Add http proxy client example

PUBLISHED_FROM=443a0d3db63df1b78555a9fa4eff808bef3a9a01

examples/http_proxy_client/Makefile

+PROG = http_proxy_client
+#SSL_LIB=openssl
+CFLAGS_EXTRA = -DMG_ENABLE_CALLBACK_USERDATA=1
+include ../examples.mk

examples/http_proxy_client/http_proxy_client.c

+/*
+ * Copyright (c) 2014 Cesanta Software Limited
+ * All rights reserved
+ *
+ * This program fetches HTTP URLs.
+ */
+
+#define MG_ENABLE_CALLBACK_USERDATA 1
+#include "mongoose.h"
+
+static int s_exit_flag = 0;
+static int s_show_headers = 0;
+
+static void ev_handler(struct mg_connection *c, int ev, void *ev_data,
+                       void *userdata) {
+  struct http_message *hm = (struct http_message *) ev_data;
+
+  switch (ev) {
+    case MG_EV_CONNECT:
+      if (*(int *) ev_data != 0) {
+        fprintf(stderr, "connect() failed: %s\n", strerror(*(int *) ev_data));
+        s_exit_flag = 1;
+      } else {
+        // Stage 2. Connection to the HTTP proxy is established.
+        // Write CONNECT request, and turn this connection to HTTP.
+        // NOTE: target URL is passed to us as userdata.
+        unsigned port = 80;
+        struct mg_str scheme, host;
+        mg_parse_uri(mg_mk_str((char *) userdata), &scheme, NULL, &host, &port,
+                     NULL, NULL, NULL);
+        if (port == 0) port = (scheme.len == 5) ? 443 : 80;
+        mg_printf(c, "CONNECT %.*s:%u HTTP/1.1\r\n\r\n", (int) host.len, host.p,
+                  port);
+        // Now set the flag and wait for the connection establishment
+        c->flags |= MG_F_USER_1;
+      }
+      break;
+    case MG_EV_RECV:
+      // Stage 3. Check if proxy replied. Here, we don't parse the reply
+      // for simplicity. Assume success, and write HTTP request.
+      if (c->flags & MG_F_USER_1) {
+        struct mg_str host, path;
+        c->flags &= ~MG_F_USER_1;
+        mg_parse_uri(mg_mk_str((char *) userdata), NULL, NULL, &host, NULL,
+                     &path, NULL, NULL);
+        if (path.len == 0) path = mg_mk_str("/");
+        mg_printf(c, "GET %.*s HTTP/1.0\r\nHost: %.*s\r\n\r\n", (int) path.len,
+                  path.p, (int) host.len, host.p);
+        mg_set_protocol_http_websocket(c);
+      }
+      break;
+    case MG_EV_HTTP_REPLY:
+      c->flags |= MG_F_CLOSE_IMMEDIATELY;
+      if (s_show_headers) {
+        fwrite(hm->message.p, 1, hm->message.len, stdout);
+      } else {
+        fwrite(hm->body.p, 1, hm->body.len, stdout);
+      }
+      putchar('\n');
+      s_exit_flag = 1;
+      break;
+    case MG_EV_CLOSE:
+      if (s_exit_flag == 0) {
+        printf("Server closed connection\n");
+        s_exit_flag = 1;
+      }
+      break;
+    default:
+      break;
+  }
+}
+
+int main(int argc, char *argv[]) {
+  struct mg_mgr mgr;
+  int i;
+
+  mg_mgr_init(&mgr, NULL);
+
+  /* Process command line arguments */
+  for (i = 1; i < argc; i++) {
+    if (strcmp(argv[i], "--show-headers") == 0) {
+      s_show_headers = 1;
+    } else if (strcmp(argv[i], "--hexdump") == 0 && i + 1 < argc) {
+      mgr.hexdump_file = argv[++i];
+    } else {
+      break;
+    }
+  }
+
+  if (i + 2 != argc) {
+    fprintf(stderr,
+            "Usage: %s [--hexdump <file>] "
+            "[--show-headers] PROXY_HOST:PROXY_PORT URL\n",
+            argv[0]);
+    exit(EXIT_FAILURE);
+  }
+
+  // Stage 1. Connect to the HTTP proxy as to a plain TCP server.
+  // Pass URL as a callback argument
+  mg_connect(&mgr, argv[i], ev_handler, argv[i + 1]);
+
+  while (s_exit_flag == 0) {
+    mg_mgr_poll(&mgr, 1000);
+  }
+  mg_mgr_free(&mgr);
+
+  return 0;
+}