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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package unsafeheader_test
import (
"bytes"
"internal/unsafeheader"
"reflect"
"testing"
"unsafe"
)
// TestTypeMatchesReflectType ensures that the name and layout of the
// unsafeheader types matches the corresponding Header types in the reflect
// package.
func TestTypeMatchesReflectType(t *testing.T) {
t.Run("Slice", func(t *testing.T) {
testHeaderMatchesReflect(t, unsafeheader.Slice{}, reflect.SliceHeader{})
})
t.Run("String", func(t *testing.T) {
testHeaderMatchesReflect(t, unsafeheader.String{}, reflect.StringHeader{})
})
}
func testHeaderMatchesReflect(t *testing.T, header, reflectHeader interface{}) {
h := reflect.TypeOf(header)
rh := reflect.TypeOf(reflectHeader)
for i := 0; i < h.NumField(); i++ {
f := h.Field(i)
rf, ok := rh.FieldByName(f.Name)
if !ok {
t.Errorf("Field %d of %v is named %s, but no such field exists in %v", i, h, f.Name, rh)
continue
}
if !typeCompatible(f.Type, rf.Type) {
t.Errorf("%v.%s has type %v, but %v.%s has type %v", h, f.Name, f.Type, rh, rf.Name, rf.Type)
}
if f.Offset != rf.Offset {
t.Errorf("%v.%s has offset %d, but %v.%s has offset %d", h, f.Name, f.Offset, rh, rf.Name, rf.Offset)
}
}
if h.NumField() != rh.NumField() {
t.Errorf("%v has %d fields, but %v has %d", h, h.NumField(), rh, rh.NumField())
}
if h.Align() != rh.Align() {
t.Errorf("%v has alignment %d, but %v has alignment %d", h, h.Align(), rh, rh.Align())
}
}
var (
unsafePointerType = reflect.TypeOf(unsafe.Pointer(nil))
uintptrType = reflect.TypeOf(uintptr(0))
)
func typeCompatible(t, rt reflect.Type) bool {
return t == rt || (t == unsafePointerType && rt == uintptrType)
}
// TestWriteThroughHeader ensures that the headers in the unsafeheader package
// can successfully mutate variables of the corresponding built-in types.
//
// This test is expected to fail under -race (which implicitly enables
// -d=checkptr) if the runtime views the header types as incompatible with the
// underlying built-in types.
func TestWriteThroughHeader(t *testing.T) {
t.Run("Slice", func(t *testing.T) {
s := []byte("Hello, checkptr!")[:5]
var alias []byte
hdr := (*unsafeheader.Slice)(unsafe.Pointer(&alias))
hdr.Data = unsafe.Pointer(&s[0])
hdr.Cap = cap(s)
hdr.Len = len(s)
if !bytes.Equal(alias, s) {
t.Errorf("alias of %T(%q) constructed via Slice = %T(%q)", s, s, alias, alias)
}
if cap(alias) != cap(s) {
t.Errorf("alias of %T with cap %d has cap %d", s, cap(s), cap(alias))
}
})
t.Run("String", func(t *testing.T) {
s := "Hello, checkptr!"
var alias string
hdr := (*unsafeheader.String)(unsafe.Pointer(&alias))
hdr.Data = (*unsafeheader.String)(unsafe.Pointer(&s)).Data
hdr.Len = len(s)
if alias != s {
t.Errorf("alias of %q constructed via String = %q", s, alias)
}
})
}
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