異步讀取失敗

我基於源代碼的編寫監控文件的程序：https://github.com/kvikas/file-monitor-service/blob/master/異步讀取失敗

我的程序使用的boost ::支持ASIO :: stream_descriptor :: async_read_some（）從異步讀取inotify的描述http://linux.die.net/man/7/inotify

我的代碼如下：

構造：

void init(){ 
    int fd = inotify_init1(IN_NONBLOCK); 
    int wd = inotify_add_watch(fd_, "./test.txt", IN_ALL_EVENTS); 
    stream_.reset(new boost::asio::posix::stream_descriptor(io_service_, fd_))); 
}

的異步讀取：

template<typename Monitor_Handler> 
void async_monitor(Monitor_Handler handler) { 
    stream_->async_read_some(boost::asio::buffer(buffer_), 
      boost::bind(&monitor::handle_monitor<Monitor_Handler>, 
        shared_from_this(), boost::asio::placeholders::error, 
        boost::asio::placeholders::bytes_transferred, handler)); 
}

的處理程序：

template<typename Monitor_Handler> 
void handle_monitor(const boost::system::error_code &ec, 
     std::size_t bytes_transferred, Monitor_Handler handler) {  
    //process buffer  
    async_monitor(handler); 

}

的錯誤是，在第一handle_monitor是在第一個變化調用幾次（多個事件如MODIFY，Access中打開...）受監控的文件。之後async_read_some方法被再次調用，但我沒有信號了（該handle_monitor不再被調用）

然而，當我試圖重啓inotify的描述，並再次重新進行添加的監視的文件==>它的工作中， handle_monitor被調用來監視這些文件中的新變化。

修改代碼：

template<typename Monitor_Handler> 
void handle_monitor(const boost::system::error_code &ec, 
     std::size_t bytes_transferred, Monitor_Handler handler) {  
    //process buffer  
    async_monitor(handler); 
    init();//for resetting the inotify desciptor 

}

難道你們幫我解釋一下這個????我渴望你的答案.....

來源

2013-05-06 khanhhh89

這看起來可疑我

void init(){ 
    int fd = inotify_init1(IN_NONBLOCK); 
    int wd = inotify_add_watch(fd_, "./test.txt", IN_ALL_EVENTS); 
    stream_.reset(new boost::asio::posix::stream_descriptor(io_service_, fd_))); 
}

您應該創建stream_descriptor從notify_init1()返回的值，這將是fd而不是fd_。我假設fd_是一個類成員，可能未初始化或初始化爲0。

來源

2013-05-06 14:19:38

謝謝您的回答，我重寫FD變量。但這不是問題。我在這個問題上縮小了我的問題的範圍。 http://stackoverflow.com/questions/16397293/the-read-method-on-the-inotify-descriptor-does-not-return你能幫我解釋一下嗎？希望看到你的回答 – khanhhh89 2013-05-07 02:43:40

-1

#include <string> 
#include <algorithm> 
#include <cstring> 
#include <assert.h> 
#include <sys/signalfd.h> 
#include <sys/inotify.h> 

#include <boost/asio.hpp> 
#include <boost/array.hpp> 
#include <boost/bind.hpp> 
#include <boost/shared_ptr.hpp> 
#include <boost/enable_shared_from_this.hpp> 
#include <iostream> 



//compile with 
//------------- 
//g++ -std=c++0x -g -I/usr/local/include -I/home/rk/Downloads/websocketpp/src asio.cc -L/home/rk/Downloads/websocketpp -L/usr/local/lib/ -lwebsocketpp -lboost_thread -lboost_exception -lboost_date_time -lboost_regex -lboost_system -o asio 

static int inotifyFd = -1; 
static int signalFd = -1; 
static boost::asio::io_service gIoSvc; 
//A simple test program to test whether signalfd works with boost::asio or not. 
static boost::asio::posix::stream_descriptor *gwMqFd = nullptr; //message queue on which the gateway listens for control requests. 
static boost::asio::posix::stream_descriptor *inFd = nullptr; //message queue on which the gateway listens for control requests. 
static void 
handleMqRead(boost::system::error_code ec) 
{ 
    std::cerr<<"\nRecvd signal"; 
    struct signalfd_siginfo fdsi; 
    memset(&fdsi, 0, sizeof(fdsi)); 
    ssize_t s = ::read(signalFd, &fdsi, sizeof(struct signalfd_siginfo)); 
    if (s != sizeof(struct signalfd_siginfo)){ 
     std::cerr<<"read() on signalfd returns inconsistent size."; 
     return; 
    } 
    gwMqFd->async_read_some(boost::asio::null_buffers(), 
      boost::bind(&handleMqRead, 
       boost::asio::placeholders::error)); 
    return; 
} 

#define EVENT_SIZE (sizeof (struct inotify_event)) 
#define EVENT_BUF_LEN (1024*(EVENT_SIZE + 16)) 
static void 
observeFilesystem(boost::system::error_code ec) 
{ 
    std::cerr<<"\nDirectory modified ..."; 
    char buf[EVENT_BUF_LEN]; 
    int length = ::read(inotifyFd, buf, sizeof(buf)); 
    inFd->async_read_some(boost::asio::null_buffers(), 
      boost::bind(&observeFilesystem, 
       boost::asio::placeholders::error)); 
    return; 
} 

int 
main(int argc, char* argv[]) 
{ 
    try{ 
     inFd = new boost::asio::posix::stream_descriptor(gIoSvc); 
     gwMqFd = new boost::asio::posix::stream_descriptor(gIoSvc); 
     sigset_t signalMask; 
     sigemptyset(&signalMask); 
     sigaddset(&signalMask, SIGCHLD); 
     sigaddset(&signalMask, SIGTERM); 
     sigprocmask(SIG_BLOCK, &signalMask, nullptr); 
     signalFd = signalfd(-1, &signalMask, SFD_NONBLOCK | SFD_CLOEXEC); 
     assert(signalFd > 0); 
     gwMqFd->assign(signalFd); 
     gwMqFd->async_read_some(boost::asio::null_buffers(), 
      boost::bind(&handleMqRead, 
       boost::asio::placeholders::error)); 

     inotifyFd = inotify_init(); 
     assert(inotifyFd > 0); 
     inFd->assign(inotifyFd); 
     std::string fqpn = "."; 
     inotify_add_watch(inotifyFd, fqpn.c_str(), IN_CREATE | IN_DELETE | IN_DELETE_SELF | IN_MOVE_SELF | IN_MODIFY); 
     inFd->async_read_some(boost::asio::null_buffers(), 
      boost::bind(&observeFilesystem, 
       boost::asio::placeholders::error)); 
     gIoSvc.run(); 
    }catch (std::exception& e){ 
     std::cerr << "Exception: " << e.what() << std::endl; 
    } 
    return 0; 
}

來源

2013-07-29 11:10:52

-1。沒有給出解釋。它依賴於一個https://github.com/zaphoyd/websocketpp ..一個替代但更高級別的庫。爲+1添加一些解釋:) – matiu 2017-06-21 18:37:01

我想說的，而不是使用

int length = ::read(inotifyFd, buf, sizeof(buf)); 
inFd->async_read_some(boost::asio::null_buffers(), 
boost::bind(&observeFilesystem, 
boost::asio::placeholders::error))

，倒不如完全利用aync_read_some如下

inFd->async_read_some(
boost::asio::buffer(buf, EVENT_BUF_LEN), 
boost::bind(&observeFilesystem, 
boost::asio::placeholders::error));

來源

2013-09-23 13:07:44 Sandeep

異步讀取失敗

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