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// Copyright 2014 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 reflect
import (
"runtime"
"unsafe"
)
// The ffi function, written in C, allocates an FFI closure. It
// returns the code and data pointers. When the code pointer is
// called, it will call callback. CIF is an FFI data structure
// allocated as part of the closure, and is returned to ensure that
// the GC retains it.
func ffi(ftyp *funcType, callback func(unsafe.Pointer, unsafe.Pointer)) (code uintptr, data uintptr, cif unsafe.Pointer)
// The ffiFree function, written in C, releases the FFI closure.
func ffiFree(uintptr)
// An ffiData holds the information needed to preserve an FFI closure
// for the garbage collector.
type ffiData struct {
code uintptr
data uintptr
cif unsafe.Pointer
callback func(unsafe.Pointer, unsafe.Pointer)
}
// The makeFuncFFI function uses libffi closures to implement
// reflect.MakeFunc. This is used for processors for which we don't
// have more efficient support.
func makeFuncFFI(ftyp *funcType, fn func(args []Value) (results []Value)) (uintptr, *ffiData) {
callback := func(params, results unsafe.Pointer) {
ffiCall(ftyp, fn, params, results)
}
code, data, cif := ffi(ftyp, callback)
c := &ffiData{code: code, data: data, cif: cif, callback: callback}
runtime.SetFinalizer(c,
func(p *ffiData) {
ffiFree(p.data)
})
return code, c
}
// ffiCall takes pointers to the parameters, calls the function, and
// stores the results back into memory.
func ffiCall(ftyp *funcType, fn func([]Value) []Value, params unsafe.Pointer, results unsafe.Pointer) {
in := make([]Value, 0, len(ftyp.in))
ap := params
for _, rt := range ftyp.in {
p := unsafe_New(rt)
memmove(p, *(*unsafe.Pointer)(ap), rt.size)
v := Value{rt, p, flag(rt.Kind()) | flagIndir}
in = append(in, v)
ap = (unsafe.Pointer)(uintptr(ap) + ptrSize)
}
out := fn(in)
off := uintptr(0)
for i, typ := range ftyp.out {
v := out[i]
if v.typ != typ {
panic("reflect: function created by MakeFunc using " + funcName(fn) +
" returned wrong type: have " +
out[i].typ.String() + " for " + typ.String())
}
if v.flag&flagRO != 0 {
panic("reflect: function created by MakeFunc using " + funcName(fn) +
" returned value obtained from unexported field")
}
off = align(off, uintptr(typ.fieldAlign))
addr := unsafe.Pointer(uintptr(results) + off)
if v.flag&flagIndir == 0 && (v.kind() == Ptr || v.kind() == UnsafePointer) {
*(*unsafe.Pointer)(addr) = v.ptr
} else {
memmove(addr, v.ptr, typ.size)
}
off += typ.size
}
}
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