(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
(*   Pierre Weis and Xavier Leroy, projet Cristal, INRIA Rocquencourt     *)
(*                                                                        *)
(*   Copyright 1999 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.          *)
(*                                                                        *)
(**************************************************************************)

(** Extensible buffers.

   This module implements buffers that automatically expand
   as necessary.  It provides accumulative concatenation of strings
   in linear time (instead of quadratic time when strings are
   concatenated pairwise). For example:

{[
     let concat_strings ss =
       let b = Buffer.create 16 in
         List.iter (Buffer.add_string b) ss;
         Buffer.contents b

]}

*)

(** {b Unsynchronized accesses} *)

[@@@alert unsynchronized_access
    "Unsynchronized accesses to buffers are a programming error."
]

 (**
    Unsynchronized accesses to a buffer may lead to an invalid buffer state.
    Thus, concurrent accesses to a buffer must be synchronized (for instance
    with a {!Mutex.t}).
*)

type t
(** The abstract type of buffers. *)

val create : int -> t
(** [create n] returns a fresh buffer, initially empty.
   The [n] parameter is the initial size of the internal byte sequence
   that holds the buffer contents. That byte sequence is automatically
   reallocated when more than [n] characters are stored in the buffer,
   but shrinks back to [n] characters when [reset] is called.
   For best performance, [n] should be of the same order of magnitude
   as the number of characters that are expected to be stored in
   the buffer (for instance, 80 for a buffer that holds one output
   line).  Nothing bad will happen if the buffer grows beyond that
   limit, however. In doubt, take [n = 16] for instance.
   If [n] is not between 1 and {!Sys.max_string_length}, it will
   be clipped to that interval. *)

val contents : t -> string
(** Return a copy of the current contents of the buffer.
    The buffer itself is unchanged. *)

val to_bytes : t -> bytes
(** Return a copy of the current contents of the buffer.
    The buffer itself is unchanged.
    @since 4.02 *)

val sub : t -> int -> int -> string
(** [Buffer.sub b off len] returns a copy of [len] bytes from the
    current contents of the buffer [b], starting at offset [off].
    @raise Invalid_argument if [off] and [len] do not designate a valid
    range of [b]. *)

val blit : t -> int -> bytes -> int -> int -> unit
(** [Buffer.blit src srcoff dst dstoff len] copies [len] characters from
   the current contents of the buffer [src], starting at offset [srcoff]
   to [dst], starting at character [dstoff].
   @raise Invalid_argument if [srcoff] and [len] do not designate a valid
   range of [src], or if [dstoff] and [len] do not designate a valid
   range of [dst].
   @since 3.11.2
*)

val nth : t -> int -> char
(** Get the n-th character of the buffer.
    @raise Invalid_argument if
    index out of bounds *)

val length : t -> int
(** Return the number of characters currently contained in the buffer. *)

val clear : t -> unit
(** Empty the buffer. *)

val reset : t -> unit
(** Empty the buffer and deallocate the internal byte sequence holding the
   buffer contents, replacing it with the initial internal byte sequence
   of length [n] that was allocated by {!Buffer.create} [n].
   For long-lived buffers that may have grown a lot, [reset] allows
   faster reclamation of the space used by the buffer. *)

val output_buffer : out_channel -> t -> unit
(** [output_buffer oc b] writes the current contents of buffer [b]
   on the output channel [oc]. *)

val truncate : t -> int -> unit
(** [truncate b len] truncates the length of [b] to [len]
  Note: the internal byte sequence is not shortened.
  @raise Invalid_argument if [len < 0] or [len > length b].
  @since 4.05 *)

(** {1 Appending} *)

(** Note: all [add_*] operations can raise [Failure] if the internal byte
    sequence of the buffer would need to grow beyond {!Sys.max_string_length}.
*)

val add_char : t -> char -> unit
(** [add_char b c] appends the character [c] at the end of buffer [b]. *)

val add_utf_8_uchar : t -> Uchar.t -> unit
(** [add_utf_8_uchar b u] appends the {{:https://tools.ietf.org/html/rfc3629}
    UTF-8} encoding of [u] at the end of buffer [b].

    @since 4.06 *)

val add_utf_16le_uchar : t -> Uchar.t -> unit
(** [add_utf_16le_uchar b u] appends the
    {{:https://tools.ietf.org/html/rfc2781}UTF-16LE} encoding of [u]
    at the end of buffer [b].

    @since 4.06 *)

val add_utf_16be_uchar : t -> Uchar.t -> unit
(** [add_utf_16be_uchar b u] appends the
    {{:https://tools.ietf.org/html/rfc2781}UTF-16BE} encoding of [u]
    at the end of buffer [b].

    @since 4.06 *)

val add_string : t -> string -> unit
(** [add_string b s] appends the string [s] at the end of buffer [b]. *)

val add_bytes : t -> bytes -> unit
(** [add_bytes b s] appends the byte sequence [s] at the end of buffer [b].
    @since 4.02 *)

val add_substring : t -> string -> int -> int -> unit
(** [add_substring b s ofs len] takes [len] characters from offset
   [ofs] in string [s] and appends them at the end of buffer [b].

    @raise Invalid_argument if [ofs] and [len] do not designate a valid
    range of [s]. *)

val add_subbytes : t -> bytes -> int -> int -> unit
(** [add_subbytes b s ofs len] takes [len] characters from offset
    [ofs] in byte sequence [s] and appends them at the end of buffer [b].

    @raise Invalid_argument if [ofs] and [len] do not designate a valid
    range of [s].

    @since 4.02 *)

val add_substitute : t -> (string -> string) -> string -> unit
(** [add_substitute b f s] appends the string pattern [s] at the end
   of buffer [b] with substitution.
   The substitution process looks for variable references in
   the pattern and substitutes each variable reference with its value, as
   obtained by applying the mapping [f] to the variable name. Inside the
   string pattern, a variable reference is a non-escaped [$] immediately
   followed by a variable name, which is one of the following:
   - a non empty sequence of alphanumeric or [_] characters,
   - an arbitrary sequence of characters enclosed by a pair of
   matching parentheses or curly brackets.
   An escaped [$] character is a [$] that immediately follows a backslash
   character; the two characters together stand for a plain [$]. *)

val add_buffer : t -> t -> unit
(** [add_buffer b1 b2] appends the current contents of buffer [b2]
   at the end of buffer [b1].  [b2] is not modified. *)

val add_channel : t -> in_channel -> int -> unit
(** [add_channel b ic n] reads at most [n] characters from the
   input channel [ic] and stores them at the end of buffer [b].
   @raise End_of_file if the channel contains fewer than [n]
   characters. In this case, the characters are still added to
   the buffer, so as to avoid loss of data.

   @raise Invalid_argument if [len < 0] or [len > Sys.max_string_length].
 *)

(** {1 Buffers and Sequences} *)

val to_seq : t -> char Seq.t
(** Iterate on the buffer, in increasing order.

    The behavior is not specified if the buffer is modified during iteration.
    @since 4.07 *)

val to_seqi : t -> (int * char) Seq.t
(** Iterate on the buffer, in increasing order, yielding indices along chars.

    The behavior is not specified if the buffer is modified during iteration.
    @since 4.07 *)

val add_seq : t -> char Seq.t -> unit
(** Add chars to the buffer
    @since 4.07 *)

val of_seq : char Seq.t -> t
(** Create a buffer from the generator
    @since 4.07 *)

(** {1 Binary encoding of integers} *)

(** The functions in this section append binary encodings of integers
    to buffers.

    Little-endian (resp. big-endian) encoding means that least
    (resp. most) significant bytes are stored first.  Big-endian is
    also known as network byte order.  Native-endian encoding is
    either little-endian or big-endian depending on {!Sys.big_endian}.

    32-bit and 64-bit integers are represented by the [int32] and
    [int64] types, which can be interpreted either as signed or
    unsigned numbers.

    8-bit and 16-bit integers are represented by the [int] type,
    which has more bits than the binary encoding.  Functions that
    encode these values truncate their inputs to their least
    significant bytes.
*)

val add_uint8 : t -> int -> unit
(** [add_uint8 b i] appends a binary unsigned 8-bit integer [i] to
    [b].
    @since 4.08
*)

val add_int8 : t -> int -> unit
(** [add_int8 b i] appends a binary signed 8-bit integer [i] to
    [b].
    @since 4.08
*)

val add_uint16_ne : t -> int -> unit
(** [add_uint16_ne b i] appends a binary native-endian unsigned 16-bit
    integer [i] to [b].
    @since 4.08
*)

val add_uint16_be : t -> int -> unit
(** [add_uint16_be b i] appends a binary big-endian unsigned 16-bit
    integer [i] to [b].
    @since 4.08
*)

val add_uint16_le : t -> int -> unit
(** [add_uint16_le b i] appends a binary little-endian unsigned 16-bit
    integer [i] to [b].
    @since 4.08
*)

val add_int16_ne : t -> int -> unit
(** [add_int16_ne b i] appends a binary native-endian signed 16-bit
    integer [i] to [b].
    @since 4.08
*)

val add_int16_be : t -> int -> unit
(** [add_int16_be b i] appends a binary big-endian signed 16-bit
    integer [i] to [b].
    @since 4.08
*)

val add_int16_le : t -> int -> unit
(** [add_int16_le b i] appends a binary little-endian signed 16-bit
    integer [i] to [b].
    @since 4.08
*)

val add_int32_ne : t -> int32 -> unit
(** [add_int32_ne b i] appends a binary native-endian 32-bit integer
    [i] to [b].
    @since 4.08
*)

val add_int32_be : t -> int32 -> unit
(** [add_int32_be b i] appends a binary big-endian 32-bit integer
    [i] to [b].
    @since 4.08
*)

val add_int32_le : t -> int32 -> unit
(** [add_int32_le b i] appends a binary little-endian 32-bit integer
    [i] to [b].
    @since 4.08
*)

val add_int64_ne  : t -> int64 -> unit
(** [add_int64_ne b i] appends a binary native-endian 64-bit integer
    [i] to [b].
    @since 4.08
*)

val add_int64_be : t -> int64 -> unit
(** [add_int64_be b i] appends a binary big-endian 64-bit integer
    [i] to [b].
    @since 4.08
*)

val add_int64_le : t -> int64 -> unit
(** [add_int64_ne b i] appends a binary little-endian 64-bit integer
    [i] to [b].
    @since 4.08
*)