lsmp.tproj/json.h

   1 /*
   2  * Copyright (c) 2017 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22
  23 /*
  24  * Provides a stream-based API for generating JSON output
  25  *
  26  * Handles tedious tasks like worrying about comma placement (and avoiding trailing commas).
  27  * Assumes strings are already escaped (if necessary) and does no error checking (thus it
  28  * may produce invalid JSON when used improperly).
  29  *
  30  * As a convenience, when the provided `json` stream is NULL (i.e. it was never initialized
  31  * by `JSON_OPEN`) these APIs will do nothing.
  32  *
  33  * Example usage:
  34  *
  35  *  JSON_t json = JSON_OPEN("/path/to/output.json")
  36  *  JSON_OBJECT_BEGIN(json); // root object
  37  *
  38  *  JSON_OBJECT_SET(json, version, %.1f, 1.0);
  39  *  JSON_OBJECT_SET_BOOL(json, has_fruit, 1);
  40  *
  41  *  // Note the required quotes for strings (formatted or not)
  42  *  char *mystr = "hello";
  43  *  JSON_OBJECT_SET(json, formatted_string, "%s", mystr);
  44  *  JSON_OBJECT_SET(json, literal_string, "my literal string");
  45  *
  46  *  JSON_KEY(json, fruit_array);
  47  *  JSON_ARRAY_BEGIN(json); // fruit_array
  48  *  JSON_ARRAY_APPEND(json, "my literal string");
  49  *  JSON_ARRAY_APPEND(json, "<0x%08llx>", 0xface);
  50  *  JSON_ARRAY_APPEND(json, %d, 3);
  51  *  JSON_ARRAY_END(json); // fruit_array
  52  *
  53  *  JSON_OBJECT_END(json); // root object
  54  *  JSON_CLOSE(json);
  55  */
  56
  57 #ifndef _JSON_H_
  58 #define _JSON_H_
  59
  60 #include <stdio.h>
  61 #include <stdlib.h>
  62 #include <stdbool.h>
  63
  64 #define _JSON_IF(json, code) \
  65   if (json != NULL) { \
  66     code; \
  67   }
  68 #define _JSON_COMMA(json) \
  69   if (json->require_comma) { \
  70     fprintf(json->stream, ","); \
  71   }
  72
  73 struct _JSON {
  74   FILE* stream;
  75   bool require_comma;
  76 };
  77 typedef struct _JSON * JSON_t;
  78
  79 #pragma mark Open/Close
  80 /* Return a new JSON_t stream */
  81 static inline JSON_t JSON_OPEN(const char *path) {
  82   JSON_t p = malloc(sizeof(struct _JSON));
  83   p->stream = fopen(path, "w+");
  84   p->require_comma = false;
  85   return p;
  86 }
  87
  88 /* Close an existing JSON stream, removing trailing commas */
  89 #define JSON_CLOSE(json) _JSON_IF(json, fclose(json->stream); free(json))
  90
  91 #pragma mark Keys/Values
  92 /* Output the `key` half of a key/value pair */
  93 #define JSON_KEY(json, key) _JSON_IF(json, _JSON_COMMA(json); fprintf(json->stream, "\"" #key "\":"); json->require_comma = false)
  94 /* Output the `value` half of a key/value pair */
  95 #define JSON_VALUE(json, format, ...) _JSON_IF(json, fprintf(json->stream, #format, ##__VA_ARGS__); json->require_comma = true)
  96
  97 #define _JSON_BEGIN(json, character) _JSON_COMMA(json); fprintf(json->stream, #character); json->require_comma = false;
  98 #define _JSON_END(json, character) fprintf(json->stream, #character); json->require_comma = true;
  99 #define _JSON_BOOL(val) ( val ? "true" : "false" )
 100
 101 #pragma mark Objects
 102 /* Start a new JSON object */
 103 #define JSON_OBJECT_BEGIN(json) _JSON_IF(json, _JSON_BEGIN(json, {))
 104 /* Set a value in the current JSON object */
 105 #define JSON_OBJECT_SET(json, key, format, ...) _JSON_IF(json, JSON_KEY(json, key); JSON_VALUE(json, format, ##__VA_ARGS__))
 106 /* Set a boolean in the current JSON object */
 107 #define JSON_OBJECT_SET_BOOL(json, key, value) JSON_OBJECT_SET(json, key, %s, _JSON_BOOL(value))
 108 /* End the current JSON object */
 109 #define JSON_OBJECT_END(json) _JSON_IF(json, _JSON_END(json, }))
 110
 111 #pragma mark Arrays
 112 /* Start a new JSON array */
 113 #define JSON_ARRAY_BEGIN(json) _JSON_IF(json, _JSON_BEGIN(json, [))
 114 /* Append a value to the current JSON array */
 115 #define JSON_ARRAY_APPEND(json, format, ...) _JSON_IF(json, _JSON_COMMA(json); JSON_VALUE(json, format, ##__VA_ARGS__))
 116 /* End the current JSON array */
 117 #define JSON_ARRAY_END(json) _JSON_IF(json, _JSON_END(json, ]))
 118
 119 #endif /* _JSON_H_ */