Merge pull request #214 from rdpoor/master

adding simple-parse example

examples/simple_parse.c

@@ -0,0 +1,196 @@
+/*
+ * Simple example of parsing and printing JSON using jansson.
+ *
+ * SYNOPSIS:
+ * $ examples/simple_parse
+ * Type some JSON > [true, false, null, 1, 0.0, -0.0, "", {"name": "barney"}]
+ * JSON Array of 8 elements:
+ *   JSON True
+ *   JSON False
+ *   JSON Null
+ *   JSON Integer: "1"
+ *   JSON Real: 0.000000
+ *   JSON Real: -0.000000
+ *   JSON String: ""
+ *   JSON Object of 1 pair:
+ *     JSON Key: "name"
+ *     JSON String: "barney"
+ * 
+ * Copyright (c) 2014 Robert Poor <rdpoor@gmail.com>
+ *
+ * Jansson is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "jansson.h"
+
+/* forward refs */
+void print_json(json_t *root);
+void print_json_aux(json_t *element, int indent);
+void print_json_indent(int indent);
+const char *json_plural(int count);
+void print_json_object(json_t *element, int indent);
+void print_json_array(json_t *element, int indent);
+void print_json_string(json_t *element, int indent);
+void print_json_integer(json_t *element, int indent);
+void print_json_real(json_t *element, int indent);
+void print_json_true(json_t *element, int indent);
+void print_json_false(json_t *element, int indent);
+void print_json_null(json_t *element, int indent);
+
+void print_json(json_t *root) {
+  print_json_aux(root, 0);
+}
+
+void print_json_aux(json_t *element, int indent) {
+  switch json_typeof(element) {
+    case JSON_OBJECT:
+      print_json_object(element, indent);
+      break;
+    case JSON_ARRAY:
+      print_json_array(element, indent);
+      break;
+    case JSON_STRING:
+      print_json_string(element, indent);
+      break;
+    case JSON_INTEGER:
+      print_json_integer(element, indent);
+      break;
+    case JSON_REAL:
+      print_json_real(element, indent);
+      break;
+    case JSON_TRUE:
+      print_json_true(element, indent);
+      break;
+    case JSON_FALSE:
+      print_json_false(element, indent);
+      break;
+    case JSON_NULL:
+      print_json_null(element, indent);
+      break;
+    default:
+      fprintf(stderr, "unrecognized JSON type %d\n", json_typeof(element));
+    }
+}
+
+void print_json_indent(int indent) {
+  for (int i=0; i<indent; i++) { putchar(' '); }
+}
+
+const char *json_plural(int count) {
+  return count == 1 ? "" : "s";
+}
+
+void print_json_object(json_t *element, int indent) {
+  print_json_indent(indent);
+  size_t size = json_object_size(element);
+  const char *key;
+  json_t *value;
+
+  printf("JSON Object of %ld pair%s:\n", size, json_plural(size));
+  json_object_foreach(element, key, value) {
+    print_json_indent(indent + 2);
+    printf("JSON Key: \"%s\"\n", key);
+    print_json_aux(value, indent + 2);
+  }
+
+}
+
+void print_json_array(json_t *element, int indent) {
+  print_json_indent(indent);
+  size_t size = json_array_size(element);
+
+  printf("JSON Array of %ld element%s:\n", size, json_plural(size));
+  for (size_t i=0; i<size; i++) {
+    print_json_aux(json_array_get(element, i), indent + 2);
+  }
+}
+
+void print_json_string(json_t *element, int indent) {
+  print_json_indent(indent);
+  printf("JSON String: \"%s\"\n", json_string_value(element));
+}
+
+void print_json_integer(json_t *element, int indent) {
+  print_json_indent(indent);
+  printf("JSON Integer: \"%" JSON_INTEGER_FORMAT "\"\n", json_integer_value(element));
+}
+
+void print_json_real(json_t *element, int indent) {
+  print_json_indent(indent);
+  printf("JSON Real: %f\n", json_real_value(element));
+}
+
+void print_json_true(json_t *element, int indent) {
+  print_json_indent(indent);
+  printf("JSON True\n");
+}
+
+void print_json_false(json_t *element, int indent) {
+  print_json_indent(indent);
+  printf("JSON False\n");
+}
+
+void print_json_null(json_t *element, int indent) {
+  print_json_indent(indent);
+  printf("JSON Null\n");
+}
+
+/* 
+ * Parse text into a JSON object. If text is valid JSON, returns a
+ * json_t structure, otherwise prints and error and returns null.
+ */
+json_t *load_json(const char *text) {
+  json_t *root;
+  json_error_t error;
+
+  root = json_loads(text, 0, &error);
+
+  if (root) {
+    return root;
+  } else {
+    fprintf(stderr, "json error on line %d: %s\n", error.line, error.text);
+    return (json_t *)0;
+  }
+}
+
+/*
+ * Print a prompt and return (by reference) a null-terminated line of
+ * text.  Returns NULL on eof or some error.
+ */
+char *read_line(char *line, int max_chars) {
+  printf("Type some JSON > ");
+  fflush(stdout);
+  return fgets(line, max_chars, stdin);
+}
+
+/* ================================================================
+ * main
+ */
+
+#define MAX_CHARS 4096
+
+int main(int argc, char *argv[]) {
+  char line[MAX_CHARS];
+  
+  if (argc != 1) {
+    fprintf(stderr, "Usage: %s\n", argv[0]);
+    exit(-1);
+  }
+
+  while (read_line(line, MAX_CHARS) != (char *)NULL) {
+
+    /* parse text into JSON structure */
+    json_t *root = load_json(line);
+
+    if (root) {
+      /* print and release the JSON structure */
+      print_json(root);         
+      json_decref(root);
+    }
+  }
+
+  return 0;
+}