From 261d57607b7f3b3fedd1143919f601207666c92c Mon Sep 17 00:00:00 2001
From: Project Nayuki <me@nayuki.io>
Date: Mon, 17 Apr 2017 18:26:29 +0000
Subject: [PATCH] Continued implementing C library by adding functions to fill
 QR Code function patterns.

---
 c/qrcodegen.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/c/qrcodegen.c b/c/qrcodegen.c
index b5ddb82..7a1c052 100644
--- a/c/qrcodegen.c
+++ b/c/qrcodegen.c
@@ -34,6 +34,9 @@ static bool getModule(const uint8_t qrcode[], int size, int x, int y);
 static void setModule(uint8_t qrcode[], int size, int x, int y, bool isBlack);
 static void setModuleBounded(uint8_t qrcode[], int size, int x, int y, bool isBlack);
 
+static void initializeFunctionalModules(int version, uint8_t qrcode[]);
+static int getAlignmentPatternPositions(int version, uint8_t result[7]);
+
 static void calcReedSolomonGenerator(int degree, uint8_t result[]);
 static void calcReedSolomonRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]);
 static uint8_t finiteFieldMultiply(uint8_t x, uint8_t y);
@@ -121,6 +124,85 @@ static void setModuleBounded(uint8_t qrcode[], int size, int x, int y, bool isBl
 }
 
 
+// Fills the given QR Code grid with white modules for the given version's size,
+// then marks every function module in the QR Code as black.
+static void initializeFunctionalModules(int version, uint8_t qrcode[]) {
+	// Initialize QR Code
+	int size = qrcodegen_getSize(version);
+	memset(qrcode, 0, (size * size + 7) / 8 * sizeof(qrcode[0]));
+	
+	// Fill horizontal and vertical timing patterns
+	for (int i = 0; i < size; i++) {
+		setModule(qrcode, size, 6, i, true);
+		setModule(qrcode, size, i, 6, true);
+	}
+	
+	// Fill 3 finder patterns (all corners except bottom right)
+	for (int i = 0; i < 8; i++) {
+		for (int j = 0; j < 8; j++) {
+			setModule(qrcode, size, j, i, true);
+			setModule(qrcode, size, size - 1 - j, i, true);
+			setModule(qrcode, size, j, size - 1 - i, true);
+		}
+	}
+	
+	// Fill numerous alignment patterns
+	uint8_t alignPatPos[7] = {};
+	int numAlign = getAlignmentPatternPositions(version, alignPatPos);
+	for (int i = 0; i < numAlign; i++) {
+		for (int j = 0; j < numAlign; j++) {
+			if ((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0))
+				continue;  // Skip the three finder corners
+			else {
+				for (int k = -2; k <= 2; k++) {
+					for (int l = -2; l <= 2; l++)
+						setModule(qrcode, size, alignPatPos[i] + l, alignPatPos[j] + k, true);
+				}
+			}
+		}
+	}
+	
+	// Fill format bits
+	for (int i = 0; i < 8; i++) {
+		setModule(qrcode, size, i, 8, true);
+		setModule(qrcode, size, 8, i, true);
+		setModule(qrcode, size, size - 1 - i, 8, true);
+		setModule(qrcode, size, 8, size - 1 - i, true);
+	}
+	setModule(qrcode, size, 8, 8, true);
+	
+	// Fill version
+	if (version >= 7) {
+		for (int i = 0; i < 3; i++) {
+			for (int j = 0; j < 6; j++) {
+				int k = size - 11 + i;
+				setModule(qrcode, size, k, j, true);
+				setModule(qrcode, size, j, k, true);
+			}
+		}
+	}
+}
+
+
+// Calculates the positions of alignment patterns in ascending order for the given version number,
+// storing them to the given array and returning an array length in the range [0, 7].
+static int getAlignmentPatternPositions(int version, uint8_t result[7]) {
+	if (version == 1)
+		return 0;
+	int size = qrcodegen_getSize(version);
+	int numAlign = version / 7 + 2;
+	int step;
+	if (version != 32)
+		step = (version * 4 + numAlign * 2 + 1) / (2 * numAlign - 2) * 2;  // ceil((size - 13) / (2*numAlign - 2)) * 2
+	else  // C-C-C-Combo breaker!
+		step = 26;
+	for (int i = numAlign - 1, pos = size - 7; i >= 1; i--, pos -= step)
+		result[i] = pos;
+	result[0] = 6;
+	return numAlign;
+}
+
+
 // Calculates the Reed-Solomon generator polynomial of the given degree, storing in result[0 : degree].
 static void calcReedSolomonGenerator(int degree, uint8_t result[]) {
 	// Start with the monomial x^0