Add huge-response example

examples/huge-response/Makefile

@@ -0,0 +1,11 @@
+PROG ?= example
+CFLAGS ?= -W -Wall -Wextra -O0 -g
+
+all: $(PROG)
+	$(RUN) ./$(PROG) $(ARGS)
+
+$(PROG): main.c
+	$(CC) ../../mongoose.c -I../.. -W -Wall -DMG_ENABLE_LINES=1 $(CFLAGS) -o $(PROG) main.c mjson.c
+
+clean:
+	rm -rf $(PROG) *.o *.dSYM *.gcov *.gcno *.gcda *.obj *.exe *.ilk *.pdb

examples/huge-response/main.c

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+// Copyright (c) 2021 Cesanta Software Limited
+// All rights reserved
+//
+// Example that demonstrates how to send a large responses with limited memory.
+// We're going to send a JSON array of many integer values, s_data.
+// The idea is to send a response in small chunks, and let the client request
+// the next chunk.
+// Periodically, s_data changes, which is tracked by s_version.
+// Client requests a range and a version, to ensure data integrity.
+//
+//  1. Start this server, type `make`
+//  2. Open http://localhost:8000 in your browser
+
+#include "mjson.h"
+#include "mongoose.h"
+
+static const char *s_listen_on = "http://localhost:8000";
+static const char *s_root_dir = "web_root";
+
+#define DATA_SIZE 10000         // Total number of elements
+#define CHUNK_SIZE 1000         // Max number returned in one API call
+static int s_data[DATA_SIZE];   // Simulate some complex big dataMax number
+                                // returned in one API call
+static unsigned s_version = 0;  // Data "version"
+
+static double getparam(struct mg_http_message *hm, const char *json_path) {
+  double dv = 0;
+  mjson_get_number(hm->body.ptr, hm->body.len, json_path, &dv);
+  return dv;
+}
+
+static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+  if (ev == MG_EV_HTTP_MSG) {
+    struct mg_http_message *hm = ev_data;
+    if (mg_http_match_uri(hm, "/api/data")) {
+      unsigned start = getparam(hm, "$.start");
+      unsigned version = getparam(hm, "$.version");
+      char *response = NULL;
+      if (version > 0 && version != s_version) {
+        // Version mismatch: s_data has changed while client fetches it
+        // Tell client to restart
+        response = mjson_aprintf("{%Q:%Q, %Q:%u}", "error", "wrong version",
+                                 "version", version);
+      } else {
+        // Return data, up to CHUNK_SIZE elements
+        unsigned max = start + CHUNK_SIZE;
+        const char *comma = "";
+        if (max > DATA_SIZE) max = DATA_SIZE;
+        mjson_printf(mjson_print_dynamic_buf, &response, "{%Q:%u,%Q:%u,%Q:[",
+                     "version", s_version, "start", start, "data");
+        while (start < max) {
+          mjson_printf(mjson_print_dynamic_buf, &response, "%s%d", comma,
+                       s_data[start]);
+          comma = ",";
+          start++;
+        }
+        mjson_printf(mjson_print_dynamic_buf, &response, "]}");
+      }
+      mg_http_reply(c, 200, "Content-Type: text/json\r\n", "%s", response);
+      free(response);
+    } else {
+      struct mg_http_serve_opts opts = {0};
+      opts.root_dir = s_root_dir;
+      mg_http_serve_dir(c, hm, &opts);
+    }
+  }
+  (void) fn_data;
+}
+
+static void timer_fn(void *arg) {
+  for (int i = 0; i < DATA_SIZE; i++) {
+    s_data[i] = rand();
+  }
+  s_version++;
+  (void) arg;
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+  struct mg_timer t1;
+  mg_mgr_init(&mgr);
+  srand(time(NULL));
+  mg_timer_init(&t1, 1000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn, NULL);
+  mg_http_listen(&mgr, s_listen_on, fn, NULL);
+  LOG(LL_INFO, ("Listening on %s", s_listen_on));
+  for (;;) mg_mgr_poll(&mgr, 1000);
+  mg_timer_free(&t1);
+  mg_mgr_free(&mgr);
+  return 0;
+}

examples/huge-response/mjson.h

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+// Copyright (c) 2018-2020 Cesanta Software Limited
+// All rights reserved
+//
+// 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.
+
+#ifndef MJSON_H
+#define MJSON_H
+
+#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef MJSON_ENABLE_PRINT
+#define MJSON_ENABLE_PRINT 1
+#endif
+
+#ifndef MJSON_ENABLE_RPC
+#define MJSON_ENABLE_RPC 1
+#endif
+
+#ifndef MJSON_ENABLE_BASE64
+#define MJSON_ENABLE_BASE64 1
+#endif
+
+#ifndef MJSON_ENABLE_MERGE
+#define MJSON_ENABLE_MERGE 1
+#endif
+
+#ifndef MJSON_ENABLE_PRETTY
+#define MJSON_ENABLE_PRETTY 1
+#endif
+
+#ifndef MJSON_ENABLE_NEXT
+#define MJSON_ENABLE_NEXT 1
+#endif
+
+#ifndef MJSON_RPC_LIST_NAME
+#define MJSON_RPC_LIST_NAME "rpc.list"
+#endif
+
+#ifndef MJSON_DYNBUF_CHUNK
+#define MJSON_DYNBUF_CHUNK 256  // Allocation granularity for print_dynamic_buf
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define MJSON_ERROR_INVALID_INPUT (-1)
+#define MJSON_ERROR_TOO_DEEP (-2)
+#define MJSON_TOK_INVALID 0
+#define MJSON_TOK_KEY 1
+#define MJSON_TOK_STRING 11
+#define MJSON_TOK_NUMBER 12
+#define MJSON_TOK_TRUE 13
+#define MJSON_TOK_FALSE 14
+#define MJSON_TOK_NULL 15
+#define MJSON_TOK_ARRAY 91
+#define MJSON_TOK_OBJECT 123
+#define MJSON_TOK_IS_VALUE(t) ((t) > 10 && (t) < 20)
+
+typedef int (*mjson_cb_t)(int ev, const char *s, int off, int len, void *ud);
+
+#ifndef MJSON_MAX_DEPTH
+#define MJSON_MAX_DEPTH 20
+#endif
+
+int mjson(const char *s, int len, mjson_cb_t cb, void *ud);
+int mjson_find(const char *s, int len, const char *jp, const char **, int *);
+int mjson_get_number(const char *s, int len, const char *path, double *v);
+int mjson_get_bool(const char *s, int len, const char *path, int *v);
+int mjson_get_string(const char *s, int len, const char *path, char *to, int n);
+int mjson_get_hex(const char *s, int len, const char *path, char *to, int n);
+
+#if MJSON_ENABLE_NEXT
+int mjson_next(const char *s, int n, int off, int *koff, int *klen, int *voff,
+               int *vlen, int *vtype);
+#endif
+
+#if MJSON_ENABLE_BASE64
+int mjson_get_base64(const char *s, int len, const char *path, char *to, int n);
+int mjson_base64_dec(const char *src, int n, char *dst, int dlen);
+#endif
+
+#if MJSON_ENABLE_PRINT
+typedef int (*mjson_print_fn_t)(const char *buf, int len, void *userdata);
+typedef int (*mjson_vprint_fn_t)(mjson_print_fn_t, void *, va_list *);
+
+struct mjson_fixedbuf {
+  char *ptr;
+  int size, len;
+};
+
+int mjson_printf(mjson_print_fn_t, void *, const char *fmt, ...);
+int mjson_vprintf(mjson_print_fn_t, void *, const char *fmt, va_list *ap);
+int mjson_print_str(mjson_print_fn_t, void *, const char *s, int len);
+int mjson_print_int(mjson_print_fn_t, void *, int value, int is_signed);
+int mjson_print_long(mjson_print_fn_t, void *, long value, int is_signed);
+int mjson_print_buf(mjson_print_fn_t fn, void *, const char *buf, int len);
+int mjson_print_dbl(mjson_print_fn_t fn, void *, double, int width);
+
+int mjson_print_null(const char *ptr, int len, void *userdata);
+int mjson_print_fixed_buf(const char *ptr, int len, void *userdata);
+int mjson_print_dynamic_buf(const char *ptr, int len, void *userdata);
+
+int mjson_snprintf(char *buf, size_t len, const char *fmt, ...);
+char *mjson_aprintf(const char *fmt, ...);
+
+#if MJSON_ENABLE_PRETTY
+int mjson_pretty(const char *, int, const char *, mjson_print_fn_t, void *);
+#endif
+
+#if MJSON_ENABLE_MERGE
+int mjson_merge(const char *, int, const char *, int, mjson_print_fn_t, void *);
+#endif
+
+#endif  // MJSON_ENABLE_PRINT
+
+#if MJSON_ENABLE_RPC
+
+void jsonrpc_init(mjson_print_fn_t, void *userdata);
+int mjson_globmatch(const char *s1, int n1, const char *s2, int n2);
+
+struct jsonrpc_request {
+  struct jsonrpc_ctx *ctx;
+  const char *frame;    // Points to the whole frame
+  int frame_len;        // Frame length
+  const char *params;   // Points to the "params" in the request frame
+  int params_len;       // Length of the "params"
+  const char *id;       // Points to the "id" in the request frame
+  int id_len;           // Length of the "id"
+  const char *method;   // Points to the "method" in the request frame
+  int method_len;       // Length of the "method"
+  mjson_print_fn_t fn;  // Printer function
+  void *fndata;         // Printer function data
+  void *userdata;       // Callback's user data as specified at export time
+};
+
+struct jsonrpc_method {
+  const char *method;
+  int method_sz;
+  void (*cb)(struct jsonrpc_request *);
+  struct jsonrpc_method *next;
+};
+
+// Main RPC context, stores current request information and a list of
+// exported RPC methods.
+struct jsonrpc_ctx {
+  struct jsonrpc_method *methods;
+  mjson_print_fn_t response_cb;
+  void *response_cb_data;
+};
+
+// Registers function fn under the given name within the given RPC context
+#define jsonrpc_ctx_export(ctx, name, fn)                                 \
+  do {                                                                    \
+    static struct jsonrpc_method m = {(name), sizeof(name) - 1, (fn), 0}; \
+    m.next = (ctx)->methods;                                              \
+    (ctx)->methods = &m;                                                  \
+  } while (0)
+
+void jsonrpc_ctx_init(struct jsonrpc_ctx *ctx, mjson_print_fn_t, void *);
+void jsonrpc_return_error(struct jsonrpc_request *r, int code,
+                          const char *message, const char *data_fmt, ...);
+void jsonrpc_return_success(struct jsonrpc_request *r, const char *result_fmt,
+                            ...);
+void jsonrpc_ctx_process(struct jsonrpc_ctx *ctx, const char *req, int req_sz,
+                         mjson_print_fn_t fn, void *fndata, void *userdata);
+
+extern struct jsonrpc_ctx jsonrpc_default_context;
+extern void jsonrpc_list(struct jsonrpc_request *r);
+
+#define jsonrpc_export(name, fn) \
+  jsonrpc_ctx_export(&jsonrpc_default_context, (name), (fn))
+
+#define jsonrpc_process(buf, len, fn, fnd, ud) \
+  jsonrpc_ctx_process(&jsonrpc_default_context, (buf), (len), (fn), (fnd), (ud))
+
+#define JSONRPC_ERROR_INVALID -32700    /* Invalid JSON was received */
+#define JSONRPC_ERROR_NOT_FOUND -32601  /* The method does not exist */
+#define JSONRPC_ERROR_BAD_PARAMS -32602 /* Invalid params passed */
+#define JSONRPC_ERROR_INTERNAL -32603   /* Internal JSON-RPC error */
+
+#endif  // MJSON_ENABLE_RPC
+#ifdef __cplusplus
+}
+#endif
+#endif  // MJSON_H

examples/huge-response/web_root/index.html

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+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <title>example</title>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <style>
+      #container { margin-right: auto; margin-left: auto; max-width: 480px; }
+      #info { background: #e0f0f0; border-radius: .5em; padding: 2em; margin-bottom: 1em; }
+      #result { margin-top: 1em; }
+    </style>
+  </head>
+  <body>
+    <div id="container">
+      <div id="info">
+        On devices with limited RAM, it is important to limit the response size
+        of API calls. This example demonstrates how to fetch a large
+        data in smaller chunks, and guarantee its integrity.
+        Data gets returned in a series of request/response transactions,
+        where each response is small enough to fit into available device RAM.
+        <br/><br/>
+        Data integrity is implemented by versioning.
+        The idea is that the first response includes the current "version" of the
+        data, and that version is passed to all subsequent requests.
+        If data version changes in the middle of the request series,
+        client fails with 'wrong version' error.
+      </div>
+      <button id="btn">fetch data</button>
+      <div id="result"></div>
+    </div>
+  </body>
+  <script>
+    const getchunk = (start, version) =>
+      fetch('/api/data', {method: 'POST', body:JSON.stringify({start, version})})
+        .then(r => r.json());
+    document.getElementById('btn').onclick = function() {
+      var data = [], version = 0;
+      const load = offset => getchunk(offset, version)
+        .then(r => {
+          // console.log(r);
+          if (r.error) {
+            document.getElementById('result').innerText = 'Error: ' + r.error;
+          } else {
+            version = r.version;
+            data = data.concat(r.data);
+            if (r.data.length == 0) {
+              document.getElementById('result').innerText = 'Version: ' +
+                version + ', data: \n' +
+                JSON.stringify(data, null, 2);
+            } else {
+              load(offset + r.data.length, version);
+            }
+          }
+        });
+      load(0);
+    };
+  </script>
+</html>