Merge pull request #1298 from Workiva/addUnsafeSliceData

nevkontakte · web-flow · commit fc3ec5687da1 · 2024-05-12T13:17:04.000+01:00
[go1.20] Added support for unsafe.SliceData
diff --git a/compiler/expressions.go b/compiler/expressions.go
@@ -1058,6 +1058,9 @@ func (fc *funcContext) translateBuiltin(name string, sig *types.Signature, args
 	case "Offsetof":
 		sel, _ := fc.selectionOf(astutil.RemoveParens(args[0]).(*ast.SelectorExpr))
 		return fc.formatExpr("%d", typesutil.OffsetOf(sizes32, sel))
+	case "SliceData":
+		t := fc.typeOf(args[0]).Underlying().(*types.Slice)
+		return fc.formatExpr(`$sliceData(%e, %s)`, args[0], fc.typeName(t))
 	default:
 		panic(fmt.Sprintf("Unhandled builtin: %s\n", name))
 	}
diff --git a/compiler/prelude/prelude.js b/compiler/prelude/prelude.js
@@ -569,3 +569,10 @@ var $instanceOf = (x, y) => {
 var $typeOf = x => {
     return typeof (x);
 };
+
+var $sliceData = (slice, typ) => {
+    if (slice === typ.nil) {
+        return $ptrType(typ.elem).nil;
+    }
+    return $indexPtr(slice.$array, slice.$offset, typ.elem);
+};
diff --git a/tests/js_test.go b/tests/js_test.go
@@ -9,6 +9,7 @@ import (
 	"strings"
 	"testing"
 	"time"
+	"unsafe"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/gopherjs/gopherjs/js"
@@ -936,3 +937,41 @@ func TestStructWithNonIdentifierJSTag(t *testing.T) {
 		t.Errorf("value via js.Object.Get gave %q, want %q", got, want)
 	}
 }
+
+func TestSliceData(t *testing.T) {
+	var (
+		s0 = []int(nil)
+		s1 = []int{}
+		s2 = []int{1, 2, 3}
+		s3 = s2[1:]
+		s4 = []int{4, 5, 6}
+
+		sd0 = unsafe.SliceData(s0)
+		sd1 = unsafe.SliceData(s1)
+		sd2 = unsafe.SliceData(s2)
+		sd3 = unsafe.SliceData(s3)
+		sd4 = unsafe.SliceData(s4)
+	)
+
+	if sd0 != nil {
+		t.Errorf("slice data for nil slice was not nil")
+	}
+	if sd1 == nil {
+		t.Errorf("slice data for empty slice was nil")
+	}
+	if sd2 == nil {
+		t.Errorf("slice data for non-empty slice was nil")
+	}
+	if sd3 == nil {
+		t.Errorf("slice data for sub-slice was nil")
+	}
+	if sd1 == sd2 {
+		t.Errorf("slice data for empty and non-empty slices were the same")
+	}
+	if sd2 == sd3 {
+		t.Errorf("slice data for slice and sub-slice were the same")
+	}
+	if sd2 == sd4 {
+		t.Errorf("slice data for different slices were the same")
+	}
+}
