AsyncAdd3ImplicitExample

此示例演示如何使用 WsAsyncExecute 实现复杂的异步函数。

该示例实现异步函数“AddThree”，该函数通过构建现有的 Add 函数（可异步添加两个整数）将三个整数相加。

AsyncAdd3Implicit.cpp

//------------------------------------------------------------
// Copyright (C) Microsoft.  All rights reserved.
//------------------------------------------------------------

#ifndef UNICODE
#define UNICODE
#endif

#include <windows.h>
#include <stdio.h>
#include <WebServices.h>

#pragma comment(lib, "WebServices.lib")

// Worker function that adds two numbers
HRESULT DoAdd(int a, int b, int* result, WS_ERROR* error)
{
    HRESULT hr;
    static const WS_STRING errorString = WS_STRING_VALUE(L"Negative numbers are not supported.");

    // To illustrate error handling, we won't support negative numbers
    if (a < 0 || b < 0)
    {
        // Add error information to error object  
        if (error != NULL)
        {
            WsAddErrorString(error, &errorString);
        }

        hr = E_NOTIMPL;
    }
    else
    {
        *result = a + b;
        hr = NOERROR;
    }

    return hr;
}

// A struct to maintain the in/out parameters to the Add function
struct AddParameters
{
    int a;
    int b;
    int* sumPointer;
    WS_ERROR* error;
    WS_ASYNC_CONTEXT asyncContext;
};

// A thread function that adds two numbers
DWORD WINAPI AdderThread(void* threadParameter)
{
    // Get the parameters for Add which were passed in CreateThread
    AddParameters* addParameters = (AddParameters*)threadParameter;

    // Do the addition
    HRESULT hr = DoAdd(
        addParameters->a, 
        addParameters->b, 
        addParameters->sumPointer, 
        addParameters->error);

    // Make a copy of the async context
    WS_ASYNC_CONTEXT asyncContext = addParameters->asyncContext;

    // Free the parameters
    HeapFree(GetProcessHeap(), 0, addParameters);

    // Notify the caller that the async operation is complete
    // Since we have a dedicated thread for the callback, we can invoke long
    (asyncContext.callback)(hr, WS_LONG_CALLBACK, asyncContext.callbackState);

    return 1;
}

// An example of a function that can be called asynchronously
HRESULT Add(int a, int b, int* sumPointer, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error)
{
    if (asyncContext == NULL)
    {
        // Invoked synchronously, so do the addition on calling thread
        return DoAdd(a, b, sumPointer, error);
    }
    else
    {
        // Invoked asynchronously

        // Decide whether to complete synchronously or asynchronously
        if (b == 0)
        {
            // Complete synchronously.  We have this case just as an illustration
            // that synchronous completion is possible when invoked asynchronously.
            return DoAdd(a, b, sumPointer, error);
        }
        else
        {
            // Complete asynchronously

            // Alloc space for in/out parameters
            AddParameters* addParameters;
            addParameters = (AddParameters*)HeapAlloc(GetProcessHeap(), 0, sizeof(AddParameters));
            if (addParameters == NULL)
            {
                return E_OUTOFMEMORY;
            }

            // Make a copy of in/out parameters
            addParameters->a = a;
            addParameters->b = b;
            addParameters->sumPointer = sumPointer;
            addParameters->error = error;
            addParameters->asyncContext = *asyncContext;

            // Create a thread which will do the work, passing parameters
            HANDLE threadHandle = CreateThread(NULL, 0, AdderThread, addParameters, 0, NULL);
            if (threadHandle == NULL)
            {
                // Free the parameters
                HeapFree(GetProcessHeap(), 0, addParameters);
                return HRESULT_FROM_WIN32(GetLastError());
            }

            // Close returned thread handle
            CloseHandle(threadHandle);

            // Indicate asynchronous completion
            return WS_S_ASYNC;
        }
    }
}

// Caller allocated state for use by AddThree.  In c++, this might be a class and
// the caller would be unaware of the internal details.
struct ADD_STATE
{
    WS_ASYNC_STATE asyncState;
    int a;
    int b;
    int c;
    int sum;
    int* result;
};

HRESULT CALLBACK Add1(HRESULT hr, WS_CALLBACK_MODEL callbackModel, void* state, WS_ASYNC_OPERATION* next, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error);

HRESULT CALLBACK Add2(HRESULT hr, WS_CALLBACK_MODEL callbackModel, void* state, WS_ASYNC_OPERATION* next, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error);

HRESULT CALLBACK Add3(HRESULT hr, WS_CALLBACK_MODEL callbackModel, void* state, WS_ASYNC_OPERATION* next, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error);

HRESULT CALLBACK Add1(HRESULT hr, WS_CALLBACK_MODEL callbackModel, void* state, WS_ASYNC_OPERATION* next, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error)
{
    UNREFERENCED_PARAMETER(callbackModel);

    ADD_STATE* addState = (ADD_STATE*)state;
    if (FAILED(hr))
    {
        return hr;
    }
    // Set up the next function execute after Add completes
    next->function = Add2;
    return Add(addState->a, addState->b, &addState->sum, asyncContext, error);
}

HRESULT CALLBACK Add2(HRESULT hr, WS_CALLBACK_MODEL callbackModel, void* state, WS_ASYNC_OPERATION* next, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error)
{
    UNREFERENCED_PARAMETER(callbackModel);

    ADD_STATE* addState = (ADD_STATE*)state;
    if (FAILED(hr))
    {
        return hr;
    }
    // Set up the next function execute after Add completes
    next->function = Add3;
    return Add(addState->sum, addState->c, &addState->sum, asyncContext, error);
}

HRESULT CALLBACK Add3(HRESULT hr, WS_CALLBACK_MODEL callbackModel, void* state, WS_ASYNC_OPERATION* next, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error)
{
    UNREFERENCED_PARAMETER(callbackModel);
    UNREFERENCED_PARAMETER(next);
    UNREFERENCED_PARAMETER(asyncContext);
    UNREFERENCED_PARAMETER(error);

    ADD_STATE* addState = (ADD_STATE*)state;
    if (FAILED(hr))
    {
        return hr;
    }
    // The operation succeeded, set the out parameter
    *addState->result = addState->sum;
    // No more functions to execute, so don't set next->function, and WsAsyncExecute will terminate.
    return NOERROR;
}

HRESULT CALLBACK AddThree(ADD_STATE* addState, int a, int b, int c, int* result, const WS_ASYNC_CONTEXT* asyncContext, WS_ERROR* error)
{
    // Set up the state for the operation
    addState->a = a;
    addState->b = b;
    addState->c = c;
    addState->sum = 0;
    addState->result = result;
    // Start the operation at Add1
    return WsAsyncExecute(&addState->asyncState, Add1, WS_SHORT_CALLBACK, addState, asyncContext, error);
}

void CALLBACK AddThreeComplete(HRESULT hr, WS_CALLBACK_MODEL callbackModel, void* state)
{
    UNREFERENCED_PARAMETER(hr);
    UNREFERENCED_PARAMETER(callbackModel);

    HANDLE handle = (HANDLE)state;
    SetEvent(handle);
}

// Main entry point
int __cdecl wmain(int argc, __in_ecount(argc) wchar_t **argv)
{
    UNREFERENCED_PARAMETER(argc);
    UNREFERENCED_PARAMETER(argv);
    
    HRESULT hr = NOERROR;
    
    // Some numbers to add asynchronously
    // Add has the behavior that if the second parameter is 0, it will perform synchronously
    int ints[] = 
    { 
        1, 0, 0, // First add sync,  second add sync
        2, 1, 0, // First add async, second add sync
        3, 0, 2, // First add sync,  second add async
        4, 3, 2, // First add async, second add async
    };
    
    // Set up the event that will get signaled each time AddThree is complete
    HANDLE handle = CreateEvent(NULL, FALSE, FALSE, NULL);
    if (handle == NULL)
    {
        goto Exit;
    }
    
    // Set up the callback to use when performing the addition asynchronously
    WS_ASYNC_CONTEXT addThreeComplete;
    addThreeComplete.callback = AddThreeComplete;
    addThreeComplete.callbackState = handle;
    
    // Declare private data for AddThree
    ADD_STATE addState;
    
    // Perform the additions synchronously and asynchronously
    for (ULONG loop = 0; loop < 2; loop++)
    {
        // Add sets of integers that will cause different execution behavior when added asynchronously
        for (ULONG i = 0; i < sizeof(ints) / sizeof(int); i += 3)
        {
            wprintf(L"Adding %d,%d,%d %s...\n", ints[i], ints[i + 1], ints[i + 2], (loop == 0 ? L"synchronously" : L"asynchronously"));
    
            // Set up how the function will be called
            WS_ASYNC_CONTEXT* asyncContext;
            if (loop == 0)
            {
                // Perform the addition synchronously
                asyncContext = NULL;
            }
            else
            {
                // Perform the addition asynchronously
                asyncContext = &addThreeComplete;
            }
    
            // Perform the addition
            int sum;
            hr = AddThree(&addState, ints[i], ints[i + 1], ints[i + 2], &sum, asyncContext, NULL);
    
            if (hr == WS_S_ASYNC)
            {
                // If the operation is being performed asynchronously, then wait for it to complete
                WaitForSingleObject(handle, INFINITE);
            }
            if (SUCCEEDED(hr))
            {
                wprintf(L"Result: %d\n", sum);
            }
            else
            {
                wprintf(L"AddThree failed.\n");
            }
        }
    }
    Exit:
    if (handle != NULL)
    {
        CloseHandle(handle);
    }
    fflush(stdout);
    return SUCCEEDED(hr) ? 0 : -1;
}