Tardigrade Backend: Dependencies

vendor/github.com/vivint/infectious/math.go

@@ -0,0 +1,179 @@
+// (C) 1996-1998 Luigi Rizzo (luigi@iet.unipi.it)
+//     2009-2010 Jack Lloyd (lloyd@randombit.net)
+//     2011 Billy Brumley (billy.brumley@aalto.fi)
+//     2016-2017 Vivint, Inc. (jeff.wendling@vivint.com)
+//
+// Portions derived from code by Phil Karn (karn@ka9q.ampr.org),
+// Robert Morelos-Zaragoza (robert@spectra.eng.hawaii.edu) and Hari
+// Thirumoorthy (harit@spectra.eng.hawaii.edu), Aug 1995
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// 1. Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in the
+//    documentation and/or other materials provided with the
+//    distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
+// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT,
+// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+// IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+package infectious
+
+import "bytes"
+
+type pivotSearcher struct {
+	k    int
+	ipiv []bool
+}
+
+func newPivotSearcher(k int) *pivotSearcher {
+	return &pivotSearcher{
+		k:    k,
+		ipiv: make([]bool, k),
+	}
+}
+
+func (p *pivotSearcher) search(col int, matrix []byte) (int, int, error) {
+	if p.ipiv[col] == false && matrix[col*p.k+col] != 0 {
+		p.ipiv[col] = true
+		return col, col, nil
+	}
+
+	for row := 0; row < p.k; row++ {
+		if p.ipiv[row] {
+			continue
+		}
+
+		for i := 0; i < p.k; i++ {
+			if p.ipiv[i] == false && matrix[row*p.k+i] != 0 {
+				p.ipiv[i] = true
+				return row, i, nil
+			}
+		}
+	}
+
+	return 0, 0, Error.New("pivot not found")
+}
+
+func swap(a, b *byte) {
+	tmp := *a
+	*a = *b
+	*b = tmp
+}
+
+// TODO(jeff): matrix is a K*K array, row major.
+func invertMatrix(matrix []byte, k int) error {
+	pivot_searcher := newPivotSearcher(k)
+	indxc := make([]int, k)
+	indxr := make([]int, k)
+	id_row := make([]byte, k)
+
+	for col := 0; col < k; col++ {
+		icol, irow, err := pivot_searcher.search(col, matrix)
+		if err != nil {
+			return err
+		}
+
+		if irow != icol {
+			for i := 0; i < k; i++ {
+				swap(&matrix[irow*k+i], &matrix[icol*k+i])
+			}
+		}
+
+		indxr[col] = irow
+		indxc[col] = icol
+		pivot_row := matrix[icol*k:][:k]
+		c := pivot_row[icol]
+
+		if c == 0 {
+			return Error.New("singular matrix")
+		}
+
+		if c != 1 {
+			c = gf_inverse[c]
+			pivot_row[icol] = 1
+			mul_c := gf_mul_table[c][:]
+
+			for i := 0; i < k; i++ {
+				pivot_row[i] = mul_c[pivot_row[i]]
+			}
+		}
+
+		id_row[icol] = 1
+		if !bytes.Equal(pivot_row, id_row) {
+			p := matrix
+			for i := 0; i < k; i++ {
+				if i != icol {
+					c = p[icol]
+					p[icol] = 0
+					addmul(p[:k], pivot_row, c)
+				}
+				p = p[k:]
+			}
+		}
+
+		id_row[icol] = 0
+	}
+
+	for i := 0; i < k; i++ {
+		if indxr[i] != indxc[i] {
+			for row := 0; row < k; row++ {
+				swap(&matrix[row*k+indxr[i]], &matrix[row*k+indxc[i]])
+			}
+		}
+	}
+	return nil
+}
+
+func createInvertedVdm(vdm []byte, k int) {
+	if k == 1 {
+		vdm[0] = 1
+		return
+	}
+
+	b := make([]byte, k)
+	c := make([]byte, k)
+
+	c[k-1] = 0
+	for i := 1; i < k; i++ {
+		mul_p_i := gf_mul_table[gf_exp[i]][:]
+		for j := k - 1 - (i - 1); j < k-1; j++ {
+			c[j] ^= mul_p_i[c[j+1]]
+		}
+		c[k-1] ^= gf_exp[i]
+	}
+
+	for row := 0; row < k; row++ {
+		index := 0
+		if row != 0 {
+			index = int(gf_exp[row])
+		}
+		mul_p_row := gf_mul_table[index][:]
+
+		t := byte(1)
+		b[k-1] = 1
+		for i := k - 2; i >= 0; i-- {
+			b[i] = c[i+1] ^ mul_p_row[b[i+1]]
+			t = b[i] ^ mul_p_row[t]
+		}
+
+		mul_t_inv := gf_mul_table[gf_inverse[t]][:]
+		for col := 0; col < k; col++ {
+			vdm[col*k+row] = mul_t_inv[b[col]]
+		}
+	}
+}