open Bigarray

type t = (char, int8_unsigned_elt, c_layout) Array1.t

let create n = Array1.create Char c_layout n
let length = Array1.dim
let sub = Array1.sub
let empty = Array1.create Char c_layout 0
let get = Array1.get

let copy t =
  let r = create (length t) in
  Array1.blit t r ;
  r

let init l f =
  let v = Array1.create Char c_layout l in
  for i = 0 to l - 1 do
    Array1.set v i (f i)
  done ;
  v

external unsafe_get_32 : t -> int -> int32 = "%caml_bigstring_get32u"
external unsafe_get_64 : t -> int -> int64 = "%caml_bigstring_get64u"

let unsafe_get_nat : t -> int -> nativeint =
 fun s i ->
  if Sys.word_size = 32
  then Nativeint.of_int32 @@ unsafe_get_32 s i
  else Int64.to_nativeint @@ unsafe_get_64 s i

external unsafe_set_32 : t -> int -> int32 -> unit = "%caml_bigstring_set32u"
external unsafe_set_64 : t -> int -> int64 -> unit = "%caml_bigstring_set64u"

let unsafe_set_nat : t -> int -> nativeint -> unit =
 fun s i v ->
  if Sys.word_size = 32
  then unsafe_set_32 s i (Nativeint.to_int32 v)
  else unsafe_set_64 s i (Int64.of_nativeint v)

let to_string v = String.init (length v) (Array1.get v)

let blit_from_bytes src src_off dst dst_off len =
  for i = 0 to len - 1 do
    Array1.set dst (dst_off + i) (Bytes.get src (src_off + i))
  done

external swap32 : int32 -> int32 = "%bswap_int32"
external swap64 : int64 -> int64 = "%bswap_int64"
external swapnat : nativeint -> nativeint = "%bswap_native"

let cpu_to_be32 s i v =
  if Sys.big_endian then unsafe_set_32 s i v else unsafe_set_32 s i (swap32 v)

let cpu_to_le32 s i v =
  if Sys.big_endian then unsafe_set_32 s i (swap32 v) else unsafe_set_32 s i v

let cpu_to_be64 s i v =
  if Sys.big_endian then unsafe_set_64 s i v else unsafe_set_64 s i (swap64 v)

let cpu_to_le64 s i v =
  if Sys.big_endian then unsafe_set_64 s i (swap64 v) else unsafe_set_64 s i v

let be32_to_cpu s i =
  if Sys.big_endian then unsafe_get_32 s i else swap32 @@ unsafe_get_32 s i

let le32_to_cpu s i =
  if Sys.big_endian then swap32 @@ unsafe_get_32 s i else unsafe_get_32 s i

let be64_to_cpu s i =
  if Sys.big_endian then unsafe_get_64 s i else swap64 @@ unsafe_get_64 s i

let le64_to_cpu s i =
  if Sys.big_endian then swap64 @@ unsafe_get_64 s i else unsafe_get_64 s i

let benat_to_cpu s i =
  if Sys.big_endian then unsafe_get_nat s i else swapnat @@ unsafe_get_nat s i

let cpu_to_benat s i v =
  if Sys.big_endian
  then unsafe_set_nat s i v
  else unsafe_set_nat s i (swapnat v)
