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Refactor detail::select_read() for up to two FDs

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Add an overload for detail::select_read() that accepts two FDs and
reports readability via two boolean out parameters. This is required to
implement interruptible reads.

Both overloads build on top of a common implementation that optimizes to
the same assembly for the common, single FD case.
This commit is contained in:
Florian Albrechtskirchinger 2025-02-03 15:53:54 +01:00
parent 9aaa7a77a0
commit 57a20366a3
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GPG Key ID: 9C4E2AE92D3A9595
1 changed files with 50 additions and 9 deletions
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59
httplib.h
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@ -3184,34 +3184,75 @@ inline ssize_t send_socket(socket_t sock, const void *ptr, size_t size,
});
}
inline ssize_t select_read(socket_t sock, time_t sec, time_t usec) {
template <bool WithExtraFD>
inline ssize_t select_read_impl(socket_t sock, socket_t extra_fd, time_t sec,
time_t usec, bool *sock_readable,
bool *extra_fd_readable) {
#ifdef CPPHTTPLIB_USE_POLL
struct pollfd pfd_read;
pfd_read.fd = sock;
pfd_read.events = POLLIN;
constexpr size_t nfds = WithExtraFD ? 2 : 1;
struct pollfd pfd_read[nfds];
pfd_read[0].fd = sock;
pfd_read[0].events = POLLIN;
if (WithExtraFD) {
pfd_read[1].fd = extra_fd;
pfd_read[1].events = POLLIN;
}
auto timeout = static_cast<int>(sec * 1000 + usec / 1000);
return handle_EINTR([&]() { return poll(&pfd_read, 1, timeout); });
size_t ret = handle_EINTR([&]() { return poll(pfd_read, nfds, timeout); });
if (WithExtraFD && ret > 0) {
assert(sock_readable && extra_fd_readable);
*sock_readable = pfd_read[0].revents & POLLIN;
*extra_fd_readable = pfd_read[1].revents & POLLIN;
}
return ret;
#else
#ifndef _WIN32
if (sock >= FD_SETSIZE) { return -1; }
if (sock >= FD_SETSIZE || (WithExtraFD && extra_fd >= FD_SETSIZE)) {
return -1;
}
#endif
int nfds;
fd_set fds;
FD_ZERO(&fds);
FD_SET(sock, &fds);
if (WithExtraFD) {
FD_SET(extra_fd, &fds);
nfds = static_cast<int>((std::max)(sock, extra_fd) + 1);
} else {
nfds = static_cast<int>(sock + 1);
}
timeval tv;
tv.tv_sec = static_cast<long>(sec);
tv.tv_usec = static_cast<decltype(tv.tv_usec)>(usec);
return handle_EINTR([&]() {
return select(static_cast<int>(sock + 1), &fds, nullptr, nullptr, &tv);
});
ssize_t ret =
handle_EINTR([&]() { return select(nfds, &fds, nullptr, nullptr, &tv); });
if (WithExtraFD && ret > 0) {
assert(sock_readable && extra_fd_readable);
*sock_readable = FD_ISSET(sock, &fds);
*extra_fd_readable = FD_ISSET(extra_fd, &fds);
}
return ret;
#endif
}
inline ssize_t select_read(socket_t sock, time_t sec, time_t usec) {
return select_read_impl<false>(sock, INVALID_SOCKET, sec, usec, nullptr,
nullptr);
}
inline ssize_t select_read(socket_t sock, socket_t extra_fd, time_t sec,
time_t usec, bool &sock_readable,
bool &extra_fd_readable) {
return select_read_impl<true>(sock, extra_fd, sec, usec, &sock_readable,
&extra_fd_readable);
}
inline ssize_t select_write(socket_t sock, time_t sec, time_t usec) {
#ifdef CPPHTTPLIB_USE_POLL
struct pollfd pfd_read;