Message ID | 20191217015106.1175515-3-niklas.soderlund@ragnatech.se |
---|---|
State | Accepted |
Headers | show |
Series |
|
Related | show |
Hi Niklas, Thank you for the patch. On Tue, Dec 17, 2019 at 02:51:05AM +0100, Niklas Söderlund wrote: > Add a helper to make it easier to pass file descriptors around. The > helper class duplicates the fd which decouples it from the original fd > which could be closed by its owner while the new FileDescriptor remains > valid. > > Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > --- > include/libcamera/file_descriptor.h | 33 ++++++ > include/libcamera/meson.build | 1 + > src/libcamera/file_descriptor.cpp | 164 ++++++++++++++++++++++++++++ > src/libcamera/meson.build | 1 + > 4 files changed, 199 insertions(+) > create mode 100644 include/libcamera/file_descriptor.h > create mode 100644 src/libcamera/file_descriptor.cpp > > diff --git a/include/libcamera/file_descriptor.h b/include/libcamera/file_descriptor.h > new file mode 100644 > index 0000000000000000..e05f111d128e0ab1 > --- /dev/null > +++ b/include/libcamera/file_descriptor.h > @@ -0,0 +1,33 @@ > +/* SPDX-License-Identifier: LGPL-2.1-or-later */ > +/* > + * Copyright (C) 2019, Google Inc. > + * > + * file_descriptor.h - File descriptor wrapper > + */ > +#ifndef __LIBCAMERA_FILE_DESCRIPTOR_H__ > +#define __LIBCAMERA_FILE_DESCRIPTOR_H__ > + > +namespace libcamera { > + > +class FileDescriptor final > +{ > +public: > + explicit FileDescriptor(int fd = -1); > + explicit FileDescriptor(const FileDescriptor &other); > + explicit FileDescriptor(FileDescriptor &&other); > + ~FileDescriptor(); > + > + FileDescriptor &operator=(const FileDescriptor &other); > + FileDescriptor &operator=(FileDescriptor &&other); > + > + int fd() const { return fd_; } > + > +private: > + void duplicate(int fd); > + > + int fd_; > +}; > + > +} /* namespace libcamera */ > + > +#endif /* __LIBCAMERA_FILE_DESCRIPTOR_H__ */ > diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build > index 99abf06099407c1f..543e6773cc5158a0 100644 > --- a/include/libcamera/meson.build > +++ b/include/libcamera/meson.build > @@ -6,6 +6,7 @@ libcamera_api = files([ > 'controls.h', > 'event_dispatcher.h', > 'event_notifier.h', > + 'file_descriptor.h', > 'geometry.h', > 'logging.h', > 'object.h', > diff --git a/src/libcamera/file_descriptor.cpp b/src/libcamera/file_descriptor.cpp > new file mode 100644 > index 0000000000000000..71d1cf27be79b288 > --- /dev/null > +++ b/src/libcamera/file_descriptor.cpp > @@ -0,0 +1,164 @@ > +/* SPDX-License-Identifier: LGPL-2.1-or-later */ > +/* > + * Copyright (C) 2019, Google Inc. > + * > + * file_descriptor.cpp - File descriptor wrapper > + */ > + > +#include <libcamera/file_descriptor.h> > + > +#include <string.h> > +#include <unistd.h> > +#include <utility> > + > +#include "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 wraps a file descriptor (expressed as a signed > + * integer) to provide an RAII-style mechanism for owning the file descriptor. > + * When constructed, the FileDescriptor instance duplicates a given file > + * descriptor and takes ownership of the duplicate as a resource. The copy > + * constructor and assignment operator duplicate the file descriptor, while the > + * move versions of those methods move the resource and make the original > + * FileDescriptor invalid. When the FileDescriptor is deleted, it closes the > + * file descriptor it owns, if any. > + */ > + > +/** > + * \brief Create a FileDescriptor wrapping a copy of a given \a fd > + * \param[in] fd File descriptor > + * > + * Construct a FileDescriptor from a numerical file descriptor duplicates the > + * \a fd and takes 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 the FileDescriptor instance > + * is destroyed. > + */ > +FileDescriptor::FileDescriptor(int fd) > + : fd_(-1) > +{ > + duplicate(fd); > +} > + > +/** > + * \brief Copy constructor, create a FileDescriptor from a copy of \a other > + * \param[in] other The other FileDescriptor > + * > + * Construct a FileDescriptor from another FileDescriptor duplicates the > + * wrapped numerical file descriptor and takes ownership of the copy. The > + * original FileDescriptor is left untouched, and the caller is responsible for > + * closing it when appropriate. The duplicated file descriptor will be closed > + * automatically when this FileDescriptor instance is destroyed. > + */ > +FileDescriptor::FileDescriptor(const FileDescriptor &other) > + : FileDescriptor(other.fd_) > +{ > +} > + > +/** > + * \brief Move constructor, create a FileDescriptor by taking over \a other > + * \param[in] other The other FileDescriptor > + * > + * Construct a FileDescriptor by taking over a wrapped numerical file > + * descriptor and taking ownership of it. The \a other FileDescriptor is > + * invalidated and set to -1. The taken over file descriptor will be closed > + * automatically when this FileDescriptor instance is destroyed. > + */ > +FileDescriptor::FileDescriptor(FileDescriptor &&other) > + : fd_(utils::exchange(other.fd_, -1)) > +{ > +} > + > +/** > + * \brief Destroy the managed file descriptor > + * > + * If the managed file descriptor, as returned by fd(), is not equal to -1, the > + * file descriptor is closed. > + */ > +FileDescriptor::~FileDescriptor() > +{ > + if (fd_ != -1) > + close(fd_); > +} > + > +/** > + * \brief Copy assignment operator, replace the wrapped file descriptor with a > + * duplicate from \a other > + * \param[in] other The other FileDescriptor > + * > + * Close the wrapped file descriptor (if any) and duplicate the file descriptor > + * from \a other. The \a other FileDescriptor is left untouched, and the caller > + * is responsible for destroying it when appropriate. The duplicated file > + * descriptor will be closed automatically when the FileDescriptor instance is s/the FileDescriptor/this FileDescriptor/ > + * destroyed. > + * > + * \return A reference to this FileDescriptor > + */ > +FileDescriptor &FileDescriptor::operator=(const FileDescriptor &other) > +{ > + duplicate(other.fd_); > + > + return *this; > +} > + > +/** > + * \brief Move assignment operator, replace the wrapped file descriptor by > + * taking over \a other > + * \param[in] other The other FileDescriptor > + * > + * Close the wrapped file descriptor (if any) and take over the file descriptor > + * from \a other. The \a other FileDescriptor is invalidated and set to -1. The > + * taken over file descriptor will be closed automatically when the s/the$/this/ > + * FileDescriptor instance is destroyed. > + * > + * \return A reference to this FileDescriptor > + */ > +FileDescriptor &FileDescriptor::operator=(FileDescriptor &&other) > +{ > + if (fd_ != -1) > + close(fd_); > + > + fd_ = utils::exchange(other.fd_, -1); > + > + return *this; > +} > + > +/** > + * \fn FileDescriptor::fd() > + * \brief Retrieve the numerical file descriptor > + * \return The numerical file descriptor, which may be -1 if the FileDescriptor > + * instance doesn't own a file descriptor > + */ > + > +void FileDescriptor::duplicate(int fd) > +{ > + if (fd_ != -1) > + close(fd_); fd_ = -1; } > + > + if (fd < 0) { > + fd_ = -1; and drop this line. > + return; > + } > + > + /* Failing to dup() a fd should not happen and is fatal. */ > + fd_ = dup(fd); > + if (fd_ == -1) { > + int ret = -errno; > + LOG(FileDescriptor, Fatal) > + << "Failed to dup() fd: " << strerror(-ret); > + } > +} > + > +} /* namespace libcamera */ > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build > index c4f965bd7413b37e..722c5bc15afe52ef 100644 > --- a/src/libcamera/meson.build > +++ b/src/libcamera/meson.build > @@ -14,6 +14,7 @@ libcamera_sources = files([ > 'event_dispatcher.cpp', > 'event_dispatcher_poll.cpp', > 'event_notifier.cpp', > + 'file_descriptor.cpp', > 'formats.cpp', > 'geometry.cpp', > 'ipa_context_wrapper.cpp',
diff --git a/include/libcamera/file_descriptor.h b/include/libcamera/file_descriptor.h new file mode 100644 index 0000000000000000..e05f111d128e0ab1 --- /dev/null +++ b/include/libcamera/file_descriptor.h @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2019, Google Inc. + * + * file_descriptor.h - File descriptor wrapper + */ +#ifndef __LIBCAMERA_FILE_DESCRIPTOR_H__ +#define __LIBCAMERA_FILE_DESCRIPTOR_H__ + +namespace libcamera { + +class FileDescriptor final +{ +public: + explicit FileDescriptor(int fd = -1); + explicit FileDescriptor(const FileDescriptor &other); + explicit FileDescriptor(FileDescriptor &&other); + ~FileDescriptor(); + + FileDescriptor &operator=(const FileDescriptor &other); + FileDescriptor &operator=(FileDescriptor &&other); + + int fd() const { return fd_; } + +private: + void duplicate(int fd); + + int fd_; +}; + +} /* namespace libcamera */ + +#endif /* __LIBCAMERA_FILE_DESCRIPTOR_H__ */ diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build index 99abf06099407c1f..543e6773cc5158a0 100644 --- a/include/libcamera/meson.build +++ b/include/libcamera/meson.build @@ -6,6 +6,7 @@ libcamera_api = files([ 'controls.h', 'event_dispatcher.h', 'event_notifier.h', + 'file_descriptor.h', 'geometry.h', 'logging.h', 'object.h', diff --git a/src/libcamera/file_descriptor.cpp b/src/libcamera/file_descriptor.cpp new file mode 100644 index 0000000000000000..71d1cf27be79b288 --- /dev/null +++ b/src/libcamera/file_descriptor.cpp @@ -0,0 +1,164 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2019, Google Inc. + * + * file_descriptor.cpp - File descriptor wrapper + */ + +#include <libcamera/file_descriptor.h> + +#include <string.h> +#include <unistd.h> +#include <utility> + +#include "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 wraps a file descriptor (expressed as a signed + * integer) to provide an RAII-style mechanism for owning the file descriptor. + * When constructed, the FileDescriptor instance duplicates a given file + * descriptor and takes ownership of the duplicate as a resource. The copy + * constructor and assignment operator duplicate the file descriptor, while the + * move versions of those methods move the resource and make the original + * FileDescriptor invalid. When the FileDescriptor is deleted, it closes the + * file descriptor it owns, if any. + */ + +/** + * \brief Create a FileDescriptor wrapping a copy of a given \a fd + * \param[in] fd File descriptor + * + * Construct a FileDescriptor from a numerical file descriptor duplicates the + * \a fd and takes 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 the FileDescriptor instance + * is destroyed. + */ +FileDescriptor::FileDescriptor(int fd) + : fd_(-1) +{ + duplicate(fd); +} + +/** + * \brief Copy constructor, create a FileDescriptor from a copy of \a other + * \param[in] other The other FileDescriptor + * + * Construct a FileDescriptor from another FileDescriptor duplicates the + * wrapped numerical file descriptor and takes ownership of the copy. The + * original FileDescriptor is left untouched, and the caller is responsible for + * closing it when appropriate. The duplicated file descriptor will be closed + * automatically when this FileDescriptor instance is destroyed. + */ +FileDescriptor::FileDescriptor(const FileDescriptor &other) + : FileDescriptor(other.fd_) +{ +} + +/** + * \brief Move constructor, create a FileDescriptor by taking over \a other + * \param[in] other The other FileDescriptor + * + * Construct a FileDescriptor by taking over a wrapped numerical file + * descriptor and taking ownership of it. The \a other FileDescriptor is + * invalidated and set to -1. The taken over file descriptor will be closed + * automatically when this FileDescriptor instance is destroyed. + */ +FileDescriptor::FileDescriptor(FileDescriptor &&other) + : fd_(utils::exchange(other.fd_, -1)) +{ +} + +/** + * \brief Destroy the managed file descriptor + * + * If the managed file descriptor, as returned by fd(), is not equal to -1, the + * file descriptor is closed. + */ +FileDescriptor::~FileDescriptor() +{ + if (fd_ != -1) + close(fd_); +} + +/** + * \brief Copy assignment operator, replace the wrapped file descriptor with a + * duplicate from \a other + * \param[in] other The other FileDescriptor + * + * Close the wrapped file descriptor (if any) and duplicate the file descriptor + * from \a other. The \a other FileDescriptor is left untouched, and the caller + * is responsible for destroying it when appropriate. The duplicated file + * descriptor will be closed automatically when the FileDescriptor instance is + * destroyed. + * + * \return A reference to this FileDescriptor + */ +FileDescriptor &FileDescriptor::operator=(const FileDescriptor &other) +{ + duplicate(other.fd_); + + return *this; +} + +/** + * \brief Move assignment operator, replace the wrapped file descriptor by + * taking over \a other + * \param[in] other The other FileDescriptor + * + * Close the wrapped file descriptor (if any) and take over the file descriptor + * from \a other. The \a other FileDescriptor is invalidated and set to -1. The + * taken over file descriptor will be closed automatically when the + * FileDescriptor instance is destroyed. + * + * \return A reference to this FileDescriptor + */ +FileDescriptor &FileDescriptor::operator=(FileDescriptor &&other) +{ + if (fd_ != -1) + close(fd_); + + fd_ = utils::exchange(other.fd_, -1); + + return *this; +} + +/** + * \fn FileDescriptor::fd() + * \brief Retrieve the numerical file descriptor + * \return The numerical file descriptor, which may be -1 if the FileDescriptor + * instance doesn't own a file descriptor + */ + +void FileDescriptor::duplicate(int fd) +{ + if (fd_ != -1) + close(fd_); + + if (fd < 0) { + fd_ = -1; + return; + } + + /* Failing to dup() a fd should not happen and is fatal. */ + fd_ = dup(fd); + if (fd_ == -1) { + int ret = -errno; + LOG(FileDescriptor, Fatal) + << "Failed to dup() fd: " << strerror(-ret); + } +} + +} /* namespace libcamera */ diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build index c4f965bd7413b37e..722c5bc15afe52ef 100644 --- a/src/libcamera/meson.build +++ b/src/libcamera/meson.build @@ -14,6 +14,7 @@ libcamera_sources = files([ 'event_dispatcher.cpp', 'event_dispatcher_poll.cpp', 'event_notifier.cpp', + 'file_descriptor.cpp', 'formats.cpp', 'geometry.cpp', 'ipa_context_wrapper.cpp',