c# - 将指针传递给 Go DLL Syscall 中的指针
问题描述
如果我有以下 C#DllImport
正在导入非 C# DLL,并且我想将它移植到 Go,我将如何去做?
[DllImport("my.dll", EntryPoint = "Greet", CallingConvention = CallingConvention.Cdecl)]
public static extern int Greet(IntPtr name, ref IntPtr greetings);
我在弄清楚如何将指针传递给greetings
参数所需的指针时遇到了问题(我假设因为类型是ref IntPtr
,所以我对 C# 一点也不熟悉)。dll 函数将填充我提供的指针指向的内存,我将在后续的系统调用中使用它。这是我到目前为止所得到的,
package main
import (
"fmt"
"syscall"
"unsafe"
)
var (
MyDll = syscall.MustLoadDLL("my.dll")
greet = MyDll.MustFindProc("Greet")
)
func Greet(name string) error {
nameP, err := syscall.UTF16PtrFromString(name)
if err != nil {
return err
}
// I need to provide a pointer to a pointer for greetings. How can I allocate some memory here
// then pass a pointer to its pointer? I tried this: create a handle with a zero-value, then
// take a pointer to it, then pass a pointer to the pointer as the second parameter to Call but
// the pointer becomes nil after the Call.
handle := syscall.Handle(0)
handleP := &handle
r1, _, _ := greet.Call(uintptr(unsafe.Pointer(nameP)), uintptr(unsafe.Pointer(&handleP)))
if r1 == 0 {
return fmt.Errorf("there was an error")
}
return nil
}
我愿意接受任何和所有建议,包括可能帮助我更好地掌握这个系统调用和不安全的东西的链接和资源。谢谢!
解决方案
首先,如果您能展示如何使用 C#Greet
方法,将会有所帮助。孤立的方法很难理解,尤其是当参数等效时,void **
这意味着任何东西都可以进入。
TL;DR
ref IntPtr
可能只是**struct{}
您不必分配任何结构的地方。该库将为您简单地管理内存。您只需给它一个指向“*MyStruct”的指针,这样它就可以将您的“*MyStruct”更改为实际指向内部资源。
REF
C#关键字在docsref
中有很好的解释。基本上它允许任何类型的引用传递。C# 中的以下声明
void Increment(ref value) { ... }
int counter = 10;
Increment(ref counter);
// counter is now 11
Increment(counter); // won't compile must be passed with 'ref'
Increment(null); // won't compile
相当于 C++
void Increment(int& value) { ... }
int counter;
Increment(counter);
// counter is now 11
Increment(null); // won't compile
不应为空的引用。
IntPtr
IntPtr
通常用于表示指针并允许本机程序和 CLR (C#) 程序之间的互操作。
如果 C 程序具有以下签名
void Increment(int* value);
C# 程序可以通过以下几种方式之一调用它
[DllImport("example.dll")]
static unsafe extern void Increment(int* value); // this way allows null to be passed in
unsafe {
int counter = 10;
Increment(&10);
}
,
[DllImport("example.dll")]
static extern void Increment(ref int value);
int counter = 10;
Increment(ref counter);
如果 C 程序具有以下签名
void AllocateStruct(struct MyStruct** ppStruct);
void IncrementStruct(struct MyStruct* pStruct);
然后
[DllImport("example.dll")]
static extern void AllocateStruct(ref IntPtr ppStruct);
// static unsafe extern void AllocateStruct(MyStruct** ppStruct)
[DllImport("example.dll")]
static extern void IncrementStruct(IntPtr pStruct);
// static unsafe extern void IncrementStruct(MyStruct* pStruct);
IntPtr pMyStruct;
AllocateStruct(ref pMyStruct);
IncrementStruct(pMyStruct);
// Free My Struct
// If you need to get inside the struct then
// MyStruct myStruct = Marshal.StructureToPtr<MyStruct>(pMyStruct)
// Often you don't (need to) or (should not) manipulate the struct directly so keeping it as IntPtr is perfectly acceptable.
从上面的示例中,您可以看到MyStruct
更多的是令牌/引用而不是其他任何东西。ref IntPtr
允许您传递对位置的引用,在库代表您分配令牌/引用后,您将使用该位置存储令牌/引用。然后所有其他方法通常只会使用引用IntPtr
对其执行后续操作。基本上没有类的面向对象编程。
“真实”生活示例ref IntPtr
它有点快速和肮脏,错误处理还有很多不足之处。它显示了调用相同
和Win32 库函数的C
,C#
和版本。Go
GetSecurityInfo
LookupAccountSid
我能找到的唯一真正用例ref IntPtr
是type**
/void**
以便库可以为您分配内存或为您提供指向它已经分配的内存的指针。
C
#include <stdio.h>
#include <windows.h>
#include <tchar.h>
#include "accctrl.h"
#include "aclapi.h"
#pragma comment(lib, "advapi32.lib")
int _tmain(int argc, _TCHAR* argv[])
{
// --- get the executing program's file path and handle -----
LPTSTR executablePath = argv[0];
_tprintf(TEXT("Opening File %s\n"), executablePath);
HANDLE hFile = CreateFile(
executablePath,
GENERIC_READ,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
if (hFile == INVALID_HANDLE_VALUE) return EXIT_FAILURE;
// -------------------------------------------------
// --------- Get the owner SID of the file ---------
PSID pSidOwner = NULL;
PSECURITY_DESCRIPTOR pSD = NULL;
DWORD dwRtnCode = GetSecurityInfo(
hFile,
SE_FILE_OBJECT,
OWNER_SECURITY_INFORMATION,
&pSidOwner,
NULL,
NULL,
NULL,
&pSD);
if (dwRtnCode != ERROR_SUCCESS) return EXIT_FAILURE;
// -------------------------------------------------
// -------
TCHAR AcctName[MAX_PATH];
DWORD dwAcctName = MAX_PATH;
TCHAR DomainName[MAX_PATH];
DWORD dwDomainName = MAX_PATH;
SID_NAME_USE eUse = SidTypeUnknown;
BOOL bRtnBool = LookupAccountSid(
NULL, // local computer
pSidOwner,
&AcctName,
&dwAcctName,
DomainName,
&dwDomainName,
&eUse);
if (bRtnBool == FALSE) return EXIT_FAILURE;
_tprintf(TEXT("Account Owner = %s\n"), AcctName);
_tprintf(TEXT("Account Owner's Domain = %s\n"), DomainName);
return 0;
}
C#
using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
public class Example
{
[DllImport("advapi32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
static extern uint GetSecurityInfo(
IntPtr handle,
uint ObjectType,
uint SecurityInfo,
ref IntPtr ppsidOwner, // <-- HERE
IntPtr ppsidGroup, // bit hacky (in safe C# you must "pass a reference" in C you can pass a pointer to a pointer or null)
IntPtr ppDacl,
IntPtr ppSacl,
ref IntPtr ppSecurityDescriptor // <-- HERE
);
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern bool LookupAccountSid(
string lpSystemName,
IntPtr Sid,
StringBuilder lpName,
ref uint cchName,
StringBuilder ReferencedDomainName,
ref uint cchReferencedDomainName,
out uint peUse);
const uint ERROR_SUCCESS = 0;
const uint OWNER_SECURITY_INFORMATION = 0x00000001;
const uint SE_FILE_OBJECT = 1;
public static void Main()
{
// get the executing program's file path and handle
string executablePath = Environment.GetCommandLineArgs().GetValue(0).ToString();
IntPtr hFile = File.Open(executablePath, FileMode.Open, FileAccess.Read, FileShare.Read)
.SafeFileHandle.DangerousGetHandle();
IntPtr pSidOwner = IntPtr.Zero; // some internal struct you shouldn't allocate or modify (acts like a token)
IntPtr pSD = IntPtr.Zero; // some internal struct you shouldn't allocate or modify (acts like a token)
// vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
uint dwRtnCode = GetSecurityInfo(
hFile,
SE_FILE_OBJECT,
OWNER_SECURITY_INFORMATION,
ref pSidOwner, // <-- HERE
IntPtr.Zero,
IntPtr.Zero,
IntPtr.Zero,
ref pSD // <-- HERE
);
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
if (dwRtnCode != ERROR_SUCCESS) throw new InvalidOperationException("GetSecurityInfo Failed");
StringBuilder name = new StringBuilder(50);
uint cchName = (uint)name.Capacity;
StringBuilder domainName = new StringBuilder(50);
uint cchDomainName = (uint)domainName.Capacity;
uint sidUse;
LookupAccountSid(
null,
pSidOwner,
name,
ref cchName,
domainName,
ref cchDomainName,
out sidUse);
Console.WriteLine("Account Owner = {0}", name);
Console.WriteLine("Account Owner's Domain = {0}", domainName);
// PLEASE FREE pSD once done
}
}
去
我写过的第二个围棋程序,所以可能有一些明显的错误(除了缺乏错误检查)
package main
import (
"fmt"
"syscall"
"unsafe"
"os"
)
var (
advapi32, _ = syscall.LoadLibrary("advapi32.dll")
kernel32, _ = syscall.LoadLibrary("kernel32.dll")
createFileW, _ = syscall.GetProcAddress(kernel32, "CreateFileW")
getSecurityInfo, _ = syscall.GetProcAddress(advapi32, "GetSecurityInfo")
lookupAccountSidW, _ = syscall.GetProcAddress(advapi32, "LookupAccountSidW")
)
type SE_OBJECT_TYPE uint32
const (SE_FILE_OBJECT = 1)
type SECURITY_INFORMATION uint32
const (OWNER_SECURITY_INFORMATION = 0x00000001)
const (
GENERIC_READ = 0x80000000
FILE_SHARE_READ = 0x00000001
OPEN_EXISTING = 0x00000003
FILE_ATTRIBUTE_NORMAL = 0x00000080
)
type Handle uintptr
func CreateFile(
name string,
access uint32,
mode uint32,
sa *uint, // *SecurityAttributes,
createmode uint32,
attrs uint32,
templatefile *uint,
) (handle Handle, err error) {
utf16name, _ := syscall.UTF16PtrFromString(name)
r0, _, _ := syscall.Syscall9(
uintptr(createFileW), 7,
uintptr(unsafe.Pointer(utf16name)),
uintptr(access),
uintptr(mode),
uintptr(unsafe.Pointer(sa)),
uintptr(createmode),
uintptr(attrs),
uintptr(unsafe.Pointer(templatefile)),
0, 0)
handle = Handle(r0)
return
}
func GetSecurityInfo(
handle Handle,
objectType SE_OBJECT_TYPE,
securityInformation SECURITY_INFORMATION,
owner **struct{},
group **struct{},
dacl **struct{},
sacl **struct{},
sd **struct{}, //**SECURITY_DESCRIPTOR,
) (ret error) {
r0, _, _ := syscall.Syscall9(
uintptr(getSecurityInfo), 8,
uintptr(handle),
uintptr(objectType),
uintptr(securityInformation),
uintptr(unsafe.Pointer(owner)),
uintptr(unsafe.Pointer(group)),
uintptr(unsafe.Pointer(dacl)),
uintptr(unsafe.Pointer(sacl)),
uintptr(unsafe.Pointer(sd)),
0)
if r0 != 0 {
ret = syscall.Errno(r0)
}
return
}
func LookupAccountSid(
systemName *uint16,
sid *struct{}, // *SID,
name *uint16,
nameLen *uint32,
refdDomainName *uint16,
refdDomainNameLen *uint32,
use *uint32,
) (err error) {
r, _, e := syscall.Syscall9(
uintptr(lookupAccountSidW), 7,
uintptr(unsafe.Pointer(systemName)),
uintptr(unsafe.Pointer(sid)),
uintptr(unsafe.Pointer(name)),
uintptr(unsafe.Pointer(nameLen)),
uintptr(unsafe.Pointer(refdDomainName)),
uintptr(unsafe.Pointer(refdDomainNameLen)),
uintptr(unsafe.Pointer(use)),
0, 0)
if r == 0 {
err = e
}
return
}
func main() {
defer syscall.FreeLibrary(advapi32)
defer syscall.FreeLibrary(kernel32)
// get the executing program's file path and handle
var hFile, _ = CreateFile(os.Args[0], GENERIC_READ, FILE_SHARE_READ, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nil);
// defer LocalFree(Handle(unsafe.Pointer(pSD))) // PLEASE FREE pSD once done
// vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
var pSD *struct{} //*SECURITY_DESCRIPTOR
var pSidOwner *struct{}
GetSecurityInfo(hFile, SE_FILE_OBJECT, OWNER_SECURITY_INFORMATION, &pSidOwner, nil, nil, nil, &pSD)
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
nameLen := uint32(50)
name := make([]uint16, nameLen)
domainLen := uint32(50)
domainName := make([]uint16, domainLen)
var sidUse uint32
LookupAccountSid(nil, pSidOwner, &name[0], &nameLen, &domainName[0], &domainLen, &sidUse)
var n = syscall.UTF16ToString(name)
var dn = syscall.UTF16ToString(domainName)
fmt.Printf("Account Owner = %s\n", n)
fmt.Printf("Account Owner's Domain = %s\n", dn)
}
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