reflect: support Len and Cap on pointer-to-array Value
Fixes #52411
Change-Id: I2fd13a453622992c52d49aade7cd058cfc8a77ca
GitHub-Last-Rev: d5987c2ec817ebd01d9e1adb3bd2e75274dbbabd
GitHub-Pull-Request: golang/go#52423
Reviewed-on: https://go-review.googlesource.com/c/go/+/400954
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index 72d01c7..9eb01bd 100644
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -7913,3 +7913,69 @@
sinkAll.RawInt = sourceAll.SliceAny.Cap()
}
}
+
+func TestValue_Cap(t *testing.T) {
+ a := &[3]int{1, 2, 3}
+ v := ValueOf(a)
+ if v.Cap() != cap(a) {
+ t.Errorf("Cap = %d want %d", v.Cap(), cap(a))
+ }
+
+ a = nil
+ v = ValueOf(a)
+ if v.Cap() != cap(a) {
+ t.Errorf("Cap = %d want %d", v.Cap(), cap(a))
+ }
+
+ getError := func(f func()) (errorStr string) {
+ defer func() {
+ e := recover()
+ if str, ok := e.(string); ok {
+ errorStr = str
+ }
+ }()
+ f()
+ return
+ }
+ e := getError(func() {
+ var ptr *int
+ ValueOf(ptr).Cap()
+ })
+ wantStr := "reflect: call of reflect.Value.Cap on ptr to non-array Value"
+ if e != wantStr {
+ t.Errorf("error is %q, want %q", e, wantStr)
+ }
+}
+
+func TestValue_Len(t *testing.T) {
+ a := &[3]int{1, 2, 3}
+ v := ValueOf(a)
+ if v.Len() != len(a) {
+ t.Errorf("Len = %d want %d", v.Len(), len(a))
+ }
+
+ a = nil
+ v = ValueOf(a)
+ if v.Len() != len(a) {
+ t.Errorf("Len = %d want %d", v.Len(), len(a))
+ }
+
+ getError := func(f func()) (errorStr string) {
+ defer func() {
+ e := recover()
+ if str, ok := e.(string); ok {
+ errorStr = str
+ }
+ }()
+ f()
+ return
+ }
+ e := getError(func() {
+ var ptr *int
+ ValueOf(ptr).Len()
+ })
+ wantStr := "reflect: call of reflect.Value.Len on ptr to non-array Value"
+ if e != wantStr {
+ t.Errorf("error is %q, want %q", e, wantStr)
+ }
+}
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 6b5ebfa..f92fa16 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -1144,7 +1144,7 @@
}
// Cap returns v's capacity.
-// It panics if v's Kind is not Array, Chan, or Slice.
+// It panics if v's Kind is not Array, Chan, Slice or pointer to Array.
func (v Value) Cap() int {
// capNonSlice is split out to keep Cap inlineable for slice kinds.
if v.kind() == Slice {
@@ -1160,6 +1160,11 @@
return v.typ.Len()
case Chan:
return chancap(v.pointer())
+ case Ptr:
+ if v.typ.Elem().Kind() == Array {
+ return v.typ.Elem().Len()
+ }
+ panic("reflect: call of reflect.Value.Cap on ptr to non-array Value")
}
panic(&ValueError{"reflect.Value.Cap", v.kind()})
}
@@ -1600,7 +1605,7 @@
}
// Len returns v's length.
-// It panics if v's Kind is not Array, Chan, Map, Slice, or String.
+// It panics if v's Kind is not Array, Chan, Map, Slice, String, or pointer to Array.
func (v Value) Len() int {
// lenNonSlice is split out to keep Len inlineable for slice kinds.
if v.kind() == Slice {
@@ -1621,6 +1626,11 @@
case String:
// String is bigger than a word; assume flagIndir.
return (*unsafeheader.String)(v.ptr).Len
+ case Ptr:
+ if v.typ.Elem().Kind() == Array {
+ return v.typ.Elem().Len()
+ }
+ panic("reflect: call of reflect.Value.Len on ptr to non-array Value")
}
panic(&ValueError{"reflect.Value.Len", v.kind()})
}
