public void T01_ReedSolomon()
{
byte[] orig = Encoding.UTF8.GetBytes("Hello, world! Velit omnis consequatur nobis. Cum omnis ipsam rerum ut velit minus. Bye!");
ReedSolomon rs = new ReedSolomon(8);
// first test the basics
byte[] encoded = rs.Encode(orig);
TestHelpers.AssertArrayEquals(encoded.Skip(rs.EccLength).ToArray(), orig); // test that the encoded data ends with the original data
Assert.IsTrue(rs.Check(encoded));
TestHelpers.AssertArrayEquals(rs.Decode(encoded), orig);
// we should be able to correct up to four errors in the encoded data
encoded[7] = 77;
encoded[22] = 44;
encoded[62] = 11;
encoded[81] = 0;
Assert.IsFalse(rs.Check(encoded));
TestHelpers.AssertArrayEquals(rs.Decode(encoded), orig);
// but not five
encoded[2] = 1;
Assert.IsNull(rs.Decode(encoded));
// however, if we specify the positions, we should be able to fix more
TestHelpers.AssertArrayEquals(rs.Decode(encoded, new[] { 2, 7, 22, 62, 81 }, true), orig);
encoded[12] = 2;
TestHelpers.AssertArrayEquals(rs.Decode(encoded, new[] { 2, 7, 12, 22, 62 }, false), orig);
// in fact should be able to fix at least eight errors
encoded[23] = 3;
encoded[40] = 4;
TestHelpers.AssertArrayEquals(rs.Decode(encoded, new[] { 2, 7, 12, 22, 23, 40, 62, 81 }, true), orig);
TestHelpers.AssertArrayEquals(rs.Decode(encoded, new[] { 2, 7, 12, 22, 23, 40, 62, 81 }, false), orig);
// but not nine errors
encoded[70] = 5;
Assert.IsNull(rs.Decode(encoded, new[] { 2, 7, 12, 22, 23, 40, 62, 70, 81 }, true));
// now try the methods that take array indexes
byte[] orig2 = new byte[orig.Length / 2];
int encodedLength = orig2.Length + rs.EccLength;
Array.Copy(orig, orig2, orig2.Length);
rs.Encode(orig, 0, orig.Length / 2, encoded, 10);
// first, try the basic decoding
Assert.IsTrue(rs.Check(encoded, 10, orig2.Length + rs.EccLength));
TestHelpers.AssertArrayEquals(rs.Decode(encoded, 10, encodedLength), orig2);
byte[] decoded = new byte[orig2.Length + 30];
Assert.AreEqual(orig2.Length, rs.Decode(encoded, 10, encodedLength, decoded, 20));
TestHelpers.AssertArrayEquals(decoded.Skip(20).Take(orig2.Length).ToArray(), orig2);
// now fix four errors with positions unspecified
encoded[11] = 77;
encoded[17] = 44;
encoded[23] = 11;
encoded[34] = 0;
Assert.AreEqual(orig2.Length, rs.Decode(encoded, 10, encodedLength, decoded, 20));
TestHelpers.AssertArrayEquals(decoded.Skip(20).Take(orig2.Length).ToArray(), orig2);
// now fix eight errors with positions specified
encoded[13] = 1;
encoded[19] = 2;
encoded[27] = 3;
encoded[31] = 4;
Assert.AreEqual(-1, rs.Decode(encoded, 10, encodedLength, decoded, 20)); // check that it gives a failure result without positions
Assert.AreEqual(orig2.Length, rs.Decode(encoded, 10, encodedLength, decoded, 20, new[] { 1, 3, 7, 9, 13, 17, 21, 24 }));
TestHelpers.AssertArrayEquals(decoded.Skip(20).Take(orig2.Length).ToArray(), orig2);
}
