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