Add .NET Standard 2.0 and .NET 6 targets (#8)

Resolves #7

.github/workflows/publish.yaml

@@ -16,7 +16,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v3
         with:
-          dotnet-version: "7.x" # TODO: Specify multiple .NET versions once we add support for other target frameworks
+          dotnet-version: 7.0.x
 
       - name: Generate the package
         # NOTE: As for the `${GITHUB_REF_NAME#v}` bit below, see https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables:~:text=branch%2D1.-,GITHUB_REF_NAME,-The%20short%20ref. We could've also done https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-environment-variable but since we're using this value in a single place, we don't need to make it an environment variable.

.github/workflows/test.yaml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: windows-latest # NOTE: Has to be Windows because the old .NET Framework 4.x (which is one of the target frameworks of the test project) is Windows-only
 
     steps:
       - name: Checkout the repository
@@ -16,7 +16,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v3
         with:
-          dotnet-version: "7.x" # TODO: Specify multiple .NET versions once we add support for other target frameworks
+          dotnet-version: 7.0.x # NOTE: The `windows-latest` container already comes pre-installed with the .NET versions that we need, but we do need to use `setup-dotnet` (and pass it one of the versions — e.g. 7.0.x), so that the relevant binaries (e.g. `dotnet`) are actually added to PATH so we can use them. See https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#preinstalled-software and https://github.com/actions/setup-dotnet
 
       # TODO: Some .NET codebases with GitHub Actions workflows seem to run `dotnet restore`, `dotnet build` and `dotnet test` as separate steps. Why?
       - name: Run the tests

src/Sqids/PolyfillExtensions.cs

@@ -0,0 +1,46 @@
+#if NETSTANDARD2_0
+
+using System.Runtime.InteropServices;
+
+namespace Sqids;
+
+internal static class PolyfillExtensions
+{
+	public static StringBuilder Append(this StringBuilder builder, ReadOnlySpan<char> value)
+	{
+		if (builder is null) throw new ArgumentNullException(nameof(builder));
+
+		if (!value.IsEmpty)
+		{
+			unsafe
+			{
+				fixed (char* p = &MemoryMarshal.GetReference(value))
+				{
+					builder.Append(p, value.Length);
+				}
+			}
+		}
+
+		return builder;
+	}
+
+	public static StringBuilder Insert(this StringBuilder builder, int index, ReadOnlySpan<char> value)
+	{
+		if (builder is null) throw new ArgumentNullException(nameof(builder));
+
+		if (!value.IsEmpty)
+		{
+			// NOTE: Unfortunately, not much we can do here; the StringBuilder.Insert(int, char*, int) method is private.
+			char[] temp = new char[value.Length];
+			value.CopyTo(temp);
+			builder.Insert(index, temp);
+		}
+
+		return builder;
+	}
+
+	public static bool Contains(this Span<char> source, char toFind) =>
+		source.IndexOf(toFind) != -1;
+}
+
+#endif

src/Sqids/Sqids.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
 	<PropertyGroup>
-		<TargetFramework>net7.0</TargetFramework>
-		<LangVersion>latest</LangVersion>
+		<TargetFrameworks>netstandard2.0;net6.0;net7.0</TargetFrameworks>
+		<LangVersion>11.0</LangVersion>
 		<ImplicitUsings>enable</ImplicitUsings>
 		<Nullable>enable</Nullable>
 		<OutputType>Library</OutputType>
@@ -25,9 +25,22 @@
 		<SymbolPackageFormat>snupkg</SymbolPackageFormat>
 	</PropertyGroup>
 
+	<PropertyGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
+		<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+	</PropertyGroup>
+
 	<ItemGroup>
 		<None Include="..\..\icon.png" Pack="true" PackagePath="" />
 		<None Include="..\..\nuget-readme.md" Pack="true" PackagePath="\" />
 	</ItemGroup>
 
+	<ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
+		<PackageReference Include="Microsoft.Bcl.HashCode" Version="1.1.1" />
+		<PackageReference Include="PolySharp" Version="1.13.2">
+			<PrivateAssets>all</PrivateAssets>
+			<IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
+		</PackageReference>
+		<PackageReference Include="System.Memory" Version="4.5.5" />
+	</ItemGroup>
+
 </Project>

src/Sqids/SqidsEncoder.cs

@@ -1,4 +1,4 @@
-namespace Sqids;
+namespace Sqids;
 
 /// <summary>
 /// The Sqids encoder/decoder. This is the main class.
@@ -179,7 +179,7 @@ private string Encode(ReadOnlySpan<int> numbers, bool partitioned = false)
 			}
 		}
 
-		if (IsBlockedId(result))
+		if (IsBlockedId(result.AsSpan()))
 		{
 			Span<int> newNumbers = numbers.Length * sizeof(int) > MaxStackallocSize
 				? new int[numbers.Length]
@@ -256,7 +256,7 @@ public int[] Decode(ReadOnlySpan<char> id)
 
 			var separatorIndex = id.IndexOf(separator);
 			var chunk = separatorIndex == -1 ? id : id[..separatorIndex]; // NOTE: The first part of `id` (every thing to the left of the separator) represents the number that we ought to decode.
-			id = separatorIndex == -1 ? string.Empty : id[(separatorIndex + 1)..]; // NOTE: Everything to the right of the separator will be `id` for the next iteration
+			id = separatorIndex == -1 ? default : id[(separatorIndex + 1)..]; // NOTE: Everything to the right of the separator will be `id` for the next iteration
 
 			if (chunk.IsEmpty)
 				continue;
@@ -277,6 +277,20 @@ public int[] Decode(ReadOnlySpan<char> id)
 		return result.ToArray(); // TODO: A way to return an array without creating a new array from the list like this?
 	}
 
+	// NOTE: Implicit `string` => `Span<char>` conversion was introduced in .NET Standard 2.1 (see https://learn.microsoft.com/en-us/dotnet/api/system.string.op_implicit), which means without this overload, calling `Decode` with a string on versions older than .NET Standard 2.1 would require calling `.AsSpan()` on the string, which is cringe.
+#if NETSTANDARD2_0
+	/// <summary>
+	/// Decodes an ID into numbers.
+	/// </summary>
+	/// <param name="id">The encoded ID.</param>
+	/// <returns>
+	/// An array of integers containing the decoded number(s) (it would contain only one element
+	/// if the ID represents a single number); or an empty array if the input ID is null,
+	/// empty, or includes characters not found in the alphabet.
+	/// </returns>
+	public int[] Decode(string id) => Decode(id.AsSpan());
+#endif
+
 	private bool IsBlockedId(ReadOnlySpan<char> id)
 	{
 		foreach (string word in _blockList)
@@ -285,15 +299,15 @@ private bool IsBlockedId(ReadOnlySpan<char> id)
 				continue;
 
 			if ((id.Length <= 3 || word.Length <= 3) &&
-				id.Equals(word, StringComparison.OrdinalIgnoreCase))
+				id.Equals(word.AsSpan(), StringComparison.OrdinalIgnoreCase))
 				return true;
 
 			if (word.Any(char.IsDigit) &&
-				(id.StartsWith(word, StringComparison.OrdinalIgnoreCase) ||
-				 id.EndsWith(word, StringComparison.OrdinalIgnoreCase)))
+				(id.StartsWith(word.AsSpan(), StringComparison.OrdinalIgnoreCase) ||
+				 id.EndsWith(word.AsSpan(), StringComparison.OrdinalIgnoreCase)))
 				return true;
 
-			if (id.Contains(word, StringComparison.OrdinalIgnoreCase))
+			if (id.Contains(word.AsSpan(), StringComparison.OrdinalIgnoreCase))
 				return true;
 		}
 
@@ -321,7 +335,7 @@ private static ReadOnlySpan<char> ToId(int num, ReadOnlySpan<char> alphabet)
 			result = result / alphabet.Length;
 		} while (result > 0);
 
-		return id.ToString(); // TODO: possibly avoid creating a string
+		return id.ToString().AsSpan(); // TODO: possibly avoid creating a string
 	}
 
 	private static int ToNumber(ReadOnlySpan<char> id, ReadOnlySpan<char> alphabet)

test/Sqids.Tests/Sqids.Tests.csproj

@@ -1,23 +1,32 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-  <PropertyGroup>
-    <TargetFramework>net7.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
-    <IsTestProject>true</IsTestProject>
-  </PropertyGroup>
+	<PropertyGroup>
+		<!-- NOTE: `net472` is used for testing `netstandard2.0` -->
+		<TargetFrameworks>net472;net6.0;net7.0</TargetFrameworks>
+		<LangVersion>11.0</LangVersion>
+		<ImplicitUsings>enable</ImplicitUsings>
+		<Nullable>enable</Nullable>
+		<IsTestProject>true</IsTestProject>
+	</PropertyGroup>
 
-  <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
-    <PackageReference Include="NUnit" Version="3.13.3" />
-    <PackageReference Include="NUnit3TestAdapter" Version="4.4.2" />
-    <PackageReference Include="NUnit.Analyzers" Version="3.6.1" />
-    <PackageReference Include="coverlet.collector" Version="3.2.0" />
-    <PackageReference Include="Shouldly" Version="4.2.1" />
-  </ItemGroup>
+	<ItemGroup>
+		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
+		<PackageReference Include="NUnit" Version="3.13.3" />
+		<PackageReference Include="NUnit3TestAdapter" Version="4.4.2" />
+		<PackageReference Include="NUnit.Analyzers" Version="3.6.1" />
+		<PackageReference Include="coverlet.collector" Version="3.2.0" />
+		<PackageReference Include="Shouldly" Version="4.2.1" />
+	</ItemGroup>
 
-  <ItemGroup>
-    <ProjectReference Include="..\..\src\Sqids\Sqids.csproj" />
-  </ItemGroup>
+	<ItemGroup>
+		<ProjectReference Include="..\..\src\Sqids\Sqids.csproj" />
+	</ItemGroup>
+
+	<ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
+		<PackageReference Include="PolySharp" Version="1.13.2">
+			<PrivateAssets>all</PrivateAssets>
+			<IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
+		</PackageReference>
+	</ItemGroup>
 
 </Project>