直接C指针转换

Question

我有这个 C 代码：

uint8_t *data[BUF_SIZE];
data = ...;

// extern void goReadData(uint8_t *data, int bufferSize);
goReadData(data, BUF_SIZE)

在 GO 代码中，我试图将 data 指针用作 GO 数组或切片，我想从 *C.uint8_t 中检索一个 []uint8。我知道 data

的大小

//export goReadData
func goReadData(data *C.uint8_t, bufferSize C.int) {

    fmt.Printf("Data type %v\n", reflect.TypeOf(data))
    // print 1: Data type *main._Ctype_uchar


    // Solution 1: GoBytes
    // works but really slow (memory copy I think)
    goBytes := C.GoBytes(unsafe.Pointer(data), bufferSize)
    fmt.Printf("goBytes type %v\n", reflect.TypeOf(goBytes))
    // print 2: goBytes type []uint8


    // Solution 2: direct pointer
    // Really fast, but wrong type at the end
    // unsafe.Pointer to the C array
    unsafePtr := unsafe.Pointer(data)

    // convert unsafePtr to a pointer of the type *[1 << 30]C.uint8_t
    arrayPtr := (*[1 << 30]C.uint8_t)(unsafePtr)

    // slice the array into a Go slice, with the same backing array
    // as data, making sure to specify the capacity as well as
    // the length.
    length := int(bufferSize)
    slice := arrayPtr[0:length:length]

    fmt.Printf("Direct slice type %v\n", reflect.TypeOf(slice))
    //Print 3: Direct type []main._Ctype_uchar
}

如何使用第二种解决方案恢复 []uint8 而不是 []main._Ctype_uchar？或者您是否有另一种解决方案可以在不复制字节的情况下做到这一点？

Answer 1

对不起各位，我发现了自己的错误：

// convert unsafePtr to a pointer of the type *[1 << 30]C.uint8_t
arrayPtr := (*[1 << 30]C.uint8_t)(unsafePtr)

==> 到

// convert unsafePtr to a pointer of the type *[1 << 30]uint8
arrayPtr := (*[1 << 30]uint8)(unsafePtr)

问题已解决！

谢谢 ;)

直接C指针转换

Direct C pointer conversion

c

pointers

type-conversion

go

cgo