Serene Runtime 1.0.0-dev
C runtime for the Serene programming language
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12_http_server.c
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1/* -*- C -*-
2 * Serene programming language
3 * Copyright (C) 2019-2026 Sameer Rahmani <[email protected]>
4 *
5 * This program is free software: you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, either version 3 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program. If not, see <https://www.gnu.org/licenses/>.
17 */
18
19// Example 12 -- A http server
20//
21// In this example we create a very dumb and basic http server that responses
22// to each reaquest with a random delay. it spawns a new fiber for each respones.
23//
24// IMPORTANT NOTE: This is a very crappy webserver, don't even think about use it
25// as a skeleton.
26
27#include <arpa/inet.h>
28#include <fcntl.h>
29#include <netinet/in.h>
30#include <stdio.h>
31#include <stdlib.h>
32#include <sys/socket.h>
33#include <unistd.h>
34
35#include <serene/rt/fiber/io.h>
36#include <serene/runtime.h>
37
38typedef struct server_args_t {
39 int listener;
40} server_args_t;
41
42static srn_fiber_result_t srn_fiber_web_worker(srn_context_t *ctx, void *arg) {
43 int client_fd = (int)(intptr_t)arg;
44 int rd_num = (rand() % (5 - 1 + 1)) + 1;
45
46 // Drain the request first. Closing a socket with unread bytes makes the
47 // kernel answer with RST instead of FIN and the client reports a reset.
48 char req[1024];
49 (void)srn_fiber_read(client_fd, req, sizeof(req), -1);
50
51 char body[256];
52 int body_len = snprintf(
53 body, sizeof(body),
54 "<!DOCTYPE html><html><head><title>12-http-server-example</title>"
55 "<body><h1>%d</h1></body></html>",
56 rd_num
57 );
58
59 // Content-Length tells the client where the body ends, so it does not
60 // depend on how the connection is torn down to finish the read.
61 char response[1024];
62 int len = snprintf(
63 response, sizeof(response),
64 "HTTP/1.1 200 OK\r\n"
65 "Content-Type: text/html; charset=UTF-8\r\n"
66 "Content-Length: %d\r\n"
67 "Connection: close\r\n\r\n"
68 "%s",
69 body_len, body
70 );
71
72 srn_fiber_sleep(rd_num);
73 auto result = srn_fiber_write(client_fd, response, (size_t)len, -1);
74 if (HAS_ERROR(result)) {
75 printf("Failed to write: %s\n", result.maybe_error->msg);
76 }
77 srn_fiber_t *self = srn_fiber_current();
78 printf("[%s] Replied back to the client\n", self->name);
79 close(client_fd);
80 return nullptr;
81}
82
83static srn_fiber_result_t server(srn_context_t *ctx, void *arg) {
84 (void)ctx;
85 server_args_t *s = arg;
86
87 for (;;) {
88 srn_io_accept_result_t conn = srn_fiber_accept(s->listener, nullptr, 0);
89
90 if (HAS_ERROR(conn)) {
91 printf("server: accept failed: %s\n", conn.maybe_error->msg);
92 return nullptr;
93 }
94
95 (void)srn_fiber_spawn(ctx, srn_fiber_web_worker, (void *)(intptr_t)conn.fd);
96 }
97 return nullptr;
98}
99
100static void set_nonblock(int fd) {
101 int fl = fcntl(fd, F_GETFL, 0);
102 (void)fcntl(fd, F_SETFL, fl | O_NONBLOCK);
103}
104
105int main(void) {
106 SERENE_RUNTIME_INIT_WITH_SCHED(engine, sched, nullptr);
107 srn_context_t *ctx = srn_context_make(engine);
108
109 int one = 1;
110 int sock = socket(AF_INET, SOCK_STREAM, 0);
111 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(int));
112
113 int port = 8080;
114 struct sockaddr_in a = {
115 .sin_family = AF_INET,
116 .sin_addr = {INADDR_ANY},
117 .sin_port = htons(port),
118 };
119
120 if (sock < 0 || bind(sock, (struct sockaddr *)&a, sizeof(a)) != 0 || listen(sock, 128) != 0) {
121 perror("listener setup");
122 return 1;
123 }
124
125 set_nonblock(sock);
126 socklen_t al = sizeof(a);
127 if (getsockname(sock, (struct sockaddr *)&a, &al) != 0) {
128 perror("getsockname");
129 return 1;
130 }
131
132 printf("Running the webserver on 0.0.0.0:%d\n", port);
133 server_args_t s = {sock};
134 (void)srn_fiber_spawn(ctx, server, &s);
135
136 srn_sched_run(sched, 1);
137 close(sock);
138
139 srn_context_release(ctx);
140 SERENE_RUNTIME_SHUTDOWN(engine);
141 return 0;
142}
server
static srn_fiber_result_t server(srn_context_t *ctx, void *arg)
Definition 09_tcp_echo.c:56
set_nonblock
static void set_nonblock(int fd)
Definition 12_http_server.c:100
main
int main(void)
Definition 12_http_server.c:105
srn_fiber_web_worker
static srn_fiber_result_t srn_fiber_web_worker(srn_context_t *ctx, void *arg)
Definition 12_http_server.c:42
server
static srn_fiber_result_t server(srn_context_t *ctx, void *arg)
Definition 12_http_server.c:83
srn_context_make
srn_context_t * srn_context_make(srn_engine_t *engine)
Make an empty context, by allocating a new memory block.
Definition context.c:39
srn_context_release
int srn_context_release(srn_context_t *ctx)
Definition context.c:64
HAS_ERROR
#define HAS_ERROR(x)
True when x – a value carrying an ERROR_HEADER – has an error attached.
Definition errors.h:63
srn_fiber_spawn
srn_fiber_t * srn_fiber_spawn(srn_context_t *ctx, srn_fiber_entry_t entry, void *arg)
Make and schedule a fiber with every default, the engine's scheduler, the configured stack size,...
Definition fiber.c:247
srn_fiber_result_t
void * srn_fiber_result_t
What a fiber's entry produces, type-erased.
Definition fiber.h:157
srn_fiber_write
srn_io_size_result_t srn_fiber_write(int fd, const void *buf, size_t len, int64_t offset)
Write len bytes from buf to fd, suspending the calling fiber until the operation completes rather tha...
Definition io.c:296
srn_fiber_accept
srn_io_accept_result_t srn_fiber_accept(int fd, struct sockaddr *addr, socklen_t addr_cap)
Accept a pending connection on the listening socket fd, suspending the calling fiber until one arrive...
Definition io.c:308
srn_fiber_sleep
srn_error_t * srn_fiber_sleep(uint64_t duration)
Suspend the calling fiber for at least duration seconds, letting its worker run other fibers meanwhil...
Definition io.c:282
srn_fiber_read
srn_io_size_result_t srn_fiber_read(int fd, void *buf, size_t len, int64_t offset)
Read up to len bytes from fd into buf, suspending the calling fiber until the operation completes rat...
Definition io.c:284
io.h
The fiber facing IO API: blocking looking calls a fiber uses to do IO.
SERENE_RUNTIME_SHUTDOWN
#define SERENE_RUNTIME_SHUTDOWN(engine)
Tear down what SERENE_RUNTIME_INIT brought up, in reverse order, the engine (reactor,...
Definition runtime.h:58
SERENE_RUNTIME_INIT_WITH_SCHED
#define SERENE_RUNTIME_INIT_WITH_SCHED(engine, sched, config)
SERENE_RUNTIME_INIT plus a sched variable bound to the engine's scheduler, which every run and fiber ...
Definition runtime.h:46
srn_fiber_current
srn_fiber_t * srn_fiber_current(void)
The fiber currently running on this os thread, or null when the calling thread is not a worker or the...
Definition scheduler.c:1058
srn_sched_run
void srn_sched_run(srn_scheduler_t *sched, size_t nworkers)
Run the scheduler with nworkers os threads draining it, returning once the pool goes quiescent (every...
Definition scheduler.c:843
server_args_t
Definition 09_tcp_echo.c:43
server_args_t::listener
int listener
Definition 09_tcp_echo.c:44
srn_context_t
Definition context.h:47
srn_fiber_t
Definition fiber.h:264
srn_fiber_t::name
char name[SRN_FIBER_NAME_MAX]
Debug name, the caller's choice copied at creation, or the autogenerated f#<id> from the engine wide ...
Definition fiber.h:330
srn_io_accept_result_t
The result of srn_fiber_accept.
Definition io.h:86
srn_io_accept_result_t::fd
int fd
Definition io.h:88