logmeow/logcat_thread.cpp

#include <cstring>
#include <fcntl.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <system_error>

#include "log.h"
#include "misc.h"
#include "logcat_thread.h"

#define EPOLL_MAX_EVENTS 10

static void mark_nonblock(int fd) {
    int flags = fcntl(fd, F_GETFL);
    if (flags < 0) {
        throw_system_error("fcntl(fd, F_GETFL)");
    }
    if (!(flags & O_NONBLOCK) && fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
        throw_system_error("fcntl(fd, F_SETFL)");
    }
}


LogcatThread::LogcatThread() {
    int fds[2];
    struct epoll_event event = {.events = EPOLLIN | EPOLLET};

    if (pipe(fds)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "pipe() for stdout");
    }
    this->_stdout_read_fd = fds[0];
    this->_stdout_write_fd = fds[1];
    try {
        mark_nonblock(this->_stdout_read_fd);
    } catch (const std::exception& e) {
        this->~LogcatThread();
        throw;
    }

    if (pipe(fds)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "pipe() for stderr");
    }
    this->_stderr_read_fd = fds[0];
    this->_stderr_write_fd = fds[1];
    try {
        mark_nonblock(this->_stderr_read_fd);
    } catch (const std::exception& e) {
        this->~LogcatThread();
        throw;
    }

    this->_epoll_fd = epoll_create1(EPOLL_CLOEXEC);
    if (this->_epoll_fd == -1) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "epoll_create1()");
    }
    event.data.fd = this->_stdout_read_fd;
    if (epoll_ctl(this->_epoll_fd, EPOLL_CTL_ADD, this->_stdout_read_fd, &event)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "epoll_ctl() for stdout");
    }
    event.data.fd = this->_stderr_read_fd;
    if (epoll_ctl(this->_epoll_fd, EPOLL_CTL_ADD, this->_stderr_read_fd, &event)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "epoll_ctl() for stderr");
    }

    this->_thread = std::thread(&LogcatThread::_run, this, this->_stop_source.get_token());
}

LogcatThread::~LogcatThread() {
    if (this->_epoll_fd != -1 && close(this->_epoll_fd)) {
        log(std::string("Failed to close epoll file descriptor: close(): ") + strerror(errno));
    }
    if (this->_stdout_read_fd != -1 && close(this->_stdout_read_fd)) {
        log(std::string("Failed to close stdout read pipe: close(): ") + strerror(errno));
    }
    if (this->_stdout_write_fd != -1 && close(this->_stdout_write_fd)) {
        log(std::string("Failed to close stdout write pipe: close(): ") + strerror(errno));
    }
    if (this->_stderr_read_fd != -1 && close(this->_stderr_read_fd)) {
        log(std::string("Failed to close stderr read pipe: close(): ") + strerror(errno));
    }
    if (this->_stderr_write_fd != -1 && close(this->_stderr_write_fd)) {
        log(std::string("Failed to close stderr write pipe: close(): ") + strerror(errno));
    }
}

void LogcatThread::request_stop() {
    this->_stop_source.request_stop();
}

void LogcatThread::join() {
    this->_thread.join();
}

void LogcatThread::_run(std::stop_token stoken) {
    struct epoll_event events[EPOLL_MAX_EVENTS];

    while (!stoken.stop_requested()) {
        printf("(boop)\n");

        int ready_fds = epoll_wait(this->_epoll_fd, events, EPOLL_MAX_EVENTS, 1000);
        if (ready_fds == -1) {
            std::string log_entry = format_log(std::string("epoll_wait(): ") + strerror(errno));
            printf("%s\n", log_entry.c_str());
            this->atomic_ring_buffer.put_and_increment_write(std::move(log_entry));
            break;
        }

        for (int i=0; i < ready_fds; i++) {
            printf("ain't no way in hell do we get a ready fd (#%d) when we haven't set up anything\n", i);
        }
    }
}