qtlockedfile_unix.cpp

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// Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
// SPDX-License-Identifier: BSD-3-Clause
 
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
 
#include "qtlockedfile.h"
 
bool QtLockedFile::lock(LockMode mode, bool block)
{
    if (!isOpen()) {
        qWarning("QtLockedFile::lock(): file is not opened");
        return false;
    }
 
    if (mode == NoLock)
        return unlock();
           
    if (mode == m_lock_mode)
        return true;
 
    if (m_lock_mode != NoLock)
        unlock();
 
    struct flock fl;
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;
    fl.l_type = (mode == ReadLock) ? F_RDLCK : F_WRLCK;
    int cmd = block ? F_SETLKW : F_SETLK;
    int ret = fcntl(handle(), cmd, &fl);
    
    if (ret == -1) {
        if (errno != EINTR && errno != EAGAIN)
            qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
        return false;
    }
 
    
    m_lock_mode = mode;
    return true;
}
 
 
bool QtLockedFile::unlock()
{
    if (!isOpen()) {
        qWarning("QtLockedFile::unlock(): file is not opened");
        return false;
    }
 
    if (!isLocked())
        return true;
 
    struct flock fl;
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;
    fl.l_type = F_UNLCK;
    int ret = fcntl(handle(), F_SETLKW, &fl);
    
    if (ret == -1) {
        qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
        return false;
    }
    
    m_lock_mode = NoLock;
    return true;
}
 
QtLockedFile::~QtLockedFile()
{
    if (isOpen())
        unlock();
}