118 lines
2.2 KiB
Markdown
118 lines
2.2 KiB
Markdown
|
|
# C JSON Parser
|
|
|
|
Just a simple project to practice writing parsers.
|
|
Not guaranteed to be safe or efficient.
|
|
|
|
## Usage
|
|
|
|
### Compile
|
|
build (release build):
|
|
```sh
|
|
make BUILD=release
|
|
```
|
|
To make a debug build just run `make`.
|
|
|
|
### Run
|
|
|
|
```sh
|
|
./bin/{release|debug}/json_parser
|
|
```
|
|
|
|
## Limitations
|
|
|
|
Does not support unicode.
|
|
|
|
## Implementation
|
|
|
|
Parsed JSON values are stored as structs containing type information and data.
|
|
|
|
```c
|
|
enum json_type { object, array, string, number, boolean, null };
|
|
|
|
struct json_value {
|
|
enum json_type type;
|
|
|
|
union {
|
|
obj_t* object;
|
|
struct json_value** array;
|
|
char* string;
|
|
bool boolean;
|
|
int64_t number;
|
|
};
|
|
};
|
|
```
|
|
|
|
### Types
|
|
|
|
#### JSON Arrays
|
|
|
|
Array values have the type field set to `(enum json_type) array`
|
|
|
|
JSON Arrays are stored as null-terminated `json_value*` arrays,
|
|
`struct json_value**`, in `json_value.array`
|
|
|
|
|
|
#### JSON Numbers
|
|
|
|
Number values have the type field set to `(enum json_type) number`
|
|
|
|
Numbers are stored as `double` values in `json_value.number`
|
|
|
|
(The JSON specification doesn't strictly specify a maximum value,
|
|
but `double` is sufficient for parsing almost all JSON data.)
|
|
|
|
|
|
#### JSON Strings
|
|
|
|
Strings have the type field set to `(enum json_type) string`
|
|
|
|
Strings are stored as null-terminated char arrays, `char*`, in `json_value.string`
|
|
|
|
|
|
#### JSON Booleans
|
|
|
|
Boolean values have the type field set to `(enum json_type) boolean`
|
|
|
|
The values are stored as `bool` in `json_value.boolean`
|
|
|
|
|
|
#### JSON Null
|
|
|
|
Null values have type field set to `(enum json_type) null`.
|
|
|
|
|
|
#### JSON Objects
|
|
|
|
Object values have the type field set to `(enum json_type) object`
|
|
|
|
They are stored using a poorly written map implementation with the type `obj_t`
|
|
in `json_value.object`
|
|
|
|
##### obj\_t
|
|
|
|
```c
|
|
typedef struct obj_entry {
|
|
char const* key;
|
|
struct json_value* val;
|
|
struct obj_entry* next;
|
|
} * __p_obj_entry;
|
|
|
|
typedef __p_obj_entry obj_t[OBJ_SIZE]; // OBJ_SIZE=1024
|
|
```
|
|
|
|
##### obj\_t methods
|
|
|
|
`void* obj_at(obj_t m, char* key)`
|
|
|
|
Returns a pointer to a value for the given key.
|
|
|
|
`bool obj_insert(obj_t m, char* const key, struct json_value* value)`
|
|
|
|
Insert a key-value pair
|
|
|
|
`void obj_delete(obj_t m)`
|
|
|
|
Free memory allocated for object
|
|
|