Start working on building a layer

.github/dependabot.yml

@@ -0,0 +1,11 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "nuget" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"

.github/workflows/dotnet.yml

@@ -16,7 +16,9 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v2
       with:
-        dotnet-version: 7.0.100-preview.4.22252.9
+        dotnet-version: |
+          6.0.x
+          7.0.100-preview.6.22352.1
     - name: Build
       run: dotnet build
     - name: Test

Directory.Packages.props

@@ -3,10 +3,10 @@
         <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
     </PropertyGroup>
     <ItemGroup>
-        <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
-        <PackageVersion Include="MSTest.TestAdapter" Version="2.2.8" />
-        <PackageVersion Include="MSTest.TestFramework" Version="2.2.8" />
+        <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.2.0" />
+        <PackageVersion Include="MSTest.TestAdapter" Version="2.2.10" />
+        <PackageVersion Include="MSTest.TestFramework" Version="2.2.10" />
         <PackageVersion Include="coverlet.collector" Version="3.1.2" />
-        <PackageVersion Include="GitHubActionsTestLogger" Version="1.4.1" />
+        <PackageVersion Include="GitHubActionsTestLogger" Version="2.0.1" />
     </ItemGroup>
 </Project>

System.Containers/Configuration.cs

@@ -0,0 +1,10 @@
+namespace System.Containers;
+
+public static class Configuration
+{
+    public static string ArtifactRoot { get; set; } = Path.Combine(Path.GetTempPath(), "Containers");
+    public static string ContentRoot
+    {
+        get => Path.Combine(ArtifactRoot, "Content");
+    }
+}

System.Containers/Descriptor.cs

@@ -0,0 +1,68 @@
+using System.Text.Json.Serialization;
+
+namespace System.Containers;
+
+/// <summary>
+/// An OCI Content Descriptor describing a component.
+/// </summary>
+/// <remarks>
+/// <see href="https://github.com/opencontainers/image-spec/blob/7b36cea86235157d78528944cb94c3323ee0905c/descriptor.md"/>.
+/// </remarks>
+public readonly record struct Descriptor
+{
+    /// <summary>
+    /// Media type of the referenced content.
+    /// </summary>
+    /// <remarks>
+    /// Likely to be an OCI media type defined at <see href="https://github.com/opencontainers/image-spec/blob/7b36cea86235157d78528944cb94c3323ee0905c/media-types.md" />.
+    /// </remarks>
+    // TODO: validate against RFC 6838 naming conventions?
+    [JsonPropertyName("mediaType")]
+    public string MediaType { get; init; }
+
+    /// <summary>
+    /// Digest of the content, specifying algorithm and value.
+    /// </summary>
+    /// <remarks>
+    /// <see href="https://github.com/opencontainers/image-spec/blob/7b36cea86235157d78528944cb94c3323ee0905c/descriptor.md#digests"/>
+    /// </remarks>
+    [JsonPropertyName("digest")]
+    public string Digest { get; init; }
+
+    /// <summary>
+    /// Size, in bytes, of the raw content.
+    /// </summary>
+    [JsonPropertyName("size")]
+    public long Size { get; init; }
+
+    /// <summary>
+    /// Optional list of URLs where the content may be downloaded.
+    /// </summary>
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    public string[]? Urls { get; init; } = null;
+
+    /// <summary>
+    /// Arbitrary metadata for this descriptor.
+    /// </summary>
+    /// <remarks>
+    /// <see href="https://github.com/opencontainers/image-spec/blob/7b36cea86235157d78528944cb94c3323ee0905c/annotations.md"/>
+    /// </remarks>
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)] 
+    public Dictionary<string, string?>? Annotations { get; init; } = null;
+
+    /// <summary>
+    /// Embedded representation of the referenced content, base-64 encoded.
+    /// </summary>
+    /// <remarks>
+    /// <see href="https://github.com/opencontainers/image-spec/blob/7b36cea86235157d78528944cb94c3323ee0905c/descriptor.md#embedded-content"/>
+    /// </remarks>
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)] 
+    public string? Data { get; init; } = null;
+
+    public Descriptor(string mediaType, string digest, long size)
+    {
+        MediaType = mediaType;
+        Digest = digest;
+        Size = size;
+    }
+}

System.Containers/Layer.cs

@@ -0,0 +1,71 @@
+using System.Formats.Tar;
+using System.Security.Cryptography;
+
+namespace System.Containers;
+
+public record struct Layer
+{
+    public Descriptor Descriptor { get; private set; }
+
+    public string BackingFile { get; private set; }
+
+    public static Layer FromDirectory(string directory, string containerPath)
+    {
+        // Docker treats a COPY instruction that copies to a path like `/app` by
+        // including `app/` as a directory, with no leading slash. Emulate that here.
+        containerPath = containerPath.TrimStart(new char[] { Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar });
+
+        DirectoryInfo di = new(directory);
+
+        string tempPath = Path.Join(Configuration.ArtifactRoot, "Temp");
+
+        Directory.CreateDirectory(tempPath);
+
+        long fileSize;
+        byte[] hash;
+
+        string tempTarballPath = Path.Join(tempPath, Path.GetRandomFileName());
+        using (FileStream fs = File.Create(tempTarballPath))
+        {
+            // using (GZipStream gz = new(fs, CompressionMode.Compress)) // TODO: https://github.com/rainersigwald/containers/issues/29
+            using (TarWriter writer = new(fs, TarEntryFormat.Gnu, leaveOpen: true))
+            {
+                foreach (var item in di.GetFileSystemInfos())
+                {
+                    if (item is FileInfo fi)
+                    {
+                        writer.WriteEntry(fi.FullName, Path.Combine(containerPath, fi.Name).Replace(Path.DirectorySeparatorChar, '/'));
+                    }
+                }
+            }
+
+            fileSize = fs.Length;
+
+            fs.Position = 0;
+
+            using SHA256 mySHA256 = SHA256.Create();
+            hash = mySHA256.ComputeHash(fs);
+        }
+
+        string contentHash = Convert.ToHexString(hash).ToLowerInvariant();
+
+        string storedContent = Path.Combine(Configuration.ContentRoot, contentHash);
+
+        Directory.CreateDirectory(Configuration.ContentRoot);
+
+        File.Move(tempTarballPath, storedContent);
+
+        Layer l = new()
+        {
+            Descriptor = new()
+            {
+                MediaType = "application/vnd.oci.image.layer.v1.tar", // TODO: configurable? gzip always?
+                Size = fileSize,
+                Digest = $"sha256:{contentHash}"
+            },
+            BackingFile = storedContent,
+        };
+
+        return l;
+    }
+}

Test.System.Containers.Filesystem/LayerEndToEnd.cs

@@ -0,0 +1,62 @@
+using System.Containers;
+using System.Security.Cryptography;
+
+namespace Test.System.Containers.Filesystem;
+
+[TestClass]
+public class LayerEndToEnd
+{
+    [TestMethod]
+    public void SingleFile()
+    {
+        using TransientTestFolder folder = new();
+
+        string testFilePath = Path.Join(folder.Path, "TestFile.txt");
+        string testString = $"Test content for {nameof(SingleFile)}";
+
+        File.WriteAllText(testFilePath, testString);
+
+        Layer l = Layer.FromDirectory(directory: folder.Path, containerPath: "/app");
+
+        Console.WriteLine(l.Descriptor);
+
+        Assert.AreEqual("application/vnd.oci.image.layer.v1.tar", l.Descriptor.MediaType);
+        Assert.AreEqual(2048, l.Descriptor.Size);
+        //Assert.AreEqual("sha256:26140bc75f2fcb3bf5da7d3b531d995c93d192837e37df0eb5ca46e2db953124", l.Descriptor.Digest); // TODO: determinism!
+
+        Assert.AreEqual(l.Descriptor.Size, new FileInfo(l.BackingFile).Length);
+
+        byte[] hashBytes;
+
+        using (SHA256 hasher = SHA256.Create())
+        using (FileStream fs = File.OpenRead(l.BackingFile))
+        {
+            hashBytes = hasher.ComputeHash(fs);
+        }
+
+        Assert.AreEqual(Convert.ToHexString(hashBytes), l.Descriptor.Digest.Substring("sha256:".Length), ignoreCase: true);
+    }
+
+    TransientTestFolder? testSpecificArtifactRoot;
+    string? priorArtifactRoot;
+
+    [TestInitialize]
+    public void TestInitialize()
+    {
+        testSpecificArtifactRoot = new();
+
+        priorArtifactRoot = Configuration.ArtifactRoot;
+
+        Configuration.ArtifactRoot = testSpecificArtifactRoot.Path;
+    }
+
+    [TestCleanup]
+    public void TestCleanup()
+    {
+        testSpecificArtifactRoot?.Dispose();
+        if (priorArtifactRoot is not null)
+        {
+            Configuration.ArtifactRoot = priorArtifactRoot;
+        }
+    }
+}

Test.System.Containers.Filesystem/Test.System.Containers.Filesystem.csproj

@@ -16,4 +16,8 @@
     <PackageReference Include="GitHubActionsTestLogger" PrivateAssets="all" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\System.Containers\System.Containers.csproj" />
+  </ItemGroup>
+
 </Project>

Test.System.Containers.Filesystem/TransientTestFolder.cs

@@ -0,0 +1,22 @@
+using static System.IO.Path;
+
+namespace Test.System.Containers.Filesystem;
+
+/// <summary>
+/// Helper class to clean up after tests that touch the filesystem.
+/// </summary>
+internal sealed class TransientTestFolder : IDisposable
+{
+    public readonly string Path = Combine(GetTempPath(), GetRandomFileName());
+    public readonly DirectoryInfo DirectoryInfo;
+
+    public TransientTestFolder()
+    {
+        DirectoryInfo = Directory.CreateDirectory(Path);
+    }
+
+    public void Dispose()
+    {
+        Directory.Delete(Path, recursive: true);
+    }
+}

Test.System.Containers/DescriptorTests.cs

@@ -0,0 +1,27 @@
+using System.Containers;
+using System.Text.Json;
+
+namespace Test.System.Containers;
+
+[TestClass]
+public class DescriptorTests
+{
+    [TestMethod]
+    public void BasicConstructor()
+    {
+        Descriptor d = new(
+            mediaType: "application/vnd.oci.image.manifest.v1+json",
+            digest: "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270",
+            size: 7682);
+
+        Console.WriteLine(JsonSerializer.Serialize(d, new JsonSerializerOptions { WriteIndented = true }));
+
+        Assert.AreEqual("application/vnd.oci.image.manifest.v1+json", d.MediaType);
+        Assert.AreEqual("sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270", d.Digest);
+        Assert.AreEqual(7_682, d.Size);
+
+        Assert.IsNull(d.Annotations);
+        Assert.IsNull(d.Data);
+        Assert.IsNull(d.Urls);
+    }
+}

Test.System.Containers/Test.System.Containers.csproj

@@ -16,4 +16,8 @@
     <PackageReference Include="GitHubActionsTestLogger" PrivateAssets="all" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\System.Containers\System.Containers.csproj" />
+  </ItemGroup>
+
 </Project>