json-c: json_util.h File Reference

json-c 0.18

Macros | Functions
json_util.h File Reference

Miscllaneous utility functions and macros. More...

## Macros
#define | json_min(a, b) ((a) < (b) ? (a) : (b))
#define | json_max(a, b) ((a) > (b) ? (a) : (b))
#define | JSON_FILE_BUF_SIZE 4096

## Functions
JSON_EXPORT struct json_object * | json_object_from_file (const char *filename)
JSON_EXPORT struct json_object * | json_object_from_fd_ex (int fd, int depth)
JSON_EXPORT struct json_object * | json_object_from_fd (int fd)
JSON_EXPORT int | json_object_to_file (const char *filename, struct json_object *obj)
JSON_EXPORT int | json_object_to_file_ext (const char *filename, struct json_object *obj, int flags)
JSON_EXPORT int | json_object_to_fd (int fd, struct json_object *obj, int flags)
JSON_EXPORT const char * | json_util_get_last_err (void)
JSON_EXPORT int | json_parse_int64 (const char *buf, int64_t *retval)
JSON_EXPORT int | json_parse_uint64 (const char *buf, uint64_t *retval)
JSON_EXPORT int | json_parse_double (const char *buf, double *retval)
JSON_EXPORT const char * | json_type_to_name (enum json_type o_type)

## Detailed Description

Miscllaneous utility functions and macros.

## Macro Definition Documentation

## ◆ JSON_FILE_BUF_SIZE

#define JSON_FILE_BUF_SIZE 4096

## ◆ json_max

#define json_max | ( |  | a,
|  |  | b
| ) |  | ((a) > (b) ? (a) : (b))

## ◆ json_min

#define json_min | ( |  | a,
|  |  | b
| ) |  | ((a) < (b) ? (a) : (b))

## Function Documentation

## ◆ json_object_from_fd()

JSON_EXPORT struct json_object * json_object_from_fd | ( | int | fd | ) |

Create a JSON object from an already opened file descriptor, using the default maximum object depth. (JSON_TOKENER_DEFAULT_DEPTH)

See json_object_from_fd_ex() for details.

## ◆ json_object_from_fd_ex()

JSON_EXPORT struct json_object * json_object_from_fd_ex | ( | int | fd,
|  | int | depth
| ) |  |

Create a JSON object from already opened file descriptor.

This function can be helpful, when you opened the file already, e.g. when you have a temp file. Note, that the fd must be readable at the actual position, i.e. use lseek(fd, 0, SEEK_SET) before.

The depth argument specifies the maximum object depth to pass to json_tokener_new_ex(). When depth == -1, JSON_TOKENER_DEFAULT_DEPTH is used instead.

Returns NULL on failure. See json_util_get_last_err() for details.

## ◆ json_object_from_file()

JSON_EXPORT struct json_object * json_object_from_file | ( | const char * | filename | ) |

Read the full contents of the given file, then convert it to a json_object using json_tokener_parse().

Returns NULL on failure. See json_util_get_last_err() for details.

## ◆ json_object_to_fd()

JSON_EXPORT int json_object_to_fd | ( | int | fd,
|  | struct json_object * | obj,
|  | int | flags
| ) |  |

Convert the json_object to a string and write it to the file descriptor. Handles partial writes and will keep writing until done, or an error occurs.

Parameters

  fd | an open, writable file descriptor to write to
  obj | the object to serializer and write
  flags | flags to pass to json_object_to_json_string_ext()

Returns
  -1 if something fails. See json_util_get_last_err() for details.

## ◆ json_object_to_file()

JSON_EXPORT int json_object_to_file | ( | const char * | filename,
|  | struct json_object * | obj
| ) |  |

Equivalent to: json_object_to_file_ext(filename, obj, JSON_C_TO_STRING_PLAIN);

Returns -1 if something fails. See json_util_get_last_err() for details.

## ◆ json_object_to_file_ext()

JSON_EXPORT int json_object_to_file_ext | ( | const char * | filename,
|  | struct json_object * | obj,
|  | int | flags
| ) |  |

Open and truncate the given file, creating it if necessary, then convert the json_object to a string and write it to the file.

Returns -1 if something fails. See json_util_get_last_err() for details.

## ◆ json_parse_double()

JSON_EXPORT int json_parse_double | ( | const char * | buf,
|  | double * | retval
| ) |  |

Deprecated:

## ◆ json_parse_int64()

JSON_EXPORT int json_parse_int64 | ( | const char * | buf,
|  | int64_t * | retval
| ) |  |

A parsing helper for integer values. Returns 0 on success, with the parsed value assigned to *retval. Overflow/underflow are NOT considered errors, but errno will be set to ERANGE, just like the strtol/strtoll functions do.

## ◆ json_parse_uint64()

JSON_EXPORT int json_parse_uint64 | ( | const char * | buf,
|  | uint64_t * | retval
| ) |  |

A parsing help for integer values, providing one extra bit of magnitude beyond json_parse_int64().

## ◆ json_type_to_name()

JSON_EXPORT const char * json_type_to_name | ( | enum json_type | o_type | ) |

Return a string describing the type of the object. e.g. "int", or "object", etc...

## ◆ json_util_get_last_err()

JSON_EXPORT const char * json_util_get_last_err | ( | void |  | ) |

Return the last error from various json-c functions, including: json_object_to_file{,ext}, json_object_to_fd() or json_object_from{file,fd}, or NULL if there is none.