reflect: make Index and Slice accept strings
Fixes #3284.
R=golang-dev, r, rsc
CC=golang-dev
https://golang.org/cl/6643043
diff --git a/src/pkg/reflect/all_test.go b/src/pkg/reflect/all_test.go
index 5ddd6be..842b507 100644
--- a/src/pkg/reflect/all_test.go
+++ b/src/pkg/reflect/all_test.go
@@ -2036,6 +2036,24 @@
}
}
+func TestIndex(t *testing.T) {
+ xs := []byte{1, 2, 3, 4, 5, 6, 7, 8}
+ v := ValueOf(xs).Index(3).Interface().(byte)
+ if v != xs[3] {
+ t.Errorf("xs.Index(3) = %v; expected %v", v, xs[3])
+ }
+ xa := [8]byte{10, 20, 30, 40, 50, 60, 70, 80}
+ v = ValueOf(xa).Index(2).Interface().(byte)
+ if v != xa[2] {
+ t.Errorf("xa.Index(2) = %v; expected %v", v, xa[2])
+ }
+ s := "0123456789"
+ v = ValueOf(s).Index(3).Interface().(byte)
+ if v != s[3] {
+ t.Errorf("s.Index(3) = %v; expected %v", v, s[3])
+ }
+}
+
func TestSlice(t *testing.T) {
xs := []int{1, 2, 3, 4, 5, 6, 7, 8}
v := ValueOf(xs).Slice(3, 5).Interface().([]int)
@@ -2048,7 +2066,6 @@
if !DeepEqual(v[0:5], xs[3:]) {
t.Errorf("xs.Slice(3, 5)[0:5] = %v", v[0:5])
}
-
xa := [8]int{10, 20, 30, 40, 50, 60, 70, 80}
v = ValueOf(&xa).Elem().Slice(2, 5).Interface().([]int)
if len(v) != 3 {
@@ -2060,6 +2077,11 @@
if !DeepEqual(v[0:6], xa[2:]) {
t.Errorf("xs.Slice(2, 5)[0:6] = %v", v[0:6])
}
+ s := "0123456789"
+ vs := ValueOf(s).Slice(3, 5).Interface().(string)
+ if vs != s[3:5] {
+ t.Errorf("s.Slice(3, 5) = %q; expected %q", vs, s[3:5])
+ }
}
func TestVariadic(t *testing.T) {
diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go
index 74addd1..be5d035 100644
--- a/src/pkg/reflect/value.go
+++ b/src/pkg/reflect/value.go
@@ -810,8 +810,10 @@
panic(&ValueError{"reflect.Value.Float", k})
}
+var uint8Type = TypeOf(uint8(0)).(*commonType)
+
// Index returns v's i'th element.
-// It panics if v's Kind is not Array or Slice or i is out of range.
+// It panics if v's Kind is not Array, Slice, or String or i is out of range.
func (v Value) Index(i int) Value {
k := v.kind()
switch k {
@@ -852,6 +854,15 @@
fl |= flag(typ.Kind()) << flagKindShift
val := unsafe.Pointer(s.Data + uintptr(i)*typ.size)
return Value{typ, val, fl}
+
+ case String:
+ fl := v.flag&flagRO | flag(Uint8<<flagKindShift)
+ s := (*StringHeader)(v.val)
+ if i < 0 || i >= s.Len {
+ panic("reflect: string index out of range")
+ }
+ val := *(*byte)(unsafe.Pointer(s.Data + uintptr(i)))
+ return Value{uint8Type, unsafe.Pointer(uintptr(val)), fl}
}
panic(&ValueError{"reflect.Value.Index", k})
}
@@ -1437,7 +1448,7 @@
}
// Slice returns a slice of v.
-// It panics if v's Kind is not Array or Slice.
+// It panics if v's Kind is not Array, Slice, or String.
func (v Value) Slice(beg, end int) Value {
var (
cap int
@@ -1447,6 +1458,7 @@
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.Slice", k})
+
case Array:
if v.flag&flagAddr == 0 {
panic("reflect.Value.Slice: slice of unaddressable array")
@@ -1455,13 +1467,25 @@
cap = int(tt.len)
typ = (*sliceType)(unsafe.Pointer(toCommonType(tt.slice)))
base = v.val
+
case Slice:
typ = (*sliceType)(unsafe.Pointer(v.typ))
s := (*SliceHeader)(v.val)
base = unsafe.Pointer(s.Data)
cap = s.Cap
+ case String:
+ s := (*StringHeader)(v.val)
+ if beg < 0 || end < beg || end > s.Len {
+ panic("reflect.Value.Slice: string slice index out of bounds")
+ }
+ var x string
+ val := (*StringHeader)(unsafe.Pointer(&x))
+ val.Data = s.Data + uintptr(beg)
+ val.Len = end - beg
+ return Value{v.typ, unsafe.Pointer(&x), v.flag}
}
+
if beg < 0 || end < beg || end > cap {
panic("reflect.Value.Slice: slice index out of bounds")
}
