QrSegment.hpp

#pragma once

#include <cstdint>
#include <vector>
#include "BitBuffer.hpp"


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 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);


			/*
			 * 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);



			/*---- Instance fields ----*/

			/* The mode indicator of this segment. Accessed through getMode(). */
	private: 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(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(Mode md, int numCh, std::vector<bool> &&dt);


			/*---- Methods ----*/

			/*
			 * Returns the mode field of this segment.
			 */
	public: 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;

	};

}