Easily creates json, just by passing a list of strings, numbers, jsons, etc.

easy-json-maker.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>

size_t counter(char *str) {
	size_t commas = 0;
	int string = 0;
	
	while (*str) {
		//escape commas inside string;
		if (*str == '"' && *(str - 1) != '\\') string = !string;
		
		//count commas
		if (string == 0)
			if (*str == ',') commas++;					
		str++;
	}
		
	return commas+1;
}

#define STR(X) #X

char JSON_CMD_FLAG = 0;
char JSON_STRING_FLAG = 0;

void json_set_cmd_flag(int flag) {
	JSON_CMD_FLAG = flag;
}
void json_set_string_flag(int flag) {
	JSON_STRING_FLAG = flag;
}

#define json(...) __json__(__FILE__, __LINE__, counter(#__VA_ARGS__), __VA_ARGS__)
char* __json__(char *file, int line, size_t count, ...) {
	//variables
	char *json;
	size_t i, length;
	va_list args;
	va_start(args, count);
	
	//check for pairs
	if (count % 2 != 0) {
		fprintf(stderr, "Number of keys and values unmatched at %s:%i", file, line);
		return 0;
	}
	
	//get length
	for (i=0, length=0; i<count; i++) {
		length += strlen(va_arg(args, char*));
	}
	
	//allocate
	json = (char*)malloc((sizeof(char) * length) 		//length
					   + (count * 10)	//enough for \"\" \"\" , : at worst case
					   + 2			//for { }
					   + 1);		//for null terminator
	
	if (json == NULL) {
		fprintf(stderr, "Couldn't allocate json at %s:%i", file, line);
		return 0;		
	}
	
	//rewind args
	va_end(args);
	va_start(args, count);
	
	//make json
	strcpy(json, "{");
	
	for (i=0; i<count/2; i++) {
		
		if (i > 0) strcat(json, ",");
		
		//key
		(JSON_CMD_FLAG) ? (strcat(json, "\\\"")) : (strcat(json, "\""));
		
		strcat(json, va_arg(args, char*));
		
		(JSON_CMD_FLAG) ? (strcat(json, "\\\"")) : (strcat(json, "\""));
		
		//value
		strcat(json, ":");
		(JSON_CMD_FLAG) ? (strcat(json, "\\\"")) : (0);
		(JSON_STRING_FLAG) ? (strcat(json, "\"")) : (0);
		strcat(json, va_arg(args, char*));
		(JSON_STRING_FLAG) ? (strcat(json, "\"")) : (0);
		(JSON_CMD_FLAG) ? (strcat(json, "\\\"")) : (0);
	}
	
	strcat(json, "}");
	
	return json;
}

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

int main() {
	//set 1 for "cmd escaped" json
	json_set_cmd_flag(0);
	
	//set 1 for string values
	json_set_string_flag(1);
		
	char *j = json("string", "Hello World", "number", "123");
	printf("%s\n", j);
	
	//free
	free(j);
}