Module `Yojson.Basic`Source

This module supports standard JSON nodes only, i.e. no special syntax for variants or tuples as supported by Yojson.Safe. Arbitrary integers are not supported as they must all fit within the standard OCaml int type (31 or 63 bits depending on the platform).

The main advantage of this module is its simplicity.

Type of the JSON tree

Sourcetype json = [

| `Null
| `Bool of bool
| `Int of int
| `Float of float
| `String of string
| `Assoc of (string * json) list
| `List of json list

]

All possible cases defined in Yojson:

`Null: JSON null
`Bool of bool: JSON boolean
`Int of int: JSON number without decimal point or exponent.
`Intlit of string: JSON number without decimal point or exponent, preserved as a string.
`Float of float: JSON number, Infinity, -Infinity or NaN.
`Floatlit of string: JSON number, Infinity, -Infinity or NaN, preserved as a string.
`String of string: JSON string. Bytes in the range 128-255 are preserved as-is without encoding validation for both reading and writing.
`Stringlit of string: JSON string literal including the double quotes.
`Assoc of (string * json) list: JSON object.
`List of json list: JSON array.
`Tuple of json list: Tuple (non-standard extension of JSON). Syntax: ("abc", 123).
`Variant of (string * json option): Variant (non-standard extension of JSON). Syntax: <"Foo"> or <"Bar":123>.

JSON writers

Sourceval to_string : ?buf:Bi_outbuf.t -> ?len:int -> ?std:bool -> json -> string

Write a compact JSON value to a string.

parameter buf
allows to reuse an existing buffer created with Bi_outbuf.create. The buffer is cleared of all contents before starting and right before returning.

parameter len
initial length of the output buffer.

parameter std
use only standard JSON syntax, i.e. convert tuples and variants into standard JSON (if applicable), refuse to print NaN and infinities, require the root node to be either an object or an array. Default is false.

Source

val to_channel : 
  ?buf:Bi_outbuf.t ->
  ?len:int ->
  ?std:bool ->
  out_channel ->
  json ->
  unit

Write a compact JSON value to a channel.

parameter buf
allows to reuse an existing buffer created with Bi_outbuf.create_channel_writer on the same channel. buf is flushed right before to_channel returns but the out_channel is not flushed automatically.

See to_string for the role of the other optional arguments.

Source

val to_output : 
  ?buf:Bi_outbuf.t ->
  ?len:int ->
  ?std:bool ->
  < output : string -> int -> int -> int.. > ->
  json ->
  unit

Write a compact JSON value to an OO channel.

parameter buf
allows to reuse an existing buffer created with Bi_outbuf.create_output_writer on the same channel. buf is flushed right before to_output returns but the channel itself is not flushed automatically.

See to_string for the role of the other optional arguments.

Sourceval to_file : ?len:int -> ?std:bool -> string -> json -> unit

Write a compact JSON value to a file. See to_string for the role of the optional arguments.

Sourceval to_outbuf : ?std:bool -> Bi_outbuf.t -> json -> unit

Write a compact JSON value to an existing buffer. See to_string for the role of the optional argument.

Source

val stream_to_string : 
  ?buf:Bi_outbuf.t ->
  ?len:int ->
  ?std:bool ->
  json Stream.t ->
  string

Write a newline-separated sequence of compact one-line JSON values to a string. See to_string for the role of the optional arguments.

Source

val stream_to_channel : 
  ?buf:Bi_outbuf.t ->
  ?len:int ->
  ?std:bool ->
  out_channel ->
  json Stream.t ->
  unit

Write a newline-separated sequence of compact one-line JSON values to a channel. See to_channel for the role of the optional arguments.

Sourceval stream_to_file : ?len:int -> ?std:bool -> string -> json Stream.t -> unit

Write a newline-separated sequence of compact one-line JSON values to a file. See to_string for the role of the optional arguments.

Sourceval stream_to_outbuf : ?std:bool -> Bi_outbuf.t -> json Stream.t -> unit

Write a newline-separated sequence of compact one-line JSON values to an existing buffer. See to_string for the role of the optional arguments.

Miscellaneous

Sourceval sort : json -> json

Sort object fields (stable sort, comparing field names and treating them as byte sequences)

JSON pretty-printing

Sourceval pretty_format : ?std:bool -> json -> Easy_format.t

Convert into a pretty-printable tree. See to_string for the role of the optional std argument.

see http://martin.jambon.free.fr/easy-format.html
Easy-format

Sourceval pretty_print : ?std:bool -> Format.formatter -> json -> unit

Pretty-print into a Format.formatter. See to_string for the role of the optional std argument.

since 1.3.1

Sourceval pretty_to_string : ?std:bool -> json -> string

Pretty-print into a string. See to_string for the role of the optional std argument.

Sourceval pretty_to_channel : ?std:bool -> out_channel -> json -> unit

Pretty-print to a channel. See to_string for the role of the optional std argument.

Sourceval prettify : ?std:bool -> string -> string

Combined parser and pretty-printer. See to_string for the role of the optional std argument.

Sourceval compact : ?std:bool -> string -> string

Combined parser and printer. See to_string for the role of the optional std argument.

JSON readers

Sourceexception Finally of exn * exn

Exception describing a failure in both finalizer and parsing.

Source

val from_string : 
  ?buf:Bi_outbuf.t ->
  ?fname:string ->
  ?lnum:int ->
  string ->
  json

Read a JSON value from a string.

parameter buf
use this buffer at will during parsing instead of creating a new one.

parameter fname
data file name to be used in error messages. It does not have to be a real file.

parameter lnum
number of the first line of input. Default is 1.

Source

val from_channel : 
  ?buf:Bi_outbuf.t ->
  ?fname:string ->
  ?lnum:int ->
  in_channel ->
  json

Read a JSON value from a channel. See from_string for the meaning of the optional arguments.

Source

val from_file : 
  ?buf:Bi_outbuf.t ->
  ?fname:string ->
  ?lnum:int ->
  string ->
  json

Read a JSON value from a file. See from_string for the meaning of the optional arguments.

Sourcetype lexer_state = Lexer_state.t = {

buf : Bi_outbuf.t;
mutable lnum : int;
mutable bol : int;
mutable fname : string option;

}

This alias is provided for backward compatibility. New code should refer to Yojson.lexer_state directly.

Source

val init_lexer : 
  ?buf:Bi_outbuf.t ->
  ?fname:string ->
  ?lnum:int ->
  unit ->
  lexer_state

This alias is provided for backward compatibility. New code should use Yojson.init_lexer directly.

Sourceval from_lexbuf : lexer_state -> ?stream:bool -> Lexing.lexbuf -> json

Read a JSON value from a lexbuf. A valid initial lexer_state can be created with init_lexer. See from_string for the meaning of the optional arguments.

parameter stream
indicates whether more data may follow. The default value is false and indicates that only JSON whitespace can be found between the end of the JSON value and the end of the input.

Source

val stream_from_string : 
  ?buf:Bi_outbuf.t ->
  ?fname:string ->
  ?lnum:int ->
  string ->
  json Stream.t

Input a sequence of JSON values from a string. Whitespace between JSON values is fine but not required. See from_string for the meaning of the optional arguments.

Source

val stream_from_channel : 
  ?buf:Bi_outbuf.t ->
  ?fin:(unit -> unit) ->
  ?fname:string ->
  ?lnum:int ->
  in_channel ->
  json Stream.t

Input a sequence of JSON values from a channel. Whitespace between JSON values is fine but not required.

parameter fin
finalization function executed once when the end of the stream is reached either because there is no more input or because the input could not be parsed, raising an exception.

raises Finally
When the parsing and the finalizer both raised, Finally (exn, fin_exn) is raised, exn being the parsing exception and fin_exn the finalizer one.

See from_string for the meaning of the other optional arguments.

Source

val stream_from_file : 
  ?buf:Bi_outbuf.t ->
  ?fname:string ->
  ?lnum:int ->
  string ->
  json Stream.t

Input a sequence of JSON values from a file. Whitespace between JSON values is fine but not required.

See from_string for the meaning of the optional arguments.

Source

val stream_from_lexbuf : 
  lexer_state ->
  ?fin:(unit -> unit) ->
  Lexing.lexbuf ->
  json Stream.t

Input a sequence of JSON values from a lexbuf. A valid initial lexer_state can be created with init_lexer. Whitespace between JSON values is fine but not required.

raises Finally
When the parsing and the finalizer both raised, Finally (exn, fin_exn) is raised, exn being the parsing exception and fin_exn the finalizer one.

See stream_from_channel for the meaning of the optional fin argument.

Sourcetype json_line = [

| `Json of json
| `Exn of exn

]

The type of values resulting from a parsing attempt of a JSON value.

Source

val linestream_from_channel : 
  ?buf:Bi_outbuf.t ->
  ?fin:(unit -> unit) ->
  ?fname:string ->
  ?lnum:int ->
  in_channel ->
  json_line Stream.t

Input a sequence of JSON values, one per line, from a channel. Exceptions raised when reading malformed lines are caught and represented using `Exn.

See stream_from_channel for the meaning of the optional fin argument. See from_string for the meaning of the other optional arguments.

Source

val linestream_from_file : 
  ?buf:Bi_outbuf.t ->
  ?fname:string ->
  ?lnum:int ->
  string ->
  json_line Stream.t

Input a sequence of JSON values, one per line, from a file. Exceptions raised when reading malformed lines are caught and represented using `Exn.

See stream_from_channel for the meaning of the optional fin argument. See from_string for the meaning of the other optional arguments.

Sourcemodule Util : sig ... end

This module provides combinators for extracting fields from JSON values. This approach is recommended for reading a few fields from data returned by public APIs. However for more complex applications we recommend Atdgen.

package yojson

Module Yojson.BasicSource

Type of the JSON tree

JSON writers

Miscellaneous

JSON pretty-printing

JSON readers

Module `Yojson.Basic`Source