json-gen-c

Overview

json-gen-c is a program for searializing C struct to JSON and deserializing JSON to C struct back. It parse structs' definition files then generate C codes to serialize and deserialize structs.

• Document

Build and Install

make
sudo make install

To build example, tests, and benchmarks

# build ./target/example
make example
# build ./target/test/unit_test
make test
# build ./target/benchmark/json_bench
make benchmark

Quick Start

example

Define Structs

For example, create a file name struct.json-gen-c as contents below:

struct A {
    int int_val1;
    int int_val2;
    long long_val;
    double double_val;
    float float_val;
    sstr_t sstr_val;
    int int_val_array[];
    B b_val;
};
 
struct B {
    int id;
};

Note that we don't use C-style string char*, a more resonable type is sstr_t. You can find more details about sstr_t in document of sstr.

Compiling Your Struct Definition File

json-gen-c -in struct.json-gen-c -out .

This generates the following files in your specified destination directory:

• json.gen.h, the header which declares your generated structures and functions.
• json.gen.c, which contains the implementation of your functions.
• sstr.h, sstr.c, the string manipulation helper functions that generated code depends on.

Use Your Generated Codes

To Serialize Structs to JSON

struct A a;
A_init(&a);
// set values to a ...
// ...
sstr_t json_str = sstr_new();
json_marshal_A(&a, json_str);
 
printf("marshal a to json> %s\n", sstr_cstr(json_str));
 
sstr_free(json_str);
A_clear(&a);

To Serialize Array of Structs to JSON

struct A a[3];
for (i = 0; i < 3; ++i) {
    A_init(&a[i]);
    // set values to a[i] ...
}
 
sstr_t json_str = sstr_new();
json_marshal_array_A(a, 3, json_str);
 
printf("marshal a[] to json> %s\n", sstr_cstr(json_str));
 
for (i = 0; i < 3; ++i) {
    A_clear(&a[i]);
}

To Deserialize JSON to Structs

// const char *p_str = "{this is a json string}";
// sstr_t json_str = sstr(pstr);
 
struct A a;
A_init(&a);
json_unmarshal_A(json_str, &a); // json_str is a type of sstr_t
// ...
A_clear(&a);

To Deserialize JSON to Array of Structs

// const char *p_str = "[this is a json string]";
// sstr_t json_str = sstr(pstr);
 
struct A *a = NULL;
int len = 0;
json_unmarshal_array_A(&a, &len, json_str);
// ...
int i;
for (i = 0; i < len; ++i) {
    A_clear(&a[i]);
}
free(a);

The Format of Structs Definition File

Define a struct like:

struct <struct_name> {
    <field_type> <field_name> []?;
    <field_type> <field_name> []?;
    ...
};

The field type can be one of the following:

• int
• long
• float
• double
• sstr_t
• bool
• a struct name

If a field is an array, just append [] after the field name.

The JSON API

// initialize a struct
// always return 0
int <struct_name>_init(struct <struct_name> *obj);
 
// uninitialize a struct
// always return 0
int <struct_name>_clear(struct <struct_name> *obj);
 
// marshal a struct to json string.
// return 0 if success.
int json_marshal_<struct_name>(struct <struct_name>*obj, sstr_t out);
 
// marshal an array of struct to json string.
// return 0 if success.
int json_marshal_array_<struct_name>(struct <struct_name>*obj, int len, sstr_t out);
 
// unmarshal a json string to a struct.
// return 0 if success.
int json_unmarshal_<struct_name>(sstr_t in, struct <struct_name>*obj);
 
// unmarshal a json string to array of struct
// return 0 if success.
int json_unmarshal_<struct_name>(sstr_t in, struct <struct_name>**obj, int *len);

License

Codes of json-gen-c are licensed under GPL-3.0, except for the codes it generated. The copy right of the codes generated by json-gen-c is owned by the user who wrote the struct definition file, same as the copy right of a PDF file generated by Latex is owned by the user who wrote the tex file.