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+/**
+ * Copyright (c) 2007-2012, Timothy Stack
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * * Neither the name of Timothy Stack nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * @file auto_fd.hh
+ */
+
+#ifndef auto_fd_hh
+#define auto_fd_hh
+
+#include <exception>
+#include <new>
+#include <string>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/select.h>
+#include <unistd.h>
+
+#include "base/lnav_log.hh"
+#include "base/result.h"
+
+/**
+ * Resource management class for file descriptors.
+ *
+ * @see auto_ptr
+ */
+class auto_fd {
+public:
+ /**
+ * Wrapper for the posix pipe(2) function that stores the file descriptor
+ * results in an auto_fd array.
+ *
+ * @param af An array of at least two auto_fd elements, where the first
+ * contains the reader end of the pipe and the second contains the writer.
+ * @return The result of the pipe(2) function.
+ */
+ static int pipe(auto_fd* af)
+ {
+ int retval, fd[2];
+
+ require(af != nullptr);
+
+ if ((retval = ::pipe(fd)) == 0) {
+ af[0] = fd[0];
+ af[1] = fd[1];
+ }
+
+ return retval;
+ }
+
+ /**
+ * dup(2) the given file descriptor and wrap it in an auto_fd.
+ *
+ * @param fd The file descriptor to duplicate.
+ * @return A new auto_fd that contains the duplicated file descriptor.
+ */
+ static auto_fd dup_of(int fd)
+ {
+ if (fd == -1) {
+ return auto_fd{};
+ }
+
+ auto new_fd = ::dup(fd);
+
+ if (new_fd == -1) {
+ throw std::bad_alloc();
+ }
+
+ return auto_fd(new_fd);
+ }
+
+ /**
+ * Construct an auto_fd to manage the given file descriptor.
+ *
+ * @param fd The file descriptor to be managed.
+ */
+ explicit auto_fd(int fd = -1) : af_fd(fd) { require(fd >= -1); }
+
+ /**
+ * Non-const copy constructor. Management of the file descriptor will be
+ * transferred from the source to this object and the source will be
+ * cleared.
+ *
+ * @param af The source of the file descriptor.
+ */
+ auto_fd(auto_fd&& af) noexcept : af_fd(af.release()) {}
+
+ /**
+ * Const copy constructor. The file descriptor from the source will be
+ * dup(2)'d and the new descriptor stored in this object.
+ *
+ * @param af The source of the file descriptor.
+ */
+ auto_fd(const auto_fd& af) = delete;
+
+ auto_fd dup() const
+ {
+ int new_fd;
+
+ if (this->af_fd == -1 || (new_fd = ::dup(this->af_fd)) == -1) {
+ throw std::bad_alloc();
+ }
+
+ return auto_fd{new_fd};
+ }
+
+ /**
+ * Destructor that will close the file descriptor managed by this object.
+ */
+ ~auto_fd() { this->reset(); }
+
+ /** @return The file descriptor as a plain integer. */
+ operator int() const { return this->af_fd; }
+
+ /**
+ * Replace the current descriptor with the given one. The current
+ * descriptor will be closed.
+ *
+ * @param fd The file descriptor to store in this object.
+ * @return *this
+ */
+ auto_fd& operator=(int fd)
+ {
+ require(fd >= -1);
+
+ this->reset(fd);
+ return *this;
+ }
+
+ /**
+ * Transfer management of the given file descriptor to this object.
+ *
+ * @param af The old manager of the file descriptor.
+ * @return *this
+ */
+ auto_fd& operator=(auto_fd&& af) noexcept
+ {
+ this->reset(af.release());
+ return *this;
+ }
+
+ /**
+ * Return a pointer that can be passed to functions that require an out
+ * parameter for file descriptors (e.g. openpty).
+ *
+ * @return A pointer to the internal integer.
+ */
+ int* out()
+ {
+ this->reset();
+ return &this->af_fd;
+ }
+
+ /**
+ * Stop managing the file descriptor in this object and return its value.
+ *
+ * @return The file descriptor.
+ */
+ int release()
+ {
+ int retval = this->af_fd;
+
+ this->af_fd = -1;
+ return retval;
+ }
+
+ /**
+ * @return The file descriptor.
+ */
+ int get() const { return this->af_fd; }
+
+ /**
+ * Closes the current file descriptor and replaces its value with the given
+ * one.
+ *
+ * @param fd The new file descriptor to be managed.
+ */
+ void reset(int fd = -1)
+ {
+ require(fd >= -1);
+
+ if (this->af_fd != fd) {
+ if (this->af_fd != -1) {
+ switch (this->af_fd) {
+ case STDIN_FILENO:
+ case STDOUT_FILENO:
+ case STDERR_FILENO:
+ break;
+ default:
+ close(this->af_fd);
+ break;
+ }
+ }
+ this->af_fd = fd;
+ }
+ }
+
+ void close_on_exec() const
+ {
+ if (this->af_fd == -1) {
+ return;
+ }
+ log_perror(fcntl(this->af_fd, F_SETFD, FD_CLOEXEC));
+ }
+
+private:
+ int af_fd; /*< The managed file descriptor. */
+};
+
+class auto_pipe {
+public:
+ static Result<auto_pipe, std::string> for_child_fd(int child_fd)
+ {
+ auto_pipe retval(child_fd);
+
+ if (retval.open() == -1) {
+ return Err(std::string(strerror(errno)));
+ }
+
+ return Ok(std::move(retval));
+ }
+
+ explicit auto_pipe(int child_fd = -1, int child_flags = O_RDONLY)
+ : ap_child_flags(child_flags), ap_child_fd(child_fd)
+ {
+ switch (child_fd) {
+ case STDIN_FILENO:
+ this->ap_child_flags = O_RDONLY;
+ break;
+ case STDOUT_FILENO:
+ case STDERR_FILENO:
+ this->ap_child_flags = O_WRONLY;
+ break;
+ }
+ }
+
+ int open() { return auto_fd::pipe(this->ap_fd); }
+
+ void close()
+ {
+ this->ap_fd[0].reset();
+ this->ap_fd[1].reset();
+ }
+
+ auto_fd& read_end() { return this->ap_fd[0]; }
+
+ auto_fd& write_end() { return this->ap_fd[1]; }
+
+ void after_fork(pid_t child_pid)
+ {
+ int new_fd;
+
+ switch (child_pid) {
+ case -1:
+ this->close();
+ break;
+ case 0:
+ if (this->ap_child_flags == O_RDONLY) {
+ this->write_end().reset();
+ if (this->read_end().get() == -1) {
+ this->read_end() = ::open("/dev/null", O_RDONLY);
+ }
+ new_fd = this->read_end().get();
+ } else {
+ this->read_end().reset();
+ if (this->write_end().get() == -1) {
+ this->write_end() = ::open("/dev/null", O_WRONLY);
+ }
+ new_fd = this->write_end().get();
+ }
+ if (this->ap_child_fd != -1) {
+ if (new_fd != this->ap_child_fd) {
+ dup2(new_fd, this->ap_child_fd);
+ this->close();
+ }
+ }
+ break;
+ default:
+ if (this->ap_child_flags == O_RDONLY) {
+ this->read_end().reset();
+ } else {
+ this->write_end().reset();
+ }
+ break;
+ }
+ }
+
+ int ap_child_flags;
+ int ap_child_fd;
+ auto_fd ap_fd[2];
+};
+
+#endif
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