JSON library based on JSMN lib

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C++ JSON wrapper over JSMN lib (https://github.com/zserge/jsmn).

This C++ Class is a set of common tools/procedures as a C++ wrapper over JSMN JSON parser library. It is intended to provide the boiler-plate code, with intentions to reduce code clutter, in more of C++ fashion.

In contrast to original library, Json is intended to work strictly with valid JSON structures. Non-standard JSON structures should result in an error.

This class works explicitly on the indices returned by underlying JSMN library. In the scope of this class, its function parameters, return types, and documentation, the term 'index' will always mean the index of JSMN tokens, parsed by the Json constructor, unless and until explicitly mentioned otherwise.

jsmn.c

Committer:
faheem_chaudhary
Date:
2016-08-16
Revision:
7:8aa4d0e98eb0
Parent:
5:dd98cf00ed9b

File content as of revision 7:8aa4d0e98eb0:

/* Author: Faheem Inayat
 * Created by "Night Crue" Team @ TechShop San Jose, CA
 *
 * --- DISCLAIMER ---
 * This code is a modified version of original JSMN lirary, written by
 *    *** Serge A. Zaitsev ***
 * and hosted at https://github.com/zserge/jsmn
 * Any modification to the original source is not guaranteed to be included
 * in this version.  As of writing of this file, the original source is 
 * licensed under MIT License
 * (http://www.opensource.org/licenses/mit-license.php).
 */

#include "jsmn.h"

/**
 * Allocates a fresh unused token from the token pull.
 */
static jsmntok_t *jsmn_alloc_token ( jsmn_parser *parser, jsmntok_t *tokens, size_t num_tokens )
{
    jsmntok_t *tok;
    if ( parser->toknext >= num_tokens )
    {
        return NULL ;
    }
    tok = &tokens [ parser->toknext++ ];
    tok->start = tok->end = -1;
    tok->childCount = 0;
    tok->parent = -1;
    return tok;
}

/**
 * Fills token type and boundaries.
 */
static void jsmn_fill_token ( jsmntok_t *token, jsmntype_t type, int start, int end )
{
    token->type = type;
    token->start = start;
    token->end = end;
    token->childCount = 0;
}

/**
 * Fills next available token with JSON primitive.
 */
static int jsmn_parse_primitive ( jsmn_parser *parser, const char *js, size_t len, jsmntok_t *tokens, size_t num_tokens )
{
    jsmntok_t *token;
    int start;

    start = parser->pos;

    for ( ; parser->pos < len && js [ parser->pos ] != '\0'; parser->pos++ )
    {
        switch ( js [ parser->pos ] )
        {
            case '\t':
            case '\r':
            case '\n':
            case ' ':
            case ',':
            case ']':
            case '}':
                goto found;
        }
        if ( js [ parser->pos ] < 32 || js [ parser->pos ] >= 127 )
        {
            parser->pos = start;
            return JSMN_ERROR_INVAL;
        }
    }
    /* primitive must be followed by a comma/object/array */
    parser->pos = start;
    return JSMN_ERROR_PART;

    found: if ( tokens == NULL )
    {
        parser->pos--;
        return 0;
    }
    token = jsmn_alloc_token ( parser, tokens, num_tokens );
    if ( token == NULL )
    {
        parser->pos = start;
        return JSMN_ERROR_NOMEM;
    }
    jsmn_fill_token ( token, JSMN_PRIMITIVE, start, parser->pos );
    token->parent = parser->toksuper;
    parser->pos--;
    return 0;
}

/**
 * Fills next token with JSON string.
 */
static int jsmn_parse_string ( jsmn_parser *parser, const char *js, size_t len, jsmntok_t *tokens, size_t num_tokens, unsigned char isKey )
{
    jsmntok_t *token;

    int start = parser->pos;

    parser->pos++;

    /* Skip starting quote */
    for ( ; parser->pos < len && js [ parser->pos ] != '\0'; parser->pos++ )
    {
        char c = js [ parser->pos ];

        /* Quote: end of string */
        if ( c == '\"' )
        {
            if ( tokens == NULL )
            {
                return 0;
            }
            token = jsmn_alloc_token ( parser, tokens, num_tokens );
            if ( token == NULL )
            {
                parser->pos = start;
                return JSMN_ERROR_NOMEM;
            }
            if ( isKey == 1 )
            {
                jsmn_fill_token ( token, JSMN_KEY, start + 1, parser->pos );
            }
            else
            {
                jsmn_fill_token ( token, JSMN_STRING, start + 1, parser->pos );
            }
            token->parent = parser->toksuper;
            return 0;
        }

        /* Backslash: Quoted symbol expected */
        if ( c == '\\' && parser->pos + 1 < len )
        {
            int i;
            parser->pos++;
            switch ( js [ parser->pos ] )
            {
                /* Allowed escaped symbols */
                case '\"':
                case '/':
                case '\\':
                case 'b':
                case 'f':
                case 'r':
                case 'n':
                case 't':
                    break;
                    /* Allows escaped symbol \uXXXX */
                case 'u':
                    parser->pos++;
                    for ( i = 0; i < 4 && parser->pos < len && js [ parser->pos ] != '\0'; i++ )
                    {
                        /* If it isn't a hex character we have an error */
                        if ( ! ( ( js [ parser->pos ] >= 48 && js [ parser->pos ] <= 57 ) || /* 0-9 */
                        ( js [ parser->pos ] >= 65 && js [ parser->pos ] <= 70 )
                                 || /* A-F */
                                 ( js [ parser->pos ] >= 97 && js [ parser->pos ] <= 102 ) ) )
                        { /* a-f */
                            parser->pos = start;
                            return JSMN_ERROR_INVAL;
                        }
                        parser->pos++;
                    }
                    parser->pos--;
                    break;
                    /* Unexpected symbol */
                default:
                    parser->pos = start;
                    return JSMN_ERROR_INVAL;
            }
        }
    }
    parser->pos = start;
    return JSMN_ERROR_PART;
}

/**
 * Parse JSON string and fill tokens.
 */
int jsmn_parse ( jsmn_parser *parser, const char *js, size_t len, jsmntok_t *tokens, unsigned int num_tokens )
{
    int r;
    int i;
    jsmntok_t *token;
    int count = parser->toknext;

    unsigned char isKey = 1;

    for ( ; parser->pos < len && js [ parser->pos ] != '\0'; parser->pos++ )
    {
        char c;
        jsmntype_t type;

        c = js [ parser->pos ];
        switch ( c )
        {
            case '{':
            case '[':
                count++;
                if ( tokens == NULL )
                {
                    break;
                }
                token = jsmn_alloc_token ( parser, tokens, num_tokens );
                if ( token == NULL )
                    return JSMN_ERROR_NOMEM;
                if ( parser->toksuper != -1 )
                {
                    tokens [ parser->toksuper ].childCount++;
                    token->parent = parser->toksuper;
                }
                token->type = ( c == '{' ? JSMN_OBJECT : JSMN_ARRAY );
                token->start = parser->pos;
                parser->toksuper = parser->toknext - 1;
                if ( token->type == JSMN_OBJECT )
                {
                    isKey = 1;
                }
                break;
            case '}':
            case ']':
                if ( tokens == NULL )
                    break;
                type = ( c == '}' ? JSMN_OBJECT : JSMN_ARRAY );
                if ( parser->toknext < 1 )
                {
                    return JSMN_ERROR_INVAL;
                }
                token = &tokens [ parser->toknext - 1 ];
                for ( ;; )
                {
                    if ( token->start != -1 && token->end == -1 )
                    {
                        if ( token->type != type )
                        {
                            return JSMN_ERROR_INVAL;
                        }
                        token->end = parser->pos + 1;
                        parser->toksuper = token->parent;
                        break;
                    }
                    if ( token->parent == -1 )
                    {
                        break;
                    }
                    token = &tokens [ token->parent ];
                }
                break;
            case '\"':
                r = jsmn_parse_string ( parser, js, len, tokens, num_tokens, isKey );
                if ( r < 0 )
                    return r;
                count++;
                if ( parser->toksuper != -1 && tokens != NULL )
                    tokens [ parser->toksuper ].childCount++;
                break;
            case '\t':
            case '\r':
            case '\n':
            case ' ':
                break;
            case ':':
                isKey = 0;
                parser->toksuper = parser->toknext - 1;
                break;
            case ',':
                if ( tokens != NULL && parser->toksuper != -1 && tokens [ parser->toksuper ].type != JSMN_ARRAY && tokens [ parser->toksuper ].type != JSMN_OBJECT )
                {
                    parser->toksuper = tokens [ parser->toksuper ].parent;
                }
                isKey = 1;
                break;
                /* In strict mode primitives are: numbers and booleans */
            case '-':
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
            case 't':
            case 'f':
            case 'n':
                /* And they must not be keys of the object */
                if ( tokens != NULL && parser->toksuper != -1 )
                {
                    jsmntok_t *t = &tokens [ parser->toksuper ];
                    if ( t->type == JSMN_OBJECT || ( t->type == JSMN_STRING && t->childCount != 0 ) )
                    {
                        return JSMN_ERROR_INVAL;
                    }
                }
                r = jsmn_parse_primitive ( parser, js, len, tokens, num_tokens );
                if ( r < 0 )
                    return r;
                count++;
                if ( parser->toksuper != -1 && tokens != NULL )
                    tokens [ parser->toksuper ].childCount++;
                break;

                /* Unexpected char in strict mode */
            default:
                return JSMN_ERROR_INVAL;
        }
    }

    if ( tokens != NULL )
    {
        for ( i = parser->toknext - 1; i >= 0; i-- )
        {
            /* Unmatched opened object or array */
            if ( tokens [ i ].start != -1 && tokens [ i ].end == -1 )
            {
                return JSMN_ERROR_PART;
            }
        }
    }

    return count;
}

/**
 * Creates a new parser based over a given  buffer with an array of tokens
 * available.
 */
void jsmn_init ( jsmn_parser *parser )
{
    parser->pos = 0;
    parser->toknext = 0;
    parser->toksuper = -1;
}