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Linux camera framework (http://www.libcamera.org) Libcamera
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path: root/src/libcamera/file_descriptor.cppblob: 640e66e6d16840243534b020f07195699a01b97f (plain)
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2019, Google Inc.
*
* file_descriptor.cpp - File descriptor wrapper
*/
#include
#include
#include
#include
#include "libcamera/internal/log.h"
/**
* \file file_descriptor.h
* \brief File descriptor wrapper
*/
namespace libcamera {
LOG_DEFINE_CATEGORY(FileDescriptor)
/**
* \class FileDescriptor
* \brief RAII-style wrapper for file descriptors
*
* The FileDescriptor class provides RAII-style lifetime management of file
* descriptors with an efficient mechanism for ownership sharing. At its core,
* an internal Descriptor object wraps a file descriptor (expressed as a signed
* integer) with an RAII-style interface. The Descriptor is then implicitly
* shared with all FileDescriptor instances constructed as copies.
*
* When constructed from a numerical file descriptor, the FileDescriptor
* instance either duplicates or takes over the file descriptor:
*
* - The FileDescriptor(const int &) constructor duplicates the numerical file
* descriptor and wraps the duplicate in a Descriptor. The caller is
* responsible for closing the original file descriptor, and the value
* returned by fd() will be different from the value passed to the
* constructor.
*
* - The FileDescriptor(int &&) constructor takes over the numerical file
* descriptor and wraps it in a Descriptor. The caller is shall not touch the
* original file descriptor once the function returns, and the value returned
* by fd() will be identical to the value passed to the constructor.
*
* The copy constructor and assignment operator create copies that share the
* Descriptor, while the move versions of those methods additionally make the
* other FileDescriptor invalid. When the last FileDescriptor that references a
* Descriptor is destroyed, the file descriptor is closed.
*
* The numerical file descriptor is available through the fd() method. All
* FileDescriptor instances created as copies of a FileDescriptor will report
* the same fd() value. Callers can perform operations on the fd(), but shall
* never close it manually.
*/
/**
* \brief Create a FileDescriptor copying a given \a fd
* \param[in] fd File descriptor
*
* Construct a FileDescriptor from a numerical file descriptor by duplicating
* the \a fd, and take ownership of the copy. The original \a fd is left
* untouched, and the caller is responsible for closing it when appropriate.
* The duplicated file descriptor will be closed automatically when all
* FileDescriptor instances that reference it are destroyed.
*
* If the \a fd is negative, the FileDescriptor is constructed as invalid and
* the fd() method will return -1.
*/
FileDescriptor::FileDescriptor(const int &fd)
{
if (fd fd() |