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/*
* Copyright (c) 2017 by Farsight Security, Inc.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
package nmsg
/*
#cgo pkg-config: libnmsg
#cgo LDFLAGS: -lnmsg
#include <nmsg.h>
#include <stdlib.h>
*/
import "C"
import (
"fmt"
"runtime"
"sync"
"unsafe"
)
type outCbEntry struct {
index int
Output
}
type inCbEntry struct {
index int
Input
}
var cbm sync.Mutex
var outCbTable []Output
var inCbTable []Input
// The C library may not hold a pointer to a Go variable, but we
// need to store enough context in the callback user data to find
// the go object which registered the callback. We solve this by
// allocating memory on the C side (with C.malloc, C.calloc) and
// storing a value in that memory which we can use to look up the
// Go value on the Go side.
//
// The approach we take here is to have a package-global list of
// Output and Input, and store the index in the list as a C.int
// in C-allocated memory. The location of this memory is returned
// as an unsafe.Pointer suitable for passing to the (void *user)
// argument of libnmsg callback registration functions.
func registerOutput(o Output) unsafe.Pointer {
cbm.Lock()
defer cbm.Unlock()
idx := len(outCbTable)
outCbTable = append(outCbTable, o)
idxptr := C.calloc(C.size_t(1), C.size_t(unsafe.Sizeof(C.int(1))))
*(*C.int)(idxptr) = C.int(idx)
return idxptr
}
func registerInput(i Input) unsafe.Pointer {
cbm.Lock()
defer cbm.Unlock()
idx := len(inCbTable)
inCbTable = append(inCbTable, i)
idxptr := C.calloc(C.size_t(1), C.size_t(unsafe.Sizeof(C.int(1))))
*(*C.int)(idxptr) = C.int(idx)
return idxptr
}
//export outputCallback
func outputCallback(msg C.nmsg_message_t, user unsafe.Pointer) {
idx := int(*(*C.int)(user))
if idx < len(outCbTable) {
o := outCbTable[idx]
o.Write(messageFromC(msg))
return
}
panic(fmt.Sprintf("outputCallback: invalid index %d", idx))
}
//export inputCallback
func inputCallback(msg, user unsafe.Pointer) C.nmsg_res {
idx := int(*(*C.int)(user))
if idx < len(inCbTable) {
i := inCbTable[idx]
for {
m, err := i.Read()
if ErrorRetry(err) {
continue
}
if err != nil {
*(*C.nmsg_message_t)(msg) = nil
if e, ok := err.(nmsgResError); ok {
return C.nmsg_res(e)
}
return C.nmsg_res_failure
}
runtime.SetFinalizer(m, nil)
*(*C.nmsg_message_t)(msg) = m.message
return C.nmsg_res_success
}
}
panic(fmt.Sprintf("inputCallback: invalid index %d", idx))
}
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