LwJSON

group LWJSON

LwJSON - Lightweight JSON format parser.

Defines

LWJSON_ARRAYSIZE(x)

Get size of statically allocated array.

Parameters

x – [in] Object to get array size of

Returns

Number of elements in array

lwjson_get_tokens_used(lwobj)

Get number of tokens used to parse JSON.

Parameters

lwobj – [in] Pointer to LwJSON instance

Returns

Number of tokens used to parse JSON

lwjson_get_first_token(lwobj)

Get very first token of LwJSON instance.

Parameters

lwobj – [in] Pointer to LwJSON instance

Returns

Pointer to first token

lwjson_get_val_int(token)

Get token value for LWJSON_TYPE_NUM_INT type.

Parameters

token – [in] token with integer type

Returns

Int number if type is integer, 0 otherwise

lwjson_get_val_real(token)

Get token value for LWJSON_TYPE_NUM_REAL type.

Parameters

token – [in] token with real type

Returns

Real numbeer if type is real, 0 otherwise

lwjson_get_first_child(token)

Get first child token for LWJSON_TYPE_OBJECT or LWJSON_TYPE_ARRAY types.

Parameters

token – [in] token with integer type

Returns

Pointer to first child or NULL if parent token is not object or array

lwjson_get_val_string_length(token)

Get length of string for LWJSON_TYPE_STRING token type.

Parameters

token – [in] token with string type

Returns

Length of string in units of bytes

Typedefs

typedef LWJSON_CFG_REAL_TYPE lwjson_real_t: Real data type.

typedef LWJSON_CFG_INT_TYPE lwjson_int_t: Integer data type.

typedef void (*lwjson_stream_parser_callback_fn)(struct lwjson_stream_parser *jsp, lwjson_stream_type_t type): Callback function for various events.

Enums

enum lwjson_type_t

List of supported JSON types.

Values:

enumerator LWJSON_TYPE_STRING: String/Text format. Everything that has beginning and ending quote character

enumerator LWJSON_TYPE_NUM_INT: Number type for integer

enumerator LWJSON_TYPE_NUM_REAL: Number type for real number

enumerator LWJSON_TYPE_OBJECT: Object data type

enumerator LWJSON_TYPE_ARRAY: Array data type

enumerator LWJSON_TYPE_TRUE: True boolean value

enumerator LWJSON_TYPE_FALSE: False boolean value

enumerator LWJSON_TYPE_NULL: Null value

enum lwjsonr_t

JSON result enumeration.

Values:

enumerator lwjsonOK = 0x00: Function returns successfully

enumerator lwjsonERR: Generic error message

enumerator lwjsonERRJSON: Error JSON format

enumerator lwjsonERRMEM: Memory error

enumerator lwjsonERRPAR: Parameter error

enumerator lwjsonSTREAMWAITFIRSTCHAR: Streaming parser did not yet receive first valid character indicating start of JSON sequence

enumerator lwjsonSTREAMDONE: Streaming parser is done, closing character matched the stream opening one

enumerator lwjsonSTREAMINPROG: Stream parsing is still in progress

enum lwjson_stream_type_t

Object type for streaming parser.

Values:

enumerator LWJSON_STREAM_TYPE_NONE: No entry - not used

enumerator LWJSON_STREAM_TYPE_OBJECT: Object indication

enumerator LWJSON_STREAM_TYPE_OBJECT_END: Object end indication

enumerator LWJSON_STREAM_TYPE_ARRAY: Array indication

enumerator LWJSON_STREAM_TYPE_ARRAY_END: Array end indication

enumerator LWJSON_STREAM_TYPE_KEY: Key string

enumerator LWJSON_STREAM_TYPE_STRING: Strin type

enumerator LWJSON_STREAM_TYPE_TRUE: True primitive

enumerator LWJSON_STREAM_TYPE_FALSE: False primitive

enumerator LWJSON_STREAM_TYPE_NULL: Null primitive

enumerator LWJSON_STREAM_TYPE_NUMBER: Generic number

enum lwjson_stream_state_t

Values:

enumerator LWJSON_STREAM_STATE_WAITINGFIRSTCHAR = 0x00: State to wait for very first opening character

enumerator LWJSON_STREAM_STATE_PARSING: In parsing of the first char state - detecting next character state

enumerator LWJSON_STREAM_STATE_PARSING_STRING: Parse string primitive

enumerator LWJSON_STREAM_STATE_PARSING_PRIMITIVE: Parse any primitive that is non-string, either “true”, “false”, “null” or a number

Functions

lwjsonr_t lwjson_init(lwjson_t *lwobj, lwjson_token_t *tokens, size_t tokens_len)

Setup LwJSON instance for parsing JSON strings.

Parameters

lwobj – [inout] LwJSON instance
tokens – [in] Pointer to array of tokens used for parsing
tokens_len – [in] Number of tokens

Returns

lwjsonOK on success, member of lwjsonr_t otherwise

lwjsonr_t lwjson_parse_ex(lwjson_t *lwobj, const void *json_data, size_t len)

Parse JSON data with length parameter JSON format must be complete and must comply with RFC4627.

Parameters

lwobj – [inout] LwJSON instance
json_data – [in] JSON string to parse
jsonČlen – [in] JSON data length

Returns

lwjsonOK on success, member of lwjsonr_t otherwise

lwjsonr_t lwjson_parse(lwjson_t *lwobj, const char *json_str)

Parse input JSON format JSON format must be complete and must comply with RFC4627.

Parameters

lwobj – [inout] LwJSON instance
json_str – [in] JSON string to parse

Returns

lwjsonOK on success, member of lwjsonr_t otherwise

const lwjson_token_t *lwjson_find(lwjson_t *lwobj, const char *path)

Find first match in the given path for JSON entry JSON must be valid and parsed with lwjson_parse function.

Parameters

lwobj – [in] JSON instance with parsed JSON string
path – [in] Path with dot-separated entries to search for the JSON key to return

Returns

Pointer to found token on success, NULL if token cannot be found

const lwjson_token_t *lwjson_find_ex(lwjson_t *lwobj, const lwjson_token_t *token, const char *path)

Find first match in the given path for JSON path JSON must be valid and parsed with lwjson_parse function.

Parameters

lwobj – [in] JSON instance with parsed JSON string
token – [in] Root token to start search at. Token must be type LWJSON_TYPE_OBJECT or LWJSON_TYPE_ARRAY. Set to NULL to use root token of LwJSON object
path – [in] path with dot-separated entries to search for JSON key

Returns

Pointer to found token on success, NULL if token cannot be found

lwjsonr_t lwjson_free(lwjson_t *lwobj)

Free token instances (specially used in case of dynamic memory allocation)

Parameters: lwobj – [inout] LwJSON instance
Returns: lwjsonOK on success, member of lwjsonr_t otherwise

void lwjson_print_token(const lwjson_token_t *token)

Prints and outputs token data to the stream output.

Note

This function is not re-entrant

Parameters: token – [in] Token to print

void lwjson_print_json(const lwjson_t *lwobj)

Prints and outputs full parsed LwJSON instance.

Note

This function is not re-entrant

Parameters: lwobj – [in] LwJSON instance to print

lwjsonr_t lwjson_stream_init(lwjson_stream_parser_t *jsp, lwjson_stream_parser_callback_fn evt_fn)

Initialize LwJSON stream object before parsing takes place.

Parameters: jsp – [inout] Stream JSON structure
Returns: lwjsonOK on success, member of lwjsonr_t otherwise

lwjsonr_t lwjson_stream_set_user_data(lwjson_stream_parser_t *jsp, void *user_data)

Set user_data in stream parser.

Parameters

jsp – [inout] LwJSON stream parser
user_data – [in] user data

Returns

lwjsonOK on success, member of lwjsonr_t otherwise

void *lwjson_stream_get_user_data(lwjson_stream_parser_t *jsp)

Get user_data in stream parser.

Parameters: jsp – [in] LwJSON stream parser
Returns: pointer to user data

lwjsonr_t lwjson_stream_reset(lwjson_stream_parser_t *jsp)

Reset LwJSON stream structure.

Parameters: jsp – [inout] LwJSON stream parser
Returns: lwjsonOK on success, member of lwjsonr_t otherwise

lwjsonr_t lwjson_stream_parse(lwjson_stream_parser_t *jsp, char c)

Parse JSON string in streaming mode.

Parameters

jsp – [inout] Stream JSON structure
chr – [in] Character to parse

Returns

lwjsonSTREAMWAITFIRSTCHAR when stream did not start parsing since no valid start character has been received

Returns

lwjsonSTREAMINPROG if parsing is in progress and no hard error detected

Returns

lwjsonSTREAMDONE when valid JSON was detected and stack level reached back 0 level

Returns

One of enumeration otherwise

static inline const char *lwjson_get_val_string(const lwjson_token_t *token, size_t *str_len)

Get string value from JSON token.

Parameters

token – [in] Token with string type
str_len – [out] Pointer to variable holding length of string. Set to NULL if not used

Returns

Pointer to string or NULL if invalid token type

static inline uint8_t lwjson_string_compare(const lwjson_token_t *token, const char *str)

Compare string token with user input string for a case-sensitive match.

Parameters

token – [in] Token with string type
str – [in] NULL-terminated string to compare

Returns

1 if equal, 0 otherwise

static inline uint8_t lwjson_string_compare_n(const lwjson_token_t *token, const char *str, size_t len)

Compare string token with user input string for a case-sensitive match.

Parameters

token – [in] Token with string type
str – [in] NULL-terminated string to compare
len – [in] Length of the string in bytes

Returns

1 if equal, 0 otherwise

struct lwjson_token_t

#include <lwjson.h>

JSON token.

Public Members

struct lwjson_token *next: Next token on a list

lwjson_type_t type: Token type

const char *token_name: Token name (if exists)

size_t token_name_len: Length of token name (this is needed to support const input strings to parse)

const char *token_value: Pointer to the beginning of the string

size_t token_value_len: Length of token value (this is needed to support const input strings to parse)

struct lwjson_token_t::[anonymous]::[anonymous] str: String data

lwjson_real_t num_real: Real number format

lwjson_int_t num_int: Int number format

struct lwjson_token *first_child: First children object for object or array type

union lwjson_token_t::[anonymous] u: Union with different data types

struct lwjson_t

#include <lwjson.h>

LwJSON instance.

Public Members

lwjson_token_t *tokens: Pointer to array of tokens

size_t tokens_len: Size of all tokens

size_t next_free_token_pos: Position of next free token instance

lwjson_token_t first_token: First token on a list

uint8_t parsed: Flag indicating JSON parsing has finished successfully

struct lwjson_t::[anonymous] flags: List of flags

struct lwjson_stream_stack_t

#include <lwjson.h>

Stream parsing stack object.

Public Members

lwjson_stream_type_t type: Streaming type - current value

char name[LWJSON_CFG_STREAM_KEY_MAX_LEN + 1]: Last known key name, used only for LWJSON_STREAM_TYPE_KEY type

uint16_t index: Current index when type is an array

union lwjson_stream_stack_t::[anonymous] meta: Meta information

struct lwjson_stream_parser_t

#include <lwjson.h>

LwJSON streaming structure.

Public Members

lwjson_stream_stack_t stack[LWJSON_CFG_STREAM_STACK_SIZE]: Stack used for parsing. TODO: Add conditional compilation flag

size_t stack_pos: Current stack position

lwjson_stream_state_t parse_state: Parser state

lwjson_stream_parser_callback_fn evt_fn: Event function for user

void *user_data: User data for callback function

char buff[LWJSON_CFG_STREAM_STRING_MAX_LEN + 1]

Buffer to write temporary data. TODO: Size to be variable with define

Temporary write buffer

size_t buff_pos

Buffer position for next write (length of bytes in buffer)

Buffer position for next write

size_t buff_total_pos: Total buffer position used up to now (in several data chunks)

uint8_t is_last: Status indicates if this is the last part of the string

struct lwjson_stream_parser_t::[anonymous]::[anonymous] str: String structure. It is only used for keys and string objects. Use primitive part for all other options

struct lwjson_stream_parser_t::[anonymous]::[anonymous] prim: Primitive object. Used for all types, except key or string

union lwjson_stream_parser_t::[anonymous] data: Data union used to parse various

char prev_c: History of characters