Functions

JsmnInit()

This function is used to (re)initialize a parser object. It removes all leftover data from parser for each new JSON packet and sets all members to initial values. In most cases this function should be called before each new JSON packet. See Reentry for special case. Note: callback and pcache member on parser object is not modified. This means that the application will need to be initialize values.

JsmnParse()

Parses a JSON string into tokens and pass them to a user defined callback function. This is the backbone of Jsmn. Note: Parse function supports js object format as well as standard JSON.

Arguments

Determining required numTokens

The numTokens needed to successfully parse a JSON string is directly dependent on number of levels expected in the JSON. 1 token is needed for every member or value following only the deepest route. For example JSON given below, JsmnParse will require at least 7 tokens:

{
    "object": {
        "subObject" : {
            "mem1": 1
        },
        "mem2": 2
    },
    "mem3": 3
}

Notice the deepest level in object is member “mem1”. So counting every member and value starting at root to “mem1” we get:

• 1 token for root object
• 1 token for “object” member
• 1 token for “object”’s value
• 1 token for “subObject” member
• 1 token for “subObject”’s value
• 1 token for “mem1” member
• 1 token for “mem1”’s value

Note: We ignored mem2 and mem3 because they are not apart of the deepest route.

Callback data

Callback Function

Application can define a callback function that will be called for every new token found while parsing. Callback function will given information regarding token via jsmn_callback_data type and have access to pUserData specified by the application. If no callback is desired set parser.callback.pFunction to 0. Example callback function definition below.

// userData - Value specified by application via parser.callback.pUserData
// data - Token data for callback
unsigned long jsonCallback(userData_typ* userData, jsmn_callback_data* data);

JsonParse()

Json parse is a wrapper for jsmnParse function that simplifies the usage but looses the ability to use callbacks and reentrance.

JsonTokenEqual()

Finds index of token pName in pTokenArray parsed with JsonParse from pJsonString.

JsonGetValue()

Finds value of token pName in pTokenArray parsed with JsonParse from pJsonString.