Module BatInnerIO

Core of the BatIO module.

This module contains the core definitions of BatIO, so as to avoid circular dependencies between modules which only need simple functions of BatIO and that module itself.

Don't use this module, use BatIO.

type input
type 'a output
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.

val read : input -> char

Read a single char from an input or raise No_more_input if no input available.

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 output. Data written from the output can be read from the input.

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.

    @raise Invalid_argument

    if n < 0.

val input : input -> Bytes.t -> int -> int -> int

input i s p len reads up to len bytes from the given input, storing them in byte sequence s, starting at position p. It returns the actual number of bytes read or raise No_more_input if no character can be read. It will raise Invalid_argument if p and len do not designate a valid subsequence of s.

val really_input : input -> Bytes.t -> int -> int -> int

really_input i s p len reads exactly len characters from the given input, storing them in the byte sequence s, starting at position p. For consistency with BatIO.input it returns len.

  • raises No_more_input

    if at least len characters are not available.

    @raise Invalid_argument

    if p and len do not designate a valid subsequence 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 nwrite_bytes : 'a output -> Bytes.t -> unit

Write a byte sequence to an output.

  • since 2.8.0
val output : 'a output -> Bytes.t -> int -> int -> int

output o s p len writes up to len characters from byte sequence len, starting at offset p. It returns the number of characters written. It will raise Invalid_argument if p and len do not designate a valid subsequence of s.

val output_substring : 'a output -> string -> int -> int -> int

like output above, but outputs from a substring instead of a subsequence of bytes

  • since 2.8.0
val really_output : 'a output -> Bytes.t -> int -> int -> int

really_output o s p len writes exactly len characters from byte sequence s onto the the output, starting with the character at offset p. For consistency with BatIO.output it returns len.

  • raises Invalid_argument

    if p and len do not designate a valid subsequence of s.

val really_output_substring : 'a output -> string -> int -> int -> int

like really_output above, but outputs from a substring instead of a subsequence of bytes

  • since 2.8.0
val flush : 'a output -> unit

Flush an output.

val flush_all : unit -> unit

Flush all outputs.

val close_out : 'a output -> 'a

Close the output and return its accumulator data. It can no longer be written.

val close_all : unit -> unit

Close all outputs. Ignore errors.

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 on_close_out : 'a output -> ('a output -> unit) -> unit

Register a function to be triggered just before an output is closed.

val create_in : read:(unit -> char) -> input:(Bytes.t -> int -> int -> int) -> close:(unit -> unit) -> input

Fully create an input by giving all the needed functions.

Note Do not use this function for creating an input which reads from one or more underlying inputs. Rather, use wrap_in.

val inherit_in : ?read:(unit -> char) -> ?input:(Bytes.t -> int -> int -> int) -> ?close:(unit -> unit) -> input -> input

Simplified and optimized version of wrap_in whenever only one input appears as dependency.

val wrap_in : read:(unit -> char) -> input:(Bytes.t -> int -> int -> int) -> close:(unit -> unit) -> underlying:input list -> input

Fully create an input reading from other inputs by giving all the needed functions.

This function is a more general version of create_in which also handles dependency management between inputs.

val create_out : write:(char -> unit) -> output:(Bytes.t -> int -> int -> int) -> flush:(unit -> unit) -> close:(unit -> 'a) -> 'a output

Fully create an output by giving all the needed functions.

  • parameter write

    Write one character to the output (see write).

  • parameter output

    Write a (sub)string to the output (see output).

  • parameter flush

    Flush any buffers of this output (see flush).

  • parameter close

    Close this output. The output will be automatically flushed.

    Note Do not use this function for creating an output which writes to one or more underlying outputs. Rather, use wrap_out.

val inherit_out : ?write:(char -> unit) -> ?output:(Bytes.t -> int -> int -> int) -> ?flush:(unit -> unit) -> ?close:(unit -> unit) -> _ output -> unit output

Simplified and optimized version of wrap_out whenever only one output appears as dependency.

val wrap_out : write:(char -> unit) -> output:(Bytes.t -> int -> int -> int) -> flush:(unit -> unit) -> close:(unit -> 'a) -> underlying:'b output list -> 'a output

Fully create an output that writes to one or more underlying outputs.

This function is a more general version of create_out, which also handles dependency management between outputs.

To illustrate the need for dependency management, let us consider the following values:

  • an output out
  • a function f : _ output -> _ output, using create_out to create a new output for writing some data to an underyling output (for instance, a function comparale to tab_out or a function performing transparent compression or transparent traduction between encodings)

With these values, let us consider the following scenario

  • a new output f out is created
  • some data is written to f out but not flushed
  • output out is closed, perhaps manually or as a consequence of garbage-collection, or because the program has ended
  • data written to f out is flushed.

In this case, data reaches out only after out has been closed, which violates the protocol. Despite appearances, it is quite easy to reach such situation, especially in short programs.

The solution is to use wrap_out rather than create_out in f. Specifying that f out writes on out will then let the run-time flush and close f out when out is closed for any reason, which in turn avoids the issue.

  • parameter write

    Write one character to the output (see write).

  • parameter output

    Write a (sub)string to the output (see output).

  • parameter flush

    Flush any buffers of this output (see flush).

  • parameter close

    Close this output. The output will be automatically flushed.

  • parameter underlying

    The list of outputs to which the new output will write.

    Note Function close should not close underlying yourself. This is a common mistake which may cause sockets or standard output to be closed while they are still being used by another part of the program.

val default_buffer_size : int

The default size of buffers.

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.

  • raises Overflow

    if the read integer cannot be represented as an OCaml 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_float : input -> float

Read an IEEE single precision floating point value.

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_float : 'a output -> float -> unit

Write an IEEE single 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 BatIO).

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.

For compatibility purposes
val input_channel : ?autoclose:bool -> ?cleanup:bool -> in_channel -> input

Create an input that will read from a channel.

  • parameter autoclose

    If true or unspecified, the input will be automatically closed when the underlying in_channel has reached its end.

  • parameter cleanup

    If true, the channel will be automatically closed when the input is closed. Otherwise, you will need to close the channel manually.

val output_channel : ?cleanup:bool -> out_channel -> unit output

Create an output that will write into a channel.

  • parameter cleanup

    If true, the channel will be automatically closed when the output is closed. Otherwise, you will need to close the channel manually.

Standard inputs/outputs
val stdin : input

Standard input, as per Unix/Windows conventions (by default, keyboard).

val stdout : unit output

Standard output, as per Unix/Windows conventions (by default, console).

Use this output to display regular messages.

val stderr : unit output

Standard error output, as per Unix/Windows conventions.

Use this output to display warnings and error messages.

val stdnull : unit output

An output which discards everything written to it.

Use this output to ignore messages.

Comparison

The following modules may be useful to create hashtables of inputs or outputs.

module Input : sig ... end
module Output : sig ... end