示例#1
0
        public void encode(int[] toEncode, int ecBytes)
        {
            if (ecBytes == 0)
            {
                throw new ArgumentException("No error correction bytes");
            }
            int dataBytes = toEncode.Length - ecBytes;

            if (dataBytes <= 0)
            {
                throw new ArgumentException("No data bytes provided");
            }

            GenericGFPoly generator = buildGenerator(ecBytes);

            int[] infoCoefficients = new int[dataBytes];
            Array.Copy(toEncode, 0, infoCoefficients, 0, dataBytes);

            GenericGFPoly info = new GenericGFPoly(field, infoCoefficients);

            info = info.multiplyByMonomial(ecBytes, 1);

            GenericGFPoly remainder = info.divide(generator)[1];

            int[] coefficients        = remainder.Coefficients;
            int   numZeroCoefficients = ecBytes - coefficients.Length;

            for (int i = 0; i < numZeroCoefficients; i++)
            {
                toEncode[dataBytes + i] = 0;
            }

            Array.Copy(coefficients, 0, toEncode, dataBytes + numZeroCoefficients, coefficients.Length);
        }
示例#2
0
        internal GenericGFPoly[] divide(GenericGFPoly other)
        {
            if (!field.Equals(other.field))
            {
                throw new ArgumentException("GenericGFPolys do not have same GenericGF field");
            }
            if (other.isZero)
            {
                throw new ArgumentException("Divide by 0");
            }

            GenericGFPoly quotient  = field.Zero;
            GenericGFPoly remainder = this;

            int denominatorLeadingTerm        = other.getCoefficient(other.Degree);
            int inverseDenominatorLeadingTerm = field.inverse(denominatorLeadingTerm);

            while (remainder.Degree >= other.Degree && !remainder.isZero)
            {
                int           degreeDifference  = remainder.Degree - other.Degree;
                int           scale             = field.multiply(remainder.getCoefficient(remainder.Degree), inverseDenominatorLeadingTerm);
                GenericGFPoly term              = other.multiplyByMonomial(degreeDifference, scale);
                GenericGFPoly iterationQuotient = field.buildMonomial(degreeDifference, scale);
                quotient  = quotient.addOrSubtract(iterationQuotient);
                remainder = remainder.addOrSubtract(term);
            }

            return(new GenericGFPoly[] { quotient, remainder });
        }
示例#3
0
        internal GenericGFPoly multiply(GenericGFPoly other)
        {
            if (!field.Equals(other.field))
            {
                throw new ArgumentException("GenericGFPolys do not have same GenericGF field");
            }
            if (isZero || other.isZero)
            {
                return(field.Zero);
            }
            int[] aCoefficients = this.coefficients;
            int   aLength       = aCoefficients.Length;

            int[] bCoefficients = other.coefficients;
            int   bLength       = bCoefficients.Length;

            int[] product = new int[aLength + bLength - 1];
            for (int i = 0; i < aLength; i++)
            {
                int aCoeff = aCoefficients[i];
                for (int j = 0; j < bLength; j++)
                {
                    product[i + j] = GenericGF.addOrSubtract(product[i + j],
                                                             field.multiply(aCoeff, bCoefficients[j]));
                }
            }
            return(new GenericGFPoly(field, product));
        }
示例#4
0
        /// <summary>
        /// Create a representation of GF(size) using the given primitive polynomial.
        /// </summary>
        /// <param name="primitive">irreducible polynomial whose coefficients are represented by
        /// *  the bits of an int, where the least-significant bit represents the constant
        /// *  coefficient</param>
        /// <param name="size">the size of the field</param>
        /// <param name="genBase">the factor b in the generator polynomial can be 0- or 1-based
        /// *  (g(x) = (x+a^b)(x+a^(b+1))...(x+a^(b+2t-1))).
        /// *  In most cases it should be 1, but for QR code it is 0.</param>
        public GenericGF(int primitive, int size, int genBase)
        {
            this.primitive     = primitive;
            this.size          = size;
            this.generatorBase = genBase;

            expTable = new int[size];
            logTable = new int[size];
            int x = 1;

            for (int i = 0; i < size; i++)
            {
                expTable[i] = x;
                x         <<= 1; // x = x * 2; we're assuming the generator alpha is 2
                if (x >= size)
                {
                    x ^= primitive;
                    x &= size - 1;
                }
            }
            for (int i = 0; i < size - 1; i++)
            {
                logTable[expTable[i]] = i;
            }
            // logTable[0] == 0 but this should never be used
            zero = new GenericGFPoly(this, new int[] { 0 });
            one  = new GenericGFPoly(this, new int[] { 1 });
        }
示例#5
0
 private GenericGFPoly buildGenerator(int degree)
 {
     if (degree >= cachedGenerators.Count)
     {
         GenericGFPoly lastGenerator = cachedGenerators[cachedGenerators.Count - 1];
         for (int d = cachedGenerators.Count; d <= degree; d++)
         {
             GenericGFPoly nextGenerator = lastGenerator.multiply(new GenericGFPoly(field, new int[] { 1, field.exp(d - 1 + field.GeneratorBase) }));
             cachedGenerators.Add(nextGenerator);
             lastGenerator = nextGenerator;
         }
     }
     return(cachedGenerators[degree]);
 }
示例#6
0
        internal GenericGFPoly addOrSubtract(GenericGFPoly other)
        {
            if (!field.Equals(other.field))
            {
                throw new ArgumentException("GenericGFPolys do not have same GenericGF field");
            }
            if (isZero)
            {
                return(other);
            }
            if (other.isZero)
            {
                return(this);
            }

            int[] smallerCoefficients = this.coefficients;
            int[] largerCoefficients  = other.coefficients;
            if (smallerCoefficients.Length > largerCoefficients.Length)
            {
                int[] temp = smallerCoefficients;
                smallerCoefficients = largerCoefficients;
                largerCoefficients  = temp;
            }
            int[] sumDiff    = new int[largerCoefficients.Length];
            int   lengthDiff = largerCoefficients.Length - smallerCoefficients.Length;

            // Copy high-order terms only found in higher-degree polynomial's coefficients
            Array.Copy(largerCoefficients, 0, sumDiff, 0, lengthDiff);

            for (int i = lengthDiff; i < largerCoefficients.Length; i++)
            {
                sumDiff[i] = GenericGF.addOrSubtract(smallerCoefficients[i - lengthDiff], largerCoefficients[i]);
            }

            return(new GenericGFPoly(field, sumDiff));
        }