enable arm64 encode

README-CN.md

@@ -10,4 +10,4 @@
 ## 致谢
 本项目的大部分纯Go代码源自 [golang base64](https://github.com/golang/go/tree/master/src/encoding/base64)，本包的使用和Go语言的base64完全相同。
 
-AMD64架构的SIMD实现 (特别是SSE版本)算法源自 [aklomp/base64](https://github.com/aklomp/base64)。
+AMD64架构(特别是SSE版本)和ARM64架构的SIMD实现算法源自 [aklomp/base64](https://github.com/aklomp/base64)。

README.md

@@ -10,4 +10,4 @@ Base64 with SIMD acceleration
 ## Acknowledgements
 This is an extension of [golang base64](https://github.com/golang/go/tree/master/src/encoding/base64).
 
-The amd64 SIMD implementation (especially SSE version) is inspired by code from [aklomp/base64](https://github.com/aklomp/base64). 
+The amd64 (especially SSE version) / arm64 SIMD implementation are inspired by code from [aklomp/base64](https://github.com/aklomp/base64). 

base64_arm64.go

@@ -5,3 +5,16 @@ package base64
 
 //go:noescape
 func encodeAsm(dst, src []byte, lut *[64]byte) int
+
+func encode(enc *Encoding, dst, src []byte) {
+	if len(src) >= 48 {
+		encoded := encodeAsm(dst, src, &enc.encode)
+		src = src[(encoded/4)*3:]
+		dst = dst[encoded:]
+	}
+	encodeGeneric(enc, dst, src)
+}
+
+func decode(enc *Encoding, dst, src []byte) (int, error) {
+	return decodeGeneric(enc, dst, src)
+}

base64_generic.go

@@ -1,5 +1,5 @@
-//go:build !amd64 || purego
-// +build !amd64 purego
+//go:build !amd64 && !arm64 || purego
+// +build !amd64,!arm64 purego
 
 package base64
 
@@ -9,4 +9,4 @@ func encode(enc *Encoding, dst, src []byte) {
 
 func decode(enc *Encoding, dst, src []byte) (int, error) {
 	return decodeGeneric(enc, dst, src)
-}
+}