Call Delphi dll from go - delphi

Question

I have a Delphi dll that needs to be called from golang (go). I can load and call the dll using syscall.Syscall, or windows.Call. Both methods execute the dll correctly. The dll returns its result by changing a string buffer that is passed to it. When I later inspect the string, it is empty (in syscall) or panics in windows.Call. I have tried several permutations but haven't had any luck getting my value out of the variable that should store the result.
Example using windows.Call:
// Package getSID calls SIDgenerator and generates a SID for Retail Pro
package main
import (
"fmt"
"unsafe"
"golang.org/x/sys/windows"
"unicode/utf16"
)
var (
sidgeneratorDLL, _ = windows.LoadDLL("sidgenerator64.dll")
getRandomSID, _ = sidgeneratorDLL.FindProc("GetRandomSID")
)
// StringToCharPtr converts a Go string into pointer to a null-terminated cstring.
// This assumes the go string is already ANSI encoded.
func StringToCharPtr(str string) *uint8 {
chars := append([]byte(str), 0) // null terminated
return &chars[0]
}
// GetRandomSID generates random SID, UPC SID or ALU SID
func GetRandomSID(Buffer []uint16, BufSize uint64) (result byte) {
// var nargs uintptr = 2
fmt.Println(Buffer)
ret, _, callErr := getRandomSID.Call(uintptr(unsafe.Pointer(&Buffer)),
uintptr(unsafe.Pointer(&BufSize)))
// fmt.Println("Buffer", Buffer)
if callErr != nil {
fmt.Println("===== CallErr =====")
fmt.Println(ret, callErr)
// fmt.Println("Buffer", Buffer)
}
result = byte(ret)
return
}
func main() {
defer sidgeneratorDLL.Release()
buffer := utf16.Encode([]rune("12345678901234567890\000"))
bufSize := uint64(len(buffer))
fmt.Printf("Result in: %v\n", buffer)
err := GetRandomSID(buffer, bufSize)
fmt.Printf("Result in: %v\n", buffer)
fmt.Println("Err =", err)
fmt.Println("Called GetRandomSID")
fmt.Printf("Result out: %v\n", buffer)
}
func init() {
fmt.Print("Starting Up\n")
}
Example using syscall:
// Package getSID calls SIDgenerator and generates a SID for Retail Pro
package main
import (
"fmt"
"syscall"
"unsafe"
)
var (
sidgeneratorDLL, _ = syscall.LoadLibrary("sidgenerator64.dll")
getRandomSID, _ = syscall.GetProcAddress(sidgeneratorDLL, "GetRandomSID")
)
// GetRandomSID generates random SID, UPC SID or ALU SID
func GetRandomSID(Buffer *[]byte, BufSize *uint32) (result byte) {
var nargs uintptr = 2
fmt.Println(*Buffer)
ret, _, callErr := syscall.Syscall(uintptr(getRandomSID),
nargs, 0,
uintptr(unsafe.Pointer(Buffer)),
uintptr(unsafe.Pointer(BufSize)),
)
fmt.Println(*Buffer)
if callErr != 0 {
fmt.Println("===== CallErr =====")
fmt.Println(callErr)
}
result = byte(ret)
return
}
func main () {
defer syscall.FreeLibrary(sidgeneratorDLL)
buffer := []byte("1234567890123456789012")
bufSize := uint32(len(buffer))
fmt.Printf("Result in: %s\n", string(buffer))
err := GetRandomSID(&buffer, &bufSize)
fmt.Println("Err =", err)
fmt.Println("Called GetRandomSID")
fmt.Printf("Result out: %s\n", string(buffer))
}
func init() {
fmt.Print("Starting Up\n")
}
Any help will be greatly appreciated. Thanks in advance!
C# external declarations: --------------------------------
[DllImport("SIDGenerator.dll", CharSet = CharSet.Ansi)] static extern Boolean GetSIDFromALU(string ALU, StringBuilder SID, ref int buflen);
[DllImport("SIDGenerator.dll", CharSet = CharSet.Ansi)] static extern Boolean GetSIDFromUPC( string UPC, StringBuilder SID, ref int buflen);
[DllImport("SIDGenerator.dll", CharSet = CharSet.Ansi)] static extern Boolean GetRandomSID(StringBuilder SID, ref int buflen);
Delphi external declarations: -----------------------------------
function GetSIDFromALU( ALU: Pchar; Buffer: PChar; var BufSize : integer ): LongBool; stdcall; external ‘SIDGenerator.dll’;
function GetSIDFromUPC( UPC: PChar; Buffer: PChar; var BufSize : integer ): LongBool; stdcall; external ‘SIDGenerator.dll’;
function GetRandomSID( Buffer: PChar; var BufSize : integer ): LongBool; stdcall; external ‘SIDGenerator.dll’;
In Python I call it with this code and it works beautifully:
# Get Retail Pro SID using dll
from ctypes import windll, create_string_buffer, c_int, byref
# os.chdir("c:\\Users\\irving\\Documents\\gitHub\\POImport")
# print(os.getcwd())
# getSID is a Retail Pro dll use to generate SIDs
getSID = windll.SIDGenerator64
randomSID = getSID.GetRandomSID
aluSID = getSID.GetSIDFromALU
upcSID = getSID.GetSIDFromUPC
# Set this by hand now, later set it interactively or by parameter
subsidiary = "1"
def getRandomSID():
""" Genera un SID aleatorio """
# Generate a new random SID
newSID = create_string_buffer(str.encode("12345678901234567890"))
size = c_int(len(newSID))
randomSID(newSID, byref(size))
return newSID.value
def getALUSID(alu):
""" Genera un SID basado en ALU """
# Generate a new ALU base SID
ALU = create_string_buffer(str.encode(alu))
newSID = create_string_buffer(str.encode("12345678901234567890"))
size = c_int(len(newSID))
aluSID(ALU, newSID, byref(size))
return newSID.value
def getUPCSID(upc):
""" Genera un SID basado en UPC """
# Generate a new UPC based SID
UPC = create_string_buffer(str.encode(upc))
newSID = create_string_buffer(str.encode("12345678901234567890"))
size = c_int(len(newSID))
upcSID(UPC, newSID, byref(size))
return newSID.value

Answer 1

You are passing the pointer to the slice, instead of a pointer to the backing array of the slice.
With your windows.Call code it should be.
ret, _, callErr := getRandomSID.Call(uintptr(unsafe.Pointer(&Buffer[0])),
uintptr(unsafe.Pointer(&BufSize)))
Or your syscall.Syscall version, where its a pointer to the slice.
ret, _, callErr := syscall.Syscall(uintptr(getRandomSID),
nargs, 0,
uintptr(unsafe.Pointer(&(*Buffer)[0])),
uintptr(unsafe.Pointer(BufSize)),
)