为事件添加书签

项目
06/13/2023

书签标识通道或日志文件中的事件。查询或订阅事件时，可以使用书签开始从该已添加书签的事件中读取事件。通常，创建结果集中最后一个事件的书签 (假定已枚举结果集中的所有事件) 。

以下过程介绍如何从事件创建书签。

从事件创建书签

调用 EvtCreateBookmark 函数以创建书签。为参数传递 NULL 。
调用 EvtUpdateBookmark 函数以使用事件更新书签。将句柄作为参数传递给事件。
调用 EvtRender 函数以创建表示书签的 XML 字符串。将 EvtRenderBookmark 作为呈现标志传递。
保留 XML 字符串以供以后使用 (例如，可以将 XML 字符串保存在文件或注册表) 中。

以下过程介绍如何使用在上一过程中保留的 XML 书签字符串创建书签。

使用 XML 书签字符串创建书签

获取表示之前保留的书签的 XML 字符串。
调用 EvtCreateBookmark 函数以创建书签。传递参数的 XML 字符串。

以下过程介绍如何在查询中使用书签。

在查询中使用书签

调用 EvtQuery 函数以获取与查询匹配的事件。
调用 EvtSeek 函数以查找带书签的事件。将句柄传递给书签和 EvtSeekRelativeToBookmark 标志。
在循环中调用 EvtNext 函数，根据在 EvtSeek) 中指定的偏移量，枚举书签事件 (之后开始的事件。

有关示例，请参阅在查询中使用书签。

以下过程介绍如何在订阅中使用书签。

在订阅中使用书签

调用 EvtSubscribe 函数以订阅与查询匹配的事件。将句柄传递给书签和 EvtSubscribeStartAfterBookmark 标志。
如果实现了 EVT_SUBSCRIBE_CALLBACK 函数，回调将接收在带书签的事件之后开始的事件。
如果未实现回调，请在循环中调用 EvtNext 函数以枚举在书签事件之后开始的事件。

有关示例，请参阅在订阅中使用书签。

在查询中使用书签

以下示例演示如何在查询中使用书签。该示例扩展了查询事件中的示例。

// Enumerate all the events in the result set beginning with the bookmarked event. 
DWORD PrintResults(EVT_HANDLE hResults)
{
    DWORD status = ERROR_SUCCESS;
    EVT_HANDLE hEvents[ARRAY_SIZE];
    DWORD dwReturned = 0;
    LPWSTR pwsBookmarkXml = NULL;
    EVT_HANDLE hBookmark = NULL;

    // Get the persisted bookmark XML string.
    pwsBookmarkXml = GetBookmarkedString();

    // If the bookmark string was persisted, create a bookmark and
    // seek to the bookmarked event in the result set.
    if (pwsBookmarkXml)
    {
        hBookmark = EvtCreateBookmark(pwsBookmarkXml);
        if (NULL == hBookmark)
        {
            wprintf(L"EvtCreateBookmark failed with %lu\n", GetLastError());
            goto cleanup;
        }

        if (!EvtSeek(hResults, 1, hBookmark, 0, EvtSeekRelativeToBookmark))
        {
            wprintf(L"EvtSeek failed with %lu\n", GetLastError());
            goto cleanup;
        }
    }

    // Enumerate the events in the result set after the bookmarked event.
    while (true)
    {
        if (!EvtNext(hResults, ARRAY_SIZE, hEvents, INFINITE, 0, &dwReturned))
        {
            if (ERROR_NO_MORE_ITEMS != (status = GetLastError()))
            {
                wprintf(L"EvtNext failed with %lu\n", status);
            }

            goto cleanup;
        }

        for (DWORD i = 0; i < dwReturned; i++)
        {
            if (status = PrintEvent(hEvents[i]))
            {
                EvtClose(hEvents[i]);
                hEvents[i] = NULL;
            }
            else
            {
                goto cleanup;
            }
        }
    }

cleanup:

    if (ERROR_NO_MORE_ITEMS == status)
    {
        // Get the last event in the result set, use it to create a
        // bookmark, render the bookmark as an XML string, and persist the string.
        if (ERROR_SUCCESS != (status = SaveBookmark(hResults)))
            wprintf(L"\nFailed to save bookmark\n");
    }
    else
    {
        for (DWORD i = 0; i < dwReturned; i++)
        {
            if (NULL != hEvents[i])
                EvtClose(hEvents[i]);
        }
    }

    if (pwsBookmarkXml)
        free(pwsBookmarkXml);

    return status;
}

// Get the bookmark XML string from wherever you persisted it.
LPWSTR GetBookmarkedString(void)
{
    LPWSTR pwsBookmarkXML = NULL;

    // TODO: Add the code to get the bookmark XML string from storage.

    return pwsBookmarkXML;
}


// Persist the bookmark XML string. This example assumes that we've read through
// the result set and are persisting the last event as the bookmark.
DWORD SaveBookmark(EVT_HANDLE hResults)
{
    DWORD status = ERROR_SUCCESS;
    DWORD dwBufferSize = 0;
    DWORD dwBufferUsed = 0;
    DWORD dwPropertyCount = 0;
    DWORD dwReturned = 0;
    LPWSTR pBookmarkXml = NULL;
    EVT_HANDLE hBookmark = NULL;
    EVT_HANDLE hEvent = NULL;

    // Seek to the last event in the result set and get the event.
    if (!EvtSeek(hResults, 0, NULL, 0, EvtSeekRelativeToLast))
    {
        wprintf(L"EvtSeek failed with %lu\n", status = GetLastError());
        goto cleanup;
    }

    if (!EvtNext(hResults, 1, &hEvent, INFINITE, 0, &dwReturned))
    {
        wprintf(L"EvtNext failed with %lu\n", status = GetLastError());
        goto cleanup;
    }

    // Create a bookmark and update it with the last event in the result set.
    hBookmark = EvtCreateBookmark(NULL);
    if (NULL == hBookmark)
    {
        wprintf(L"EvtCreateBookmark failed with %lu\n", GetLastError());
        goto cleanup;
    }

    if (!EvtUpdateBookmark(hBookmark, hEvent))
    {
        wprintf(L"EvtUpdateBookmark failed with %lu\n", GetLastError());
        goto cleanup;
    }

    // Render the bookmark as an XML string that you can then persist.
    if (!EvtRender(NULL, hBookmark, EvtRenderBookmark, dwBufferSize, pBookmarkXml, &dwBufferUsed, &dwPropertyCount))
    {
        if (ERROR_INSUFFICIENT_BUFFER == (status = GetLastError()))
        {
            dwBufferSize = dwBufferUsed;
            pBookmarkXml = (LPWSTR)malloc(dwBufferSize);
            if (pBookmarkXml)
            {
                EvtRender(NULL, hBookmark, EvtRenderBookmark, dwBufferSize, pBookmarkXml, &dwBufferUsed, &dwPropertyCount);
            }
            else
            {
                wprintf(L"malloc failed\n");
                status = ERROR_OUTOFMEMORY;
                goto cleanup;
            }
        }

        if (ERROR_SUCCESS != (status = GetLastError()))
        {
            wprintf(L"EvtRender failed with %d\n", GetLastError());
            goto cleanup;
        }
    }

    // TODO: Add code to persist bookmark XML string.

cleanup:

    if (pBookmarkXml)
        free(pBookmarkXml);

    if (hBookmark)
        EvtClose(hBookmark);

    if (hEvent)
        EvtClose(hEvent);

    return status;
}

在订阅中使用书签

以下示例演示如何在推送订阅中使用书签。

#include <windows.h>
#include <conio.h>
#include <stdio.h>
#include <winevt.h>

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

DWORD WINAPI SubscriptionCallback(EVT_SUBSCRIBE_NOTIFY_ACTION action, PVOID pContext, EVT_HANDLE hEvent);
DWORD PrintEvent(EVT_HANDLE hEvent);
EVT_HANDLE GetBookmark();
DWORD SaveBookmark(EVT_HANDLE hBookmark);


void main(void)
{
    DWORD status = ERROR_SUCCESS;
    EVT_HANDLE hSubscription = NULL;
    EVT_HANDLE hBookmark = NULL;
    LPWSTR pwsPath = L"<channel name goes here>";
    LPWSTR pwsQuery = L"<xpath query goes here>";

    // Get the saved bookmark.
    hBookmark = GetBookmark();

    // Subscribe to existing and furture events beginning with the bookmarked event.
    // If the bookmark has not been persisted, pass an empty bookmark and the subscription
    // will begin with the second event that matches the query criteria.
    hSubscription = EvtSubscribe(NULL, NULL, pwsPath, pwsQuery, hBookmark, (PVOID)hBookmark, 
                                 (EVT_SUBSCRIBE_CALLBACK)SubscriptionCallback, EvtSubscribeStartAfterBookmark);
    if (NULL == hSubscription)
    {
        wprintf(L"EvtSubscribe failed with %lu.\n", GetLastError());
        goto cleanup;
    }

    wprintf(L"Hit any key to quit\n\n");
    while (!_kbhit())
        Sleep(10);

    status = SaveBookmark(hBookmark);

cleanup:

    if (hSubscription)
        EvtClose(hSubscription);

    if (hBookmark)
        EvtClose(hBookmark);
 }


// The callback that receives the events that match the query criteria. Use the 
// context parameter to pass the handle to the bookmark, so you can update the bookmark
// with each event that you receive.
DWORD WINAPI SubscriptionCallback(EVT_SUBSCRIBE_NOTIFY_ACTION action, PVOID pContext, EVT_HANDLE hEvent)
{
    DWORD status = ERROR_SUCCESS;
    EVT_HANDLE hBookmark = (EVT_HANDLE)pContext;

    switch(action)
    {
        // You should only get the EvtSubscribeActionError action if your subscription flags 
        // includes EvtSubscribeStrict and the channel contains missing event records.
        case EvtSubscribeActionError:
            if (ERROR_EVT_QUERY_RESULT_STALE == (DWORD)hEvent)
            {
                wprintf(L"The subscription callback was notified that event records are missing.\n");
                // Handle if this is an issue for your application.
            }
            else
            {
                wprintf(L"The subscription callback received the following Win32 error: %lu\n", (DWORD)hEvent);
            }

            break;

        case EvtSubscribeActionDeliver:
            if (ERROR_SUCCESS != (status = PrintEvent(hEvent)))
            {
                goto cleanup;
            }

            if (!EvtUpdateBookmark(hBookmark, hEvent))
            {
                wprintf(L"EvtUpdateBookmark failed with %lu\n", status = GetLastError());
                goto cleanup;
            }

            break;

        default:
            wprintf(L"SubscriptionCallback: Unknown action.\n");
    }

cleanup:

    if (ERROR_SUCCESS != status)
    {
        // End subscription - Use some kind of IPC mechanism to signal
        // your application to close the subscription handle.
    }

    return status; // The service ignores the returned status.
}


EVT_HANDLE GetBookmark(void)
{
    DWORD status = ERROR_SUCCESS;
    EVT_HANDLE hBookmark = NULL;
    LPWSTR pBookmarkXml = NULL;

    // Set pBookmarkXml to the XML string that you persisted in SaveBookmark.

    hBookmark = EvtCreateBookmark(pBookmarkXml);
    if (NULL == hBookmark)
    {
        wprintf(L"EvtCreateBookmark failed with %lu\n", GetLastError());
        goto cleanup;
    }

cleanup:

    if (pBookmarkXml)
        free(pBookmarkXml);

    return hBookmark;
}


DWORD SaveBookmark(EVT_HANDLE hBookmark)
{
    DWORD status = ERROR_SUCCESS;
    DWORD dwBufferSize = 0;
    DWORD dwBufferUsed = 0;
    DWORD dwPropertyCount = 0;
    LPWSTR pBookmarkXml = NULL;

    if (!EvtRender(NULL, hBookmark, EvtRenderBookmark, dwBufferSize, pBookmarkXml, &dwBufferUsed, &dwPropertyCount))
    {
        if (ERROR_INSUFFICIENT_BUFFER == (status = GetLastError()))
        {
            dwBufferSize = dwBufferUsed;
            pBookmarkXml = (LPWSTR)malloc(dwBufferSize);
            if (pBookmarkXml)
            {
                EvtRender(NULL, hBookmark, EvtRenderBookmark, dwBufferSize, pBookmarkXml, &dwBufferUsed, &dwPropertyCount);
            }
            else
            {
                wprintf(L"malloc failed\n");
                status = ERROR_OUTOFMEMORY;
                goto cleanup;
            }
        }

        if (ERROR_SUCCESS != (status = GetLastError()))
        {
            wprintf(L"EvtRender failed with %d\n", status);
            goto cleanup;
        }
    }

    // Persist bookmark to a file or the registry.

cleanup:

    if (pBookmarkXml)
        free(pBookmarkXml);

    return status;
}


// Render the event as an XML string and print it.
DWORD PrintEvent(EVT_HANDLE hEvent)
{
    DWORD status = ERROR_SUCCESS;
    DWORD dwBufferSize = 0;
    DWORD dwBufferUsed = 0;
    DWORD dwPropertyCount = 0;
    LPWSTR pRenderedContent = NULL;

    if (!EvtRender(NULL, hEvent, EvtRenderEventXml, dwBufferSize, pRenderedContent, &dwBufferUsed, &dwPropertyCount))
    {
        if (ERROR_INSUFFICIENT_BUFFER == (status = GetLastError()))
        {
            dwBufferSize = dwBufferUsed;
            pRenderedContent = (LPWSTR)malloc(dwBufferSize);
            if (pRenderedContent)
            {
                EvtRender(NULL, hEvent, EvtRenderEventXml, dwBufferSize, pRenderedContent, &dwBufferUsed, &dwPropertyCount);
            }
            else
            {
                wprintf(L"malloc failed\n");
                status = ERROR_OUTOFMEMORY;
                goto cleanup;
            }
        }

        if (ERROR_SUCCESS != (status = GetLastError()))
        {
            wprintf(L"EvtRender failed with %d\n", status);
            goto cleanup;
        }
    }

    wprintf(L"%s\n\n", pRenderedContent);

cleanup:

    if (pRenderedContent)
        free(pRenderedContent);

    return status;
}

通过

为事件添加书签

在查询中使用书签

在订阅中使用书签

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