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/**
* Unit tests for Galois
*
* Copyright 2015, Klaus Post
* Copyright 2015, Backblaze, Inc.
*/
package reedsolomon
import (
"bytes"
"testing"
)
func TestAssociativity(t *testing.T) {
for i := 0; i < 256; i++ {
a := byte(i)
for j := 0; j < 256; j++ {
b := byte(j)
for k := 0; k < 256; k++ {
c := byte(k)
x := galAdd(a, galAdd(b, c))
y := galAdd(galAdd(a, b), c)
if x != y {
t.Fatal("add does not match:", x, "!=", y)
}
x = galMultiply(a, galMultiply(b, c))
y = galMultiply(galMultiply(a, b), c)
if x != y {
t.Fatal("multiply does not match:", x, "!=", y)
}
}
}
}
}
func TestIdentity(t *testing.T) {
for i := 0; i < 256; i++ {
a := byte(i)
b := galAdd(a, 0)
if a != b {
t.Fatal("Add zero should yield same result", a, "!=", b)
}
b = galMultiply(a, 1)
if a != b {
t.Fatal("Mul by one should yield same result", a, "!=", b)
}
}
}
func TestInverse(t *testing.T) {
for i := 0; i < 256; i++ {
a := byte(i)
b := galSub(0, a)
c := galAdd(a, b)
if c != 0 {
t.Fatal("inverse sub/add", c, "!=", 0)
}
if a != 0 {
b = galDivide(1, a)
c = galMultiply(a, b)
if c != 1 {
t.Fatal("inverse div/mul", c, "!=", 1)
}
}
}
}
func TestCommutativity(t *testing.T) {
for i := 0; i < 256; i++ {
a := byte(i)
for j := 0; j < 256; j++ {
b := byte(j)
x := galAdd(a, b)
y := galAdd(b, a)
if x != y {
t.Fatal(x, "!= ", y)
}
x = galMultiply(a, b)
y = galMultiply(b, a)
if x != y {
t.Fatal(x, "!= ", y)
}
}
}
}
func TestDistributivity(t *testing.T) {
for i := 0; i < 256; i++ {
a := byte(i)
for j := 0; j < 256; j++ {
b := byte(j)
for k := 0; k < 256; k++ {
c := byte(k)
x := galMultiply(a, galAdd(b, c))
y := galAdd(galMultiply(a, b), galMultiply(a, c))
if x != y {
t.Fatal(x, "!= ", y)
}
}
}
}
}
func TestExp(t *testing.T) {
for i := 0; i < 256; i++ {
a := byte(i)
power := byte(1)
for j := 0; j < 256; j++ {
x := galExp(a, j)
if x != power {
t.Fatal(x, "!=", power)
}
power = galMultiply(power, a)
}
}
}
func TestGalois(t *testing.T) {
// These values were copied output of the Python code.
if galMultiply(3, 4) != 12 {
t.Fatal("galMultiply(3, 4) != 12")
}
if galMultiply(7, 7) != 21 {
t.Fatal("galMultiply(7, 7) != 21")
}
if galMultiply(23, 45) != 41 {
t.Fatal("galMultiply(23, 45) != 41")
}
// Test slices (>16 entries to test assembler)
in := []byte{0, 1, 2, 3, 4, 5, 6, 10, 50, 100, 150, 174, 201, 255, 99, 32, 67, 85}
out := make([]byte, len(in))
galMulSlice(25, in, out)
expect := []byte{0x0, 0x19, 0x32, 0x2b, 0x64, 0x7d, 0x56, 0xfa, 0xb8, 0x6d, 0xc7, 0x85, 0xc3, 0x1f, 0x22, 0x7, 0x25, 0xfe}
if 0 != bytes.Compare(out, expect) {
t.Errorf("got %#v, expected %#v", out, expect)
}
galMulSlice(177, in, out)
expect = []byte{0x0, 0xb1, 0x7f, 0xce, 0xfe, 0x4f, 0x81, 0x9e, 0x3, 0x6, 0xe8, 0x75, 0xbd, 0x40, 0x36, 0xa3, 0x95, 0xcb}
if 0 != bytes.Compare(out, expect) {
t.Errorf("got %#v, expected %#v", out, expect)
}
if galExp(2, 2) != 4 {
t.Fatal("galExp(2, 2) != 4")
}
if galExp(5, 20) != 235 {
t.Fatal("galExp(5, 20) != 235")
}
if galExp(13, 7) != 43 {
t.Fatal("galExp(13, 7) != 43")
}
}
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