From ccdaf8ec9012b060b9cc49f5cdaa99b474c54e27 Mon Sep 17 00:00:00 2001 From: Hirokazu Honda Date: Thu, 10 Jun 2021 16:50:18 +0900 Subject: libcamera: base: Introduce UniqueFD This introduces UniqueFD. It acts like unique_ptr to a file descriptor. Signed-off-by: Hirokazu Honda Signed-off-by: Laurent Pinchart Reviewed-by: Hirokazu Honda --- include/libcamera/base/meson.build | 1 + include/libcamera/base/unique_fd.h | 69 +++++++++++++++++++++ src/libcamera/base/meson.build | 1 + src/libcamera/base/unique_fd.cpp | 123 +++++++++++++++++++++++++++++++++++++ 4 files changed, 194 insertions(+) create mode 100644 include/libcamera/base/unique_fd.h create mode 100644 src/libcamera/base/unique_fd.cpp diff --git a/include/libcamera/base/meson.build b/include/libcamera/base/meson.build index abd4cfc7..fce6eaa4 100644 --- a/include/libcamera/base/meson.build +++ b/include/libcamera/base/meson.build @@ -24,6 +24,7 @@ libcamera_base_headers = files([ 'thread.h', 'thread_annotations.h', 'timer.h', + 'unique_fd.h', 'utils.h', ]) diff --git a/include/libcamera/base/unique_fd.h b/include/libcamera/base/unique_fd.h new file mode 100644 index 00000000..ae4d96b7 --- /dev/null +++ b/include/libcamera/base/unique_fd.h @@ -0,0 +1,69 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2021, Google Inc. + * + * unique_fd.h - File descriptor wrapper that owns a file descriptor. + */ + +#pragma once + +#include + +#include +#include + +namespace libcamera { + +class UniqueFD final +{ +public: + UniqueFD() + : fd_(-1) + { + } + + explicit UniqueFD(int fd) + : fd_(fd) + { + } + + UniqueFD(UniqueFD &&other) + : fd_(other.release()) + { + } + + ~UniqueFD() + { + reset(); + } + + UniqueFD &operator=(UniqueFD &&other) + { + reset(other.release()); + return *this; + } + + __nodiscard int release() + { + int fd = fd_; + fd_ = -1; + return fd; + } + + void reset(int fd = -1); + + void swap(UniqueFD &other) + { + std::swap(fd_, other.fd_); + } + + int get() const { return fd_; } + bool isValid() const { return fd_ >= 0; } + +private: + LIBCAMERA_DISABLE_COPY(UniqueFD) + + int fd_; +}; + +} /* namespace libcamera */ diff --git a/src/libcamera/base/meson.build b/src/libcamera/base/meson.build index 55692015..352ec6f0 100644 --- a/src/libcamera/base/meson.build +++ b/src/libcamera/base/meson.build @@ -18,6 +18,7 @@ libcamera_base_sources = files([ 'signal.cpp', 'thread.cpp', 'timer.cpp', + 'unique_fd.cpp', 'utils.cpp', ]) diff --git a/src/libcamera/base/unique_fd.cpp b/src/libcamera/base/unique_fd.cpp new file mode 100644 index 00000000..83d6919c --- /dev/null +++ b/src/libcamera/base/unique_fd.cpp @@ -0,0 +1,123 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2021, Google Inc. + * + * unique_fd.cpp - File descriptor wrapper that owns a file descriptor + */ + +#include + +#include +#include + +#include + +/** + * \file base/unique_fd.h + * \brief File descriptor wrapper that owns a file descriptor + */ + +namespace libcamera { + +LOG_DEFINE_CATEGORY(UniqueFD) + +/** + * \class UniqueFD + * \brief unique_ptr-like wrapper for a file descriptor + * + * The UniqueFD is a wrapper that owns and manages the lifetime of a file + * descriptor. It is constructed from a numerical file descriptor, and takes + * over its ownership. The file descriptor is closed when the UniqueFD is + * destroyed, or when it is assigned another file descriptor with operator=() + * or reset(). + */ + +/** + * \fn UniqueFD::UniqueFD() + * \brief Construct a UniqueFD that owns no file descriptor + */ + +/** + * \fn UniqueFD::UniqueFD(int fd) + * \brief Construct a UniqueFD that owns \a fd + * \param[in] fd A file descriptor to manage + */ + +/** + * \fn UniqueFD::UniqueFD(UniqueFD &&other) + * \brief Move constructor, create a UniqueFD by taking over \a other + * \param[in] other The other UniqueFD + * + * Create a UniqueFD by transferring ownership of the file descriptor owned by + * \a other. Upon return, the \a other UniqueFD is invalid. + */ + +/** + * \fn UniqueFD::~UniqueFD() + * \brief Destroy the UniqueFD instance + * + * If a file descriptor is owned, it is closed. + */ + +/** + * \fn UniqueFD::operator=(UniqueFD &&other) + * \brief Move assignment operator, replace a UniqueFD by taking over \a other + * \param[in] other The other UniqueFD + * + * If this UniqueFD owns a file descriptor, the file descriptor is closed + * first. The file descriptor is then replaced by the one of \a other. Upon + * return, \a other is invalid. + * + * \return A reference to this UniqueFD + */ + +/** + * \fn UniqueFD::release() + * \brief Release ownership of the file descriptor without closing it + * + * This function releases and returns the owned file descriptor without closing + * it. The caller owns the returned value and must take care of handling its + * life time to avoid file descriptor leakages. Upon return this UniqueFD is + * invalid. + * + * \return The managed file descriptor, or -1 if no file descriptor was owned + */ + +/** + * \brief Replace the managed file descriptor + * \param[in] fd The new file descriptor to manage + * + * Close the managed file descriptor, if any, and replace it with the new \a fd. + * + * Self-resetting (passing an \a fd already managed by this instance) is invalid + * and results in undefined behaviour. + */ +void UniqueFD::reset(int fd) +{ + ASSERT(!isValid() || fd != fd_); + + std::swap(fd, fd_); + + if (fd >= 0) + close(fd); +} + +/** + * \fn UniqueFD::swap(UniqueFD &other) + * \brief Swap the managed file descriptors with another UniqueFD + * \param[in] other Another UniqueFD to swap the file descriptor with + */ + +/** + * \fn UniqueFD::get() + * \brief Retrieve the managed file descriptor + * \return The managed file descriptor, or -1 if no file descriptor is owned + */ + +/** + * \fn UniqueFD::isValid() + * \brief Check if the UniqueFD owns a valid file descriptor + * \return True if the UniqueFD owns a valid file descriptor, false otherwise + */ + +} /* namespace libcamera */ -- cgit v1.2.1