initial commit

ecc/BCH15_5.cs

@@ -0,0 +1,238 @@
+using System;
+
+namespace ThoughtWorks.QRCode.Codec.Ecc
+{
+	public class BCH15_5
+	{
+        internal int[][] gf16;
+        internal bool[] recieveData;
+        internal int numCorrectedError;
+
+		virtual public int NumCorrectedError
+		{
+			get
+			{
+				return numCorrectedError;
+			}		
+		}
+		
+		public BCH15_5(bool[] source)
+		{
+			gf16 = createGF16();
+			recieveData = source;
+		}
+		
+		public virtual bool[] correct()
+		{
+			int[] s = calcSyndrome(recieveData);
+			
+			int[] errorPos = detectErrorBitPosition(s);
+			bool[] output = correctErrorBit(recieveData, errorPos);
+			return output;
+		}
+		
+		internal virtual int[][] createGF16()
+		{
+			gf16 = new int[16][];
+			for (int i = 0; i < 16; i++)
+			{
+				gf16[i] = new int[4];
+			}
+			int[] seed = new int[]{1, 1, 0, 0};
+			for (int i = 0; i < 4; i++)
+				gf16[i][i] = 1;
+			for (int i = 0; i < 4; i++)
+				gf16[4][i] = seed[i];
+			for (int i = 5; i < 16; i++)
+			{
+				for (int j = 1; j < 4; j++)
+				{
+					gf16[i][j] = gf16[i - 1][j - 1];
+				}
+				if (gf16[i - 1][3] == 1)
+				{
+					for (int j = 0; j < 4; j++)
+						gf16[i][j] = (gf16[i][j] + seed[j]) % 2;
+				}
+			}
+			return gf16;
+		}
+		
+		internal virtual int searchElement(int[] x)
+		{
+			int k;
+			for (k = 0; k < 15; k++)
+			{
+				if (x[0] == gf16[k][0] && x[1] == gf16[k][1] && x[2] == gf16[k][2] && x[3] == gf16[k][3])
+					break;
+			}
+			return k;
+		}
+			
+		internal virtual int[] getCode(int input)
+		{
+			int[] f = new int[15];
+			int[] r = new int[8];
+			
+			for (int i = 0; i < 15; i++)
+			{
+				//1 + x + x^3
+				int w1, w2;
+				int yin;
+				
+				w1 = r[7];
+				if (i < 7)
+				{
+					yin = (input >> (6 - i)) % 2;
+					w2 = (yin + w1) % 2;
+				}
+				else
+				{
+					yin = w1;
+					w2 = 0;
+				}
+				r[7] = (r[6] + w2) % 2;
+				r[6] = (r[5] + w2) % 2;
+				r[5] = r[4];
+				r[4] = (r[3] + w2) % 2;
+				r[3] = r[2];
+				r[2] = r[1];
+				r[1] = r[0];
+				r[0] = w2;
+				f[14 - i] = yin;
+			}
+			return f;
+		}
+		
+		internal static String[] bitName = new String[]{"c0", "c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8", "c9", "d0", "d1", "d2", "d3", "d4"};
+		
+		internal virtual int addGF(int arg1, int arg2)
+		{
+			int[] p = new int[4];
+			for (int m = 0; m < 4; m++)
+			{
+				int w1 = (arg1 < 0 || arg1 >= 15)?0:gf16[arg1][m];
+				int w2 = (arg2 < 0 || arg2 >= 15)?0:gf16[arg2][m];
+				p[m] = (w1 + w2) % 2;
+			}
+			return searchElement(p);
+		}
+	
+		internal virtual int[] calcSyndrome(bool[] y)
+		{
+			int[] s = new int[5];
+			int[] p = new int[4];
+			int k;
+			for (k = 0; k < 15; k++)
+			{
+				if (y[k] == true)
+					for (int m = 0; m < 4; m++)
+						p[m] = (p[m] + gf16[k][m]) % 2;
+			}
+			k = searchElement(p);
+			s[0] = (k >= 15)?- 1:k;
+	
+			p = new int[4];
+			for (k = 0; k < 15; k++)
+			{
+				if (y[k] == true)
+					for (int m = 0; m < 4; m++)
+						p[m] = (p[m] + gf16[(k * 3) % 15][m]) % 2;
+			}
+			
+			k = searchElement(p);
+			
+			s[2] = (k >= 15)?- 1:k;		
+			p = new int[4];
+			for (k = 0; k < 15; k++)
+			{
+				if (y[k] == true)
+					for (int m = 0; m < 4; m++)
+						p[m] = (p[m] + gf16[(k * 5) % 15][m]) % 2;
+			}
+			k = searchElement(p);
+			s[4] = (k >= 15)?- 1:k;		
+			return s;
+		}
+		
+		
+		internal virtual int[] calcErrorPositionVariable(int[] s)
+		{
+			int[] e = new int[4];
+			// calc σ1
+			e[0] = s[0];
+			//Console.out.println("σ1 = " + String.valueOf(e[0]));
+			
+			// calc σ2
+			int t = (s[0] + s[1]) % 15;
+			int mother = addGF(s[2], t);
+			mother = (mother >= 15)?- 1:mother;
+			
+			t = (s[2] + s[1]) % 15;
+			int child = addGF(s[4], t);
+			child = (child >= 15)?- 1:child;
+			e[1] = (child < 0 && mother < 0)?- 1:(child - mother + 15) % 15;
+		
+			// calc σ3
+			t = (s[1] + e[0]) % 15;
+			int t1 = addGF(s[2], t);
+			t = (s[0] + e[1]) % 15;
+			e[2] = addGF(t1, t);
+				
+			return e;
+		}
+		
+		internal virtual int[] detectErrorBitPosition(int[] s)
+		{			
+			int[] e = calcErrorPositionVariable(s);
+			int[] errorPos = new int[4];
+			if (e[0] == - 1)
+			{
+				//Console.out.println("No errors.");               
+				return errorPos;
+			}
+			else if (e[1] == - 1)
+			{
+				errorPos[0] = 1;
+				errorPos[1] = e[0];
+				return errorPos;
+			}
+			int x3, x2, x1;
+			int t, t1, t2, anError;
+			//error detection
+			for (int i = 0; i < 15; i++)
+			{
+				x3 = (i * 3) % 15;
+				x2 = (i * 2) % 15;
+				x1 = i;
+				
+				//p = new int[4];
+				
+				t = (e[0] + x2) % 15;
+				t1 = addGF(x3, t);
+				
+				t = (e[1] + x1) % 15;
+				t2 = addGF(t, e[2]);
+				
+				anError = addGF(t1, t2);
+				
+				if (anError >= 15)
+				{
+					errorPos[0]++;
+					errorPos[errorPos[0]] = i;
+				}
+			}
+			
+			return errorPos;
+		}
+		
+		internal virtual bool[] correctErrorBit(bool[] y, int[] errorPos)
+		{
+			for (int i = 1; i <= errorPos[0]; i++)
+				y[errorPos[i]] = !y[errorPos[i]];
+			
+			numCorrectedError = errorPos[0];
+			return y;
+		}
+	}
+}