On Sun, Aug 06, 2017 at 07:08:03PM -0700, [email protected] wrote:
> Thanks your reply, I also used this way, but it still not work. code as the
> following.
>
> gonameunits := []string{"gpu0", "gpu1", "gpu2", "gpu3"}
> nameunits := make([]*C.char, len(gonameunits))
> for i, _ := range gonameunits {
> nameunits[i] = C.CString(gonameunits[i])
> defer C.free(unsafe.Pointer(nameunits[i]))
> }
> fmt.Println("nameunits:", nameunits)
This looks correct...
> golevelmatrix := [][]int{{1}, {3, 3}, {3, 3, 2}}
> levelmatrix := make([][]C.int, len(golevelmatrix))
> for i, _ := range golevelmatrix {
> levelmatrix[i] = make([]C.int, len(golevelmatrix[i]))
> for j, _ := range golevelmatrix[i] {
> levelmatrix[i][j] = C.int(golevelmatrix[i][j])
> }
> }
...but this is not: remember that in Go, the type []T denotes *a slice* of
elements of type T. A slice is a dynamic construct which is a view into
underlying array, and as such it itself consists of a pointer into that
array's contents, the current length of the slice and the capacity of
it.
> fmt.Println("levelmatrix:", levelmatrix)
>
> C.test_settopologyresource(mod, C.CString("node1"), C.int(2), (**C.char
> )(unsafe.Pointer(&nameunits[0])), (**C.int)(unsafe.Pointer(&levelmatrix[0][0
> ])))
That thing about slices means that passing a pointer to a single slice
element to C is OK; passing a pointer to an Nth element of a slice to C
and expecting it to access it and the elements following it up to the
slice's length is also OK but interpreting a slice of slices (which
[][]*C.int really is) is wrong: it's not represented by a contiguous
array: it's a slice of N independent slices -- each backed by its
independent array.
So what you really want is something like:
1. Know the dimensions of your matrix (let's denote them by N and M).
2. Allocate a slice of the length N*M.
3. Fill it up with the values from your source slice of slices.
4. Pass the pointer to the array to C.
Like this (untested, may not even compile):
n := len(golevelmatrix)
m := 0
for _, row := range golevelmatrix {
if len(row) > m {
m = len(row)
}
}
a := make([]int, n*m)
i := 0
for _, row := range golevelmatrix {
for j, v := range row {
a[i*n+j] = v
}
i++
}
C.my_func(&a[0])
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