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trampoline.go
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trampoline.go
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package dl
// #include <stdlib.h>
// #include "trampoline.h"
import "C"
import (
"errors"
"fmt"
"math"
"reflect"
"unsafe"
)
var (
emptyType = reflect.TypeOf((*interface{})(nil)).Elem()
)
type rFunc func([]reflect.Value) []reflect.Value
func makeTrampoline(typ reflect.Type, handle unsafe.Pointer) (rFunc, error) {
numOut := typ.NumOut()
if numOut > 1 {
return nil, fmt.Errorf("C functions can return 0 or 1 values, not %d", numOut)
}
var out reflect.Type
var kind reflect.Kind
outFlag := C.int(0)
if numOut == 1 {
out = typ.Out(0)
kind = out.Kind()
if kind == reflect.Float32 || kind == reflect.Float64 {
outFlag |= C.ARG_FLAG_FLOAT
}
}
return func(in []reflect.Value) []reflect.Value {
if typ.IsVariadic() && len(in) > 0 {
last := in[len(in)-1]
in = in[:len(in)-1]
if last.Len() > 0 {
for ii := 0; ii < last.Len(); ii {
in = append(in, last.Index(ii))
}
}
}
count := len(in)
args := make([]unsafe.Pointer, count)
flags := make([]C.int, count 1)
flags[count] = outFlag
for ii, v := range in {
if v.Type() == emptyType {
v = reflect.ValueOf(v.Interface())
}
switch v.Kind() {
case reflect.String:
s := C.CString(v.String())
defer C.free(unsafe.Pointer(s))
args[ii] = unsafe.Pointer(s)
flags[ii] |= C.ARG_FLAG_SIZE_PTR
case reflect.Int:
args[ii] = unsafe.Pointer(uintptr(v.Int()))
if v.Type().Size() == 4 {
flags[ii] = C.ARG_FLAG_SIZE_32
} else {
flags[ii] = C.ARG_FLAG_SIZE_64
}
case reflect.Int8:
args[ii] = unsafe.Pointer(uintptr(v.Int()))
flags[ii] = C.ARG_FLAG_SIZE_8
case reflect.Int16:
args[ii] = unsafe.Pointer(uintptr(v.Int()))
flags[ii] = C.ARG_FLAG_SIZE_16
case reflect.Int32:
args[ii] = unsafe.Pointer(uintptr(v.Int()))
flags[ii] = C.ARG_FLAG_SIZE_32
case reflect.Int64:
args[ii] = unsafe.Pointer(uintptr(v.Int()))
flags[ii] = C.ARG_FLAG_SIZE_64
case reflect.Uint:
args[ii] = unsafe.Pointer(uintptr(v.Uint()))
if v.Type().Size() == 4 {
flags[ii] = C.ARG_FLAG_SIZE_32
} else {
flags[ii] = C.ARG_FLAG_SIZE_64
}
case reflect.Uint8:
args[ii] = unsafe.Pointer(uintptr(v.Uint()))
flags[ii] = C.ARG_FLAG_SIZE_8
case reflect.Uint16:
args[ii] = unsafe.Pointer(uintptr(v.Uint()))
flags[ii] = C.ARG_FLAG_SIZE_16
case reflect.Uint32:
args[ii] = unsafe.Pointer(uintptr(v.Uint()))
flags[ii] = C.ARG_FLAG_SIZE_32
case reflect.Uint64:
args[ii] = unsafe.Pointer(uintptr(v.Uint()))
flags[ii] = C.ARG_FLAG_SIZE_64
case reflect.Float32:
args[ii] = unsafe.Pointer(uintptr(math.Float32bits(float32(v.Float()))))
flags[ii] |= C.ARG_FLAG_FLOAT | C.ARG_FLAG_SIZE_32
case reflect.Float64:
args[ii] = unsafe.Pointer(uintptr(math.Float64bits(v.Float())))
flags[ii] |= C.ARG_FLAG_FLOAT | C.ARG_FLAG_SIZE_64
case reflect.Ptr:
args[ii] = unsafe.Pointer(v.Pointer())
flags[ii] |= C.ARG_FLAG_SIZE_PTR
case reflect.Slice:
if v.Len() > 0 {
args[ii] = unsafe.Pointer(v.Index(0).UnsafeAddr())
}
flags[ii] |= C.ARG_FLAG_SIZE_PTR
case reflect.Uintptr:
args[ii] = unsafe.Pointer(uintptr(v.Uint()))
flags[ii] |= C.ARG_FLAG_SIZE_PTR
case reflect.UnsafePointer:
args[ii] = v.UnsafePointer()
flags[ii] |= C.ARG_FLAG_SIZE_PTR
default:
panic(fmt.Errorf("can't bind value of type %s,kind:%s", v.Type(), v.Kind()))
}
}
var argp *unsafe.Pointer
if count > 0 {
argp = &args[0]
}
var ret unsafe.Pointer
if C.call(handle, argp, &flags[0], C.int(count), &ret) != 0 {
s := C.GoString((*C.char)(ret))
C.free(ret)
panic(errors.New(s))
}
if numOut > 0 {
var v reflect.Value
switch kind {
case reflect.Int:
v = reflect.ValueOf(int(uintptr(ret)))
case reflect.Int8:
v = reflect.ValueOf(int8(uintptr(ret)))
case reflect.Int16:
v = reflect.ValueOf(int16(uintptr(ret)))
case reflect.Int32:
v = reflect.ValueOf(int32(uintptr(ret)))
case reflect.Int64:
v = reflect.ValueOf(int64(uintptr(ret)))
case reflect.Uint:
v = reflect.ValueOf(uint(uintptr(ret)))
case reflect.Uint8:
v = reflect.ValueOf(uint8(uintptr(ret)))
case reflect.Uint16:
v = reflect.ValueOf(uint16(uintptr(ret)))
case reflect.Uint32:
v = reflect.ValueOf(uint32(uintptr(ret)))
case reflect.Uint64:
v = reflect.ValueOf(uint64(uintptr(ret)))
case reflect.Float32:
v = reflect.ValueOf(math.Float32frombits(uint32(uintptr(ret))))
case reflect.Float64:
v = reflect.ValueOf(math.Float64frombits(uint64(uintptr(ret))))
case reflect.Ptr:
if out.Elem().Kind() == reflect.String && ret != nil {
s := C.GoString((*C.char)(ret))
v = reflect.ValueOf(&s)
break
}
v = reflect.NewAt(out.Elem(), ret)
case reflect.String:
s := C.GoString((*C.char)(ret))
v = reflect.ValueOf(s)
case reflect.Uintptr:
v = reflect.ValueOf(uintptr(ret))
case reflect.UnsafePointer:
v = reflect.ValueOf(ret)
default:
panic(fmt.Errorf("can't retrieve value of type %s", out))
}
return []reflect.Value{v}
}
return nil
}, nil
}