JSMN Parser

Provides helper functions for jsmn. Since jsmn provides tokenization of the JSON string and those tokens are inside an array, additional parsing is needed to quickly access name/value pairs and indexes within the JSON objects.

Philosophy

Same as jsmn, so robust, fast, portable and simple.

Usage

As with jsmn, download jsmn_parser.h include it and done. (Also need to download jsmn.h from github, however it is included by jsmn_parser.h)

#include "jsmn_parser.h"

const char* example_json =
"{"
"\"Paul\":"
"   {"
"       \"Age\": 30,"
"       \"Children\":"
"       ["
"           \"Barbara\","
"           \"Peter\""
"       ]"
"   },"
"\"Anna\":"
"   {"
"       \"Age\":41,"
"       \"Children\":"
"       []"
"   }"
"}";

...

// Do jsmn things
jsmn_parser p;
jsmntok_t t[128]; /* We expect no more than 128 JSON tokens */

jsmn_init(&p);
r = jsmn_parse(&p, example_json, strlen(example_json), t, 128);

// Access the tokens
const jsmntok_t* pauls_second_child = tok_get_index(tok_get_name(tok_get_index(t, 0), s, "Children"), 1);

...

API

All functions return either the found token or if nothing was found, the token that was provided. So always check if the token changed before continuing.

tok_get_index

Returns the token at the given index. Provide a base token pointing either to an object or an array or to their names. (I.e. the token for Paul or the token after which is the actual object token.)

// Gets the token pointing to "Anna"
const jsmntok_t* anna = tok_get_index(t, 1);

tok_get_name

Returns the token with the given name. Provide a base token pointing to an object or its name. Also need to provide the json string to compare the name.

// Gets the token pointing to "Anna"
const jsmntok_t* anna = tok_get_name(t, example_json, "Anna");

tok_get_value

Returns the value of the given name.

// Gets the token pointing to the age of "Anna"
const jsmntok_t* anna = tok_get_name(t, example_json, "Anna");
const jsmntok_t* age_name = tok_get_name(anna, example_json, "Age");
const jsmntok_t* age_value = tok_get_value(age_name);

tok_get_leaf

Returns the token of the value with the given name, if this value is not nested anymore.

// Gets the token pointing to the age of "Anna"
const jsmntok_t* anna = tok_get_name(t, example_json, "Anna");
const jsmntok_t* age_value = tok_get_leaf(anna, example_json, "Age");