为 ELS 服务提供回调

如果应用程序使用异步操作进行文本识别，则必须提供一个回调函数供 ELS 服务使用。 回调函数基于 MappingCallbackProc 原型。

请求文本识别主题介绍了应用程序如何从 ELS 服务请求异步文本识别。 以下示例演示对 MappingRecognizeText 进行异步调用的应用程序。 用于文本识别的回调函数称为 RecognizeCallback。 请注意，应用程序必须确保属性包、输入文本、选项和服务在回调函数完成执行之前都有效。 此外，应用程序必须确保在回调函数使用包后立即调用 MappingFreePropertyBag 。

注意

应用程序在完成处理或复制资源后，最好使用回调函数释放资源。

 

#include <windows.h>
#include <stdio.h>
#include <elscore.h>
#include <elssrvc.h>

#define USER_TEXT ( \
    L"Skip This is a simple sentence. " \
    L"\x0422\x0445\x0438\x0441 \x0438\x0441 \x0415\x043d\x0433\x043b\x0438\x0441\x0445.")
#define USER_TEXT_SKIP (5)

int __cdecl main();
HRESULT CallMappingRecognizeText(PMAPPING_SERVICE_INFO pService);
void RecognizeCallback(
     PMAPPING_PROPERTY_BAG pBag, 
     LPVOID data, DWORD dwDataSize, 
     HRESULT Result); 

int __cdecl main()
{
    MAPPING_ENUM_OPTIONS    EnumOptions;
    PMAPPING_SERVICE_INFO   prgServices = NULL;
    DWORD                   dwServicesCount = 0;
    HRESULT                 hResult;

    ZeroMemory(&EnumOptions, sizeof (MAPPING_ENUM_OPTIONS));
    EnumOptions.Size = sizeof (MAPPING_ENUM_OPTIONS);
    // Using the Language Auto-Detection GUID to enumerate LAD only:
    EnumOptions.pGuid = (GUID *)&ELS_GUID_LANGUAGE_DETECTION;
    hResult = MappingGetServices(&EnumOptions, &prgServices, &dwServicesCount);

    if (SUCCEEDED(hResult))
    {
        hResult = CallMappingRecognizeText(&prgServices[0]);
        if (SUCCEEDED(hResult))
        {
            printf("Calling the service %ws has succeeded!\n",
                prgServices[0].pszDescription);
        }
        else
        {
            printf("Calling the service %ws has failed, failure = 0x%x!\n",
                prgServices[0].pszDescription, hResult);
        }
        MappingFreeServices(prgServices);
    }

    return 0;
}

HRESULT CallMappingRecognizeText(PMAPPING_SERVICE_INFO pService)
{
    MAPPING_PROPERTY_BAG    bag;
    MAPPING_OPTIONS         Options;
    HRESULT                 hResult;
    HANDLE                  SyncEvent;
    DWORD                   dwWaitResult;

    SyncEvent = CreateEvent(NULL, FALSE, FALSE, NULL);

    if (SyncEvent == NULL)
    {
        hResult = E_FAIL;
    }
    else
    {
        ZeroMemory(&bag, sizeof (MAPPING_PROPERTY_BAG));
        bag.Size = sizeof (MAPPING_PROPERTY_BAG);

        ZeroMemory(&Options, sizeof (MAPPING_OPTIONS));
        Options.Size = sizeof (MAPPING_OPTIONS);
        Options.pfnRecognizeCallback = (PFN_MAPPINGCALLBACKPROC)RecognizeCallback;
        Options.pRecognizeCallerData = &SyncEvent;
        Options.dwRecognizeCallerDataSize = sizeof (HANDLE);

        // MappingRecognizeText's dwIndex parameter specifies the first
        // index inside the text from where the recognition should start.
        // We pass USER_TEXT_SKIP, thus skipping the "Skip " part
        // of the input string.
        hResult = MappingRecognizeText(pService, USER_TEXT, wcslen(USER_TEXT), USER_TEXT_SKIP, &Options, &bag);
        if (SUCCEEDED(hResult))
        {
            // We are using an event to synchronize our waiting for the call to end,
            // because some objects have to be valid till the end of the callback call:
            // - the input text
            // - the property bag
            // - the options
            // - the service
            dwWaitResult = WaitForSingleObject(SyncEvent, INFINITE);
            if (dwWaitResult != WAIT_OBJECT_0)
            {
                hResult = E_FAIL;
            }
        }
        CloseHandle(SyncEvent);
    }
    return hResult;
}

void RecognizeCallback(PMAPPING_PROPERTY_BAG pBag, LPVOID data, DWORD dwDataSize, HRESULT Result)
{
    HANDLE SyncEvent;
    WCHAR * p;

    UNREFERENCED_PARAMETER(dwDataSize);

    if (SUCCEEDED(Result))
    {
        for (p = (WCHAR *)pBag->prgResultRanges[0].pData; *p; p += wcslen(p) + 1)
        {
            printf("%ws\n", p);
        }
        MappingFreePropertyBag(pBag);
    }

    SyncEvent = *((HANDLE *)data);
    SetEvent(SyncEvent);
} 

相关主题

使用扩展语言服务

请求文本识别

MappingCallbackProc

MappingFreePropertyBag

MappingRecognizeText