// system headers

#include <algorithm>

#include <cstring>

#include <poll.h>

#include <unistd.h>

#include <stdexcept>

// local headers

#include "linuxdeploy/subprocess/pipe_reader.h"

pipe_reader::pipe_reader(int pipe_fd) : pollfd_(pollfd{pipe_fd, POLLIN | POLLHUP}) {}

pipe_reader::result pipe_reader::read(std::vector<std::string::value_type>& buffer, std::chrono::milliseconds read_timeout) {

const auto timeout_msec = std::chrono::duration_cast<std::chrono::milliseconds>(read_timeout).count();

// we could (and probably should) be using poll on multiple fds at once

// however given the low bandwidth of data to handle, this should be fine, given we use a small-enough timeout

// also the read buffer sizes could be further increased to improve the overall performance

switch (poll(&pollfd_, 1, static_cast<int>(timeout_msec))) {

case -1:

// TODO: introduce custom subprocess_error

throw std::runtime_error{"unexpected error reading from pipe: " + std::string(strerror(errno))};

case 0:

return result::TIMEOUT;

case 1: {

if ((pollfd_.revents & POLLIN) != 0) {

ssize_t rv = ::read(pollfd_.fd, buffer.data(), buffer.size());

switch (rv) {

case -1: {

throw std::runtime_error{"unexpected error reading from pipe: " + std::string(strerror(errno))};

}

case 0: {

return result::END_OF_FILE;

}

default: {

// set the size correctly so the caller can just query the vector's size if the number of read chars is needed

buffer.resize(rv);

return result::SUCCESS;

}

}

}

if ((pollfd_.revents & POLLHUP) != 0) {

// appears like this can be considered eof

return result::END_OF_FILE;

}

if ((pollfd_.revents & POLLERR) != 0 || (pollfd_.revents & POLLNVAL) != 0) {

throw std::runtime_error{"poll() failed unexpectedly"};

}

break;

}

default:

// this is a should-never-ever-happen case, a return value not handled by the lines above is actually not possible

throw std::runtime_error{"unexpected return value from pollfd"};

}

}