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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . V A L U E _ D --
-- --
-- B o d y --
-- --
-- Copyright (C) 2020-2022, 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 --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with System.Unsigned_Types; use System.Unsigned_Types;
with System.Val_Util; use System.Val_Util;
with System.Value_R;
package body System.Value_D is
pragma Assert (Int'Size <= Uns'Size);
-- We need an unsigned type large enough to represent the mantissa
package Impl is new Value_R (Uns, 2**(Int'Size - 1), Round => False);
-- We do not use the Extra digit for decimal fixed-point types
function Integer_to_Decimal
(Str : String;
Val : Uns;
Base : Unsigned;
ScaleB : Integer;
Minus : Boolean;
Scale : Integer) return Int;
-- Convert the real value from integer to decimal representation
------------------------
-- Integer_to_Decimal --
------------------------
function Integer_to_Decimal
(Str : String;
Val : Uns;
Base : Unsigned;
ScaleB : Integer;
Minus : Boolean;
Scale : Integer) return Int
is
function Safe_Expont
(Base : Int;
Exp : in out Natural;
Factor : Int) return Int;
-- Return (Base ** Exp) * Factor if the computation does not overflow,
-- or else the number of the form (Base ** K) * Factor with the largest
-- magnitude if the former computation overflows. In both cases, Exp is
-- updated to contain the remaining power in the computation. Note that
-- Factor is expected to be positive in this context.
function Unsigned_To_Signed (Val : Uns) return Int;
-- Convert an integer value from unsigned to signed representation
-----------------
-- Safe_Expont --
-----------------
function Safe_Expont
(Base : Int;
Exp : in out Natural;
Factor : Int) return Int
is
pragma Assert (Base /= 0 and then Factor > 0);
Max : constant Int := Int'Last / Base;
Result : Int := Factor;
begin
while Exp > 0 and then Result <= Max loop
Result := Result * Base;
Exp := Exp - 1;
end loop;
return Result;
end Safe_Expont;
------------------------
-- Unsigned_To_Signed --
------------------------
function Unsigned_To_Signed (Val : Uns) return Int is
begin
-- Deal with overflow cases, and also with largest negative number
if Val > Uns (Int'Last) then
if Minus and then Val = Uns (-(Int'First)) then
return Int'First;
else
Bad_Value (Str);
end if;
-- Negative values
elsif Minus then
return -(Int (Val));
-- Positive values
else
return Int (Val);
end if;
end Unsigned_To_Signed;
begin
-- If the base of the value is 10 or its scaling factor is zero, then
-- add the scales (they are defined in the opposite sense) and apply
-- the result to the value, checking for overflow in the process.
if Base = 10 or else ScaleB = 0 then
declare
S : Integer := ScaleB + Scale;
V : Uns := Val;
begin
while S < 0 loop
V := V / 10;
S := S + 1;
end loop;
while S > 0 loop
if V <= Uns'Last / 10 then
V := V * 10;
S := S - 1;
else
Bad_Value (Str);
end if;
end loop;
return Unsigned_To_Signed (V);
end;
-- If the base of the value is not 10, use a scaled divide operation
-- to compute Val * (Base ** ScaleB) * (10 ** Scale).
else
declare
B : constant Int := Int (Base);
S : constant Integer := ScaleB;
V : Uns := Val;
Y, Z, Q, R : Int;
begin
-- If S is too negative, then drop trailing digits
if S < 0 then
declare
LS : Integer := -S;
begin
Y := 10 ** Integer'Max (0, Scale);
Z := Safe_Expont (B, LS, 10 ** Integer'Max (0, -Scale));
for J in 1 .. LS loop
V := V / Uns (B);
end loop;
end;
-- If S is too positive, then scale V up, which may then overflow
elsif S > 0 then
declare
LS : Integer := S;
begin
Y := Safe_Expont (B, LS, 10 ** Integer'Max (0, Scale));
Z := 10 ** Integer'Max (0, -Scale);
for J in 1 .. LS loop
if V <= Uns'Last / Uns (B) then
V := V * Uns (B);
else
Bad_Value (Str);
end if;
end loop;
end;
-- The case S equal to zero should have been handled earlier
else
raise Program_Error;
end if;
-- Perform a scale divide operation with rounding to match 'Image
Scaled_Divide (Unsigned_To_Signed (V), Y, Z, Q, R, Round => True);
return Q;
end;
end if;
exception
when Constraint_Error => Bad_Value (Str);
end Integer_to_Decimal;
------------------
-- Scan_Decimal --
------------------
function Scan_Decimal
(Str : String;
Ptr : not null access Integer;
Max : Integer;
Scale : Integer) return Int
is
Base : Unsigned;
ScaleB : Integer;
Extra : Unsigned;
Minus : Boolean;
Val : Uns;
begin
Val := Impl.Scan_Raw_Real (Str, Ptr, Max, Base, ScaleB, Extra, Minus);
return Integer_to_Decimal (Str, Val, Base, ScaleB, Minus, Scale);
end Scan_Decimal;
-------------------
-- Value_Decimal --
-------------------
function Value_Decimal (Str : String; Scale : Integer) return Int is
Base : Unsigned;
ScaleB : Integer;
Extra : Unsigned;
Minus : Boolean;
Val : Uns;
begin
Val := Impl.Value_Raw_Real (Str, Base, ScaleB, Extra, Minus);
return Integer_to_Decimal (Str, Val, Base, ScaleB, Minus, Scale);
end Value_Decimal;
end System.Value_D;
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