[examples] Create HTTP2 example with http2.golang.org

Intention is to partition the demo into multiple files, so that the
main program is quite easy to follow.
1. connectlib.c: For any URL parsing and TCP connection related stuff
2. sh2lib.c: Convenience functions for HTTP2+TLS. The goal here is to
   expose a simpler API than nghttp2. If most usecases end up being
   served with this library, it could potentially be moved into a separate
   component

examples/protocols/http2_request/components/sh2lib/connectlib.c

@@ -0,0 +1,164 @@
+/* With adaptations by Espressif Systems
+ *
+ * Copyright (c) 2013 Tatsuhiro Tsujikawa
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <stdlib.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <netdb.h>
+
+#include "connectlib.h"
+
+/* Basic parser from nghttp2/examples/client.c */
+int parse_uri(struct uri *res, const char *uri)
+{
+    /* We only interested in https */
+    size_t len, i, offset;
+    int ipv6addr = 0;
+    memset(res, 0, sizeof(struct uri));
+    len = strlen(uri);
+    if (len < 9 || memcmp("https://", uri, 8) != 0) {
+        return -1;
+    }
+    offset = 8;
+    res->host = res->hostport = &uri[offset];
+    res->hostlen = 0;
+    if (uri[offset] == '[') {
+        /* IPv6 literal address */
+        ++offset;
+        ++res->host;
+        ipv6addr = 1;
+        for (i = offset; i < len; ++i) {
+            if (uri[i] == ']') {
+                res->hostlen = i - offset;
+                offset = i + 1;
+                break;
+            }
+        }
+    } else {
+        const char delims[] = ":/?#";
+        for (i = offset; i < len; ++i) {
+            if (strchr(delims, uri[i]) != NULL) {
+                break;
+            }
+        }
+        res->hostlen = i - offset;
+        offset = i;
+    }
+    if (res->hostlen == 0) {
+        return -1;
+    }
+    /* Assuming https */
+    res->port = 443;
+    if (offset < len) {
+        if (uri[offset] == ':') {
+            /* port */
+            const char delims[] = "/?#";
+            int port = 0;
+            ++offset;
+            for (i = offset; i < len; ++i) {
+                if (strchr(delims, uri[i]) != NULL) {
+                    break;
+                }
+                if ('0' <= uri[i] && uri[i] <= '9') {
+                    port *= 10;
+                    port += uri[i] - '0';
+                    if (port > 65535) {
+                        return -1;
+                    }
+                } else {
+                    return -1;
+                }
+            }
+            if (port == 0) {
+                return -1;
+            }
+            offset = i;
+            res->port = (uint16_t)port;
+        }
+    }
+    res->hostportlen = (size_t)(uri + offset + ipv6addr - res->host);
+    for (i = offset; i < len; ++i) {
+        if (uri[i] == '#') {
+            break;
+        }
+    }
+    if (i - offset == 0) {
+        res->path = "/";
+        res->pathlen = 1;
+    } else {
+        res->path = &uri[offset];
+        res->pathlen = i - offset;
+    }
+    return 0;
+}
+
+int connect_to_host(const char *host, size_t hostlen, uint16_t port)
+{
+    int ret;
+    struct addrinfo hints = {
+        .ai_family = AF_UNSPEC,
+        .ai_socktype = SOCK_STREAM,
+    };
+
+    char service[6];
+    snprintf(service, sizeof(service), "%u", port);
+
+    char *use_host = calloc(1, hostlen + 1);
+    if (!use_host) {
+         return -1;
+    }
+    strncpy(use_host, host, hostlen);
+
+    struct addrinfo *res;
+    ret = getaddrinfo(use_host, service, &hints, &res);
+    if (ret) {
+        free(use_host);
+        return -1;
+    }
+    free(use_host);
+
+    ret = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
+    if (ret < 0) {
+        goto err_freeaddr;
+    }
+
+    int fd = ret;
+    ret = connect(fd, res->ai_addr, res->ai_addrlen);
+    if (ret < 0) {
+        goto err_freesocket;
+    }
+
+    return fd;
+
+err_freesocket:
+    close(fd);
+err_freeaddr:
+    freeaddrinfo(res);
+    return -1;
+}
+