CXPathJson is a library to set and get values from a json string using a path string.
CXpathJson is made to be as dumb as possible and adopt the idea of single file library. For installation, simply copy the CXpathJson.h into your project and compile with gcc/g++ or clang.
you also can download the entire src project and include with src/one.c
#include "src/one.c"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonObject();
xpath.set_str(t,"hello world","['a']");
char *content = xpath.dump_to_string(t,true);
printf("%s",content);
free(content);
xpath.free(t);
}In all examples, we will use the json files in the tests/target directory.
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonObject();
xpath.set_str(t,"hello world","['a']");
char *content = xpath.dump_to_string(t,true);
printf("%s",content);
free(content);
xpath.free(t);
}For loading a function from a json file you just need to call the function xpath.new_from_file passing the json path Example:
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/str.json");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("%d",code);
printf("%s",message);
xpath.free(t);
return 0;
}
char *dumped = xpath.dump_to_string(t,true);
printf("%s",dumped);
xpath.free(t);
free(dumped);
printf("OK");
}new_from_stringto read the json string from a string. This function receives 1 parameter: the json string. Example:
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_string("{\"a\":1}");
xpath.free(t);
printf("OK");
}newJsonArrayto create an empty json array. Example:
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonArray();
xpath.free(t);
printf("OK");
}newJsonObjectto create an empty json object. Example:
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonObject();
xpath.free(t);
printf("OK");
}Important: Note that every example already create the errors object. Every example also has a free function to free the memory allocated by the json object.
Every get function gets 2 parameters: the json object and the path string. The first
parameter is the json object and the second parameter is the path string. The path string is a list of keys separated by a comma. For example, the path string "['a', 0, 'b']" will get the value of the key b in the json string {"a": [ {"b": 1} ]}.
tests/target/all.json:
{
"height": 1.79,
"name": "test",
"age": 100,
"maried": false
}#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/all.json");
char *name = xpath.get_str(t,"['name']");
int age =xpath.get_int(t,"['age']");
bool maried = xpath.get_bool(t,"['maried']");
double height = xpath.get_double(t,"['height']");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
printf("name: %s\n",name);
printf("age: %d\n",age);
printf("height: %lf\n",height);
printf("maried: %s\n", maried ? "true": "false");
xpath.free(t);
}tests/target/str.json:
{
"a":{
"b":"value"
}
}#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/str.json");
CxpathJson *a = xpath.get_object(t, "['a']");
char *a1 = xpath.get_str(a,"['b']");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
printf("%s",a1);
xpath.free(t);
}tests/target/array.json:
{
"a":{
"b": ["test"]
}
}#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/array.json");
CxpathJson *a = xpath.get_array(t, "['a','b']");
char *a1 =xpath.get_str(a,"[0]");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
printf("%s\n",a1);
xpath.free(t);
}tests/target/array.json:
{
"a":{
"b": ["test"]
}
}sizeto get the size of an array.
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/array.json");
int content = xpath.size(t,"['a','b']");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
printf("%d",content);
xpath.free(t);
}tests/target/all_list.json:
[{
"height": 1.79,
"name": "test1",
"age": 101,
"maried": false
},
{
"height": 2.00,
"name": "test2",
"age": 11,
"maried": true
},
{
"height": 1.79,
"name": "test",
"age": 100,
"maried": false
}
]You can easly iterate over array by using get_size function
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/all_list.json");
int size = xpath.size(t,"[]");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
for(int i = 0; i< size; i++){
char *name = xpath.get_str(t,"[%d,'name']",i);
int age =xpath.get_int(t,"[%d,'age']",i);
bool maried = xpath.get_bool(t,"[%d,'maried']",i);
double height = xpath.get_double(t,"[%d,'height']",i);
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
printf("name: %s\n",name);
printf("age: %d\n",age);
printf("height: %lf\n",height);
printf("maried: %s\n", maried ? "true": "false");
printf("\n");
}
xpath.free(t);
}if you pass a negative number (-1) for example, you can get the last element of an array
tests/target/all_list.json:
[{
"height": 1.79,
"name": "test1",
"age": 101,
"maried": false
},
{
"height": 2.00,
"name": "test2",
"age": 11,
"maried": true
},
{
"height": 1.79,
"name": "test",
"age": 100,
"maried": false
}
]#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/all_list.json");
int size = xpath.size(t,"[]");
char *name = xpath.get_str(t,"[-1,'name']");
int age =xpath.get_int(t,"[-1,'age']");
bool maried = xpath.get_bool(t,"[-1,'maried']");
double height = xpath.get_double(t,"[-1,'height']");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
printf("name: %s\n",name);
printf("age: %d\n",age);
printf("height: %lf\n",height);
printf("maried: %s\n", maried ? "true": "false");
xpath.free(t);
}you also can get type information about the current element
tests/target/str.json:
{
"a":{
"b":"value"
}
}#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/str.json");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
printf("exist :%d\n" , xpath.types.exist(t,"['a','b']"));
printf("type code:%d\n" , xpath.types.type(t,"['a','b']"));
printf("type str:%s\n" , xpath.types.type_str(t,"['a','b']"));
xpath.free(t);
}Every set function gets 3 parameters: the json object, the value to set and the path string.
To set a value in the json object, you can use a range of functions. The functions are:
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonObject();
xpath.set_str(t, "Mateus","['a', 'name']");
xpath.set_int(t, 27,"['a', 'age']");
xpath.set_double(t, 1.80,"['a', 'height']");
xpath.set_bool(t,true,"['a', 'maried']");
char *result = xpath.dump_to_string(t, false);
printf("%s",result);
xpath.free(t);
free(result);
}You alson can append elements into the array by using the $append key world in the middle of the path in these case, in the first set we use the $append, to indicate the library that its to append a new object there
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonObject();
for(int i = 0; i < 3; i++){
char name_formated[20] ={0};
sprintf(name_formated,"name %d",i);
xpath.set_str(t,name_formated,"['elements','$append','name']");
xpath.set_int(t,i,"['elements',-1,'age']");
}
char * result = xpath.dump_to_string(t,true);
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
printf("path %s\n",errors.get_error_path(t));
xpath.free(t);
return 0;
}
printf("%s",result);
free(result);
xpath.free(t);
}You can dump the json object to a file using dump_to_file or to a string using dump_to_string.
dump_to_fileto dump the json object to a file. The code below will dump the json object to create a file calledb.json. This function receives 3 parameters: the json object, the file path and and boolean to indicate if the file should be idented.
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonObject();
xpath.set_str(t,"test","['a']['b']");
xpath.dump_to_file(t,"side_effect/b.json", true);
xpath.free(t);
printf("OK");
}dump_to_stringto dump the json object to a string. This function receives 2 parameters: the json object and a boolean to indicate if the string should be idented.
#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.newJsonObject();
xpath.set_str(t,"teste","['a']['b']");
char *content = xpath.dump_to_string(t, false);
printf("%s", content);
xpath.free(t);
free(content);
}The library has a built-in error handling system. You can use the error object to get the error message if the json string is invalid. The error message will be stored in the error object. You can use the error object to get the error message as shown below.
tests/target/str.json:
{
"a":{
"b":"value"
}
}#include "CxpathJson.h"
CxpathJsonNamespace xpath;
CxpathJsonErrorNamespace errors;
int main(){
xpath = newCxpathJsonNamespace();
errors = xpath.errors;
CxpathJson *t = xpath.new_from_file("tests/target/str.json");
char *content = xpath.get_str(t,"['c', 1, 'd']");
if(errors.has_errors(t)){
char *message =errors.get_error_message(t);
int code = errors.get_error_code(t);
printf("code: %d\n",code);
printf("message: %s\n",message);
xpath.free(t);
return 0;
}
}The code above will print the following error message:
5-Element not exist
where 5 is the code of the error and Element not exist is the message of the error.