internal/pkg: cache computed identifiers

This eliminates duplicate identifier computations. The new implementation also significantly reduces allocations while computing identifier for a large dependency tree.

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

internal/pkg/file.go

@@ -9,7 +9,7 @@ import (
 // A fileArtifact is an [Artifact] that cures into data known ahead of time.
 type fileArtifact []byte
 
-var _ KnownChecksum = fileArtifact{}
+var _ KnownChecksum = new(fileArtifact)
 
 // fileArtifactNamed embeds fileArtifact alongside a caller-supplied name.
 type fileArtifactNamed struct {
@@ -18,10 +18,11 @@ type fileArtifactNamed struct {
 	name string
 }
 
-var _ fmt.Stringer = fileArtifactNamed{}
+var _ fmt.Stringer = new(fileArtifactNamed)
+var _ KnownChecksum = new(fileArtifactNamed)
 
 // String returns the caller-supplied reporting name.
-func (a fileArtifactNamed) String() string { return a.name }
+func (a *fileArtifactNamed) String() string { return a.name }
 
 // NewFile returns a [File] that cures into a caller-supplied byte slice.
 //
@@ -29,26 +30,26 @@ func (a fileArtifactNamed) String() string { return a.name }
 func NewFile(name string, data []byte) File {
 	f := fileArtifact(data)
 	if name != "" {
-		return fileArtifactNamed{f, name}
+		return &fileArtifactNamed{f, name}
 	}
-	return f
+	return &f
 }
 
 // Kind returns the hardcoded [Kind] constant.
-func (a fileArtifact) Kind() Kind { return KindFile }
+func (a *fileArtifact) Kind() Kind { return KindFile }
 
-// Params returns the result of Data.
-func (a fileArtifact) Params() []byte { return a }
+// Params writes the result of Cure.
+func (a *fileArtifact) Params(ctx *IContext) { ctx.GetHash().Write(*a) }
 
 // Dependencies returns a nil slice.
-func (a fileArtifact) Dependencies() []Artifact { return nil }
+func (a *fileArtifact) Dependencies() []Artifact { return nil }
 
 // Checksum computes and returns the checksum of caller-supplied data.
-func (a fileArtifact) Checksum() Checksum {
+func (a *fileArtifact) Checksum() Checksum {
 	h := sha512.New384()
-	h.Write(a)
+	h.Write(*a)
 	return Checksum(h.Sum(nil))
 }
 
 // Cure returns the caller-supplied data.
-func (a fileArtifact) Cure(context.Context) ([]byte, error) { return a, nil }
+func (a *fileArtifact) Cure(context.Context) ([]byte, error) { return *a, nil }