespace qrcodegen {
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/*
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* Represents an immutable square grid of black and white cells for a QR Code symbol, and
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* provides static functions to create a QR Code from user-supplied textual or binary data.
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* This class covers the QR Code Model 2 specification, supporting all versions (sizes)
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* from 1 to 40, all 4 error correction levels, and 4 character encoding modes.
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*/
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class QrCode final {
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/*---- Public helper enumeration ----*/
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/*
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* Represents the error correction level used in a QR Code symbol.
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*/
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public: enum class Ecc {
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// Constants declared in ascending order of error protection.
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LOW = 0, MEDIUM = 1, QUARTILE = 2, HIGH = 3
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};
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// Returns a value in the range 0 to 3 (unsigned 2-bit integer).
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private: static int getFormatBits(Ecc ecl);
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/*---- Static factory functions (high level) ----*/
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/*
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* Returns a QR Code symbol representing the given Unicode text string at the given error correction level.
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* As a conservative upper bound, this function is guaranteed to succeed for strings that have 2953 or fewer
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* UTF-8 code units (not Unicode code points) if the low error correction level is used. The smallest possible
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* QR Code version is automatically chosen for the output. The ECC level of the result may be higher than
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* the ecl argument if it can be done without increasing the version.
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*/
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public: static QrCode encodeText(const char *text, Ecc ecl);
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/*
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* Returns a QR Code symbol representing the given binary data string at the given error correction level.
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* This function always encodes using the binary segment mode, not any text mode. The maximum number of
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* bytes allowed is 2953. The smallest possible QR Code version is automatically chosen for the output.
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* The ECC level of the result may be higher than the ecl argument if it can be done without increasing the version.
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*/
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public: static QrCode encodeBinary(const std::vector<std::uint8_t> &data, Ecc ecl);
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/*---- Static factory functions (mid level) ----*/
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/*
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* Returns a QR Code symbol representing the given segments with the given encoding parameters.
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* The smallest possible QR Code version within the given range is automatically chosen for the output.
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* This function allows the user to create a custom sequence of segments that switches
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* between modes (such as alphanumeric and binary) to encode text more efficiently.
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* This function is considered to be lower level than simply encoding text or binary data.
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*/
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public: static QrCode encodeSegments(const std::vector<QrSegment> &segs, Ecc ecl,
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int minVersion=1, int maxVersion=40, int mask=-1, bool boostEcl=true); // All optional parameters
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/*---- Instance fields ----*/
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// Immutable scalar parameters:
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/* This QR Code symbol's version number, which is always between 1 and 40 (inclusive). */
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private: int version;
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/* The width and height of this QR Code symbol, measured in modules.
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* Always equal to version × 4 + 17, in the range 21 to 177. */
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private: int size;
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/* The error correction level used in this QR Code symbol. */
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private: Ecc errorCorrectionLevel;
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/* The mask pattern used in this QR Code symbol, in the range 0 to 7 (i.e. unsigned 3-bit integer).
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* Note that even if a constructor was called with automatic masking requested
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* (mask = -1), the resulting object will still have a mask value between 0 and 7. */
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private: int mask;
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// Private grids of modules/pixels, with dimensions of size*size:
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// The modules of this QR Code symbol (false = white, true = black). Immutable after constructor finishes.
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private: std::vector<std::vector<bool> > modules;
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// Indicates function modules that are not subjected to masking. Discarded when constructor finishes.
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private: std::vector<std::vector<bool> > isFunction;
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/*---- Constructor (low level) ----*/
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/*
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* Creates a new QR Code symbol with the given version number, error correction level, binary data array,
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* and mask number. This is a cumbersome low-level constructor that should not be invoked directly by the user.
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* To go one level up, see the encodeSegments() function.
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*/
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public: QrCode(int ver, Ecc ecl, const std::vector<std::uint8_t> &dataCodewords, int mask);
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/*---- Public instance methods ----*/
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public: int getVersion() const;
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public: int getSize() const;
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public: Ecc getErrorCorrectionLevel() const;
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public: int getMask() const;
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/*
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* Returns the color of the module (pixel) at the given coordinates, which is either
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* false for white or true for black. The top left corner has the coordinates (x=0, y=0).
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* If the given coordinates are out of bounds, then false (white) is returned.
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*/
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public: bool getModule(int x, int y) const;
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/*
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* Returns a string of SVG XML code representing an image of this QR Code symbol with the given
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* number of border modules. Note that Unix newlines (\n) are always used, regardless of the platform.
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*/
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public: std::string toSvgString(int border) const;
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/*---- Private helper methods for constructor: Drawing function modules ----*/
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// Reads this object's version field, and draws and marks all function modules.
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private: void drawFunctionPatterns();
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// Draws two copies of the format bits (with its own error correction code)
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// based on the given mask and this object's error correction level field.
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private: void drawFormatBits(int mask);
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// Draws two copies of the version bits (with its own error correction code),
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// based on this object's version field, iff 7 <= version <= 40.
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private: void drawVersion();
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// Draws a 9*9 finder pattern including the border separator,
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// with the center module at (x, y). Modules can be out of bounds.
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private: void drawFinderPattern(int x, int y);
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// Draws a 5*5 alignment pattern, with the center module
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// at (x, y). All modules must be in bounds.
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private: void drawAlignmentPattern(int x, int y);
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// Sets the color of a module and marks it as a function module.
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// Only used by the constructor. Coordinates must be in bounds.
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private: void setFunctionModule(int x, int y, bool isBlack);
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// Returns the color of the module at the given coordinates, which must be in range.
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private: bool module(int x, int y) const;
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/*---- Private helper methods for constructor: Codewords and masking ----*/
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// Returns a new byte string representing the given data with the appropriate error correction
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// codewords appended to it, based on this object's version and error correction level.
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private: std::vector<std::uint8_t> addEccAndInterleave(const std::vector<std::uint8_t> &data) const;
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// Draws the given sequence of 8-bit codewords (data and error correction) onto the entire
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// data area of this QR Code symbol. Function modules need to be marked off before this is called.
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private: void drawCodewords(const std::vector<std::uint8_t> &data);
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// XORs the codeword modules in this QR Code with the given mask pattern.
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// The function modules must be marked and the codeword bits must be drawn
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// before masking. Due to the arithmetic of XOR, calling applyMask() with
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// the same mask value a second time will undo the mask. A final well-formed
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// QR Code symbol needs exactly one (not zero, two, etc.) mask applied.
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private: void applyMask(int mask);
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// A messy helper function for the constructors. This QR Code must be in an unmasked state when this
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// method is called. The given argument is the requested mask, which is -1 for auto or 0 to 7 for fixed.
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// This method applies and returns the actual mask chosen, from 0 to 7.
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private: int handleConstructorMasking(int mask);
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// Calculates and returns the penalty score based on state of this QR Code's current modules.
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// This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
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private: long getPenaltyScore() const;
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/*---- Private helper functions ----*/
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// Returns an ascending list of positions of alignment patterns for this version number.
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// Each position is in the range [0,177), and are used on both the x and y axes.
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// This could be implemented as lookup table of 40 variable-length lists of unsigned bytes.
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private: std::vector<int> getAlignmentPatternPositions() const;
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// Returns the number of data bits that can be stored in a QR Code of the given version number, after
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// all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
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// The result is in the range [208, 29648]. This could be implemented as a 40-entry lookup table.
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private: static int getNumRawDataModules(int ver);
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// Returns the number of 8-bit data (i.e. not error correction) codewords contained in any
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// QR Code of the given version number and error correction level, with remainder bits discarded.
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// This stateless pure function could be implemented as a (40*4)-cell lookup table.
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private: static int getNumDataCodewords(int ver, Ecc ecl);
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// Returns true iff the i'th bit of x is set to 1.
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private: static bool getBit(long x, int i);
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/*---- Constants and tables ----*/
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public: static constexpr int MIN_VERSION = 1;
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public: static constexpr int MAX_VERSION = 40;
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// For use in getPenaltyScore(), when evaluating which mask is best.
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private: static const int PENALTY_N1;
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private: static const int PENALTY_N2;
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private: static const int PENALTY_N3;
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private: static const int PENALTY_N4;
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private: static const std::int8_t ECC_CODEWORDS_PER_BLOCK[4][41];
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private: static const std::int8_t NUM_ERROR_CORRECTION_BLOCKS[4][41];
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/*---- Private helper class ----*/
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/*
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* Computes the Reed-Solomon error correction codewords for a sequence of data codewords
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* at a given degree. Objects are immutable, and the state only depends on the degree.
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* This class exists because each data block in a QR Code shares the same the divisor polynomial.
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*/
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private: class ReedSolomonGenerator final {
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/*-- Immutable field --*/
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// Coefficients of the divisor polynomial, stored from highest to lowest power, excluding the leading term which
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// is always 1. For example the polynomial x^3 + 255x^2 + 8x + 93 is stored as the uint8 array {255, 8, 93}.
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private: std::vector<std::uint8_t> coefficients;
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/*-- Constructor --*/
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/*
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* Creates a Reed-Solomon ECC generator for the given degree. This could be implemented
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* as a lookup table over all possible parameter values, instead of as an algorithm.
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*/
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public: explicit ReedSolomonGenerator(int degree);
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/*-- Method --*/
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/*
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* Computes and returns the Reed-Solomon error correction codewords for the given
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* sequence of data codewords. The returned object is always a new byte array.
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* This method does not alter this object's state (because it is immutable).
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*/
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public: std::vector<std::uint8_t> getRemainder(const std::vector<std::uint8_t> &data) const;
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/*-- Static function --*/
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// Returns the product of the two given field elements modulo GF(2^8/0x11D).
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// All inputs are valid. This could be implemented as a 256*256 lookup table.
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private: static std::uint8_t multiply(std::uint8_t x, std::uint8_t y);
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};
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};
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}
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