hans-avr/json_decoder

JSON Decoder

JSON Decoder aims to:

1. Be highly optimized for constrained embedded systems
2. Work on both PIC18 and AVR

Example Usage

#define TEST_JSON "{\"main\":{\"key\" : 10,\"foo\":\"bar\"}, \"alt\":2}"

...

jsonNode_t *root, *objmain;
char foo[10], str[50];
int alt;

memcpy(str, TEST_JSON, sizeof(TEST_JSON));

JSON_DECODER_fromString(str)

JSON_DECODER_getRoot(&root);
JSON_DECODER_getObject(root, "main", &objmain);

JSON_DECODER_getNumber(root, "alt", &alt)
JSON_DECODER_getString(objmain, "foo", strlen(foo), foo)

API

jsonDecoderStatus_t JSON_DECODER_fromString(char *str)

Description

Parses a JSON string into a C representation. It supports string, number and object values.

Params

Name	Type	Description
str	IN	A string representation of a JSON object. After parsing, the string will have been altered.

Return

Name	Description
JSON_DECODER_OK	Decoding was successful
JSON_DECODER_BAD_FORMAT	The input is invalid.

JSON_DECODER_getRoot(jsonNode_t **pNode)

Description

The outermost object in a JSON is called the root. This function must not be called before JSON_DECODER_fromString.

Params

Name	Type	Description
pNode	OUT	Pointer to the root. When the function is called this parameter does not need to point to a valid jsonNode_t address.

Return

Name	Description
JSON_DECODER_OK	pNode now points to the root

jsonDecoderStatus_t JSON_DECODER_getObject(jsonNode_t *current, char *key, jsonNode_t **pNode)

Description

Finds a JSON object by key in another JOSN object. This function must not be called before JSON_DECODER_fromString.

Params

Name	Type	Description
current	IN	The JSON object to search into
key	IN	The key of the object to find
pNode	OUT	Pointer to the object, if found. When the function is called this parameter does not need to point to a valid jsonNode_t address.

Return

Name	Description
JSON_DECODER_OK	Object was found and pNode now points to in
JSON_DECODER_KEY_NOT_FOUND	The specified key does not exist

jsonDecoderStatus_t JSON_DECODER_getString(jsonNode_t *current, char *key, uint8_t size, char *pVal)

Description

Finds a string by key in a JOSN object. This function must not be called before JSON_DECODER_fromString.

Params

Name	Type	Description
current	IN	The JSON object to search into
key	IN	The key of the string to find
size	IN	Maximum size of the string. Should not be bigger than the length of the pVal buffer
pVal	OUT	Pointer to the string, if found

Return

Name	Description
JSON_DECODER_OK	String was found and pVal now points to in
JSON_DECODER_KEY_NOT_FOUND	The specified key does not exist

jsonDecoderStatus_t JSON_DECODER_getNumber(jsonNode_t *current, char *key, int *pVal)

Description

Finds a number by key in a JSON object. This function must not be called before JSON_DECODER_fromString.

Params

Name	Type	Description
current	IN	The JSON object to search into
key	IN	The key of the string to find
pVal	OUT	Pointer to the number, if found

Return

Name	Description
JSON_DECODER_OK	Number was found and pVal now points to in
JSON_DECODER_KEY_NOT_FOUND	The specified key does not exist