first pass at a "builder" interface

internal/gen/build.go

@@ -0,0 +1,42 @@
+package gen
+
+import "github.com/mmcloughlin/avo/internal/inst"
+
+type build struct {
+	cfg Config
+	printer
+}
+
+func NewBuild(cfg Config) Interface {
+	return GoFmt(&build{cfg: cfg})
+}
+
+func (b *build) Generate(is []inst.Instruction) ([]byte, error) {
+	b.Printf("// %s\n\n", b.cfg.GeneratedWarning())
+	b.Printf("package build\n\n")
+
+	b.Printf("import (\n")
+	b.Printf("\t\"%s\"\n", pkg)
+	b.Printf("\t\"%s/x86\"\n", pkg)
+	b.Printf(")\n\n")
+
+	for _, i := range is {
+		b.instruction(i)
+	}
+
+	return b.Result()
+}
+
+func (b *build) instruction(i inst.Instruction) {
+	s := params(i)
+
+	// Context method.
+	b.Printf("func (c *Context) %s(%s) {\n", i.Opcode, s.ParameterList())
+	b.Printf("if inst, err := x86.%s(%s); err == nil", i.Opcode, s.Arguments())
+	b.Printf(" { c.Instruction(*inst) }")
+	b.Printf(" else { c.AddError(err) }\n")
+	b.Printf("}\n")
+
+	// Global version.
+	b.Printf("func %s(%s) { ctx.%s(%s) }\n\n", i.Opcode, s.ParameterList(), i.Opcode, s.Arguments())
+}