------------------------------------------------------------------------------ | |

-- -- | |

-- GNAT COMPILER COMPONENTS -- | |

-- -- | |

-- S Y S T E M . V A L _ R E A L -- | |

-- -- | |

-- B o d y -- | |

-- -- | |

-- Copyright (C) 1992-2015, 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.Powten_Table; use System.Powten_Table; | |

with System.Val_Util; use System.Val_Util; | |

with System.Float_Control; | |

package body System.Val_Real is | |

--------------- | |

-- Scan_Real -- | |

--------------- | |

function Scan_Real | |

(Str : String; | |

Ptr : not null access Integer; | |

Max : Integer) return Long_Long_Float | |

is | |

P : Integer; | |

-- Local copy of string pointer | |

Base : Long_Long_Float; | |

-- Base value | |

Uval : Long_Long_Float; | |

-- Accumulated float result | |

subtype Digs is Character range '0' .. '9'; | |

-- Used to check for decimal digit | |

Scale : Integer := 0; | |

-- Power of Base to multiply result by | |

Start : Positive; | |

-- Position of starting non-blank character | |

Minus : Boolean; | |

-- Set to True if minus sign is present, otherwise to False | |

Bad_Base : Boolean := False; | |

-- Set True if Base out of range or if out of range digit | |

After_Point : Natural := 0; | |

-- Set to 1 after the point | |

Num_Saved_Zeroes : Natural := 0; | |

-- This counts zeroes after the decimal point. A non-zero value means | |

-- that this number of previously scanned digits are zero. If the end | |

-- of the number is reached, these zeroes are simply discarded, which | |

-- ensures that trailing zeroes after the point never affect the value | |

-- (which might otherwise happen as a result of rounding). With this | |

-- processing in place, we can ensure that, for example, we get the | |

-- same exact result from 1.0E+49 and 1.0000000E+49. This is not | |

-- necessarily required in a case like this where the result is not | |

-- a machine number, but it is certainly a desirable behavior. | |

procedure Scanf; | |

-- Scans integer literal value starting at current character position. | |

-- For each digit encountered, Uval is multiplied by 10.0, and the new | |

-- digit value is incremented. In addition Scale is decremented for each | |

-- digit encountered if we are after the point (After_Point = 1). The | |

-- longest possible syntactically valid numeral is scanned out, and on | |

-- return P points past the last character. On entry, the current | |

-- character is known to be a digit, so a numeral is definitely present. | |

----------- | |

-- Scanf -- | |

----------- | |

procedure Scanf is | |

Digit : Natural; | |

begin | |

loop | |

Digit := Character'Pos (Str (P)) - Character'Pos ('0'); | |

P := P + 1; | |

-- Save up trailing zeroes after the decimal point | |

if Digit = 0 and then After_Point = 1 then | |

Num_Saved_Zeroes := Num_Saved_Zeroes + 1; | |

-- Here for a non-zero digit | |

else | |

-- First deal with any previously saved zeroes | |

if Num_Saved_Zeroes /= 0 then | |

while Num_Saved_Zeroes > Maxpow loop | |

Uval := Uval * Powten (Maxpow); | |

Num_Saved_Zeroes := Num_Saved_Zeroes - Maxpow; | |

Scale := Scale - Maxpow; | |

end loop; | |

Uval := Uval * Powten (Num_Saved_Zeroes); | |

Scale := Scale - Num_Saved_Zeroes; | |

Num_Saved_Zeroes := 0; | |

end if; | |

-- Accumulate new digit | |

Uval := Uval * 10.0 + Long_Long_Float (Digit); | |

Scale := Scale - After_Point; | |

end if; | |

-- Done if end of input field | |

if P > Max then | |

return; | |

-- Check next character | |

elsif Str (P) not in Digs then | |

if Str (P) = '_' then | |

Scan_Underscore (Str, P, Ptr, Max, False); | |

else | |

return; | |

end if; | |

end if; | |

end loop; | |

end Scanf; | |

-- Start of processing for System.Scan_Real | |

begin | |

-- We do not tolerate strings with Str'Last = Positive'Last | |

if Str'Last = Positive'Last then | |

raise Program_Error with | |

"string upper bound is Positive'Last, not supported"; | |

end if; | |

-- We call the floating-point processor reset routine so that we can | |

-- be sure the floating-point processor is properly set for conversion | |

-- calls. This is notably need on Windows, where calls to the operating | |

-- system randomly reset the processor into 64-bit mode. | |

System.Float_Control.Reset; | |

Scan_Sign (Str, Ptr, Max, Minus, Start); | |

P := Ptr.all; | |

Ptr.all := Start; | |

-- If digit, scan numeral before point | |

if Str (P) in Digs then | |

Uval := 0.0; | |

Scanf; | |

-- Initial point, allowed only if followed by digit (RM 3.5(47)) | |

elsif Str (P) = '.' | |

and then P < Max | |

and then Str (P + 1) in Digs | |

then | |

Uval := 0.0; | |

-- Any other initial character is an error | |

else | |

Bad_Value (Str); | |

end if; | |

-- Deal with based case. We reognize either the standard '#' or the | |

-- allowed alternative replacement ':' (see RM J.2(3)). | |

if P < Max and then (Str (P) = '#' or else Str (P) = ':') then | |

declare | |

Base_Char : constant Character := Str (P); | |

Digit : Natural; | |

Fdigit : Long_Long_Float; | |

begin | |

-- Set bad base if out of range, and use safe base of 16.0, | |

-- to guard against division by zero in the loop below. | |

if Uval < 2.0 or else Uval > 16.0 then | |

Bad_Base := True; | |

Uval := 16.0; | |

end if; | |

Base := Uval; | |

Uval := 0.0; | |

P := P + 1; | |

-- Special check to allow initial point (RM 3.5(49)) | |

if Str (P) = '.' then | |

After_Point := 1; | |

P := P + 1; | |

end if; | |

-- Loop to scan digits of based number. On entry to the loop we | |

-- must have a valid digit. If we don't, then we have an illegal | |

-- floating-point value, and we raise Constraint_Error, note that | |

-- Ptr at this stage was reset to the proper (Start) value. | |

loop | |

if P > Max then | |

Bad_Value (Str); | |

elsif Str (P) in Digs then | |

Digit := Character'Pos (Str (P)) - Character'Pos ('0'); | |

elsif Str (P) in 'A' .. 'F' then | |

Digit := | |

Character'Pos (Str (P)) - (Character'Pos ('A') - 10); | |

elsif Str (P) in 'a' .. 'f' then | |

Digit := | |

Character'Pos (Str (P)) - (Character'Pos ('a') - 10); | |

else | |

Bad_Value (Str); | |

end if; | |

-- Save up trailing zeroes after the decimal point | |

if Digit = 0 and then After_Point = 1 then | |

Num_Saved_Zeroes := Num_Saved_Zeroes + 1; | |

-- Here for a non-zero digit | |

else | |

-- First deal with any previously saved zeroes | |

if Num_Saved_Zeroes /= 0 then | |

Uval := Uval * Base ** Num_Saved_Zeroes; | |

Scale := Scale - Num_Saved_Zeroes; | |

Num_Saved_Zeroes := 0; | |

end if; | |

-- Now accumulate the new digit | |

Fdigit := Long_Long_Float (Digit); | |

if Fdigit >= Base then | |

Bad_Base := True; | |

else | |

Scale := Scale - After_Point; | |

Uval := Uval * Base + Fdigit; | |

end if; | |

end if; | |

P := P + 1; | |

if P > Max then | |

Bad_Value (Str); | |

elsif Str (P) = '_' then | |

Scan_Underscore (Str, P, Ptr, Max, True); | |

else | |

-- Skip past period after digit. Note that the processing | |

-- here will permit either a digit after the period, or the | |

-- terminating base character, as allowed in (RM 3.5(48)) | |

if Str (P) = '.' and then After_Point = 0 then | |

P := P + 1; | |

After_Point := 1; | |

if P > Max then | |

Bad_Value (Str); | |

end if; | |

end if; | |

exit when Str (P) = Base_Char; | |

end if; | |

end loop; | |

-- Based number successfully scanned out (point was found) | |

Ptr.all := P + 1; | |

end; | |

-- Non-based case, check for being at decimal point now. Note that | |

-- in Ada 95, we do not insist on a decimal point being present | |

else | |

Base := 10.0; | |

After_Point := 1; | |

if P <= Max and then Str (P) = '.' then | |

P := P + 1; | |

-- Scan digits after point if any are present (RM 3.5(46)) | |

if P <= Max and then Str (P) in Digs then | |

Scanf; | |

end if; | |

end if; | |

Ptr.all := P; | |

end if; | |

-- At this point, we have Uval containing the digits of the value as | |

-- an integer, and Scale indicates the negative of the number of digits | |

-- after the point. Base contains the base value (an integral value in | |

-- the range 2.0 .. 16.0). Test for exponent, must be at least one | |

-- character after the E for the exponent to be valid. | |

Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True); | |

-- At this point the exponent has been scanned if one is present and | |

-- Scale is adjusted to include the exponent value. Uval contains the | |

-- the integral value which is to be multiplied by Base ** Scale. | |

-- If base is not 10, use exponentiation for scaling | |

if Base /= 10.0 then | |

Uval := Uval * Base ** Scale; | |

-- For base 10, use power of ten table, repeatedly if necessary | |

elsif Scale > 0 then | |

while Scale > Maxpow loop | |

Uval := Uval * Powten (Maxpow); | |

Scale := Scale - Maxpow; | |

end loop; | |

-- Note that we still know that Scale > 0, since the loop | |

-- above leaves Scale in the range 1 .. Maxpow. | |

Uval := Uval * Powten (Scale); | |

elsif Scale < 0 then | |

while (-Scale) > Maxpow loop | |

Uval := Uval / Powten (Maxpow); | |

Scale := Scale + Maxpow; | |

end loop; | |

-- Note that we still know that Scale < 0, since the loop | |

-- above leaves Scale in the range -Maxpow .. -1. | |

Uval := Uval / Powten (-Scale); | |

end if; | |

-- Here is where we check for a bad based number | |

if Bad_Base then | |

Bad_Value (Str); | |

-- If OK, then deal with initial minus sign, note that this processing | |

-- is done even if Uval is zero, so that -0.0 is correctly interpreted. | |

else | |

if Minus then | |

return -Uval; | |

else | |

return Uval; | |

end if; | |

end if; | |

end Scan_Real; | |

---------------- | |

-- Value_Real -- | |

---------------- | |

function Value_Real (Str : String) return Long_Long_Float is | |

begin | |

-- We have to special case Str'Last = Positive'Last because the normal | |

-- circuit ends up setting P to Str'Last + 1 which is out of bounds. We | |

-- deal with this by converting to a subtype which fixes the bounds. | |

if Str'Last = Positive'Last then | |

declare | |

subtype NT is String (1 .. Str'Length); | |

begin | |

return Value_Real (NT (Str)); | |

end; | |

-- Normal case where Str'Last < Positive'Last | |

else | |

declare | |

V : Long_Long_Float; | |

P : aliased Integer := Str'First; | |

begin | |

V := Scan_Real (Str, P'Access, Str'Last); | |

Scan_Trailing_Blanks (Str, P); | |

return V; | |

end; | |

end if; | |

end Value_Real; | |

end System.Val_Real; |