82 lines
2.5 KiB
C
82 lines
2.5 KiB
C
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// Copyright (c) 2022 Cesanta Software Limited
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// All rights reserved
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//
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// This example demonstrates how to push data over a REST API
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// We're going to send a JSON array of some integer values, s_data.
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// Periodically, s_data changes, which is tracked by s_version.
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// Clients inform their current version, we only send on version mismatch,
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// or when version is zero (client has no data); this minimizes traffic and
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// avoids updating the UI unnecesarily.
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//
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// 1. Start this server, type `make`
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// 2. Open http://localhost:8000 in your browser
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#include "mongoose.h"
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static const char *s_listen_on = "http://localhost:8000";
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static const char *s_root_dir = "web_root";
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#define DATA_SIZE 10 // Total number of elements
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static int s_data[DATA_SIZE]; // Simulate some complex data
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static long s_version = 0; // Data "version"
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static long getparam(struct mg_http_message *hm, const char *json_path) {
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double dv = 0;
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mg_json_get_num(hm->body, json_path, &dv);
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return dv;
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}
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static size_t printdata(mg_pfn_t out, void *ptr, va_list *ap) {
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const char *comma = "";
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size_t n = 0;
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for (int i = 0; i < DATA_SIZE; ++i) {
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n += mg_xprintf(out, ptr, "%s%d", comma, s_data[i]);
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comma = ",";
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}
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return n;
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(void) ap;
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}
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static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
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if (ev == MG_EV_HTTP_MSG) {
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struct mg_http_message *hm = ev_data;
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if (mg_http_match_uri(hm, "/api/data")) {
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long version = getparam(hm, "$.version");
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if (version > 0 && version == s_version) {
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// Version match: no changes
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mg_http_reply(c, 200, "Content-Type: application/json\r\n",
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"{%m:%m,%m:%ld}\n", MG_ESC("status"), MG_ESC("no change"),
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MG_ESC("version"), version);
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} else {
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// Version mismatch, return data
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mg_http_reply(c, 200, "Content-Type: application/json\r\n",
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"{%m:%ld,%m:[%M]}\n", MG_ESC("version"), s_version,
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MG_ESC("data"), printdata);
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}
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} else {
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struct mg_http_serve_opts opts = {.root_dir = s_root_dir};
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mg_http_serve_dir(c, hm, &opts);
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}
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}
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(void) fn_data;
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}
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static void timer_fn(void *arg) {
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for (int i = 0; i < DATA_SIZE; i++) {
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s_data[i] = rand();
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}
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s_version++;
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(void) arg;
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}
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int main(void) {
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struct mg_mgr mgr;
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mg_mgr_init(&mgr);
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srand(time(NULL));
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mg_timer_add(&mgr, 5000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn, NULL);
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mg_http_listen(&mgr, s_listen_on, fn, NULL);
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for (;;) mg_mgr_poll(&mgr, 1000);
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mg_mgr_free(&mgr);
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return 0;
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}
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