internal/rosa: lazy initialise all artifacts

This improves performance, though not as drastically as lazy initialising llvm.

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

internal/rosa/all.go

@@ -0,0 +1,53 @@
+package rosa
+
+import (
+	"sync"
+
+	"hakurei.app/internal/pkg"
+)
+
+// PArtifact is a lazily-initialised [pkg.Artifact] preset.
+type PArtifact int
+
+const (
+	Autoconf PArtifact = iota
+	Bash
+	Busybox
+	CMake
+	Coreutils
+	Diffutils
+	Gettext
+	Git
+	Go
+	KernelHeaders
+	Libffi
+	M4
+	Make
+	Ninja
+	Perl
+	Patch
+	Python
+	Rsync
+	Zlib
+
+	// _presetEnd is the total number of presets and does not denote a preset.
+	_presetEnd
+)
+
+var (
+	// artifactsF is an array of functions for the result of [PArtifact].
+	artifactsF [_presetEnd]func(t Toolchain) pkg.Artifact
+
+	// artifacts stores the result of artifactsF.
+	artifacts [_toolchainEnd][len(artifactsF)]pkg.Artifact
+	// artifactsOnce is for lazy initialisation of artifacts.
+	artifactsOnce [_toolchainEnd][len(artifactsF)]sync.Once
+)
+
+// Load returns the resulting [pkg.Artifact] of [PArtifact].
+func (t Toolchain) Load(p PArtifact) pkg.Artifact {
+	artifactsOnce[t][p].Do(func() {
+		artifacts[t][p] = artifactsF[p](t)
+	})
+	return artifacts[t][p]
+}