reflect.go

package xunsafe

/*
Copyright (c) 2009 The Go Authors. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

   * Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
   * Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

import (
	"reflect"
	"unsafe"
)

//flag copied from reflect pacakge
type flag uintptr

//rtype copied from reflect package
type rtype struct {
	size       uintptr
	ptrdata    uintptr // number of bytes in the type that can contain pointers
	hash       uint32  // hash of type; avoids computation in hash tables
	tflag      uint8   // extra type information flags
	align      uint8   // alignment of variable with this type
	fieldAlign uint8   // alignment of struct field with this type
	kind       uint8   // enumeration for C
	// function for comparing objects of this type
	// (ptr to object A, ptr to object B) -> ==?
	equal     func(unsafe.Pointer, unsafe.Pointer) bool
	gcdata    *byte // garbage collection data
	str       int32 // string form
	ptrToThis int32 // type for pointer to this type, may be zero
}

func (t *rtype) Size() uintptr { return t.size }

func (t *rtype) Align() int { return int(t.align) }

func (t *rtype) FieldAlign() int { return int(t.fieldAlign) }

func (t *rtype) Kind() reflect.Kind { return reflect.Kind(t.kind & kindMask) }

func (t *rtype) pointers() bool { return t.ptrdata != 0 }

//emptyInterface copied from reflect package
type emptyInterface struct {
	typ  *rtype
	word unsafe.Pointer
}

//value is simplied reflect value
type value struct {
	typ  *rtype
	ptr  unsafe.Pointer
	flag flag
}

//ValuePointer returns value pointer
func ValuePointer(v *reflect.Value) unsafe.Pointer {
	return (*value)(unsafe.Pointer(v)).ptr
}

const (
	kindDirectIface      = 1 << 5
	kindGCProg           = 1 << 6 // Type.gc points to GC program
	kindMask             = (1 << 5) - 1
	flagIndir       flag = 1 << 7
)

//AsPointer returns a  pointer for an empty interface
func asInterface(ptr unsafe.Pointer, rtype *rtype, canDeref bool) (v interface{}) {
	empty := (*emptyInterface)(unsafe.Pointer(&v))
	empty.word = ptr
	if rtype.kind&kindDirectIface != 0 && canDeref {
		empty.word = *(*unsafe.Pointer)(ptr)
	}
	empty.typ = rtype
	return v
}