internal/pkg: implement file artifact

This is an Artifact implementing File, backed by a constant, caller-supplied byte slice.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/dir_test.go

@@ -410,6 +410,27 @@ func TestFlatten(t *testing.T) {
 			{Mode: fs.ModeDir | 0700, Path: "temp"},
 			{Mode: fs.ModeDir | 0700, Path: "work"},
 		}, pkg.MustDecode("_r1IBeMWCkLwQ9Im9w0tV9_CWIOfQlXkkP2CogPHLmZp_AB6W3_8HVZqDV00dNAm")},
+
+		{"sample file short", fstest.MapFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX": {Mode: 0400, Data: []byte{0}},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/lIx_W4M7tVOcQ8jh08EJOfXf4brRmkEEjvUa7c17vVUzlmtUxlhhrgqmc9aZhjbn": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX")},
+
+			"work": {Mode: fs.ModeDir | 0700},
+		}, []pkg.FlatEntry{
+			{Mode: fs.ModeDir | 0700, Path: "."},
+			{Mode: fs.ModeDir | 0700, Path: "checksum"},
+			{Mode: 0400, Path: "checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX", Data: []byte{0}},
+
+			{Mode: fs.ModeDir | 0700, Path: "identifier"},
+			{Mode: fs.ModeSymlink | 0777, Path: "identifier/lIx_W4M7tVOcQ8jh08EJOfXf4brRmkEEjvUa7c17vVUzlmtUxlhhrgqmc9aZhjbn", Data: []byte("../checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX")},
+
+			{Mode: fs.ModeDir | 0700, Path: "work"},
+		}, pkg.MustDecode("hnrfmJtivNKcgtETsKnU9gP_OwPgpNY3DSUJnmxnmeOODSO-YBvEBiTgieY4AAd7")},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {

internal/pkg/file.go

@@ -0,0 +1,40 @@
+package pkg
+
+import (
+	"crypto/sha512"
+	"syscall"
+)
+
+// A fileArtifact is an [Artifact] that cures into data known ahead of time.
+type fileArtifact []byte
+
+var _ KnownChecksum = fileArtifact{}
+
+// NewFile returns a [File] that cures into a caller-supplied byte slice.
+//
+// Caller must not modify data after NewBin returns.
+func NewFile(data []byte) File { return fileArtifact(data) }
+
+// Kind returns the hardcoded [Kind] constant.
+func (a fileArtifact) Kind() Kind { return KindFile }
+
+// Params returns the result of Data.
+func (a fileArtifact) Params() []byte { return a }
+
+// Dependencies returns a nil slice.
+func (a fileArtifact) Dependencies() []Artifact { return nil }
+
+// Checksum computes and returns the checksum of caller-supplied data.
+func (a fileArtifact) Checksum() Checksum {
+	h := sha512.New384()
+	h.Write(a)
+	return Checksum(h.Sum(nil))
+}
+
+// Data returns the caller-supplied data.
+func (a fileArtifact) Data() ([]byte, error) { return a, nil }
+
+// Cure returns syscall.ENOTSUP. Callers should use Data instead.
+func (a fileArtifact) Cure(*CureContext) (err error) {
+	return syscall.ENOTSUP
+}

internal/pkg/file_test.go

@@ -0,0 +1,29 @@
+package pkg_test
+
+import (
+	"testing"
+
+	"hakurei.app/container/check"
+	"hakurei.app/internal/pkg"
+)
+
+func TestFile(t *testing.T) {
+	t.Parallel()
+
+	checkWithCache(t, []cacheTestCase{
+		{"file", nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
+			c.SetStrict(true)
+
+			cureMany(t, c, []cureStep{
+				{"short", pkg.NewFile([]byte{0}), base.Append(
+					"identifier",
+					"lIx_W4M7tVOcQ8jh08EJOfXf4brRmkEEjvUa7c17vVUzlmtUxlhhrgqmc9aZhjbn",
+				), pkg.MustDecode(
+					"vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX",
+				), nil},
+			})
+		}, pkg.MustDecode(
+			"hnrfmJtivNKcgtETsKnU9gP_OwPgpNY3DSUJnmxnmeOODSO-YBvEBiTgieY4AAd7",
+		)},
+	})
+}

internal/pkg/pkg.go

@@ -188,6 +188,8 @@ const (
 	// KindExecNet is the kind of [Artifact] returned by [NewExec] but with a
 	// non-nil checksum.
 	KindExecNet
+	// KindFile is the kind of [Artifact] returned by [NewFile].
+	KindFile
 )
 
 // Ident returns a deterministic identifier for the supplied params and