YAJL  2.1.0
Data Structures | Macros | Typedefs | Enumerations | Functions
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_syajl_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 };
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]);
}
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
vPointer 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
parentthe node under which you'd like to extract values.
pathA null terminated array of strings, each the name of an object key
typethe 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
inputPointer to a null-terminated utf8 string containing JSON data.
error_bufferPointer 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_sizeSize 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.