如何通过interop将delphi记录正确传递给C结构?

我终于想出了一个解决方案,它可以避免所有的alloc/freehglobal,但是如果这真的是关于垃圾收集器的bulletproff,那就另当别论了。

解决方案是首先用fillchar清除tcustomer结构,然后使用move过程复制数据。

Delphi记录如下:

  TCustomer = packed record
    CustomerNo: Integer;
    FirstName: array [1..50] of Char;
    LastName: array [1..50] of Char;
  end;

然后我用一个过程将字符串复制到结构中:

procedure StrToBuf(Str: String; var buf);
begin
  Move(Pointer(str)^, buf, Length(str));
end;

在这样的过程中:

procedure LoadCustomerFromQuery(var Query: TQuery; var Customer: TCustomer); stdcall;
begin

  FillChar(Customer, SizeOf(Customer), 0);

  StrToBuf(Query.FieldByName('FNAVN').AsString, Customer.FirstName);
  StrToBuf(Query.FieldByName('ENAVN').AsString, Customer.LastName);

  Customer.CustomerNo := Query.FieldByName('KUNDENR').AsInteger;

end;

最后,C结构看起来是这样的:

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi, Pack=1)]
public struct TCustomer
{
    public Int32 CustomerNo;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
    public string FirstName;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
    public string LastName;
}

extern static void GetCustomer(Int32 CustomerNo, IntPtr CustomerInfo);
...
var info = default(CUSTOMER_INFO);
var ptr = Marshal.AllocHGlobal(Marshal.SizeOf(info));
Marshal.StructureToPtr(info, ptr, false);
GetCustomer(n, ptr);
Marshal.PtrToStructure(ptr, info);
Marshal.FreeHGlobal(ptr);