fix: go1.19 compile

common/utils/string_unsafe.go

@@ -0,0 +1,49 @@
+package utils
+
+import "unsafe"
+
+// sliceHeader is equivalent to reflect.SliceHeader, but represents the pointer
+// to the underlying array as unsafe.Pointer rather than uintptr, allowing
+// sliceHeaders to be directly converted to slice objects.
+type sliceHeader struct {
+	Data unsafe.Pointer
+	Len  int
+	Cap  int
+}
+
+// slice returns a slice whose underlying array starts at ptr an which length
+// and capacity are len.
+func slice[T any](ptr *T, length int) []T {
+	var s []T
+	hdr := (*sliceHeader)(unsafe.Pointer(&s))
+	hdr.Data = unsafe.Pointer(ptr)
+	hdr.Len = length
+	hdr.Cap = length
+	return s
+}
+
+// stringHeader is equivalent to reflect.StringHeader, but represents the
+// pointer to the underlying array as unsafe.Pointer rather than uintptr,
+// allowing StringHeaders to be directly converted to strings.
+type stringHeader struct {
+	Data unsafe.Pointer
+	Len  int
+}
+
+// ImmutableBytesFromString is equivalent to []byte(s), except that it uses the
+// same memory backing s instead of making a heap-allocated copy. This is only
+// valid if the returned slice is never mutated.
+func ImmutableBytesFromString(s string) []byte {
+	shdr := (*stringHeader)(unsafe.Pointer(&s))
+	return slice((*byte)(shdr.Data), shdr.Len)
+}
+
+// StringFromImmutableBytes is equivalent to string(bs), except that it uses
+// the same memory backing bs instead of making a heap-allocated copy. This is
+// only valid if bs is never mutated after StringFromImmutableBytes returns.
+func StringFromImmutableBytes(bs []byte) string {
+	// This is cheaper than messing with StringHeader and SliceHeader, which as
+	// of this writing produces many dead stores of zeroes. Compare
+	// strings.Builder.String().
+	return *(*string)(unsafe.Pointer(&bs))
+}