------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S Y S T E M . V A L _ R E A L -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2020, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ with System.Float_Control; with System.Unsigned_Types; use System.Unsigned_Types; with System.Val_Util; use System.Val_Util; with System.Value_R; package body System.Val_Real is pragma Assert (Num'Machine_Mantissa <= Uns'Size); -- We need an unsigned type large enough to represent the mantissa Precision_Limit : constant Uns := 2**Num'Machine_Mantissa - 1; -- We use the precision of the floating-point type package Impl is new Value_R (Uns, Precision_Limit, Floating => True); subtype Base_T is Unsigned range 2 .. 16; -- The following tables compute the maximum exponent of the base that can -- fit in the given floating-point format, that is to say the element at -- index N is the largest K such that N**K <= Num'Last. Maxexp32 : constant array (Base_T) of Positive := (2 => 127, 3 => 80, 4 => 63, 5 => 55, 6 => 49, 7 => 45, 8 => 42, 9 => 40, 10 => 38, 11 => 37, 12 => 35, 13 => 34, 14 => 33, 15 => 32, 16 => 31); Maxexp64 : constant array (Base_T) of Positive := (2 => 1023, 3 => 646, 4 => 511, 5 => 441, 6 => 396, 7 => 364, 8 => 341, 9 => 323, 10 => 308, 11 => 296, 12 => 285, 13 => 276, 14 => 268, 15 => 262, 16 => 255); Maxexp80 : constant array (Base_T) of Positive := (2 => 16383, 3 => 10337, 4 => 8191, 5 => 7056, 6 => 6338, 7 => 5836, 8 => 5461, 9 => 5168, 10 => 4932, 11 => 4736, 12 => 4570, 13 => 4427, 14 => 4303, 15 => 4193, 16 => 4095); function Integer_to_Real (Str : String; Val : Uns; Base : Unsigned; Scale : Integer; Extra : Unsigned; Minus : Boolean) return Num; -- Convert the real value from integer to real representation --------------------- -- Integer_to_Real -- --------------------- function Integer_to_Real (Str : String; Val : Uns; Base : Unsigned; Scale : Integer; Extra : Unsigned; Minus : Boolean) return Num is pragma Assert (Base in 2 .. 16); pragma Unsuppress (Range_Check); Maxexp : constant Positive := (if Num'Size = 32 then Maxexp32 (Base) elsif Num'Size = 64 then Maxexp64 (Base) elsif Num'Machine_Mantissa = 64 then Maxexp80 (Base) else raise Program_Error); -- Maximum exponent of the base that can fit in Num B : constant Num := Num (Base); R_Val : Num; S : Integer := Scale; begin -- We call the floating-point processor reset routine so we can be sure -- that the x87 FPU is properly set for conversions. This is especially -- needed on Windows, where calls to the operating system randomly reset -- the processor into 64-bit mode. if Num'Machine_Mantissa = 64 then System.Float_Control.Reset; end if; -- Take into account the extra digit R_Val := Num (Val); if Extra > 0 then R_Val := R_Val * B + Num (Extra); S := S - 1; end if; -- Compute the final value. When the exponent is positive, we can do the -- computation directly because, if the exponentiation overflows, then -- the final value overflows as well. But when the exponent is negative, -- we may need to do it in two steps to avoid an artificial underflow. if S > 0 then R_Val := R_Val * B ** S; elsif S < 0 then if S < -Maxexp then R_Val := R_Val / B ** Maxexp; S := S + Maxexp; end if; R_Val := R_Val / B ** (-S); end if; -- Finally deal with initial minus sign, note that this processing is -- done even if Uval is zero, so that -0.0 is correctly interpreted. return (if Minus then -R_Val else R_Val); exception when Constraint_Error => Bad_Value (Str); end Integer_to_Real; --------------- -- Scan_Real -- --------------- function Scan_Real (Str : String; Ptr : not null access Integer; Max : Integer) return Num is Base : Unsigned; Scale : Integer; Extra : Unsigned; Minus : Boolean; Val : Uns; begin Val := Impl.Scan_Raw_Real (Str, Ptr, Max, Base, Scale, Extra, Minus); return Integer_to_Real (Str, Val, Base, Scale, Extra, Minus); end Scan_Real; ---------------- -- Value_Real -- ---------------- function Value_Real (Str : String) return Num is Base : Unsigned; Scale : Integer; Extra : Unsigned; Minus : Boolean; Val : Uns; begin Val := Impl.Value_Raw_Real (Str, Base, Scale, Extra, Minus); return Integer_to_Real (Str, Val, Base, Scale, Extra, Minus); end Value_Real; end System.Val_Real;