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Module IO


module IO: sig .. end
High-order abstract I/O.

IO module simply deals with abstract inputs/outputs. It provides a set of methods for working with these IO as well as several constructors that enable to write to an underlying channel, buffer, or enum.

type input
The abstract input type.
type 'a output
The abstract output type, 'a is the accumulator data, it is returned when the close_out function is called.
exception No_more_input
This exception is raised when reading on an input with the read or nread functions while there is no available token to read.
exception Input_closed
This exception is raised when reading on a closed input.
exception Output_closed
This exception is raised when reading on a closed output.

Standard API

val read : input -> char
Read a single char from an input or raise No_more_input if no input available.
val nread : input -> int -> string
nread i n reads a string of size up to n from an input. The function will raise No_more_input if no input is available. It will raise Invalid_argument if n < 0.
val really_nread : input -> int -> string
really_nread i n reads a string of exactly n characters from the input. Raises No_more_input if at least n characters are not available. Raises Invalid_argument if n < 0.
val input : input -> string -> int -> int -> int
input i s p l reads up to l characters from the given input, storing them in string s, starting at character number p. It returns the actual number of characters read or raise No_more_input if no character can be read. It will raise Invalid_argument if p and l do not designate a valid substring of s.
val really_input : input -> string -> int -> int -> int
really_input i s p l reads exactly l characters from the given input, storing them in the string s, starting at position p. For consistency with IO.input it returns l. Raises No_more_input if at l characters are not available. Raises Invalid_argument if p and l do not designate a valid substring of s.
val close_in : input -> unit
Close the input. It can no longer be read from.
val write : 'a output -> char -> unit
Write a single char to an output.
val nwrite : 'a output -> string -> unit
Write a string to an output.
val output : 'a output -> string -> int -> int -> int
output o s p l writes up to l characters from string s, starting at offset p. It returns the number of characters written. It will raise Invalid_argument if p and l do not designate a valid substring of s.
val really_output : 'a output -> string -> int -> int -> int
really_output o s p l writes exactly l characters from string s onto the the output, starting with the character at offset p. For consistency with IO.output it returns l. Raises Invalid_argument if p and l do not designate a valid substring of s.
val flush : 'a output -> unit
Flush an output.
val close_out : 'a output -> 'a
Close the output and return its accumulator data. It can no longer be written.

Creation of IO Inputs/Outputs

val input_string : string -> input
Create an input that will read from a string.
val output_string : unit -> string output
Create an output that will write into a string in an efficient way. When closed, the output returns all the data written into it.
val input_channel : Pervasives.in_channel -> input
Create an input that will read from a channel.
val output_channel : Pervasives.out_channel -> unit output
Create an output that will write into a channel.
val input_enum : char Enum.t -> input
Create an input that will read from an enum.
val output_enum : unit -> char Enum.t output
Create an output that will write into an enum. The final enum is returned when the output is closed.
val create_in : read:(unit -> char) ->
       input:(string -> int -> int -> int) -> close:(unit -> unit) -> input
Fully create an input by giving all the needed functions.
val create_out : write:(char -> unit) ->
       output:(string -> int -> int -> int) ->
       flush:(unit -> unit) -> close:(unit -> 'a) -> 'a output
Fully create an output by giving all the needed functions.

Utilities

val printf : 'a output -> ('b, unit, string, unit) format4 -> 'b
The printf function works for any output.
val read_all : input -> string
read all the contents of the input until No_more_input is raised.
val pipe : unit -> input * unit output
Create a pipe between an input and an ouput. Data written from the output can be read from the input.
val pos_in : input -> input * (unit -> int)
Create an input that provide a count function of the number of bytes read from it.
val pos_out : 'a output -> 'a output * (unit -> int)
Create an output that provide a count function of the number of bytes written through it.
val cast_output : 'a output -> unit output
You can safely transform any output to an unit output in a safe way by using this function.

Binary files API

Here is some API useful for working with binary files, in particular binary files generated by C applications. By default, encoding of multibyte integers is low-endian. The BigEndian module provide multibyte operations with other encoding.

exception Overflow of string
Exception raised when a read or write operation cannot be completed.
val read_byte : input -> int
Read an unsigned 8-bit integer.
val read_signed_byte : input -> int
Read an signed 8-bit integer.
val read_ui16 : input -> int
Read an unsigned 16-bit word.
val read_i16 : input -> int
Read a signed 16-bit word.
val read_i32 : input -> int
Read a signed 32-bit integer. Raise Overflow if the read integer cannot be represented as a Caml 31-bit integer.
val read_real_i32 : input -> int32
Read a signed 32-bit integer as an OCaml int32.
val read_i64 : input -> int64
Read a signed 64-bit integer as an OCaml int64.
val read_double : input -> float
Read an IEEE double precision floating point value.
val read_string : input -> string
Read a null-terminated string.
val read_line : input -> string
Read a LF or CRLF terminated string.
val write_byte : 'a output -> int -> unit
Write an unsigned 8-bit byte.
val write_ui16 : 'a output -> int -> unit
Write an unsigned 16-bit word.
val write_i16 : 'a output -> int -> unit
Write a signed 16-bit word.
val write_i32 : 'a output -> int -> unit
Write a signed 32-bit integer.
val write_real_i32 : 'a output -> int32 -> unit
Write an OCaml int32.
val write_i64 : 'a output -> int64 -> unit
Write an OCaml int64.
val write_double : 'a output -> float -> unit
Write an IEEE double precision floating point value.
val write_string : 'a output -> string -> unit
Write a string and append an null character.
val write_line : 'a output -> string -> unit
Write a line and append a LF (it might be converted to CRLF on some systems depending on the underlying IO).
module BigEndian: sig .. end
Same as operations above, but use big-endian encoding

Bits API

This enable you to read and write from an IO bit-by-bit or several bits at the same time.

type in_bits 
type out_bits 
exception Bits_error
val input_bits : input -> in_bits
Read bits from an input
val output_bits : 'a output -> out_bits
Write bits to an output
val read_bits : in_bits -> int -> int
Read up to 31 bits, raise Bits_error if n < 0 or n > 31
val write_bits : out_bits -> nbits:int -> int -> unit
Write up to 31 bits represented as a value, raise Bits_error if nbits < 0 or nbits > 31 or the value representation excess nbits.
val flush_bits : out_bits -> unit
Flush remaining unwritten bits, adding up to 7 bits which values 0.
val drop_bits : in_bits -> unit
Drop up to 7 buffered bits and restart to next input character.

Generic IO Object Wrappers

Theses OO Wrappers have been written to provide easy support of ExtLib IO by external librairies. If you want your library to support ExtLib IO without actually requiring ExtLib to compile, you can should implement the classes in_channel, out_channel, poly_in_channel and/or poly_out_channel which are the common IO specifications established for ExtLib, OCamlNet and Camomile.

(see http://www.ocaml-programming.de/tmp/IO-Classes.html for more details).

class in_channel : input -> object .. end
class out_channel : 'a output -> object .. end
class in_chars : input -> object .. end
class out_chars : 'a output -> object .. end
val from_in_channel : #in_channel -> input
val from_out_channel : #out_channel -> unit output
val from_in_chars : #in_chars -> input
val from_out_chars : #out_chars -> unit output