Windows Embedded Compact。
看起来写入工作正常,但读取给出了错误的参数错误。
任何想法缺少什么?
我不确定创建队列功能。它说必须两次调用它才能获得读或写句柄-是吗?
int main()
{
MSGQUEUEOPTIONS options = {0};
options.dwSize = sizeof(options); //
options.dwFlags = MSGQUEUE_NOPRECOMMIT;
options.dwMaxMessages = 10000; // msg max for queue
options.cbMaxMessage = 50; // max number of bytes in each msg
options.bReadAccess = TRUE; // read
HANDLE hRead = CreateMsgQueue(LPCWSTR("MSG_QUEUE"), &options);
if ( hRead == NULL )
{
printf("CreateMsgQueue hRead failed! Err code: %d\n", GetLastError());
}
// Thread A will read msg queue
HANDLE hTg = CreateThread(NULL, 0, threadA, hRead, 0, 0);
if ( NULL == hTg )
{
printf("CreateThread failed - A!\n");
return 1;
}
Sleep(1000); //give time before sending msg
options.bReadAccess = FALSE; // write to
HANDLE hWrte = CreateMsgQueue(LPCWSTR("MSG_QUEUE"), &options);
if ( hWrte == NULL )
{
printf("CreateMsgQueue hWrte failed! Err code: %d\n", GetLastError());
}
// Thread B write to queue
HANDLE hTt = CreateThread(NULL, 0, threadB, hWrte, 0, 0);
if ( NULL == hTt )
{
printf("CreateThread failed - B!\n");
return 1;
}
// quit on <ENTER> key
getchar();
}
DWORD WINAPI threadB(LPVOID lpParameter)
{
HANDLE msgH = HANDLE(lpParameter);
if ( msgH == NULL)
{
printf("Null handle in write!\n");
}
char message[10] = "ABCDEFGHI";
printf("Size of message sent: %d bytes\n", sizeof(message));
// know that a queue is not full and that it's safe to write
WaitForSingleObject(msgH, INFINITE);
BOOL ret = WriteMsgQueue(
msgH,
&message,
sizeof(message),
INFINITE,
NULL);
if ( ret == FALSE )
{
printf("WriteMsgQueue failed! Err code: %d\n", GetLastError());
}
return 0;
}
DWORD WINAPI threadA(LPVOID lpParameter)
{
HANDLE hQ = HANDLE(lpParameter);
if ( hQ == NULL )
{
printf("null handle in read!\n");
}
char readIn[50] = {0};
LPDWORD numRead = 0;
//DWORD flag;
// need to wait on sinfle object
WaitForSingleObject(hQ, INFINITE);
BOOL ret = ReadMsgQueue(
hQ,
&readIn,
DWORD(sizeof(readIn)),
numRead,
INFINITE,
NULL
);
if ( ret == FALSE )
{
printf(" ReadMsgQueue failed! Err code: %d\n", GetLastError());
}
printf("Size received: %d\n", numRead);
printf("Msg Received: %s\n", readIn);
return 0;
}
编辑
这是@WhozCraig之后的有效读取功能,如果有人需要此功能,则会发现另一个问题:
DWORD WINAPI threadA(LPVOID lpParameter)
{
HANDLE hQ = HANDLE(lpParameter);
if ( hQ == NULL )
{
printf("null handle in read!\n");
}
char readIn[50] = {0};
DWORD numRead = 0;
DWORD flag;
// need to wait on sinfle object
WaitForSingleObject(hQ, INFINITE);
BOOL ret = ReadMsgQueue(
hQ,
&readIn,
sizeof(readIn),
&numRead,
INFINITE,
&flag
);
if ( ret == FALSE )
{
printf(" ReadMsgQueue failed! Err code: %d\n", GetLastError());
}
printf("Size received: %d\n", numRead);
printf("Msg Received: %s\n", readIn);
return 0;
}
是的,这就是您设置发送/接收消息队列的方式。通常使用两个打开。
我相信您ReadMsgQueue()
调用的问题是接收大小参数。它是一个LPDWORD,并且不能为NULL。您当前正在执行此操作:
char readIn[50] = {0};
LPDWORD numRead = 0; // SHOULD NOT BE A POINTER
// need to wait on sinfle object
WaitForSingleObject(hQ, INFINITE);
BOOL ret = ReadMsgQueue(
hQ,
&readIn,
DWORD(sizeof(readIn)),
numRead, // THIS IS A PROBLEM
INFINITE,
NULL
);
您正在传递NULL。您需要这样做:
char readIn[50] = {0};
DWORD numRead = 0; // NOTE: regular DWORD
// need to wait on sinfle object
WaitForSingleObject(hQ, INFINITE);
BOOL ret = ReadMsgQueue(
hQ,
&readIn,
DWORD(sizeof(readIn)),
&numRead, // NOTE: address of DWORD
INFINITE,
NULL
);
我不清楚最后一个参数(接收到的消息标志超出参数)是否可以为NULL。在文档中并没有像在This parameter cannot be NULL
其他参数中明确指出的那样,像读取大小的DWORD地址那样专门调用它。因此,您的里程可能会有所不同。
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