cyberdot · Sep 15, 2026 · Sep 15, 2026 · Sep 15, 2026
diff --git a/.gitattributes b/.gitattributes
@@ -0,0 +1,11 @@
+# These directories hold test fixtures captured verbatim from reference
+# implementations - raw encoded/decoded bytes, not human-authored text. Some of those
+# byte sequences happen to contain a lone LF (0x0A); without this, Git's line-ending
+# conversion (autocrlf) can silently rewrite it to CRLF on checkout, corrupting the
+# fixture without the tracked blob ever changing. Disable text conversion for them.
+src/CyberDot.Encoding.Base2048.Tests/test-data/** -text
+src/CyberDot.Encoding.Base65536.Tests/Bad/** -text
+src/CyberDot.Encoding.Base65536.Tests/DoubledBytes/** -text
+src/CyberDot.Encoding.Base65536.Tests/IgnoreGarbage/** -text
+src/CyberDot.Encoding.Base65536.Tests/Pairs/** -text
+src/CyberDot.Encoding.Base65536.Tests/SingleBytes/** -text
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -43,6 +43,7 @@ jobs:
         run: |
           for project in \
             src/CyberDot.Encoding.Base65536/CyberDot.Encoding.Base65536.csproj \
-            src/CyberDot.Encoding.Base2048/CyberDot.Encoding.Base2048.csproj; do
+            src/CyberDot.Encoding.Base2048/CyberDot.Encoding.Base2048.csproj \
+            src/CyberDot.Encoding.Base84/CyberDot.Encoding.Base84.csproj; do
             dotnet pack "$project" --configuration Debug --no-build --output "${{ runner.temp }}/nupkg-verify"
           done
diff --git a/.github/workflows/release-base84.yml b/.github/workflows/release-base84.yml
@@ -0,0 +1,22 @@
+name: Release CyberDot.Encoding.Base84
+
+# Manually-triggered release for the Base84 package. See _release-package.yml for
+# what this actually does.
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Release version override (e.g. 1.2.0). Leave empty to use the version in the csproj.'
+        required: false
+        type: string
+
+jobs:
+  release:
+    permissions:
+      contents: write
+    uses: ./.github/workflows/_release-package.yml
+    with:
+      project-path: src/CyberDot.Encoding.Base84/CyberDot.Encoding.Base84.csproj
+      tag-prefix: base84
+      version: ${{ inputs.version }}
diff --git a/CyberDot.Encoding.sln b/CyberDot.Encoding.sln
@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 18
-VisualStudioVersion = 18.9.12105.275 stable
+VisualStudioVersion = 18.9.12105.275
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CyberDot.Encoding.Base65536", "src\CyberDot.Encoding.Base65536\CyberDot.Encoding.Base65536.csproj", "{C021E149-EB05-4EF0-9A4C-78A0808AC413}"
 EndProject
@@ -11,6 +11,16 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CyberDot.Encoding.Base2048"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CyberDot.Encoding.Base2048.Tests", "src\CyberDot.Encoding.Base2048.Tests\CyberDot.Encoding.Base2048.Tests.csproj", "{287EE26D-CAE7-4AA3-93C5-4A6B2C8A9D05}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CyberDot.Encoding.Base84", "src\CyberDot.Encoding.Base84\CyberDot.Encoding.Base84.csproj", "{9551EC7C-8F4A-462A-AABC-50D1FD1E60B5}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Base2048", "Base2048", "{7F2B409E-7822-462C-8152-0DE5BEE42CAD}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Base65536", "Base65536", "{EF960794-148F-4CC2-A1B6-4001FA1A9095}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CyberDot.Encoding.Base84.Tests", "src\CyberDot.Encoding.Base84.Tests\CyberDot.Encoding.Base84.Tests.csproj", "{3762FA86-26D7-4037-B7CF-E5CA94F03D8B}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Base84", "Base84", "{4C6BEADC-6B8C-425C-9EC4-559597A7915C}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -33,10 +43,26 @@ Global
 		{287EE26D-CAE7-4AA3-93C5-4A6B2C8A9D05}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{287EE26D-CAE7-4AA3-93C5-4A6B2C8A9D05}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{287EE26D-CAE7-4AA3-93C5-4A6B2C8A9D05}.Release|Any CPU.Build.0 = Release|Any CPU
+		{9551EC7C-8F4A-462A-AABC-50D1FD1E60B5}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9551EC7C-8F4A-462A-AABC-50D1FD1E60B5}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9551EC7C-8F4A-462A-AABC-50D1FD1E60B5}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9551EC7C-8F4A-462A-AABC-50D1FD1E60B5}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3762FA86-26D7-4037-B7CF-E5CA94F03D8B}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3762FA86-26D7-4037-B7CF-E5CA94F03D8B}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3762FA86-26D7-4037-B7CF-E5CA94F03D8B}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3762FA86-26D7-4037-B7CF-E5CA94F03D8B}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
+	GlobalSection(NestedProjects) = preSolution
+		{C021E149-EB05-4EF0-9A4C-78A0808AC413} = {EF960794-148F-4CC2-A1B6-4001FA1A9095}
+		{F4232660-0EA0-432E-8713-F4612E88AA80} = {EF960794-148F-4CC2-A1B6-4001FA1A9095}
+		{C7494689-9E71-4F15-883E-027E244E3E6D} = {7F2B409E-7822-462C-8152-0DE5BEE42CAD}
+		{287EE26D-CAE7-4AA3-93C5-4A6B2C8A9D05} = {7F2B409E-7822-462C-8152-0DE5BEE42CAD}
+		{9551EC7C-8F4A-462A-AABC-50D1FD1E60B5} = {4C6BEADC-6B8C-425C-9EC4-559597A7915C}
+		{3762FA86-26D7-4037-B7CF-E5CA94F03D8B} = {4C6BEADC-6B8C-425C-9EC4-559597A7915C}
+	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {9D040A49-47AE-4503-B1C2-7D3E82AF66AB}
 	EndGlobalSection

diff --git a/src/CyberDot.Encoding.Base84.Tests/Base84Tests.cs b/src/CyberDot.Encoding.Base84.Tests/Base84Tests.cs
@@ -0,0 +1,218 @@
+using AwesomeAssertions;
+
+namespace CyberDot.Encoding.Base84.Tests
+{
+    public class Base84Tests
+    {
+        // Vectors below are taken from the reference Zig implementation's test suite.
+        [Fact]
+        public void Should_encode_and_decode_known_vectors()
+        {
+            AssertVector("", "");
+            AssertVector("M", "]A");
+            AssertVector("Ma", "tsD");
+            AssertVector("Man", "pRRM");
+            AssertVector("Man ", ";dA^K");
+            AssertVector("Hello, World!", "s@Etk'#Qedrxz+hhA");
+            AssertVector("The quick brown fox jumps over the lazy dog.",
+                "wBB]KdJ}phb-#tmbNB^K!!J_K^3h=l_pj[nJXJLnkB3kkhkT_KM}r1P");
+        }
+
+        [Fact]
+        public void Should_encode_and_decode_runs_of_zero_bytes()
+        {
+            AssertVector(new byte[] { 0x00 }, "AA");
+            AssertVector(new byte[] { 0x00, 0x00 }, "AAA");
+            AssertVector(new byte[] { 0x00, 0x00, 0x00 }, "AAAA");
+            AssertVector(new byte[] { 0x00, 0x00, 0x00, 0x00 }, "AAAAA");
+            AssertVector(new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00 }, "AAAAAAA");
+        }
+
+        [Fact]
+        public void Should_encode_and_decode_runs_of_ff_bytes()
+        {
+            AssertVector(new byte[] { 0xff }, "DD");
+            AssertVector(new byte[] { 0xff, 0xff }, "PYJ");
+            AssertVector(new byte[] { 0xff, 0xff, 0xff }, "#8Zc");
+            AssertVector(new byte[] { 0xff, 0xff, 0xff, 0xff }, "rxQLrB");
+            AssertVector(new byte[] { 0xff, 0xff, 0xff, 0xff, 0xff }, "rxQLrHG");
+        }
+
+        [Fact]
+        public void Should_encode_and_decode_mixed_bytes()
+        {
+            AssertVector(new byte[] { 0x00, 0xe0, 0xff, 0x01 }, "AYy4A");
+            AssertVector(
+                new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f },
+                "8%LBB${'eC(No8D-dMGF");
+        }
+
+        [Theory]
+        [InlineData("AA/")]
+        [InlineData("A A")]
+        [InlineData("AA\x00")]
+        [InlineData("AA\xff")]
+        [InlineData("AA<")]
+        public void Should_throw_on_unrecognised_character(string input)
+        {
+            var act = () => Base84.Decode(input);
+
+            act.Should().Throw<ArgumentException>();
+        }
+
+        [Theory]
+        [InlineData("A")]
+        [InlineData("AE")]
+        [InlineData("AAK")]
+        [InlineData("AAAd")]
+        [InlineData("rxQLr")]
+        [InlineData("oi'-o")]
+        [InlineData("AAAAAA")]
+        [InlineData("rxQLrrxQLrrxQLrrxQLrrxQLrrxQLrrxQLrAA")]
+        public void Should_throw_on_invalid_padding(string input)
+        {
+            var act = () => Base84.Decode(input);
+
+            act.Should().Throw<ArgumentException>();
+        }
+
+        [Fact]
+        public void Should_throw_on_null_input()
+        {
+            var encodeAct = () => Base84.Encode(null);
+            var decodeAct = () => Base84.Decode(null);
+
+            encodeAct.Should().Throw<ArgumentNullException>();
+            decodeAct.Should().Throw<ArgumentNullException>();
+        }
+
+        [Fact]
+        public void Should_round_trip_all_single_bytes()
+        {
+            for (var b = 0; b <= 255; b++)
+            {
+                var data = new[] { (byte)b };
+
+                var encoded = Base84.Encode(data);
+                Base84.Decode(encoded).Should().BeEquivalentTo(data);
+            }
+        }
+
+        [Fact]
+        public void Should_round_trip_all_byte_pairs()
+        {
+            for (var a = 0; a <= 255; a++)
+            {
+                for (var b = 0; b <= 255; b++)
+                {
+                    var data = new[] { (byte)a, (byte)b };
+
+                    var encoded = Base84.Encode(data);
+                    Base84.Decode(encoded).Should().BeEquivalentTo(data);
+                }
+            }
+        }
+
+        [Theory]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(5)]
+        [InlineData(6)]
+        [InlineData(17)]
+        [InlineData(31)]
+        [InlineData(32)]
+        [InlineData(33)]
+        [InlineData(256)]
+        public void Should_round_trip_random_data(int length)
+        {
+            var data = new byte[length];
+            new Random(length).NextBytes(data);
+
+            var encoded = Base84.Encode(data);
+            Base84.Decode(encoded).Should().BeEquivalentTo(data);
+        }
+
+        [Fact]
+        public void Should_round_trip_many_random_lengths()
+        {
+            var random = new Random(12345);
+            var buffer = new byte[256];
+
+            for (var i = 0; i < 5000; i++)
+            {
+                var len = random.Next(0, buffer.Length + 1);
+                random.NextBytes(buffer);
+                var data = new byte[len];
+                Array.Copy(buffer, data, len);
+
+                var encoded = Base84.Encode(data);
+                Base84.Decode(encoded).Should().BeEquivalentTo(data);
+            }
+        }
+
+        private const string AlphabetChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!#$%&'()+,-;=@[]^_`{}~";
+
+        [Fact]
+        public void Should_reject_altered_encoded_data_or_accept_it_and_round_trip()
+        {
+            // Any mutation of a validly-encoded string must either be rejected as invalid
+            // padding, or - if it happens to still be well-formed - round trip cleanly
+            // through a fresh encode.
+            var random = new Random(999);
+            var buffer = new byte[32];
+
+            for (var i = 0; i < 5000; i++)
+            {
+                var len = random.Next(0, buffer.Length + 1);
+                random.NextBytes(buffer);
+                var data = new byte[len];
+                Array.Copy(buffer, data, len);
+
+                var encodedChars = Base84.Encode(data).ToCharArray();
+                var alphabetChar = AlphabetChars[random.Next(AlphabetChars.Length)];
+
+                switch (random.Next(3))
+                {
+                    case 0 when encodedChars.Length > 0:
+                        encodedChars[random.Next(encodedChars.Length)] = alphabetChar;
+                        break;
+                    case 1:
+                        Array.Resize(ref encodedChars, encodedChars.Length + 1);
+                        encodedChars[encodedChars.Length - 1] = alphabetChar;
+                        break;
+                    case 2 when encodedChars.Length > 0:
+                        Array.Resize(ref encodedChars, encodedChars.Length - 1);
+                        break;
+                }
+
+                var altered = new string(encodedChars);
+
+                byte[] decoded;
+                try
+                {
+                    decoded = Base84.Decode(altered);
+                }
+                catch (ArgumentException)
+                {
+                    continue;
+                }
+
+                Base84.Encode(decoded).Should().Be(altered);
+            }
+        }
+
+        private static void AssertVector(string decoded, string encoded)
+        {
+            AssertVector(System.Text.Encoding.UTF8.GetBytes(decoded), encoded);
+        }
+
+        private static void AssertVector(byte[] decoded, string encoded)
+        {
+            Base84.Encode(decoded).Should().Be(encoded);
+            Base84.Decode(encoded).Should().BeEquivalentTo(decoded);
+        }
+    }
+}
diff --git a/src/CyberDot.Encoding.Base84.Tests/CyberDot.Encoding.Base84.Tests.csproj b/src/CyberDot.Encoding.Base84.Tests/CyberDot.Encoding.Base84.Tests.csproj
@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="AwesomeAssertions" Version="9.5.0" />
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\CyberDot.Encoding.Base84\CyberDot.Encoding.Base84.csproj" />
+  </ItemGroup>
+
+</Project>