core/crypto/chacha20: Use 128-bit/256-bit SIMD

core/crypto/chacha20/chacha20_impl.odin

@@ -0,0 +1,52 @@
+package chacha20
+
+import "base:intrinsics"
+import "core:crypto/_chacha20/ref"
+import "core:crypto/_chacha20/simd128"
+import "core:crypto/_chacha20/simd256"
+
+// Implementation is a ChaCha20 implementation.  Most callers will not need
+// to use this as the package will automatically select the most performant
+// implementation available.
+Implementation :: enum {
+	Portable,
+	Simd128,
+	Simd256,
+}
+
+@(private)
+init_impl :: proc(ctx: ^Context, impl: Implementation) {
+	impl := impl
+	if impl == .Simd256 && !simd256.is_performant() {
+			impl = .Simd128
+	}
+	if impl == .Simd128 && !simd128.is_performant() {
+		impl = .Portable
+	}
+
+	ctx._impl = impl
+}
+
+@(private)
+stream_blocks :: proc(ctx: ^Context, dst, src: []byte, nr_blocks: int) {
+	switch ctx._impl {
+	case .Simd256:
+		simd256.stream_blocks(&ctx._state, dst, src, nr_blocks)
+	case .Simd128:
+		simd128.stream_blocks(&ctx._state, dst, src, nr_blocks)
+	case .Portable:
+		ref.stream_blocks(&ctx._state, dst, src, nr_blocks)
+	}
+}
+
+@(private)
+hchacha20 :: proc "contextless" (dst, key, nonce: []byte, impl: Implementation) {
+	switch impl {
+	case .Simd256:
+		simd256.hchacha20(dst, key, nonce)
+	case .Simd128:
+		simd128.hchacha20(dst, key, nonce)
+	case .Portable:
+		ref.hchacha20(dst, key, nonce)
+	}
+}