reflect: allow Slice of arrays
R=r
CC=golang-dev
https://golang.org/cl/4444049
diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go
index b31aa5a..44aaebd 100644
--- a/src/pkg/reflect/value.go
+++ b/src/pkg/reflect/value.go
@@ -1244,20 +1244,32 @@
*(*string)(iv.addr) = x
}
-// BUG(rsc): Value.Slice should allow slicing arrays.
-
// Slice returns a slice of v.
-// It panics if v's Kind is not Slice.
+// It panics if v's Kind is not Array or Slice.
func (v Value) Slice(beg, end int) Value {
iv := v.internal()
- iv.mustBe(Slice)
+ if iv.kind != Array && iv.kind != Slice {
+ panic(&ValueError{"reflect.Value.Slice", iv.kind})
+ }
cap := v.Cap()
if beg < 0 || end < beg || end > cap {
panic("reflect.Value.Slice: slice index out of bounds")
}
- typ := iv.typ.toType()
+ var typ Type
+ var base uintptr
+ switch iv.kind {
+ case Array:
+ if iv.flag&flagAddr == 0 {
+ panic("reflect.Value.Slice: slice of unaddressable array")
+ }
+ typ = toType((*arrayType)(unsafe.Pointer(iv.typ)).slice)
+ base = uintptr(iv.addr)
+ case Slice:
+ typ = iv.typ.toType()
+ base = (*SliceHeader)(iv.addr).Data
+ }
s := new(SliceHeader)
- s.Data = uintptr((*SliceHeader)(iv.addr).Data) + uintptr(beg)*typ.Elem().Size()
+ s.Data = base + uintptr(beg)*typ.Elem().Size()
s.Len = end - beg
s.Cap = cap - beg
return valueFromAddr(iv.flag&flagRO, typ, unsafe.Pointer(s))
