simplewallet: add show_qr_code command

Thanks to iDunk for helping with Windows.

7 files changed, 1491 insertions, 0 deletions

diff --git a/external/CMakeLists.txt b/external/CMakeLists.txt
index 71b165f4f..a8916a7d0 100644
--- a/external/CMakeLists.txt
+++ b/external/CMakeLists.txt
@@ -80,4 +80,5 @@ endif()
 
 add_subdirectory(db_drivers)
 add_subdirectory(easylogging++)
+add_subdirectory(qrcodegen)
 add_subdirectory(randomx EXCLUDE_FROM_ALL)
diff --git a/external/qrcodegen/CMakeLists.txt b/external/qrcodegen/CMakeLists.txt
new file mode 100644
index 000000000..a9060e3e8
--- /dev/null
+++ b/external/qrcodegen/CMakeLists.txt
@@ -0,0 +1,7 @@
+project(libqrcodegen)
+
+add_library(qrcodegen STATIC QrCode.cpp)
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
+
+target_include_directories(qrcodegen PUBLIC 
+    ${CMAKE_CURRENT_SOURCE_DIR})
diff --git a/external/qrcodegen/QrCode.cpp b/external/qrcodegen/QrCode.cpp
new file mode 100644
index 000000000..b9de86215
--- /dev/null
+++ b/external/qrcodegen/QrCode.cpp
@@ -0,0 +1,862 @@
+/* 
+ * 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.
+ */
+
+#include <algorithm>
+#include <climits>
+#include <cstddef>
+#include <cstdlib>
+#include <cstring>
+#include <sstream>
+#include <stdexcept>
+#include <utility>
+#include "QrCode.hpp"
+
+using std::int8_t;
+using std::uint8_t;
+using std::size_t;
+using std::vector;
+
+
+namespace qrcodegen {
+
+QrSegment::Mode::Mode(int mode, int cc0, int cc1, int cc2) :
+		modeBits(mode) {
+	numBitsCharCount[0] = cc0;
+	numBitsCharCount[1] = cc1;
+	numBitsCharCount[2] = cc2;
+}
+
+
+int QrSegment::Mode::getModeBits() const {
+	return modeBits;
+}
+
+
+int QrSegment::Mode::numCharCountBits(int ver) const {
+	return numBitsCharCount[(ver + 7) / 17];
+}
+
+
+const QrSegment::Mode QrSegment::Mode::NUMERIC     (0x1, 10, 12, 14);
+const QrSegment::Mode QrSegment::Mode::ALPHANUMERIC(0x2,  9, 11, 13);
+const QrSegment::Mode QrSegment::Mode::BYTE        (0x4,  8, 16, 16);
+const QrSegment::Mode QrSegment::Mode::KANJI       (0x8,  8, 10, 12);
+const QrSegment::Mode QrSegment::Mode::ECI         (0x7,  0,  0,  0);
+
+
+QrSegment QrSegment::makeBytes(const vector<uint8_t> &data) {
+	if (data.size() > static_cast<unsigned int>(INT_MAX))
+		throw std::length_error("Data too long");
+	BitBuffer bb;
+	for (uint8_t b : data)
+		bb.appendBits(b, 8);
+	return QrSegment(Mode::BYTE, static_cast<int>(data.size()), std::move(bb));
+}
+
+
+QrSegment QrSegment::makeNumeric(const char *digits) {
+	BitBuffer bb;
+	int accumData = 0;
+	int accumCount = 0;
+	int charCount = 0;
+	for (; *digits != '\0'; digits++, charCount++) {
+		char c = *digits;
+		if (c < '0' || c > '9')
+			throw std::domain_error("String contains non-numeric characters");
+		accumData = accumData * 10 + (c - '0');
+		accumCount++;
+		if (accumCount == 3) {
+			bb.appendBits(static_cast<uint32_t>(accumData), 10);
+			accumData = 0;
+			accumCount = 0;
+		}
+	}
+	if (accumCount > 0)  // 1 or 2 digits remaining
+		bb.appendBits(static_cast<uint32_t>(accumData), accumCount * 3 + 1);
+	return QrSegment(Mode::NUMERIC, charCount, std::move(bb));
+}
+
+
+QrSegment QrSegment::makeAlphanumeric(const char *text) {
+	BitBuffer bb;
+	int accumData = 0;
+	int accumCount = 0;
+	int charCount = 0;
+	for (; *text != '\0'; text++, charCount++) {
+		const char *temp = std::strchr(ALPHANUMERIC_CHARSET, *text);
+		if (temp == nullptr)
+			throw std::domain_error("String contains unencodable characters in alphanumeric mode");
+		accumData = accumData * 45 + static_cast<int>(temp - ALPHANUMERIC_CHARSET);
+		accumCount++;
+		if (accumCount == 2) {
+			bb.appendBits(static_cast<uint32_t>(accumData), 11);
+			accumData = 0;
+			accumCount = 0;
+		}
+	}
+	if (accumCount > 0)  // 1 character remaining
+		bb.appendBits(static_cast<uint32_t>(accumData), 6);
+	return QrSegment(Mode::ALPHANUMERIC, charCount, std::move(bb));
+}
+
+
+vector<QrSegment> QrSegment::makeSegments(const char *text) {
+	// Select the most efficient segment encoding automatically
+	vector<QrSegment> result;
+	if (*text == '\0');  // Leave result empty
+	else if (isNumeric(text))
+		result.push_back(makeNumeric(text));
+	else if (isAlphanumeric(text))
+		result.push_back(makeAlphanumeric(text));
+	else {
+		vector<uint8_t> bytes;
+		for (; *text != '\0'; text++)
+			bytes.push_back(static_cast<uint8_t>(*text));
+		result.push_back(makeBytes(bytes));
+	}
+	return result;
+}
+
+
+QrSegment QrSegment::makeEci(long assignVal) {
+	BitBuffer bb;
+	if (assignVal < 0)
+		throw std::domain_error("ECI assignment value out of range");
+	else if (assignVal < (1 << 7))
+		bb.appendBits(static_cast<uint32_t>(assignVal), 8);
+	else if (assignVal < (1 << 14)) {
+		bb.appendBits(2, 2);
+		bb.appendBits(static_cast<uint32_t>(assignVal), 14);
+	} else if (assignVal < 1000000L) {
+		bb.appendBits(6, 3);
+		bb.appendBits(static_cast<uint32_t>(assignVal), 21);
+	} else
+		throw std::domain_error("ECI assignment value out of range");
+	return QrSegment(Mode::ECI, 0, std::move(bb));
+}
+
+
+QrSegment::QrSegment(Mode md, int numCh, const std::vector<bool> &dt) :
+		mode(md),
+		numChars(numCh),
+		data(dt) {
+	if (numCh < 0)
+		throw std::domain_error("Invalid value");
+}
+
+
+QrSegment::QrSegment(Mode md, int numCh, std::vector<bool> &&dt) :
+		mode(md),
+		numChars(numCh),
+		data(std::move(dt)) {
+	if (numCh < 0)
+		throw std::domain_error("Invalid value");
+}
+
+
+int QrSegment::getTotalBits(const vector<QrSegment> &segs, int version) {
+	int result = 0;
+	for (const QrSegment &seg : segs) {
+		int ccbits = seg.mode.numCharCountBits(version);
+		if (seg.numChars >= (1L << ccbits))
+			return -1;  // The segment's length doesn't fit the field's bit width
+		if (4 + ccbits > INT_MAX - result)
+			return -1;  // The sum will overflow an int type
+		result += 4 + ccbits;
+		if (seg.data.size() > static_cast<unsigned int>(INT_MAX - result))
+			return -1;  // The sum will overflow an int type
+		result += static_cast<int>(seg.data.size());
+	}
+	return result;
+}
+
+
+bool QrSegment::isAlphanumeric(const char *text) {
+	for (; *text != '\0'; text++) {
+		if (std::strchr(ALPHANUMERIC_CHARSET, *text) == nullptr)
+			return false;
+	}
+	return true;
+}
+
+
+bool QrSegment::isNumeric(const char *text) {
+	for (; *text != '\0'; text++) {
+		char c = *text;
+		if (c < '0' || c > '9')
+			return false;
+	}
+	return true;
+}
+
+
+QrSegment::Mode QrSegment::getMode() const {
+	return mode;
+}
+
+
+int QrSegment::getNumChars() const {
+	return numChars;
+}
+
+
+const std::vector<bool> &QrSegment::getData() const {
+	return data;
+}
+
+
+const char *QrSegment::ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
+
+
+
+int QrCode::getFormatBits(Ecc ecl) {
+	switch (ecl) {
+		case Ecc::LOW     :  return 1;
+		case Ecc::MEDIUM  :  return 0;
+		case Ecc::QUARTILE:  return 3;
+		case Ecc::HIGH    :  return 2;
+		default:  throw std::logic_error("Assertion error");
+	}
+}
+
+
+QrCode QrCode::encodeText(const char *text, Ecc ecl) {
+	vector<QrSegment> segs = QrSegment::makeSegments(text);
+	return encodeSegments(segs, ecl);
+}
+
+
+QrCode QrCode::encodeBinary(const vector<uint8_t> &data, Ecc ecl) {
+	vector<QrSegment> segs{QrSegment::makeBytes(data)};
+	return encodeSegments(segs, ecl);
+}
+
+
+QrCode QrCode::encodeSegments(const vector<QrSegment> &segs, Ecc ecl,
+		int minVersion, int maxVersion, int mask, bool boostEcl) {
+	if (!(MIN_VERSION <= minVersion && minVersion <= maxVersion && maxVersion <= MAX_VERSION) || mask < -1 || mask > 7)
+		throw std::invalid_argument("Invalid value");
+	
+	// Find the minimal version number to use
+	int version, dataUsedBits;
+	for (version = minVersion; ; version++) {
+		int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;  // Number of data bits available
+		dataUsedBits = QrSegment::getTotalBits(segs, version);
+		if (dataUsedBits != -1 && dataUsedBits <= dataCapacityBits)
+			break;  // This version number is found to be suitable
+		if (version >= maxVersion) {  // All versions in the range could not fit the given data
+			std::ostringstream sb;
+			if (dataUsedBits == -1)
+				sb << "Segment too long";
+			else {
+				sb << "Data length = " << dataUsedBits << " bits, ";
+				sb << "Max capacity = " << dataCapacityBits << " bits";
+			}
+			throw data_too_long(sb.str());
+		}
+	}
+	if (dataUsedBits == -1)
+		throw std::logic_error("Assertion error");
+	
+	// Increase the error correction level while the data still fits in the current version number
+	for (Ecc newEcl : vector<Ecc>{Ecc::MEDIUM, Ecc::QUARTILE, Ecc::HIGH}) {  // From low to high
+		if (boostEcl && dataUsedBits <= getNumDataCodewords(version, newEcl) * 8)
+			ecl = newEcl;
+	}
+	
+	// Concatenate all segments to create the data bit string
+	BitBuffer bb;
+	for (const QrSegment &seg : segs) {
+		bb.appendBits(static_cast<uint32_t>(seg.getMode().getModeBits()), 4);
+		bb.appendBits(static_cast<uint32_t>(seg.getNumChars()), seg.getMode().numCharCountBits(version));
+		bb.insert(bb.end(), seg.getData().begin(), seg.getData().end());
+	}
+	if (bb.size() != static_cast<unsigned int>(dataUsedBits))
+		throw std::logic_error("Assertion error");
+	
+	// Add terminator and pad up to a byte if applicable
+	size_t dataCapacityBits = static_cast<size_t>(getNumDataCodewords(version, ecl)) * 8;
+	if (bb.size() > dataCapacityBits)
+		throw std::logic_error("Assertion error");
+	bb.appendBits(0, std::min(4, static_cast<int>(dataCapacityBits - bb.size())));
+	bb.appendBits(0, (8 - static_cast<int>(bb.size() % 8)) % 8);
+	if (bb.size() % 8 != 0)
+		throw std::logic_error("Assertion error");
+	
+	// Pad with alternating bytes until data capacity is reached
+	for (uint8_t padByte = 0xEC; bb.size() < dataCapacityBits; padByte ^= 0xEC ^ 0x11)
+		bb.appendBits(padByte, 8);
+	
+	// Pack bits into bytes in big endian
+	vector<uint8_t> dataCodewords(bb.size() / 8);
+	for (size_t i = 0; i < bb.size(); i++)
+		dataCodewords[i >> 3] |= (bb.at(i) ? 1 : 0) << (7 - (i & 7));
+	
+	// Create the QR Code object
+	return QrCode(version, ecl, dataCodewords, mask);
+}
+
+
+QrCode::QrCode(int ver, Ecc ecl, const vector<uint8_t> &dataCodewords, int msk) :
+		// Initialize fields and check arguments
+		version(ver),
+		errorCorrectionLevel(ecl) {
+	if (ver < MIN_VERSION || ver > MAX_VERSION)
+		throw std::domain_error("Version value out of range");
+	if (msk < -1 || msk > 7)
+		throw std::domain_error("Mask value out of range");
+	size = ver * 4 + 17;
+	size_t sz = static_cast<size_t>(size);
+	modules    = vector<vector<bool> >(sz, vector<bool>(sz));  // Initially all white
+	isFunction = vector<vector<bool> >(sz, vector<bool>(sz));
+	
+	// Compute ECC, draw modules
+	drawFunctionPatterns();
+	const vector<uint8_t> allCodewords = addEccAndInterleave(dataCodewords);
+	drawCodewords(allCodewords);
+	
+	// Do masking
+	if (msk == -1) {  // Automatically choose best mask
+		long minPenalty = LONG_MAX;
+		for (int i = 0; i < 8; i++) {
+			applyMask(i);
+			drawFormatBits(i);
+			long penalty = getPenaltyScore();
+			if (penalty < minPenalty) {
+				msk = i;
+				minPenalty = penalty;
+			}
+			applyMask(i);  // Undoes the mask due to XOR
+		}
+	}
+	if (msk < 0 || msk > 7)
+		throw std::logic_error("Assertion error");
+	this->mask = msk;
+	applyMask(msk);  // Apply the final choice of mask
+	drawFormatBits(msk);  // Overwrite old format bits
+	
+	isFunction.clear();
+	isFunction.shrink_to_fit();
+}
+
+
+int QrCode::getVersion() const {
+	return version;
+}
+
+
+int QrCode::getSize() const {
+	return size;
+}
+
+
+QrCode::Ecc QrCode::getErrorCorrectionLevel() const {
+	return errorCorrectionLevel;
+}
+
+
+int QrCode::getMask() const {
+	return mask;
+}
+
+
+bool QrCode::getModule(int x, int y) const {
+	return 0 <= x && x < size && 0 <= y && y < size && module(x, y);
+}
+
+
+std::string QrCode::toSvgString(int border) const {
+	if (border < 0)
+		throw std::domain_error("Border must be non-negative");
+	if (border > INT_MAX / 2 || border * 2 > INT_MAX - size)
+		throw std::overflow_error("Border too large");
+	
+	std::ostringstream sb;
+	sb << "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
+	sb << "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n";
+	sb << "<svg xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\" viewBox=\"0 0 ";
+	sb << (size + border * 2) << " " << (size + border * 2) << "\" stroke=\"none\">\n";
+	sb << "\t<rect width=\"100%\" height=\"100%\" fill=\"#FFFFFF\"/>\n";
+	sb << "\t<path d=\"";
+	for (int y = 0; y < size; y++) {
+		for (int x = 0; x < size; x++) {
+			if (getModule(x, y)) {
+				if (x != 0 || y != 0)
+					sb << " ";
+				sb << "M" << (x + border) << "," << (y + border) << "h1v1h-1z";
+			}
+		}
+	}
+	sb << "\" fill=\"#000000\"/>\n";
+	sb << "</svg>\n";
+	return sb.str();
+}
+
+
+void QrCode::drawFunctionPatterns() {
+	// Draw horizontal and vertical timing patterns
+	for (int i = 0; i < size; i++) {
+		setFunctionModule(6, i, i % 2 == 0);
+		setFunctionModule(i, 6, i % 2 == 0);
+	}
+	
+	// Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules)
+	drawFinderPattern(3, 3);
+	drawFinderPattern(size - 4, 3);
+	drawFinderPattern(3, size - 4);
+	
+	// Draw numerous alignment patterns
+	const vector<int> alignPatPos = getAlignmentPatternPositions();
+	size_t numAlign = alignPatPos.size();
+	for (size_t i = 0; i < numAlign; i++) {
+		for (size_t j = 0; j < numAlign; j++) {
+			// Don't draw on the three finder corners
+			if (!((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0)))
+				drawAlignmentPattern(alignPatPos.at(i), alignPatPos.at(j));
+		}
+	}
+	
+	// Draw configuration data
+	drawFormatBits(0);  // Dummy mask value; overwritten later in the constructor
+	drawVersion();
+}
+
+
+void QrCode::drawFormatBits(int msk) {
+	// Calculate error correction code and pack bits
+	int data = getFormatBits(errorCorrectionLevel) << 3 | msk;  // errCorrLvl is uint2, msk is uint3
+	int rem = data;
+	for (int i = 0; i < 10; i++)
+		rem = (rem << 1) ^ ((rem >> 9) * 0x537);
+	int bits = (data << 10 | rem) ^ 0x5412;  // uint15
+	if (bits >> 15 != 0)
+		throw std::logic_error("Assertion error");
+	
+	// Draw first copy
+	for (int i = 0; i <= 5; i++)
+		setFunctionModule(8, i, getBit(bits, i));
+	setFunctionModule(8, 7, getBit(bits, 6));
+	setFunctionModule(8, 8, getBit(bits, 7));
+	setFunctionModule(7, 8, getBit(bits, 8));
+	for (int i = 9; i < 15; i++)
+		setFunctionModule(14 - i, 8, getBit(bits, i));
+	
+	// Draw second copy
+	for (int i = 0; i < 8; i++)
+		setFunctionModule(size - 1 - i, 8, getBit(bits, i));
+	for (int i = 8; i < 15; i++)
+		setFunctionModule(8, size - 15 + i, getBit(bits, i));
+	setFunctionModule(8, size - 8, true);  // Always black
+}
+
+
+void QrCode::drawVersion() {
+	if (version < 7)
+		return;
+	
+	// Calculate error correction code and pack bits
+	int rem = version;  // version is uint6, in the range [7, 40]
+	for (int i = 0; i < 12; i++)
+		rem = (rem << 1) ^ ((rem >> 11) * 0x1F25);
+	long bits = static_cast<long>(version) << 12 | rem;  // uint18
+	if (bits >> 18 != 0)
+		throw std::logic_error("Assertion error");
+	
+	// Draw two copies
+	for (int i = 0; i < 18; i++) {
+		bool bit = getBit(bits, i);
+		int a = size - 11 + i % 3;
+		int b = i / 3;
+		setFunctionModule(a, b, bit);
+		setFunctionModule(b, a, bit);
+	}
+}
+
+
+void QrCode::drawFinderPattern(int x, int y) {
+	for (int dy = -4; dy <= 4; dy++) {
+		for (int dx = -4; dx <= 4; dx++) {
+			int dist = std::max(std::abs(dx), std::abs(dy));  // Chebyshev/infinity norm
+			int xx = x + dx, yy = y + dy;
+			if (0 <= xx && xx < size && 0 <= yy && yy < size)
+				setFunctionModule(xx, yy, dist != 2 && dist != 4);
+		}
+	}
+}
+
+
+void QrCode::drawAlignmentPattern(int x, int y) {
+	for (int dy = -2; dy <= 2; dy++) {
+		for (int dx = -2; dx <= 2; dx++)
+			setFunctionModule(x + dx, y + dy, std::max(std::abs(dx), std::abs(dy)) != 1);
+	}
+}
+
+
+void QrCode::setFunctionModule(int x, int y, bool isBlack) {
+	size_t ux = static_cast<size_t>(x);
+	size_t uy = static_cast<size_t>(y);
+	modules   .at(uy).at(ux) = isBlack;
+	isFunction.at(uy).at(ux) = true;
+}
+
+
+bool QrCode::module(int x, int y) const {
+	return modules.at(static_cast<size_t>(y)).at(static_cast<size_t>(x));
+}
+
+
+vector<uint8_t> QrCode::addEccAndInterleave(const vector<uint8_t> &data) const {
+	if (data.size() != static_cast<unsigned int>(getNumDataCodewords(version, errorCorrectionLevel)))
+		throw std::invalid_argument("Invalid argument");
+	
+	// Calculate parameter numbers
+	int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[static_cast<int>(errorCorrectionLevel)][version];
+	int blockEccLen = ECC_CODEWORDS_PER_BLOCK  [static_cast<int>(errorCorrectionLevel)][version];
+	int rawCodewords = getNumRawDataModules(version) / 8;
+	int numShortBlocks = numBlocks - rawCodewords % numBlocks;
+	int shortBlockLen = rawCodewords / numBlocks;
+	
+	// Split data into blocks and append ECC to each block
+	vector<vector<uint8_t> > blocks;
+	const vector<uint8_t> rsDiv = reedSolomonComputeDivisor(blockEccLen);
+	for (int i = 0, k = 0; i < numBlocks; i++) {
+		vector<uint8_t> dat(data.cbegin() + k, data.cbegin() + (k + shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1)));
+		k += static_cast<int>(dat.size());
+		const vector<uint8_t> ecc = reedSolomonComputeRemainder(dat, rsDiv);
+		if (i < numShortBlocks)
+			dat.push_back(0);
+		dat.insert(dat.end(), ecc.cbegin(), ecc.cend());
+		blocks.push_back(std::move(dat));
+	}
+	
+	// Interleave (not concatenate) the bytes from every block into a single sequence
+	vector<uint8_t> result;
+	for (size_t i = 0; i < blocks.at(0).size(); i++) {
+		for (size_t j = 0; j < blocks.size(); j++) {
+			// Skip the padding byte in short blocks
+			if (i != static_cast<unsigned int>(shortBlockLen - blockEccLen) || j >= static_cast<unsigned int>(numShortBlocks))
+				result.push_back(blocks.at(j).at(i));
+		}
+	}
+	if (result.size() != static_cast<unsigned int>(rawCodewords))
+		throw std::logic_error("Assertion error");
+	return result;
+}
+
+
+void QrCode::drawCodewords(const vector<uint8_t> &data) {
+	if (data.size() != static_cast<unsigned int>(getNumRawDataModules(version) / 8))
+		throw std::invalid_argument("Invalid argument");
+	
+	size_t i = 0;  // Bit index into the data
+	// Do the funny zigzag scan
+	for (int right = size - 1; right >= 1; right -= 2) {  // Index of right column in each column pair
+		if (right == 6)
+			right = 5;
+		for (int vert = 0; vert < size; vert++) {  // Vertical counter
+			for (int j = 0; j < 2; j++) {
+				size_t x = static_cast<size_t>(right - j);  // Actual x coordinate
+				bool upward = ((right + 1) & 2) == 0;
+				size_t y = static_cast<size_t>(upward ? size - 1 - vert : vert);  // Actual y coordinate
+				if (!isFunction.at(y).at(x) && i < data.size() * 8) {
+					modules.at(y).at(x) = getBit(data.at(i >> 3), 7 - static_cast<int>(i & 7));
+					i++;
+				}
+				// If this QR Code has any remainder bits (0 to 7), they were assigned as
+				// 0/false/white by the constructor and are left unchanged by this method
+			}
+		}
+	}
+	if (i != data.size() * 8)
+		throw std::logic_error("Assertion error");
+}
+
+
+void QrCode::applyMask(int msk) {
+	if (msk < 0 || msk > 7)
+		throw std::domain_error("Mask value out of range");
+	size_t sz = static_cast<size_t>(size);
+	for (size_t y = 0; y < sz; y++) {
+		for (size_t x = 0; x < sz; x++) {
+			bool invert;
+			switch (msk) {
+				case 0:  invert = (x + y) % 2 == 0;                    break;
+				case 1:  invert = y % 2 == 0;                          break;
+				case 2:  invert = x % 3 == 0;                          break;
+				case 3:  invert = (x + y) % 3 == 0;                    break;
+				case 4:  invert = (x / 3 + y / 2) % 2 == 0;            break;
+				case 5:  invert = x * y % 2 + x * y % 3 == 0;          break;
+				case 6:  invert = (x * y % 2 + x * y % 3) % 2 == 0;    break;
+				case 7:  invert = ((x + y) % 2 + x * y % 3) % 2 == 0;  break;
+				default:  throw std::logic_error("Assertion error");
+			}
+			modules.at(y).at(x) = modules.at(y).at(x) ^ (invert & !isFunction.at(y).at(x));
+		}
+	}
+}
+
+
+long QrCode::getPenaltyScore() const {
+	long result = 0;
+	
+	// Adjacent modules in row having same color, and finder-like patterns
+	for (int y = 0; y < size; y++) {
+		bool runColor = false;
+		int runX = 0;
+		std::array<int,7> runHistory = {};
+		for (int x = 0; x < size; x++) {
+			if (module(x, y) == runColor) {
+				runX++;
+				if (runX == 5)
+					result += PENALTY_N1;
+				else if (runX > 5)
+					result++;
+			} else {
+				finderPenaltyAddHistory(runX, runHistory);
+				if (!runColor)
+					result += finderPenaltyCountPatterns(runHistory) * PENALTY_N3;
+				runColor = module(x, y);
+				runX = 1;
+			}
+		}
+		result += finderPenaltyTerminateAndCount(runColor, runX, runHistory) * PENALTY_N3;
+	}
+	// Adjacent modules in column having same color, and finder-like patterns
+	for (int x = 0; x < size; x++) {
+		bool runColor = false;
+		int runY = 0;
+		std::array<int,7> runHistory = {};
+		for (int y = 0; y < size; y++) {
+			if (module(x, y) == runColor) {
+				runY++;
+				if (runY == 5)
+					result += PENALTY_N1;
+				else if (runY > 5)
+					result++;
+			} else {
+				finderPenaltyAddHistory(runY, runHistory);
+				if (!runColor)
+					result += finderPenaltyCountPatterns(runHistory) * PENALTY_N3;
+				runColor = module(x, y);
+				runY = 1;
+			}
+		}
+		result += finderPenaltyTerminateAndCount(runColor, runY, runHistory) * PENALTY_N3;
+	}
+	
+	// 2*2 blocks of modules having same color
+	for (int y = 0; y < size - 1; y++) {
+		for (int x = 0; x < size - 1; x++) {
+			bool  color = module(x, y);
+			if (  color == module(x + 1, y) &&
+			      color == module(x, y + 1) &&
+			      color == module(x + 1, y + 1))
+				result += PENALTY_N2;
+		}
+	}
+	
+	// Balance of black and white modules
+	int black = 0;
+	for (const vector<bool> &row : modules) {
+		for (bool color : row) {
+			if (color)
+				black++;
+		}
+	}
+	int total = size * size;  // Note that size is odd, so black/total != 1/2
+	// Compute the smallest integer k >= 0 such that (45-5k)% <= black/total <= (55+5k)%
+	int k = static_cast<int>((std::abs(black * 20L - total * 10L) + total - 1) / total) - 1;
+	result += k * PENALTY_N4;
+	return result;
+}
+
+
+vector<int> QrCode::getAlignmentPatternPositions() const {
+	if (version == 1)
+		return vector<int>();
+	else {
+		int numAlign = version / 7 + 2;
+		int step = (version == 32) ? 26 :
+			(version*4 + numAlign*2 + 1) / (numAlign*2 - 2) * 2;
+		vector<int> result;
+		for (int i = 0, pos = size - 7; i < numAlign - 1; i++, pos -= step)
+			result.insert(result.begin(), pos);
+		result.insert(result.begin(), 6);
+		return result;
+	}
+}
+
+
+int QrCode::getNumRawDataModules(int ver) {
+	if (ver < MIN_VERSION || ver > MAX_VERSION)
+		throw std::domain_error("Version number out of range");
+	int result = (16 * ver + 128) * ver + 64;
+	if (ver >= 2) {
+		int numAlign = ver / 7 + 2;
+		result -= (25 * numAlign - 10) * numAlign - 55;
+		if (ver >= 7)
+			result -= 36;
+	}
+	if (!(208 <= result && result <= 29648))
+		throw std::logic_error("Assertion error");
+	return result;
+}
+
+
+int QrCode::getNumDataCodewords(int ver, Ecc ecl) {
+	return getNumRawDataModules(ver) / 8
+		- ECC_CODEWORDS_PER_BLOCK    [static_cast<int>(ecl)][ver]
+		* NUM_ERROR_CORRECTION_BLOCKS[static_cast<int>(ecl)][ver];
+}
+
+
+vector<uint8_t> QrCode::reedSolomonComputeDivisor(int degree) {
+	if (degree < 1 || degree > 255)
+		throw std::domain_error("Degree out of range");
+	// Polynomial coefficients are stored from highest to lowest power, excluding the leading term which is always 1.
+	// For example the polynomial x^3 + 255x^2 + 8x + 93 is stored as the uint8 array {255, 8, 93}.
+	vector<uint8_t> result(static_cast<size_t>(degree));
+	result.at(result.size() - 1) = 1;  // Start off with the monomial x^0
+	
+	// Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
+	// and drop the highest monomial term which is always 1x^degree.
+	// Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
+	uint8_t root = 1;
+	for (int i = 0; i < degree; i++) {
+		// Multiply the current product by (x - r^i)
+		for (size_t j = 0; j < result.size(); j++) {
+			result.at(j) = reedSolomonMultiply(result.at(j), root);
+			if (j + 1 < result.size())
+				result.at(j) ^= result.at(j + 1);
+		}
+		root = reedSolomonMultiply(root, 0x02);
+	}
+	return result;
+}
+
+
+vector<uint8_t> QrCode::reedSolomonComputeRemainder(const vector<uint8_t> &data, const vector<uint8_t> &divisor) {
+	vector<uint8_t> result(divisor.size());
+	for (uint8_t b : data) {  // Polynomial division
+		uint8_t factor = b ^ result.at(0);
+		result.erase(result.begin());
+		result.push_back(0);
+		for (size_t i = 0; i < result.size(); i++)
+			result.at(i) ^= reedSolomonMultiply(divisor.at(i), factor);
+	}
+	return result;
+}
+
+
+uint8_t QrCode::reedSolomonMultiply(uint8_t x, uint8_t y) {
+	// Russian peasant multiplication
+	int z = 0;
+	for (int i = 7; i >= 0; i--) {
+		z = (z << 1) ^ ((z >> 7) * 0x11D);
+		z ^= ((y >> i) & 1) * x;
+	}
+	if (z >> 8 != 0)
+		throw std::logic_error("Assertion error");
+	return static_cast<uint8_t>(z);
+}
+
+
+int QrCode::finderPenaltyCountPatterns(const std::array<int,7> &runHistory) const {
+	int n = runHistory.at(1);
+	if (n > size * 3)
+		throw std::logic_error("Assertion error");
+	bool core = n > 0 && runHistory.at(2) == n && runHistory.at(3) == n * 3 && runHistory.at(4) == n && runHistory.at(5) == n;
+	return (core && runHistory.at(0) >= n * 4 && runHistory.at(6) >= n ? 1 : 0)
+	     + (core && runHistory.at(6) >= n * 4 && runHistory.at(0) >= n ? 1 : 0);
+}
+
+
+int QrCode::finderPenaltyTerminateAndCount(bool currentRunColor, int currentRunLength, std::array<int,7> &runHistory) const {
+	if (currentRunColor) {  // Terminate black run
+		finderPenaltyAddHistory(currentRunLength, runHistory);
+		currentRunLength = 0;
+	}
+	currentRunLength += size;  // Add white border to final run
+	finderPenaltyAddHistory(currentRunLength, runHistory);
+	return finderPenaltyCountPatterns(runHistory);
+}
+
+
+void QrCode::finderPenaltyAddHistory(int currentRunLength, std::array<int,7> &runHistory) const {
+	if (runHistory.at(0) == 0)
+		currentRunLength += size;  // Add white border to initial run
+	std::copy_backward(runHistory.cbegin(), runHistory.cend() - 1, runHistory.end());
+	runHistory.at(0) = currentRunLength;
+}
+
+
+bool QrCode::getBit(long x, int i) {
+	return ((x >> i) & 1) != 0;
+}
+
+
+/*---- Tables of constants ----*/
+
+const int QrCode::PENALTY_N1 =  3;
+const int QrCode::PENALTY_N2 =  3;
+const int QrCode::PENALTY_N3 = 40;
+const int QrCode::PENALTY_N4 = 10;
+
+
+const int8_t QrCode::ECC_CODEWORDS_PER_BLOCK[4][41] = {
+	// Version: (note that index 0 is for padding, and is set to an illegal value)
+	//0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level
+	{-1,  7, 10, 15, 20, 26, 18, 20, 24, 30, 18, 20, 24, 26, 30, 22, 24, 28, 30, 28, 28, 28, 28, 30, 30, 26, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30},  // Low
+	{-1, 10, 16, 26, 18, 24, 16, 18, 22, 22, 26, 30, 22, 22, 24, 24, 28, 28, 26, 26, 26, 26, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28},  // Medium
+	{-1, 13, 22, 18, 26, 18, 24, 18, 22, 20, 24, 28, 26, 24, 20, 30, 24, 28, 28, 26, 30, 28, 30, 30, 30, 30, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30},  // Quartile
+	{-1, 17, 28, 22, 16, 22, 28, 26, 26, 24, 28, 24, 28, 22, 24, 24, 30, 28, 28, 26, 28, 30, 24, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30},  // High
+};
+
+const int8_t QrCode::NUM_ERROR_CORRECTION_BLOCKS[4][41] = {
+	// Version: (note that index 0 is for padding, and is set to an illegal value)
+	//0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level
+	{-1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 4,  4,  4,  4,  4,  6,  6,  6,  6,  7,  8,  8,  9,  9, 10, 12, 12, 12, 13, 14, 15, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25},  // Low
+	{-1, 1, 1, 1, 2, 2, 4, 4, 4, 5, 5,  5,  8,  9,  9, 10, 10, 11, 13, 14, 16, 17, 17, 18, 20, 21, 23, 25, 26, 28, 29, 31, 33, 35, 37, 38, 40, 43, 45, 47, 49},  // Medium
+	{-1, 1, 1, 2, 2, 4, 4, 6, 6, 8, 8,  8, 10, 12, 16, 12, 17, 16, 18, 21, 20, 23, 23, 25, 27, 29, 34, 34, 35, 38, 40, 43, 45, 48, 51, 53, 56, 59, 62, 65, 68},  // Quartile
+	{-1, 1, 1, 2, 4, 4, 4, 5, 6, 8, 8, 11, 11, 16, 16, 18, 16, 19, 21, 25, 25, 25, 34, 30, 32, 35, 37, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 70, 74, 77, 81},  // High
+};
+
+
+data_too_long::data_too_long(const std::string &msg) :
+	std::length_error(msg) {}
+
+
+
+BitBuffer::BitBuffer()
+	: std::vector<bool>() {}
+
+
+void BitBuffer::appendBits(std::uint32_t val, int len) {
+	if (len < 0 || len > 31 || val >> len != 0)
+		throw std::domain_error("Value out of range");
+	for (int i = len - 1; i >= 0; i--)  // Append bit by bit
+		this->push_back(((val >> i) & 1) != 0);
+}
+
+}
diff --git a/external/qrcodegen/QrCode.hpp b/external/qrcodegen/QrCode.hpp
new file mode 100644
index 000000000..7341e4102
--- /dev/null
+++ b/external/qrcodegen/QrCode.hpp
@@ -0,0 +1,556 @@
+/* 
+ * 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.
+ */
+
+#pragma once
+
+#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 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;
+	
+};
+
+
+
+/* 
+ * 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 black and white 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 class Ecc {
+		LOW = 0 ,  // The QR Code can tolerate about  7% erroneous codewords
+		MEDIUM  ,  // The QR Code can tolerate about 15% erroneous codewords
+		QUARTILE,  // The QR Code can tolerate about 25% erroneous codewords
+		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 = white, true = black).
+	// 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 white or true for black. The top left corner has the coordinates (x=0, y=0).
+	 * If the given coordinates are out of bounds, then false (white) is returned.
+	 */
+	public: bool getModule(int x, int y) const;
+	
+	
+	/* 
+	 * Returns a string of SVG code for an image depicting this QR Code, with the given number
+	 * of border modules. The string always uses Unix newlines (\n), regardless of the platform.
+	 */
+	public: std::string toSvgString(int border) 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 isBlack);
+	
+	
+	// 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 white 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);
+	
+};
+
+}
diff --git a/src/simplewallet/CMakeLists.txt b/src/simplewallet/CMakeLists.txt
index 030867dc0..c1be41e0d 100644
--- a/src/simplewallet/CMakeLists.txt
+++ b/src/simplewallet/CMakeLists.txt
@@ -49,6 +49,7 @@ target_link_libraries(simplewallet
     common
     mnemonics
     ${EPEE_READLINE}
+    qrcodegen
     version
     ${Boost_CHRONO_LIBRARY}
     ${Boost_PROGRAM_OPTIONS_LIBRARY}
diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
index 4a22dfa25..6cab628e6 100644
--- a/src/simplewallet/simplewallet.cpp
+++ b/src/simplewallet/simplewallet.cpp
@@ -69,10 +69,12 @@
 #include "version.h"
 #include <stdexcept>
 #include "wallet/message_store.h"
+#include "QrCode.hpp"
 
 #ifdef WIN32
 #include <boost/locale.hpp>
 #include <boost/filesystem.hpp>
+#include <fcntl.h>
 #endif
 
 #ifdef HAVE_READLINE
@@ -268,6 +270,7 @@ namespace
   const char* USAGE_RPC_PAYMENT_INFO("rpc_payment_info");
   const char* USAGE_START_MINING_FOR_RPC("start_mining_for_rpc");
   const char* USAGE_STOP_MINING_FOR_RPC("stop_mining_for_rpc");
+  const char* USAGE_SHOW_QR_CODE("show_qr_code [<subaddress_index>]");
   const char* USAGE_VERSION("version");
   const char* USAGE_HELP_ADVANCED("help_advanced [<command>]");
   const char* USAGE_HELP("help");
@@ -2387,6 +2390,62 @@ bool simple_wallet::stop_mining_for_rpc(const std::vector<std::string> &args)
   return true;
 }
 
+bool simple_wallet::show_qr_code(const std::vector<std::string> &args)
+{
+  uint32_t subaddress_index = 0;
+  if (args.size() >= 1)
+  {
+    if (!string_tools::get_xtype_from_string(subaddress_index, args[0]))
+    {
+      fail_msg_writer() << tr("invalid index: must be an unsigned integer");
+      return true;
+    }
+    if (subaddress_index >= m_wallet->get_num_subaddresses(m_current_subaddress_account))
+    {
+      fail_msg_writer() << tr("<subaddress_index> is out of bounds");
+      return true;
+    }
+  }
+
+#ifdef _WIN32
+#define PRINT_UTF8(pre, x) std::wcout << pre ## x
+#define WTEXTON() _setmode(_fileno(stdout), _O_WTEXT)
+#define WTEXTOFF() _setmode(_fileno(stdout), _O_TEXT)
+#else
+#define PRINT_UTF8(pre, x) std::cout << x
+#define WTEXTON()
+#define WTEXTOFF()
+#endif
+
+  WTEXTON();
+  try
+  {
+    const std::string address = "monero:" + m_wallet->get_subaddress_as_str({m_current_subaddress_account, subaddress_index});
+    const qrcodegen::QrCode qr = qrcodegen::QrCode::encodeText(address.c_str(), qrcodegen::QrCode::Ecc::LOW);
+    for (int y = -2; y < qr.getSize() + 2; y+=2)
+    {
+      for (int x = -2; x < qr.getSize() + 2; x++)
+      {
+        if (qr.getModule(x, y) && qr.getModule(x, y + 1))
+          PRINT_UTF8(L, "\u2588");
+        else if (qr.getModule(x, y) && !qr.getModule(x, y + 1))
+          PRINT_UTF8(L, "\u2580");
+        else if (!qr.getModule(x, y) && qr.getModule(x, y + 1))
+          PRINT_UTF8(L, "\u2584");
+        else
+          PRINT_UTF8(L, " ");
+      }
+      PRINT_UTF8(, std::endl);
+    }
+  }
+  catch (const std::length_error&)
+  {
+    fail_msg_writer() << tr("Failed to generate QR code, input too large");
+  }
+  WTEXTOFF();
+  return true;
+}
+
 bool simple_wallet::set_always_confirm_transfers(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
 {
   const auto pwd_container = get_and_verify_password();
@@ -3610,6 +3669,10 @@ simple_wallet::simple_wallet()
                            boost::bind(&simple_wallet::stop_mining_for_rpc, this, _1),
                            tr(USAGE_STOP_MINING_FOR_RPC),
                            tr("Stop mining to pay for RPC access"));
+  m_cmd_binder.set_handler("show_qr_code",
+                           boost::bind(&simple_wallet::on_command, this, &simple_wallet::show_qr_code, _1),
+                           tr(USAGE_SHOW_QR_CODE),
+                           tr("Show address as QR code"));
   m_cmd_binder.set_handler("help_advanced",
                            boost::bind(&simple_wallet::on_command, this, &simple_wallet::help_advanced, _1),
                            tr(USAGE_HELP_ADVANCED),
diff --git a/src/simplewallet/simplewallet.h b/src/simplewallet/simplewallet.h
index 59818b303..ec2e86250 100644
--- a/src/simplewallet/simplewallet.h
+++ b/src/simplewallet/simplewallet.h
@@ -258,6 +258,7 @@ namespace cryptonote
     bool rpc_payment_info(const std::vector<std::string> &args);
     bool start_mining_for_rpc(const std::vector<std::string> &args);
     bool stop_mining_for_rpc(const std::vector<std::string> &args);
+    bool show_qr_code(const std::vector<std::string> &args);
     bool net_stats(const std::vector<std::string>& args);
     bool public_nodes(const std::vector<std::string>& args);
     bool welcome(const std::vector<std::string>& args);