git.ozlabs.org Git - ccan/blob - ccan/json/_info

   1 #include "config.h"
   2 #include <stdio.h>
   3 #include <string.h>
   4
   5 /**
   6  * json - Parse and generate JSON (JavaScript Object Notation)
   7  *
   8  * This is a library for encoding and decoding JSON that strives to be
   9  * easy to learn, use, and incorporate into an application.
  10  *
  11  * JSON (JavaScript Object Notation) facilitates passing data among different
  12  * programming languages, particularly JavaScript.  It looks like this:
  13  *
  14  *     [
  15  *         {
  16  *             "id":           1,
  17  *             "firstname":    "John",
  18  *             "lastname":     "Smith",
  19  *             "email":        "john@example.com",
  20  *             "likes_pizza":  false
  21  *         },
  22  *         {
  23  *             "id":           2,
  24  *             "firstname":    "Linda",
  25  *             "lastname":     "Jones",
  26  *             "email":        null,
  27  *             "likes_pizza":  true
  28  *         }
  29  *     ]
  30  *
  31  * Example:
  32  *      #include <ccan/json/json.h>
  33  *      #include <math.h>
  34  *      #include <stdio.h>
  35  *      #include <stdlib.h>
  36  *
  37  *      static int find_number(JsonNode *object, const char *name, double *out)
  38  *      {
  39  *              JsonNode *node = json_find_member(object, name);
  40  *              if (node && node->tag == JSON_NUMBER) {
  41  *                      *out = node->number_;
  42  *                      return 1;
  43  *              }
  44  *              return 0;
  45  *      }
  46  *
  47  *      static void solve_pythagorean(JsonNode *triple)
  48  *      {
  49  *              double a = 0, b = 0, c = 0;
  50  *              int a_given, b_given, c_given;
  51  *
  52  *              if (triple->tag != JSON_OBJECT) {
  53  *                      fprintf(stderr, "Error: Expected a JSON object.\n");
  54  *                      exit(EXIT_FAILURE);
  55  *              }
  56  *
  57  *              a_given = find_number(triple, "a", &a);
  58  *              b_given = find_number(triple, "b", &b);
  59  *              c_given = find_number(triple, "c", &c);
  60  *
  61  *              if (a_given + b_given + c_given != 2) {
  62  *                      fprintf(stderr, "Error: I need two sides to compute the length of the third.\n");
  63  *                      exit(EXIT_FAILURE);
  64  *              }
  65  *
  66  *              if (a_given && b_given) {
  67  *                      c = sqrt(a*a + b*b);
  68  *                      json_append_member(triple, "c", json_mknumber(c));
  69  *              } else if (a_given && c_given) {
  70  *                      b = sqrt(c*c - a*a);
  71  *                      json_append_member(triple, "b", json_mknumber(b));
  72  *              } else if (b_given && c_given) {
  73  *                      a = sqrt(c*c - b*b);
  74  *                      json_append_member(triple, "a", json_mknumber(a));
  75  *              }
  76  *      }
  77  *
  78  *      int main(void)
  79  *      {
  80  *              JsonNode *triples = json_mkarray();
  81  *
  82  *              json_append_element(triples, json_decode("{\"a\": 3, \"b\": 4}"));
  83  *              json_append_element(triples, json_decode("{\"a\": 5, \"c\": 13}"));
  84  *              json_append_element(triples, json_decode("{\"b\": 24, \"c\": 25}"));
  85  *
  86  *              JsonNode *triple;
  87  *              json_foreach(triple, triples)
  88  *                      solve_pythagorean(triple);
  89  *
  90  *              char *tmp = json_stringify(triples, "\t");
  91  *              puts(tmp);
  92  *              free(tmp);
  93  *
  94  *              json_delete(triples);
  95  *              return 0;
  96  *      }
  97  *
  98  * Author: Joey Adams
  99  * Version: 0.1
 100  * License: MIT
 101  */
 102 int main(int argc, char *argv[])
 103 {
 104         /* Expect exactly one argument */
 105         if (argc != 2)
 106                 return 1;
 107
 108         if (strcmp(argv[1], "depends") == 0) {
 109                 /* Nothing */
 110                 return 0;
 111         }
 112
 113         if (strcmp(argv[1], "libs") == 0) {
 114                 printf("m\n"); /* Needed for sqrt() used in example code above. */
 115                 return 0;
 116         }
 117
 118         return 1;
 119 }