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/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")
}
