Intro
This time, I will call some Go functions from C#.
To do this, I should generate a Go dll file and call it from C#.
Calling with int values
First, I will try sending an int value as an argument of a Go funtion and receiving int value from it.
[C#] CallSample.cs
using System.Runtime.InteropServices;
namespace CallDllSample;
public class CallSample
{
[DllImport("dllsample")]
private static extern int CallInt(int num);
public int CallGoInt(int num)
{
return CallInt(num);
}
}
[Go] main.go
package main
import "C"
func main() { }
// publish functions by "//export ~"
//export CallInt
func CallInt(num int) int {
return num + 3
}
Build a dll file
go build -buildmode=c-shared -o dllsample.dll .
Calling with string values
Because C#'s string type and Go's string type are not compatible, these codes cause an exception.
[C#] CallSample.cs
...
[DllImport("dllsample")]
private static extern string CallString(string text);
...
public string CallGoString(string text)
{
return CallString(text);
}
}
[Go] main.go
...
// DON'T DO THIS
//export CallString
func CallString(text string) string {
return fmt.Sprintf("%s World!", text)
}
Result
Fatal error. System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Repeat 2 times:
--------------------------------
at CallDllSample.CallSample.CallString(System.String)
--------------------------------
at CallDllSample.CallSample.CallGoString(System.String)
at Program.<Main>$(System.String[])
To resolve that, I have to use "C.char".
[C#] CallSample.cs
...
[DllImport("dllsample")]
private static extern IntPtr CallString(string text);
...
public string CallGoString(string text)
{
var result = CallString(text);
Console.WriteLine(result);
return Marshal.PtrToStringAnsi(result) ?? "";
}
}
[Go] main.go
...
//export CallString
func CallString(text *C.char) *C.char {
gs := C.GoString(text)
return C.CString(fmt.Sprintf("%s World!", gs))
}
- cgo common - cmd/cgo - Go Packages
- How to call go from c with string (char *) as the parameter without making a copy - GitHub
- GoからCのライブラリを呼ぶ - Qiita
Calling with arrays
To send int array to the Go function, I should convert it to IntPtr.
And to receive int array from the Go function, I should convert from IntPtr.
[C#] CallSample.cs
...
public void CallGoArray()
{
// Convert from C# int array to IntPtr
var nums = new int[]{ 4, 2, 5, 8 };
IntPtr intPtr = Marshal.AllocCoTaskMem(Marshal.SizeOf(typeof(int)) * nums.Length);
Marshal.Copy(nums, 0, intPtr, nums.Length);
var pointerResult = CallArray(intPtr, nums.Length);
// Convert from IntPtr to C# int array
var results = new int[nums.Length];
Marshal.Copy(pointerResult, results, 0, results.Length);
for(var i = 0; i < results.Length; i++)
{
Console.WriteLine($"From Go Index: {i} Value: {results[i]}");
}
}
...
[Go] main.go
...
//export CallArray
func CallArray(values *C.int, length C.int) *C.int {
// Convert from C int array to Go int array
cInts := (*[1 << 30]C.int)(unsafe.Pointer(values))[:length:length]
goResults := make([]int, int(length))
for i, v := range cInts {
goResults[i] = int(v)
log.Printf("From C# Index: %d Value: %d", int(i), int(v))
}
// Convert from Go int array to C int array
results := C.malloc(C.size_t(length) * C.size_t(unsafe.Sizeof(uintptr(0))))
pointerResult := (*[1 << 30]C.int)(results)
for i := 0; i < int(length); i++ {
pointerResult[i] = C.int(goResults[i] + 2)
}
return (*C.int)(results)
}
Top comments (0)