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-- GHDL Run Time (GRT) - Floating point conversions.
-- Copyright (C) 2017 Tristan Gingold
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 2 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program. If not, see <gnu.org/licenses>.
--
-- As a special exception, if other files instantiate generics from this
-- unit, or you link this unit with other files to produce an executable,
-- this unit does not by itself cause the resulting executable to be
-- covered by the GNU General Public License. This exception does not
-- however invalidate any other reasons why the executable file might be
-- covered by the GNU Public License.
-- IMPORTANT: this unit can also be used by the front-end, so it must NOT
-- depend on anything else from grt (except the grt parent package), including
-- grt.types.
with Interfaces; use Interfaces;
package Grt.Fcvt is
pragma Preelaborate;
-- Convert (without formatting) number V.
-- The result is LEN characters stored to STR. If STR is too short, then
-- the output is truncated but LEN contains the number of characters that
-- would be needed. The procedure assumes STR'First = 1.
-- The digits are the digits after the point. The output has to be read as
-- 0.NNNNN * 10**EXP
-- IS_NUM is true if V is a number and false for NaN or Infinite.
-- IS_NEG is true if the number if negative.
procedure To_String (Str : out String;
Len : out Natural;
Is_Num : out Boolean;
Is_Neg : out Boolean;
Exp : out Integer;
V : IEEE_Float_64);
-- Formatting.
-- For 'Image
-- STR must have at least 24 characters:
-- Sign (1) + digit (1) + dot (1) + digits (15) + 'e' (1) + sign (1)
-- + exp_digits (4) -> 24.
procedure Format_Image
(Str : out String; Last : out Natural; N : IEEE_Float_64);
-- For To_String (Value : Real; Digits : Natural)
procedure Format_Digits (Str : out String;
Last : out Natural;
N : IEEE_Float_64;
Ndigits : Natural);
-- Reduce the precision of STR to PREC digits after the point. If PREC is
-- too large, this is no-op.
-- STR, LEN, EXP are the output of To_String, that is:
-- 0.STR * 10**EXP
procedure Format_Precision (Str : in out String;
Len : in out Natural;
Exp : in out Integer;
Prec : Positive);
-- Input format is [+-]int[.int][e[+-]int]
-- where int is digit { _ digit }
-- and [+-] means optional + or -.
-- The input string must be correctly formatted.
function From_String (Str : String) return IEEE_Float_64;
-- Ad-hoc implementation of bignums, with the minimal features to support
-- radix conversion.
type Bignum is private;
-- Compute L * R + CARRY_IN.
procedure Bignum_Mul_Int
(L : in out Bignum; R : Positive; Carry_In : Natural := 0);
-- Multiply two bignums.
function Bignum_Mul (L, R : Bignum) return Bignum;
-- Compute L**N
function Bignum_Pow (L : Natural; N : Natural) return Bignum;
-- Create a bignum from a natural.
procedure Bignum_Int (Res : out Bignum; N : Natural);
-- Convert N to RES. OK is set to True if the number fits in RES.
procedure Bignum_To_Int
(N : Bignum; Res : out Unsigned_64; OK : out Boolean);
-- Return (-1)**Neg * F * BASE**EXP to a float.
function To_Float_64
(Neg : Boolean; F : Bignum; Base : Positive; Exp : Integer)
return IEEE_Float_64;
private
type Unsigned_32_Array is array (Natural range <>) of Unsigned_32;
type Bignum is record
-- Number of digits. Must be 0 for number 0.
N : Natural;
-- Digits. The leading digit V(N + 1) must not be 0.
V : Unsigned_32_Array (1 .. 37);
end record;
end Grt.Fcvt;
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