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