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_reset(lwjson_stream_parser_t *jsp)

Reset LwJSON stream structure.

Parameters: jsp – 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
c – [in] Character to parse

Returns

lwjsonOK if parsing is in progress and no hard error detected lwjsonSTREAMDONE when valid JSON was detected and stack level reached back 0 level

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

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