147 lines
3.7 KiB
C
147 lines
3.7 KiB
C
//
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// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
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// Copyright 2018 Capitar IT Group BV <info@capitar.com>
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//
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// This software is supplied under the terms of the MIT License, a
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// copy of which should be located in the distribution where this
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// file was obtained (LICENSE.txt). A copy of the license may also be
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// found online at https://opensource.org/licenses/MIT.
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//
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// This is a very simple HTTP client. It only performs HTTP GET
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// operations, and does not follow HTTP redirects. Think of it as
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// a trivialized version of CURL. It is super simple, taking the
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// URL on the command line, and emitting the results to stdout.
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// For clarity, we are eliding TLS support.
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// It may not work on all systems, but it should work anywhere that
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// both the standard C library and nng itself are available.
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// We check for errors, but no effort is made to clean up resources,
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// since this program just exits. In longer running programs or libraries,
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// callers should take care to clean up things that they allocate.
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// Unfortunately many famous sites use redirects, so you won't see that
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// emitted.
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// Example usage:
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//
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// % export CPPFLAGS="-I /usr/local/include"
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// % export LDFLAGS="-L /usr/local/lib -lnng"
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// % export CC="cc"
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// % ${CC} ${CPPFLAGS} http_client.c -o http_client ${LDFLAGS}
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// % ./http_client http://httpbin.org/ip
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//
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#include <nng/nng.h>
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#include <nng/supplemental/http/http.h>
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#include <stdio.h>
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#include <stdlib.h>
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void
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fatal(int rv)
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{
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fprintf(stderr, "%s\n", nng_strerror(rv));
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exit(1);
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}
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int
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main(int argc, char **argv)
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{
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nng_http_client *client;
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nng_http_conn * conn;
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nng_url * url;
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nng_aio * aio;
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nng_http_req * req;
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nng_http_res * res;
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const char * hdr;
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int rv;
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int len;
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void * data;
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nng_iov iov;
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if (argc < 2) {
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fprintf(stderr, "No URL supplied!\n");
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exit(1);
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}
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if (((rv = nng_url_parse(&url, argv[1])) != 0) ||
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((rv = nng_http_client_alloc(&client, url)) != 0) ||
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((rv = nng_http_req_alloc(&req, url)) != 0) ||
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((rv = nng_http_res_alloc(&res)) != 0) ||
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((rv = nng_aio_alloc(&aio, NULL, NULL)) != 0)) {
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fatal(rv);
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}
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// Start connection process...
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nng_http_client_connect(client, aio);
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// Wait for it to finish.
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nng_aio_wait(aio);
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if ((rv = nng_aio_result(aio)) != 0) {
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fatal(rv);
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}
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// Get the connection, at the 0th output.
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conn = nng_aio_get_output(aio, 0);
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// Request is already set up with URL, and for GET via HTTP/1.1.
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// The Host: header is already set up too.
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// Send the request, and wait for that to finish.
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nng_http_conn_write_req(conn, req, aio);
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nng_aio_wait(aio);
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if ((rv = nng_aio_result(aio)) != 0) {
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fatal(rv);
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}
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// Read a response.
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nng_http_conn_read_res(conn, res, aio);
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nng_aio_wait(aio);
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if ((rv = nng_aio_result(aio)) != 0) {
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fatal(rv);
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}
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if (nng_http_res_get_status(res) != NNG_HTTP_STATUS_OK) {
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fprintf(stderr, "HTTP Server Responded: %d %s\n",
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nng_http_res_get_status(res),
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nng_http_res_get_reason(res));
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}
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// This only supports regular transfer encoding (no Chunked-Encoding,
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// and a Content-Length header is required.)
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if ((hdr = nng_http_res_get_header(res, "Content-Length")) == NULL) {
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fprintf(stderr, "Missing Content-Length header.\n");
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exit(1);
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}
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len = atoi(hdr);
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if (len == 0) {
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return (0);
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}
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// Allocate a buffer to receive the body data.
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data = malloc(len);
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// Set up a single iov to point to the buffer.
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iov.iov_len = len;
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iov.iov_buf = data;
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// Following never fails with fewer than 5 elements.
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nng_aio_set_iov(aio, 1, &iov);
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// Now attempt to receive the data.
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nng_http_conn_read_all(conn, aio);
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// Wait for it to complete.
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nng_aio_wait(aio);
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if ((rv = nng_aio_result(aio)) != 0) {
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fatal(rv);
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}
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fwrite(data, 1, len, stdout);
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return (0);
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}
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