yajl_tree.h File Reference

#include <yajl/yajl_common.h>

Go to the source code of this file.

Data Structures
struct	yajl_val_s

Macros
#define	YAJL_NUMBER_INT_VALID   0x01
#define	YAJL_NUMBER_DOUBLE_VALID   0x02
#define	YAJL_IS_STRING(v)   (((v) != NULL) && ((v)->type == yajl_t_string))
#define	YAJL_IS_NUMBER(v)   (((v) != NULL) && ((v)->type == yajl_t_number))
#define	YAJL_IS_INTEGER(v)   (YAJL_IS_NUMBER(v) && ((v)->u.number.flags & YAJL_NUMBER_INT_VALID))
#define	YAJL_IS_DOUBLE(v)   (YAJL_IS_NUMBER(v) && ((v)->u.number.flags & YAJL_NUMBER_DOUBLE_VALID))
#define	YAJL_IS_OBJECT(v)   (((v) != NULL) && ((v)->type == yajl_t_object))
#define	YAJL_IS_ARRAY(v)   (((v) != NULL) && ((v)->type == yajl_t_array ))
#define	YAJL_IS_TRUE(v)   (((v) != NULL) && ((v)->type == yajl_t_true ))
#define	YAJL_IS_FALSE(v)   (((v) != NULL) && ((v)->type == yajl_t_false ))
#define	YAJL_IS_NULL(v)   (((v) != NULL) && ((v)->type == yajl_t_null ))
#define	YAJL_GET_STRING(v)   (YAJL_IS_STRING(v) ? (v)->u.string : NULL)
#define	YAJL_GET_NUMBER(v)   ((v)->u.number.r)
#define	YAJL_GET_DOUBLE(v)   ((v)->u.number.d)
#define	YAJL_GET_INTEGER(v)   ((v)->u.number.i)
#define	YAJL_GET_OBJECT(v)   (YAJL_IS_OBJECT(v) ? &(v)->u.object : NULL)
#define	YAJL_GET_ARRAY(v)   (YAJL_IS_ARRAY(v) ? &(v)->u.array : NULL)

Typedefs
typedef struct yajl_val_s *	yajl_val

Enumerations
enum	yajl_type {   yajl_t_string = 1, yajl_t_number = 2, yajl_t_object = 3, yajl_t_array = 4,   yajl_t_true = 5, yajl_t_false = 6, yajl_t_null = 7, yajl_t_any = 8 }

Functions
YAJL_API yajl_val	yajl_tree_parse (const char *input, char *error_buffer, size_t error_buffer_size)
YAJL_API void	yajl_tree_free (yajl_val v)
YAJL_API yajl_val	yajl_tree_get (yajl_val parent, const char **path, yajl_type type)

Detailed Description

Parses JSON data and returns the data in tree form.

Author

Florian Forster

Date

August 2010

This interface makes quick parsing and extraction of smallish JSON docs trivial:

/*
 * Copyright (c) 2007-2014, Lloyd Hilaiel <me@lloyd.io>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdio.h>
#include <string.h>

#include "yajl/yajl_tree.h"

static unsigned char fileData[65536];

int
main(void)
{
    size_t rd;
    yajl_val node;
    char errbuf[1024];

    /* null plug buffers */
    fileData[0] = errbuf[0] = 0;

    /* read the entire config file */
    rd = fread((void *) fileData, 1, sizeof(fileData) - 1, stdin);

    /* file read error handling */
    if (rd == 0 && !feof(stdin)) {
        fprintf(stderr, "error encountered on file read\n");
        return 1;
    } else if (rd >= sizeof(fileData) - 1) {
        fprintf(stderr, "config file too big\n");
        return 1;
    }

    /* we have the whole config file in memory.  let's parse it ... */
    node = yajl_tree_parse((const char *) fileData, errbuf, sizeof(errbuf));

    /* parse error handling */
    if (node == NULL) {
        fprintf(stderr, "parse_error: ");
        if (strlen(errbuf)) fprintf(stderr, " %s", errbuf);
        else fprintf(stderr, "unknown error");
        fprintf(stderr, "\n");
        return 1;
    }

    /* ... and extract a nested value from the config file */
    {
        const char * path[] = { "Logging", "timeFormat", (const char *) 0 };
        yajl_val v = yajl_tree_get(node, path, yajl_t_string);
        if (v) printf("%s/%s: %s\n", path[0], path[1], YAJL_GET_STRING(v));
        else   printf("no such node: %s/%s\n", path[0], path[1]);
    }

    yajl_tree_free(node);

    return 0;
}

Macro Definition Documentation

#define YAJL_GET_ARRAY

(

v

)

(YAJL_IS_ARRAY(v) ? &(v)->u.array : NULL)

Get a pointer to a yajl_val_array or NULL if the value is not an object.

#define YAJL_GET_DOUBLE

(

v

)

((v)->u.number.d)

Get the double representation of a number. You should check type first, perhaps using YAJL_IS_DOUBLE

#define YAJL_GET_INTEGER

(

v

)

((v)->u.number.i)

Get the 64bit (long long) integer representation of a number. You should check type first, perhaps using YAJL_IS_INTEGER

#define YAJL_GET_NUMBER

(

v

)

((v)->u.number.r)

Get the string representation of a number. You should check type first, perhaps using YAJL_IS_NUMBER

#define YAJL_GET_OBJECT

(

v

)

(YAJL_IS_OBJECT(v) ? &(v)->u.object : NULL)

Get a pointer to a yajl_val_object or NULL if the value is not an object.

#define YAJL_GET_STRING

(

v

)

(YAJL_IS_STRING(v) ? (v)->u.string : NULL)

Given a yajl_val_string return a ptr to the bare string it contains, or NULL if the value is not a string.

Examples:

example/parse_config.c.

#define YAJL_IS_ARRAY

(

v

)

(((v) != NULL) && ((v)->type == yajl_t_array ))

#define YAJL_IS_DOUBLE

(

v

)

(YAJL_IS_NUMBER(v) && ((v)->u.number.flags & YAJL_NUMBER_DOUBLE_VALID))

#define YAJL_IS_FALSE

(

v

)

(((v) != NULL) && ((v)->type == yajl_t_false ))

#define YAJL_IS_INTEGER

(

v

)

(YAJL_IS_NUMBER(v) && ((v)->u.number.flags & YAJL_NUMBER_INT_VALID))

#define YAJL_IS_NULL

(

v

)

(((v) != NULL) && ((v)->type == yajl_t_null ))

#define YAJL_IS_NUMBER

(

v

)

(((v) != NULL) && ((v)->type == yajl_t_number))

#define YAJL_IS_OBJECT

(

v

)

(((v) != NULL) && ((v)->type == yajl_t_object))

#define YAJL_IS_STRING

(

v

)

(((v) != NULL) && ((v)->type == yajl_t_string))

#define YAJL_IS_TRUE

(

v

)

(((v) != NULL) && ((v)->type == yajl_t_true ))

#define YAJL_NUMBER_DOUBLE_VALID   0x02

#define YAJL_NUMBER_INT_VALID   0x01

Typedef Documentation

typedef struct yajl_val_s* yajl_val

A pointer to a node in the parse tree

Enumeration Type Documentation

enum yajl_type

possible data types that a yajl_val_s can hold

Enumerator
yajl_t_string
yajl_t_number
yajl_t_object
yajl_t_array
yajl_t_true
yajl_t_false
yajl_t_null
yajl_t_any	The any type isn't valid for yajl_val_s.type, but can be used as an argument to routines like yajl_tree_get().

Function Documentation

YAJL_API void yajl_tree_free

(

yajl_val

v

)

Free a parse tree returned by "yajl_tree_parse".

Parameters

v	Pointer to a JSON value returned by "yajl_tree_parse". Passing NULL is valid and results in a no-op.

Examples:

example/parse_config.c.

YAJL_API yajl_val yajl_tree_get	(	yajl_val	parent,
		const char **	path,
		yajl_type	type
	)

Access a nested value inside a tree.

Parameters

parent	the node under which you'd like to extract values.
path	A null terminated array of strings, each the name of an object key
type	the yajl_type of the object you seek, or yajl_t_any if any will do.

Returns

a pointer to the found value, or NULL if we came up empty.

Future Ideas: it'd be nice to move path to a string and implement support for a teeny tiny micro language here, so you can extract array elements, do things like .first and .last, even .length. Inspiration from JSONPath and css selectors? No it wouldn't be fast, but that's not what this API is about.

Examples:

example/parse_config.c.

YAJL_API yajl_val yajl_tree_parse	(	const char *	input,
		char *	error_buffer,
		size_t	error_buffer_size
	)

Parse a string.

Parses an null-terminated string containing JSON data and returns a pointer to the top-level value (root of the parse tree).

Parameters

input	Pointer to a null-terminated utf8 string containing JSON data.
error_buffer	Pointer to a buffer in which an error message will be stored if yajl_tree_parse fails, or NULL. The buffer will be initialized before parsing, so its content will be destroyed even if yajl_tree_parse succeeds.
error_buffer_size	Size of the memory area pointed to by error_buffer_size. If error_buffer_size is NULL, this argument is ignored.

Returns

Pointer to the top-level value or NULL on error. The memory pointed to must be freed using yajl_tree_free. In case of an error, a null terminated message describing the error in more detail is stored in error_buffer if it is not NULL.

Examples:

example/parse_config.c.