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diff --git a/src/libcamera/base/shared_fd.cpp b/src/libcamera/base/shared_fd.cpp
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * shared_fd.cpp - File descriptor wrapper with shared ownership
+ */
+
+#include <libcamera/base/shared_fd.h>
+
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <utility>
+
+#include <libcamera/base/log.h>
+#include <libcamera/base/unique_fd.h>
+
+/**
+ * \file base/shared_fd.h
+ * \brief File descriptor wrapper
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(SharedFD)
+
+/**
+ * \class SharedFD
+ * \brief RAII-style wrapper for file descriptors
+ *
+ * The SharedFD 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 SharedFD instances constructed as copies.
+ *
+ * When constructed from a numerical file descriptor, the SharedFD instance
+ * either duplicates or takes over the file descriptor:
+ *
+ * - The SharedFD(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 SharedFD(int &&) constructor takes over the numerical file descriptor
+ *   and wraps it in a Descriptor. The caller 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 functions additionally make the
+ * other SharedFD invalid. When the last SharedFD that references a Descriptor
+ * is destroyed, the file descriptor is closed.
+ *
+ * The numerical file descriptor is available through the fd() function. All
+ * SharedFD instances created as copies of a SharedFD will report the same fd()
+ * value. Callers can perform operations on the fd(), but shall never close it
+ * manually.
+ */
+
+/**
+ * \brief Create a SharedFD copying a given \a fd
+ * \param[in] fd File descriptor
+ *
+ * Construct a SharedFD 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 SharedFD instances that
+ * reference it are destroyed.
+ *
+ * If the \a fd is negative, the SharedFD is constructed as invalid and the fd()
+ * function will return -1.
+ */
+SharedFD::SharedFD(const int &fd)
+{
+	if (fd < 0)
+		return;
+
+	fd_ = std::make_shared<Descriptor>(fd, true);
+	if (fd_->fd() < 0)
+		fd_.reset();
+}
+
+/**
+ * \brief Create a SharedFD taking ownership of a given \a fd
+ * \param[in] fd File descriptor
+ *
+ * Construct a SharedFD from a numerical file descriptor by taking ownership of
+ * the \a fd. The original \a fd is set to -1 and shall not be touched by the
+ * caller anymore. In particular, the caller shall not close the original \a fd
+ * manually. The duplicated file descriptor will be closed automatically when
+ * all SharedFD instances that reference it are destroyed.
+ *
+ * If the \a fd is negative, the SharedFD is constructed as invalid and the fd()
+ * function will return -1.
+ */
+SharedFD::SharedFD(int &&fd)
+{
+	if (fd < 0)
+		return;
+
+	fd_ = std::make_shared<Descriptor>(fd, false);
+	/*
+	 * The Descriptor constructor can't have failed here, as it took over
+	 * the fd without duplicating it. Just set the original fd to -1 to
+	 * implement move semantics.
+	 */
+	fd = -1;
+}
+
+/**
+ * \brief Create a SharedFD taking ownership of a given UniqueFD \a fd
+ * \param[in] fd UniqueFD
+ *
+ * Construct a SharedFD from UniqueFD by taking ownership of the \a fd. The
+ * original \a fd becomes invalid.
+ */
+SharedFD::SharedFD(UniqueFD fd)
+	: SharedFD(fd.release())
+{
+}
+
+/**
+ * \brief Copy constructor, create a SharedFD from a copy of \a other
+ * \param[in] other The other SharedFD
+ *
+ * Copying a SharedFD implicitly shares ownership of the wrapped file
+ * descriptor. The original SharedFD is left untouched, and the caller is
+ * responsible for destroying it when appropriate. The wrapped file descriptor
+ * will be closed automatically when all SharedFD instances that reference it
+ * are destroyed.
+ */
+SharedFD::SharedFD(const SharedFD &other)
+	: fd_(other.fd_)
+{
+}
+
+/**
+ * \brief Move constructor, create a SharedFD by taking over \a other
+ * \param[in] other The other SharedFD
+ *
+ * Moving a SharedFD moves the reference to the wrapped descriptor owned by
+ * \a other to the new SharedFD. The \a other SharedFD is invalidated and its
+ * fd() function will return -1. The wrapped file descriptor will be closed
+ * automatically when all SharedFD instances that reference it are destroyed.
+ */
+SharedFD::SharedFD(SharedFD &&other)
+	: fd_(std::move(other.fd_))
+{
+}
+
+/**
+ * \brief Destroy the SharedFD instance
+ *
+ * Destroying a SharedFD instance releases its reference to the wrapped
+ * descriptor, if any. When the last instance that references a wrapped
+ * descriptor is destroyed, the file descriptor is automatically closed.
+ */
+SharedFD::~SharedFD()
+{
+}
+
+/**
+ * \brief Copy assignment operator, replace the wrapped file descriptor with a
+ * copy of \a other
+ * \param[in] other The other SharedFD
+ *
+ * Copying a SharedFD creates a new reference to the wrapped file descriptor
+ * owner by \a other. If \a other is invalid, *this will also be invalid. The
+ * original SharedFD is left untouched, and the caller is responsible for
+ * destroying it when appropriate. The wrapped file descriptor will be closed
+ * automatically when all SharedFD instances that reference it are destroyed.
+ *
+ * \return A reference to this SharedFD
+ */
+SharedFD &SharedFD::operator=(const SharedFD &other)
+{
+	fd_ = other.fd_;
+
+	return *this;
+}
+
+/**
+ * \brief Move assignment operator, replace the wrapped file descriptor by
+ * taking over \a other
+ * \param[in] other The other SharedFD
+ *
+ * Moving a SharedFD moves the reference to the wrapped descriptor owned by
+ * \a other to the new SharedFD. If \a other is invalid, *this will also be
+ * invalid. The \a other SharedFD is invalidated and its fd() function will
+ * return -1. The wrapped file descriptor will be closed automatically when
+ * all SharedFD instances that reference it are destroyed.
+ *
+ * \return A reference to this SharedFD
+ */
+SharedFD &SharedFD::operator=(SharedFD &&other)
+{
+	fd_ = std::move(other.fd_);
+
+	return *this;
+}
+
+/**
+ * \fn SharedFD::isValid()
+ * \brief Check if the SharedFD instance is valid
+ * \return True if the SharedFD is valid, false otherwise
+ */
+
+/**
+ * \fn SharedFD::fd()
+ * \brief Retrieve the numerical file descriptor
+ * \return The numerical file descriptor, which may be -1 if the SharedFD
+ * instance is invalid
+ */
+
+/**
+ * \brief Duplicate a SharedFD
+ *
+ * Duplicating a SharedFD creates a duplicate of the wrapped file descriptor and
+ * returns a UniqueFD that owns the duplicate. The fd() function of the original
+ * and the get() function of the duplicate will return different values. The
+ * duplicate instance will not be affected by destruction of the original
+ * instance or its copies.
+ *
+ * \return A UniqueFD owning a duplicate of the original file descriptor
+ */
+UniqueFD SharedFD::dup() const
+{
+	UniqueFD dupFd(::dup(fd()));
+	if (!dupFd.isValid()) {
+		int ret = -errno;
+		LOG(SharedFD, Error)
+			<< "Failed to dup() fd: " << strerror(-ret);
+	}
+
+	return dupFd;
+}
+
+SharedFD::Descriptor::Descriptor(int fd, bool duplicate)
+{
+	if (!duplicate) {
+		fd_ = fd;
+		return;
+	}
+
+	/* Failing to dup() a fd should not happen and is fatal. */
+	fd_ = ::dup(fd);
+	if (fd_ == -1) {
+		int ret = -errno;
+		LOG(SharedFD, Fatal)
+			<< "Failed to dup() fd: " << strerror(-ret);
+	}
+}
+
+SharedFD::Descriptor::~Descriptor()
+{
+	if (fd_ != -1)
+		close(fd_);
+}
+
+} /* namespace libcamera */