windows监控文件变化

windows上使用ReadDirectoryChangesW监控某个文件发生了改变。（这个api是阻塞的，最好放到一个线程中去使用）

#include <iostream>
#include <windows.h> 
#include <string>
#include <atlstr.h> 
#include <tchar.h>

using namespace std;

void fileWatcher()
{
    DWORD cbBytes;
    char file_name[1024] = ""; //设置文件名
    char file_name2[1024] = ""; //设置文件重命名后的名字
    char notify[1024] = "";
    int count = 0; //文件数量。可能同时拷贝、删除多个文件，可以进行更友好的提示。
    CString dir = "c:\\test";  //一定是个目录，不是文件

    HANDLE dirHandle = CreateFile(dir, GENERIC_READ | GENERIC_WRITE | FILE_LIST_DIRECTORY,
        FILE_SHARE_READ | FILE_SHARE_WRITE,
        NULL,
        OPEN_EXISTING,
        FILE_FLAG_BACKUP_SEMANTICS,
        NULL);

    if (dirHandle == INVALID_HANDLE_VALUE) 
    {
        std::cout << "CreateFile error:" + GetLastError() << std::endl;
        return;
    }

    FILE_NOTIFY_INFORMATION *pNotification = (FILE_NOTIFY_INFORMATION *)notify;

    cout << "start...." << endl;
    
    BOOL watch_state;

    while (true)
    {
        watch_state = ReadDirectoryChangesW(dirHandle, &notify, 1024, true,
            FILE_NOTIFY_CHANGE_FILE_NAME | FILE_NOTIFY_CHANGE_DIR_NAME
            //| FILE_NOTIFY_CHANGE_CREATION
            //| FILE_NOTIFY_CHANGE_LAST_WRITE
            | FILE_NOTIFY_CHANGE_SIZE,
            &cbBytes, NULL, NULL);
        
        if(watch_state == FALSE)
        {
            DWORD dwErr = GetLastError();;
            cout <<"文件监控失败！" << dwErr << endl;
            break;
        }
        else if (GetLastError() == ERROR_INVALID_FUNCTION)
        {
            cout << "系统不支持" << endl;
            break;
        }
        else if (GetLastError() == ERROR_NOTIFY_ENUM_DIR)
        {
            cout << "内存溢出" << endl;
            continue;
        }
        else {
            CString szFileName(pNotification->FileName, pNotification->FileNameLength / sizeof(wchar_t));//获取监控到的文件名

            if (pNotification->Action == FILE_ACTION_ADDED)
            {
                cout <<"add file:" << szFileName  << endl;
            }
            else if (pNotification->Action == FILE_ACTION_REMOVED)
            {
                cout << "del file:" << szFileName <<endl;
            }
            else if (pNotification->Action == FILE_ACTION_MODIFIED)
            {
                cout << "mod file:" << szFileName <<endl;
            }
            else if (pNotification->Action == FILE_ACTION_RENAMED_OLD_NAME)
            {
                cout << "rename file:" << szFileName << endl;
            }
            else if (pNotification->Action == FILE_ACTION_RENAMED_NEW_NAME) //还没出现过这种情况
            {
                cout << "rename2 file:" << szFileName << endl;
            }
        }
    }
    CloseHandle(dirHandle);
}

int main(int argc, char* argv[])
{
    fileWatcher();
    system("pause");
    return 0;
}