internal: create package for unsafe bytes convertion (#8733)

Co-authored-by: Alessio Treglia <alessio@tendermint.com>

internal/conv/string.go

@@ -0,0 +1,23 @@
+package conv
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// UnsafeStrToBytes uses unsafe to convert string into byte array. Returned bytes
+// must not be altered after this function is called as it will cause a segmentation fault.
+func UnsafeStrToBytes(s string) []byte {
+	var buf = *(*[]byte)(unsafe.Pointer(&s))
+	(*reflect.SliceHeader)(unsafe.Pointer(&buf)).Cap = len(s)
+	return buf
+}
+
+// UnsafeBytesToStr is meant to make a zero allocation conversion
+// from []byte -> string to speed up operations, it is not meant
+// to be used generally, but for a specific pattern to delete keys
+// from a map.
+func UnsafeBytesToStr(b []byte) string {
+	hdr := (*reflect.StringHeader)(unsafe.Pointer(&b))
+	return *(*string)(unsafe.Pointer(hdr))
+}