unique: not duplication implement cloneString

Change-Id: I3af3bc01be3730172838a2fd4992e9db11cb6f37

src/internal/stringslite/strings.go

@@ -8,7 +8,10 @@
 // Tests for these functions are in the strings package.
 package stringslite
 
-import "internal/bytealg"
+import (
+	"internal/bytealg"
+	"unsafe"
+)
 
 func HasPrefix(s, prefix string) bool {
 	return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
@@ -122,3 +125,12 @@ func CutSuffix(s, suffix string) (before string, found bool) {
 	}
 	return s[:len(s)-len(suffix)], true
 }
+
+func Clone(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+	b := make([]byte, len(s))
+	copy(b, s)
+	return unsafe.String(&b[0], len(b))
+}

src/strings/clone.go

@@ -4,9 +4,7 @@
 
 package strings
 
-import (
-	"unsafe"
-)
+import "internal/stringslite"
 
 // Clone returns a fresh copy of s.
 // It guarantees to make a copy of s into a new allocation,
@@ -19,10 +17,5 @@ import (
 // For strings of length zero the string "" will be returned
 // and no allocation is made.
 func Clone(s string) string {
-	if len(s) == 0 {
-		return ""
-	}
-	b := make([]byte, len(s))
-	copy(b, s)
-	return unsafe.String(&b[0], len(b))
+	return stringslite.Clone(s)
 }

src/unique/clone.go

@@ -6,6 +6,7 @@ package unique
 
 import (
 	"internal/abi"
+	"internal/stringslite"
 	"unsafe"
 )
 
@@ -20,7 +21,7 @@ import (
 func clone[T comparable](value T, seq *cloneSeq) T {
 	for _, offset := range seq.stringOffsets {
 		ps := (*string)(unsafe.Pointer(uintptr(unsafe.Pointer(&value)) + offset))
-		*ps = cloneString(*ps)
+		*ps = stringslite.Clone(*ps)
 	}
 	return value
 }
@@ -86,15 +87,3 @@ func buildArrayCloneSeq(typ *abi.Type, seq *cloneSeq, baseOffset uintptr) {
 		offset = (offset + align - 1) &^ (align - 1)
 	}
 }
-
-// cloneString is a copy of strings.Clone, because we can't depend on the strings
-// package here. Several packages that might make use of unique, like net, explicitly
-// forbid depending on unicode, which strings depends on.
-func cloneString(s string) string {
-	if len(s) == 0 {
-		return ""
-	}
-	b := make([]byte, len(s))
-	copy(b, s)
-	return unsafe.String(&b[0], len(b))
-}