1 /*
2 * Contributed by Jacob Teplitsky <jacob.teplitsky@ericsson.com>
3 *
4 * libcbor is free software; you can redistribute it and/or modify
5 * it under the terms of the MIT license. See LICENSE for details.
6 */
7
8 /**
9 * This code demonstrates how cJSON (https://github.com/DaveGamble/cJSON)
10 * callbacks can be used in conjuction with the streaming parser to translate
11 * JSON to CBOR. Please note that cbor_builder_* APIs are internal and thus
12 * subject to change.
13 *
14 * The example will only be compiled when cJSON is available
15 */
16
17 #include <cjson/cJSON.h>
18 #include <float.h>
19 #include <math.h>
20 #include <string.h>
21 #include "cbor.h"
22 #include "cbor/internal/builder_callbacks.h"
23 #include "cbor/internal/loaders.h"
24
25 typedef void (*cbor_load_callback_t)(cJSON *, const struct cbor_callbacks *,
26 void *);
27
cjson_cbor_load(void * source,cbor_load_callback_t cbor_load_callback)28 cbor_item_t *cjson_cbor_load(void *source,
29 cbor_load_callback_t cbor_load_callback) {
30 static struct cbor_callbacks callbacks = {
31 .uint64 = &cbor_builder_uint64_callback,
32 .negint64 = &cbor_builder_negint64_callback,
33 .string = &cbor_builder_string_callback,
34 .array_start = &cbor_builder_array_start_callback,
35 .map_start = &cbor_builder_map_start_callback,
36 .null = &cbor_builder_null_callback,
37 .boolean = &cbor_builder_boolean_callback,
38 .float4 = &cbor_builder_float4_callback,
39 };
40
41 /* Context stack */
42 struct _cbor_stack stack = _cbor_stack_init();
43
44 /* Target for callbacks */
45 struct _cbor_decoder_context context = (struct _cbor_decoder_context){
46 .stack = &stack,
47 };
48
49 cbor_load_callback(source, &callbacks, &context);
50
51 return context.root;
52 }
53
cjson_cbor_stream_decode(cJSON * source,const struct cbor_callbacks * callbacks,void * context)54 void cjson_cbor_stream_decode(cJSON *source,
55 const struct cbor_callbacks *callbacks,
56 void *context) {
57 switch (source->type) {
58 case cJSON_False: {
59 callbacks->boolean(context, false);
60 return;
61 }
62 case cJSON_True: {
63 callbacks->boolean(context, true);
64 return;
65 }
66 case cJSON_NULL: {
67 callbacks->null(context);
68 return;
69 }
70 case cJSON_Number: {
71 // This is stupid -- ints and doubles cannot are not distinguished
72 if (fabs(source->valuedouble - source->valueint) > DBL_EPSILON) {
73 callbacks->float4(context, source->valuedouble);
74 } else {
75 // XXX: This is not portable
76 if (source->valueint >= 0) {
77 callbacks->uint64(context, source->valueint);
78 } else {
79 callbacks->negint64(context, source->valueint + 1);
80 }
81 }
82 return;
83 }
84 case cJSON_String: {
85 // XXX: Assume cJSON handled unicode correctly
86 callbacks->string(context, (unsigned char *)source->valuestring,
87 strlen(source->valuestring));
88 return;
89 }
90 case cJSON_Array: {
91 callbacks->array_start(context, cJSON_GetArraySize(source));
92 cJSON *item = source->child;
93 while (item != NULL) {
94 cjson_cbor_stream_decode(item, callbacks, context);
95 item = item->next;
96 }
97 return;
98 }
99 case cJSON_Object: {
100 callbacks->map_start(context, cJSON_GetArraySize(source));
101 cJSON *item = source->child;
102 while (item != NULL) {
103 callbacks->string(context, (unsigned char *)item->string,
104 strlen(item->string));
105 cjson_cbor_stream_decode(item, callbacks, context);
106 item = item->next;
107 }
108 return;
109 }
110 }
111 }
112
usage(void)113 void usage(void) {
114 printf("Usage: cjson [input JSON file]\n");
115 exit(1);
116 }
117
main(int argc,char * argv[])118 int main(int argc, char *argv[]) {
119 if (argc != 2) usage();
120 FILE *f = fopen(argv[1], "rb");
121 if (f == NULL) usage();
122 /* Read input file into a buffer (cJSON doesn't work with streams) */
123 fseek(f, 0, SEEK_END);
124 size_t length = (size_t)ftell(f);
125 fseek(f, 0, SEEK_SET);
126 char *json_buffer = malloc(length + 1);
127 fread(json_buffer, length, 1, f);
128 json_buffer[length] = '\0';
129
130 /* Convert between JSON and CBOR */
131 cJSON *json = cJSON_Parse(json_buffer);
132 cbor_item_t *cbor = cjson_cbor_load(json, cjson_cbor_stream_decode);
133
134 /* Print out CBOR bytes */
135 unsigned char *buffer;
136 size_t buffer_size;
137 cbor_serialize_alloc(cbor, &buffer, &buffer_size);
138
139 fwrite(buffer, 1, buffer_size, stdout);
140
141 free(buffer);
142 fflush(stdout);
143 cJSON_Delete(json);
144 cbor_decref(&cbor);
145 }
146