Vendor dependencies

vendor/github.com/aws/smithy-go/schema_ext.go

@@ -0,0 +1,38 @@
+package smithy
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+// ExtensionID identifies a schema extension slot. Each codec family
+// (JSON, CBOR, etc.) uses a distinct slot to cache precomputed data.
+type ExtensionID int
+
+const numExtensionSlots = 5
+
+const (
+	ExtJSON        ExtensionID = iota // transport/http/protocol/internal/json
+	ExtCBOR                           // transport/http/protocol/internal/cbor
+	ExtXML                            // transport/http/protocol/internal/xml
+	ExtQuery                          // transport/http/protocol/internal/query
+	ExtHTTPBinding                    // transport/http/protocol/internal/httpbinding
+)
+
+// SchemaExtension retrieves or lazily computes the extension for the given
+// slot. build is called on first access for a schema and the result is cached.
+// The build function must return a pointer to an immutable value.
+func SchemaExtension[T any](s *Schema, id ExtensionID, build func(*Schema) *T) *T {
+	p := atomic.LoadPointer(&s.ext[id])
+	if p != nil {
+		return (*T)(p)
+	}
+	return computeSchemaExtension(s, id, build)
+}
+
+//go:noinline
+func computeSchemaExtension[T any](s *Schema, id ExtensionID, build func(*Schema) *T) *T {
+	v := build(s)
+	atomic.StorePointer(&s.ext[id], unsafe.Pointer(v))
+	return v
+}