/* ************************************************************************ */
/*  */
/* OCaml */
/*  */
/* Xavier Leroy, projet Cristal, INRIA Rocquencourt */
/*  */
/* Copyright 1996 Institut National de Recherche en Informatique et */
/* en Automatique. */
/*  */
/* All rights reserved.  This file is distributed under the terms of */
/* the GNU Lesser General Public License version 2.1, with the */
/* special exception on linking described in the file LICENSE. */
/*  */
/* ************************************************************************ */

/*** System interface.

  Every function in this module raises [Sys_error] with an
  informative message when the underlying system call signal
  an error.
*/

/** The command line arguments given to the process.
   The first element is the command name used to invoke the program.
   The following elements are the command-line arguments
   given to the program. */
let argv: array<string>

/** The name of the file containing the executable currently running. */
let executable_name: string

/** Test if a file with the given name exists. */
external file_exists: string => bool = "?sys_file_exists"

/** Returns [true] if the given name refers to a directory,
    [false] if it refers to another kind of file.
    Raise [Sys_error] if no file exists with the given name.
    @since 3.10.0
*/
external is_directory: string => bool = "?sys_is_directory"

/** Remove the given file name from the file system. */
external remove: string => unit = "?sys_remove"

/** Rename a file.  [rename oldpath newpath] renames the file
    called [oldpath], giving it [newpath] as its new name,
    moving it between directories if needed.  If [newpath] already
    exists, its contents will be replaced with those of [oldpath].
    Depending on the operating system, the metadata (permissions,
    owner, etc) of [newpath] can either be preserved or be replaced by
    those of [oldpath].
   @since 4.06 concerning the "replace existing file" behavior */
external rename: (string, string) => unit = "?sys_rename"

/** Return the value associated to a variable in the process
   environment. Raise [Not_found] if the variable is unbound. */
external getenv: string => string = "?sys_getenv"

/** Return the value associated to a variable in the process
    environment or [None] if the variable is unbound.
    @since 4.05
*/
let getenv_opt: string => option<string>

/** Execute the given shell command and return its exit code. */
let command: string => int

/** Return the processor time, in seconds, used by the program
   since the beginning of execution. */
external time: unit => float = "?sys_time"

/** Change the current working directory of the process. */
external chdir: string => unit = "?sys_chdir"

/** Return the current working directory of the process. */
external getcwd: unit => string = "?sys_getcwd"

/** Return the names of all files present in the given directory.
   Names denoting the current directory and the parent directory
   (["."] and [".."] in Unix) are not returned.  Each string in the
   result is a file name rather than a complete path.  There is no
   guarantee that the name strings in the resulting array will appear
   in any specific order; they are not, in particular, guaranteed to
   appear in alphabetical order. */
external readdir: string => array<string> = "?sys_read_directory"

/** This reference is initially set to [false] in standalone
   programs and to [true] if the code is being executed under
   the interactive toplevel system [ocaml]. */
let interactive: ref<bool>

/** Operating system currently executing the OCaml program. One of
-  ["Unix"] (for all Unix versions, including Linux and Mac OS X),
-  ["Win32"] (for MS-Windows, OCaml compiled with MSVC++ or Mingw),
-  ["Cygwin"] (for MS-Windows, OCaml compiled with Cygwin). */
let os_type: string

/** Currently, the official distribution only supports [Native] and
    [Bytecode], but it can be other backends with alternative
    compilers, for example, javascript.

    @since 4.04.0
*/
type backend_type =
  | Native
  | Bytecode
  | Other(string)

/** Backend type  currently executing the OCaml program.
    @since 4.04.0
 */
let backend_type: backend_type

/** True if [Sys.os_type = "Unix"].
    @since 4.01.0 */
let unix: bool

/** True if [Sys.os_type = "Win32"].
    @since 4.01.0 */
let win32: bool

/** True if [Sys.os_type = "Cygwin"].
    @since 4.01.0 */
let cygwin: bool

/** Size of one word on the machine currently executing the OCaml
   program, in bits: 32 or 64. */
let word_size: int

/** Size of an int.  It is 31 bits (resp. 63 bits) when using the
    OCaml compiler on a 32 bits (resp. 64 bits) platform.  It may
    differ for other compilers, e.g. it is 32 bits when compiling to
    JavaScript.
    @since 4.03.0 */
let int_size: int

/** Whether the machine currently executing the Caml program is big-endian.
    @since 4.00.0 */
let big_endian: bool

/** Maximum length of strings and byte sequences. */
let max_string_length: int

/** Maximum length of a normal array.  The maximum length of a float
    array is [max_array_length/2] on 32-bit machines and
    [max_array_length] on 64-bit machines. */
let max_array_length: int

/** Return the name of the runtime variant the program is running on.
    This is normally the argument given to [-runtime-variant] at compile
    time, but for byte-code it can be changed after compilation.
    @since 4.03.0 */
external runtime_variant: unit => string = "?runtime_variant"

/** Return the value of the runtime parameters, in the same format
    as the contents of the [OCAMLRUNPARAM] environment variable.
    @since 4.03.0 */
external runtime_parameters: unit => string = "?runtime_parameters"

/* {1 Signal handling} */

/** What to do when receiving a signal:
   - [Signal_default]: take the default behavior
     (usually: abort the program)
   - [Signal_ignore]: ignore the signal
   - [Signal_handle f]: call function [f], giving it the signal
   number as argument. */
type signal_behavior =
  | Signal_default
  | Signal_ignore
  | /** */ Signal_handle(int => unit)

/** Set the behavior of the system on receipt of a given signal.  The
   first argument is the signal number.  Return the behavior
   previously associated with the signal. If the signal number is
   invalid (or not available on your system), an [Invalid_argument]
   exception is raised. */
let signal: (int, signal_behavior) => signal_behavior

/** Same as {!Sys.signal} but return value is ignored. */
let set_signal: (int, signal_behavior) => unit

/* {2 Signal numbers for the standard POSIX signals.} */

/** Abnormal termination */
let sigabrt: int

/** Timeout */
let sigalrm: int

/** Arithmetic exception */
let sigfpe: int

/** Hangup on controlling terminal */
let sighup: int

/** Invalid hardware instruction */
let sigill: int

/** Interactive interrupt (ctrl-C) */
let sigint: int

/** Termination (cannot be ignored) */
let sigkill: int

/** Broken pipe */
let sigpipe: int

/** Interactive termination */
let sigquit: int

/** Invalid memory reference */
let sigsegv: int

/** Termination */
let sigterm: int

/** Application-defined signal 1 */
let sigusr1: int

/** Application-defined signal 2 */
let sigusr2: int

/** Child process terminated */
let sigchld: int

/** Continue */
let sigcont: int

/** Stop */
let sigstop: int

/** Interactive stop */
let sigtstp: int

/** Terminal read from background process */
let sigttin: int

/** Terminal write from background process */
let sigttou: int

/** Timeout in virtual time */
let sigvtalrm: int

/** Profiling interrupt */
let sigprof: int

/** Bus error
    @since 4.03 */
let sigbus: int

/** Pollable event
    @since 4.03 */
let sigpoll: int

/** Bad argument to routine
    @since 4.03 */
let sigsys: int

/** Trace/breakpoint trap
    @since 4.03 */
let sigtrap: int

/** Urgent condition on socket
    @since 4.03 */
let sigurg: int

/** Timeout in cpu time
    @since 4.03 */
let sigxcpu: int

/** File size limit exceeded
    @since 4.03 */
let sigxfsz: int

/** Exception raised on interactive interrupt if {!Sys.catch_break}
   is on. */ exception Break

/** [catch_break] governs whether interactive interrupt (ctrl-C)
   terminates the program or raises the [Break] exception.
   Call [catch_break true] to enable raising [Break],
   and [catch_break false] to let the system
   terminate the program on user interrupt. */
let catch_break: bool => unit

/** [ocaml_version] is the version of OCaml.
    It is a string of the form ["major.minor[.patchlevel][+additional-info]"],
    where [major], [minor], and [patchlevel] are integers, and
    [additional-info] is an arbitrary string. The [[.patchlevel]] and
    [[+additional-info]] parts may be absent. */
let ocaml_version: string

/** Control whether the OCaml runtime system can emit warnings
    on stderr.  Currently, the only supported warning is triggered
    when a channel created by [open_*] functions is finalized without
    being closed.  Runtime warnings are enabled by default.

    @since 4.03.0 */
let enable_runtime_warnings: bool => unit

/** Return whether runtime warnings are currently enabled.

    @since 4.03.0 */
let runtime_warnings_enabled: unit => bool

/* {1 Optimization} */

/** For the purposes of optimization, [opaque_identity] behaves like an
    unknown (and thus possibly side-effecting) function.

    At runtime, [opaque_identity] disappears altogether.

    A typical use of this function is to prevent pure computations from being
    optimized away in benchmarking loops.  For example:
    {[
      for _round = 1 to 100_000 do
        ignore (Sys.opaque_identity (my_pure_computation ()))
      done
    ]}

    @since 4.03.0
*/
external opaque_identity: 'a => 'a = "%opaque"