Add Checksum tests

Author: jzebedee

test/LibDeflate.Tests/ChecksumTests.cs

@@ -0,0 +1,101 @@
+using LibDeflate.Checksums;
+using System;
+using Xunit;
+
+namespace LibDeflate.Tests
+{
+    public class ChecksumTests
+    {
+        private static readonly Random _rand = new();
+        private static byte[] GetRandomBuffer(int length)
+        {
+            var input = new byte[length];
+            _rand.NextBytes(input);
+            return input;
+        }
+
+        private uint NaiveCrc32(ReadOnlySpan<byte> input, uint poly = 0xEDB88320)
+        {
+            uint crc = unchecked((uint)-1);
+
+            while (!input.IsEmpty)
+            {
+                crc ^= input[0];
+                input = input.Slice(1);
+                for (int bit = 0; bit < 8; bit++)
+                {
+                    if ((crc & 1) == 1) crc = (crc >> 1) ^ poly;
+                    else crc >>= 1;
+                }
+            }
+            return ~crc;
+        }
+
+        [Fact]
+        public void Crc32ComputeTest()
+        {
+            var testBuffer = GetRandomBuffer(0x1000);
+
+            var naiveCrc32 = NaiveCrc32(testBuffer);
+            var lbdCrc32 = new Crc32().Compute(testBuffer);
+
+            Assert.Equal(naiveCrc32, lbdCrc32);
+        }
+
+        [Fact]
+        public void Crc32AppendTest()
+        {
+            Span<byte> testBuffer = GetRandomBuffer(0x1000);
+
+            var naiveCrc32 = NaiveCrc32(testBuffer);
+            var lbdCrc32 = new Crc32();
+            while (!testBuffer.IsEmpty)
+            {
+                var chunk = testBuffer[..0x100];
+                lbdCrc32.Append(chunk);
+                testBuffer = testBuffer[0x100..];
+            }
+
+            Assert.Equal(naiveCrc32, lbdCrc32.Hash);
+        }
+
+        private uint NaiveAdler32(ReadOnlySpan<byte> input, uint mparam = 65521)
+        {
+            uint a = 1, b = 0;
+            for (int i = 0; i < input.Length; i++)
+            {
+                uint p = input[i];
+                b = (b + (a = (a + p) % (p = mparam))) % p;
+            }
+            return b << 16 | a;
+        }
+
+        [Fact]
+        public void Adler32ComputeTest()
+        {
+            var testBuffer = GetRandomBuffer(0x1000);
+
+            var naiveAdler32 = NaiveAdler32(testBuffer);
+            var lbdAdler32 = new Adler32().Compute(testBuffer);
+
+            Assert.Equal(naiveAdler32, lbdAdler32);
+        }
+
+        [Fact]
+        public void Adler32AppendTest()
+        {
+            Span<byte> testBuffer = GetRandomBuffer(0x1000);
+
+            var naiveAdler32 = NaiveAdler32(testBuffer);
+            var lbdAdler32 = new Adler32();
+            while (!testBuffer.IsEmpty)
+            {
+                var chunk = testBuffer[..0x100];
+                lbdAdler32.Append(chunk);
+                testBuffer = testBuffer[0x100..];
+            }
+
+            Assert.Equal(naiveAdler32, lbdAdler32.Hash);
+        }
+    }
+}