59 lines
1.4 KiB
OCaml
59 lines
1.4 KiB
OCaml
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(* revise once lower bound OCaml 4.13 *)
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let string_get_uint8 s idx =
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Bytes.get_uint8 (Bytes.unsafe_of_string s) idx
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let string_get_uint16 s idx =
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Bytes.get_uint16_le (Bytes.unsafe_of_string s) idx
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let string_get_int32 s idx =
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Bytes.get_int32_le (Bytes.unsafe_of_string s) idx
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let string_get_int64 s idx =
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Bytes.get_int64_le (Bytes.unsafe_of_string s) idx
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type int8 = int
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let int8 g = string_get_uint8 (g 1) 0
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type int16 = int
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let int16 g = string_get_uint16 (g 2) 0
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let int32 g = string_get_int32 (g 4) 0
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let int64 g = string_get_int64 (g 8) 0
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let bitmask n =
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let rec go c = function
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| 0 -> c
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| n -> go (c lsl 1) (n lsr 1)
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in
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go 1 n - 1
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let rec int ?(bound = max_int) g =
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if bound <= 0 then invalid_arg "bound smaller or equal 0 not supported" ;
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if bound = 1 then 0
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else
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let r =
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if bound <= 256 then
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int8 g
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else if bound <= 65536 then
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int16 g
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else
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match Sys.word_size with
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| 32 -> Int32.to_int (int32 g)
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| 64 -> Int64.to_int (int64 g)
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| _ -> invalid_arg "unknown word size"
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in
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let r = r land bitmask (pred bound) in
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if r < bound then r else int ~bound g
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let float ?(bound = 1.) g =
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if bound <= 0. then invalid_arg "bound smaller or equal 0 not supported" ;
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let scale = float_of_int max_int
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and r1 = int g
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and r2 = int g
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in
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bound *. ((float_of_int r1 /. scale +. float_of_int r2) /. scale)
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