Qt QSharedMemory 공유 메모리 위치를 업데이트하는 방법

Question

2 개의 다른 Qt Apps와 연결된 라이브러리 (testlib-lib.so)가 있습니다. 내 문제는 그것을 초기화 한 후 공유 메모리를 업데이트 할 수 없다는 것입니다. 공유 초기화 후

void Control::updateText() { 

    // Create seed for the random 
    // That is needed only once on application startup 
    QTime time = QTime::currentTime(); 
    qsrand((uint)time.msec()); 

    // Get random value between 0-100 
    int randomValue = qrand() % ((1000 + 1) - 2) + 2; 

    // Create the shared memory and load some data 
    TestLib loadData; 
    QString randomText = QString("%1 test asdf %2 test asdf %3 test asdf %4").arg(randomValue).arg(randomValue).arg(randomValue).arg(randomValue); 
    loadData.writeToSharedMemory(randomText); 

} 

을 :

// Create the shared memory and load some data 
TestLib loadData; 
loadData.createInitialSharedMemory(); 
loadData.writeToSharedMemory("12345 init shared memory"); 

// This is the key 
QSharedMemory sharedAudioMemory("globalAudioBufferSharedMemory"); 

// Attempt to attach to shared memory for the audio buffer 
if (!sharedAudioMemory.attach()) { 

    //If an attempt of reading from the shared memory before data is written 
    qDebug() << "ERROR: Failed to attach to shared memory..."; 
    return -1; 

} 

// Define a buffer to read the data in 
QBuffer buffer; 
QDataStream in(&buffer); 
QString text; 

// Lock the memory and read the data 
sharedAudioMemory.lock(); 
char* pointer = (char*)sharedAudioMemory.constData(); 
buffer.setData((char*)sharedAudioMemory.constData(), sharedAudioMemory.size()); // Sets the contents of the internal buffer to be the first size bytes of data. 
buffer.open(QBuffer::ReadOnly); 
in >> text; 
sharedAudioMemory.unlock(); 
sharedAudioMemory.detach(); 

Qt는 응용 프로그램 B는, 수행하여 공유 메모리를 업데이트하려고 시도합니다 : 그것은() 주의에

void TestLib::createInitialSharedMemory() { 

    // Create shared memory 
    qDebug() << "Creating new shared memory..."; 
    sharedAudioMemory.setKey("globalAudioBufferSharedMemory"); 

    // First, test whether a shared memory segment is already attached to the process. 
    // If so, detach it 
    if (sharedAudioMemory.isAttached()) 
    { 
     sharedAudioMemory.detach(); 
    } 

    // Try to create memory of our required size 
    int sizeOfSharedData = 60 * 8000 * 2; // 60 Seconds x 8 KHz * 2 Bytes (signed short) 
    if (!sharedAudioMemory.create(sizeOfSharedData)) 
    { 
     qDebug() << "ERROR: Failed to Allocate Shared Memory of size: " << sizeOfSharedData; 
    } 

} 

void TestLib::writeToSharedMemory(QString text) { 

    // Create a buffer and data stream and some text to shove in there 
    QBuffer buffer; 
    buffer.open(QBuffer::ReadWrite); 
    QDataStream out(&buffer); 
    out << text; 
    int size = buffer.size(); 

    if (!sharedAudioMemory.attach()) { 

     // If an attempt of reading from the shared memory before data is written 
     qDebug() << "Cannot attach to shared memory to update!"; 

    } 

    // Write into the shared memory 
    sharedAudioMemory.lock(); 
    qDebug() << "Writing data to buffer: " << text; 
    char *to = (char*)sharedAudioMemory.data(); 
    const char *from = buffer.data().data(); 
    memcpy(to, from, qMin(sharedAudioMemory.size(), size)); 
    sharedAudioMemory.unlock(); 

} 

Qt는 응용 프로그램 A는 다음이있다 메모리를 "12345 init shared memory"로 설정하면 텍스트 저장소를 업데이트 할 수 없습니다. App B에서 updateText() 메서드를 호출하면 라이브러리 메서드 writeToSharedMemory()가 호출되고 메서드의 qDebug()가 공유 메모리에서 업데이트하려는 텍스트를 인쇄하지만 시도한 후에 다음 코드를 호출 할 때

// Attempt to attach to shared memory for the audio buffer 
if (!sharedAudioMemory.attach()) { 

    // If an attempt of reading from the shared memory before data is written 
    qDebug() << "ERROR: Failed to attach to shared memory..."; 

} 

// Define a buffer to read the data in 
QBuffer buffer; 
QDataStream in(&buffer); 
QString text; 

// Lock the memory and read the data 
sharedAudioMemory.lock(); 
char* pointer = (char*)sharedAudioMemory.constData(); 
buffer.setData((char*)sharedAudioMemory.constData(), sharedAudioMemory.size()); // Sets the contents of the internal buffer to be the first size bytes of data. 
buffer.open(QBuffer::ReadOnly); 
in >> text; 
sharedAudioMemory.unlock(); 
sharedAudioMemory.detach(); 

// Print the data 
qDebug() << "SHARED TEXT IS: " << text; 

왜 내가 공유 메모리를 업데이트하는 것 can'y : 공유 메모리를 업데이트, 항상 기원 inital 텍스트 "12345 초기화하기 공유 메모리를"인쇄? 내가 도대체 ​​뭘 잘못하고있는 겁니까? 감사합니다 -

Answer 1

은 여기 ') Errorstring이 ('는을 인쇄 한 후 오류를 발견 :

if (!sharedAudioMemory.attach()) { 

     // If an attempt of reading from the shared memory before data is written 
     qDebug() << "Cannot attach to shared memory to update! ERROR: " << sharedAudioMemory.errorString(); 

} 

가 분리되지 않도록 관련된 키가 없었다. 그래서 나는이 기능을 변경 :

// Assign the key so we can update the data 
sharedAudioMemory.setKey("globalAudioBufferSharedMemory"); 
if (!sharedAudioMemory.attach()) { 

    // If an attempt of reading from the shared memory before data is written 
    qDebug() << "Cannot attach to shared memory to update! ERROR: " << sharedAudioMemory.errorString(); 

} 

그리고 그것은 작동합니다 - 나는 잘 공유 메모리를 수정할 수 있습니다.