pipe_response_example.cpp

/*
     This file is part of libhttpserver
     Copyright (C) 2011-2025 Sebastiano Merlino

     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, or (at your option) any later version.

     This library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.

     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
     USA
*/

// pipe_response_example.cpp - stream a response from the read end of a
// pipe that a background thread writes into. The lambda owns the
// short-lived pipe + writer; ownership of the read-end fd transfers
// into the response.

#if defined(_WIN32) && !defined(__CYGWIN__)
#include <io.h>
#include <fcntl.h>
#else
#include <unistd.h>
#endif

#include <cerrno>
#include <cstring>
#include <thread>

#include <httpserver.hpp>

namespace {
// Production-ready: writes the whole buffer, retrying short writes and
// resuming after an EINTR-interrupted call. Returns false on a hard
// error. On Windows `write`/`errno` are the CRT `_write`/`errno`; EINTR
// never fires there, so the loop is a zero-cost wrapper and stays
// portable.
bool write_all(int fd, const char* buf, size_t len) {
    size_t off = 0;
    while (off < len) {
        ssize_t n = write(fd, buf + off, len - off);
        if (n < 0) {
            if (errno == EINTR) continue;
            return false;
        }
        if (n == 0) return false;
        off += static_cast<size_t>(n);
    }
    return true;
}
}  // namespace

int main() {
    httpserver::webserver ws{httpserver::create_webserver(8080)};

    ws.on_get("/stream", [](const httpserver::http_request&) {
        int pipefd[2];
#if defined(_WIN32) && !defined(__CYGWIN__)
        if (_pipe(pipefd, 4096, _O_BINARY) == -1) {
#else
        if (pipe(pipefd) == -1) {
#endif
            return httpserver::http_response::string("pipe failed").with_status(500);
        }

        std::thread writer([fd = pipefd[1]]() {
            const char* messages[] = {"Hello ", "from ", "a pipe!\n"};
            for (const char* msg : messages) {
                // Production-ready: write_all loops to handle partial
                // writes and EINTR. Stop streaming on a hard error --
                // closing the write end signals EOF to the reader.
                if (!write_all(fd, msg, strlen(msg))) {
                    break;
                }
            }
            close(fd);
        });
        writer.detach();

        return httpserver::http_response::pipe(pipefd[0])
                   .with_header("Content-Type", "text/plain");
    });

    ws.start(true);
    return 0;
}