mongoose/examples/http-streaming-client/main.c

// Copyright (c) 2021 Cesanta Software Limited
// All rights reserved
//
// Example streaming HTTP client.
// The default HTTP handler waits until the whole HTTP message is buffered in
// c->recv IO buffer. It can be large. This example shows how to receive
// a potentially large response in chunks by handling the MG_EV_READ events.
//
// You can change `s_url` from the command line by executing: ./example YOUR_URL
// To enable SSL/TLS, see https://mongoose.ws/tutorials/tls/#how-to-build

#include "mongoose.h"

// The very first web page in history. You can replace it from command line
static const char *s_url = "http://info.cern.ch";

// Print HTTP response and signal that we're done
static void fn(struct mg_connection *c, int ev, void *ev_data) {
  if (ev == MG_EV_CONNECT) {
    // Connected to server. Extract host name from URL
    struct mg_str host = mg_url_host(s_url);
    if (mg_url_is_ssl(s_url)) {
      struct mg_tls_opts opts = {.ca = mg_unpacked("/certs/ca.pem"),
                                 .name = host};
      mg_tls_init(c, &opts);
    }
    // Send request
    mg_printf(c,
              "GET %s HTTP/1.1\r\n"
              "Connection: close\r\n"
              "Host: %.*s\r\n"
              "\r\n",
              mg_url_uri(s_url), (int) host.len, host.ptr);
  } else if (ev == MG_EV_READ) {
    // c->data[0] holds a flag, whether we have parsed the request already
    if (c->data[0] == 0) {
      struct mg_http_message hm;
      int n = mg_http_parse((char *) c->recv.buf, c->recv.len, &hm);
      if (n < 0) mg_error(c, "Bad response");
      if (n > 0) {
        fwrite(c->recv.buf + n, 1, c->recv.len - n, stdout);  // Print body
        c->recv.len = 0;  // Cleanup receive buffer
        c->data[0] = 1;   // Request parsed, set the flag
      }
    } else {
      fwrite(c->recv.buf, 1, c->recv.len, stdout);
      c->recv.len = 0;  // Cleanup the receive buffer
    }
  } else if (ev == MG_EV_CLOSE) {
    *(bool *) c->fn_data = true;  // Done, tell event loop to stop
  } else if (ev == MG_EV_ERROR) {
    *(bool *) c->fn_data = true;  // Error, Tell event loop to stop
  }
  (void) ev_data;
}

int main(int argc, char *argv[]) {
  struct mg_mgr mgr;  // Event manager
  bool done = false;  // Event handler flips it to true

  mg_mgr_init(&mgr);       // Initialise event manager
  mg_log_set(MG_LL_INFO);  // Set to 0 to disable debug log

  if (argc > 1) s_url = argv[1];          // Use URL from command line
  mg_connect(&mgr, s_url, fn, &done);     // Create client connection
  while (!done) mg_mgr_poll(&mgr, 1000);  // Infinite event loop
  mg_mgr_free(&mgr);                      // Free resources

  return 0;
}