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

-- -- | |

-- GNAT COMPILER COMPONENTS -- | |

-- -- | |

-- I N T E R F A C E S . P A C K E D _ D E C I M A L -- | |

-- -- | |

-- S p e c -- | |

-- (Version for IBM Mainframe Packed Decimal Format) -- | |

-- -- | |

-- Copyright (C) 1992-2022, 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. -- | |

-- -- | |

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

-- This unit defines the packed decimal format used by GNAT in response to | |

-- a specification of Machine_Radix 10 for a decimal fixed-point type. The | |

-- format and operations are completely encapsulated in this unit, so all | |

-- that is necessary to compile using different packed decimal formats is | |

-- to replace this single unit. | |

-- Note that the compiler access the spec of this unit during compilation | |

-- to obtain the data length that needs allocating, so the correct version | |

-- of the spec must be available to the compiler, and must correspond to | |

-- the spec and body made available to the linker, and all units of a given | |

-- program must be compiled with the same version of the spec and body. | |

-- This consistency will be enforced automatically using the normal binder | |

-- consistency checking, since any unit declaring Machine_Radix 10 types or | |

-- containing operations on such data will implicitly with Packed_Decimal. | |

with System; | |

package Interfaces.Packed_Decimal is | |

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

-- Format Description -- | |

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

-- IBM Mainframe packed decimal format uses a byte string of length one | |

-- to 10 bytes, with the most significant byte first. Each byte contains | |

-- two decimal digits (with the high order digit in the left nibble, and | |

-- the low order four bits contain the sign, using the following code: | |

-- 16#A# 2#1010# positive | |

-- 16#B# 2#1011# negative | |

-- 16#C# 2#1100# positive (preferred representation) | |

-- 16#D# 2#1101# negative (preferred representation) | |

-- 16#E# 2#1110# positive | |

-- 16#F# 2#1011# positive | |

-- In this package, all six sign representations are interpreted as | |

-- shown above when an operand is read, when an operand is written, | |

-- the preferred representations are always used. Constraint_Error | |

-- is raised if any other bit pattern is found in the sign nibble, | |

-- or if a digit nibble contains an invalid digit code. | |

-- Some examples follow: | |

-- 05 76 3C +5763 | |

-- 00 01 1D -11 | |

-- 00 04 4E +44 (non-standard sign) | |

-- 00 00 00 invalid (incorrect sign nibble) | |

-- 0A 01 1C invalid (bad digit) | |

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

-- Length Array -- | |

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

-- The following array must be declared in exactly the form shown, since | |

-- the compiler accesses the associated tree to determine the size to be | |

-- allocated to a machine radix 10 type, depending on the number of digits. | |

subtype Byte_Length is Positive range 1 .. 10; | |

-- Range of possible byte lengths | |

Packed_Size : constant array (1 .. 18) of Byte_Length := | |

[01 => 01, -- Length in bytes for digits 1 | |

02 => 02, -- Length in bytes for digits 2 | |

03 => 02, -- Length in bytes for digits 2 | |

04 => 03, -- Length in bytes for digits 2 | |

05 => 03, -- Length in bytes for digits 2 | |

06 => 04, -- Length in bytes for digits 2 | |

07 => 04, -- Length in bytes for digits 2 | |

08 => 05, -- Length in bytes for digits 2 | |

09 => 05, -- Length in bytes for digits 2 | |

10 => 06, -- Length in bytes for digits 2 | |

11 => 06, -- Length in bytes for digits 2 | |

12 => 07, -- Length in bytes for digits 2 | |

13 => 07, -- Length in bytes for digits 2 | |

14 => 08, -- Length in bytes for digits 2 | |

15 => 08, -- Length in bytes for digits 2 | |

16 => 09, -- Length in bytes for digits 2 | |

17 => 09, -- Length in bytes for digits 2 | |

18 => 10]; -- Length in bytes for digits 2 | |

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

-- Conversion Routines -- | |

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

subtype D32 is Positive range 1 .. 9; | |

-- Used to represent number of digits in a packed decimal value that | |

-- can be represented in a 32-bit binary signed integer form. | |

subtype D64 is Positive range 10 .. 18; | |

-- Used to represent number of digits in a packed decimal value that | |

-- requires a 64-bit signed binary integer for representing all values. | |

function Packed_To_Int32 (P : System.Address; D : D32) return Integer_32; | |

-- The argument P is the address of a packed decimal value and D is the | |

-- number of digits (in the range 1 .. 9, as implied by the subtype). | |

-- The returned result is the corresponding signed binary value. The | |

-- exception Constraint_Error is raised if the input is invalid. | |

function Packed_To_Int64 (P : System.Address; D : D64) return Integer_64; | |

-- The argument P is the address of a packed decimal value and D is the | |

-- number of digits (in the range 10 .. 18, as implied by the subtype). | |

-- The returned result is the corresponding signed binary value. The | |

-- exception Constraint_Error is raised if the input is invalid. | |

procedure Int32_To_Packed (V : Integer_32; P : System.Address; D : D32); | |

-- The argument V is a signed binary integer, which is converted to | |

-- packed decimal format and stored using P, the address of a packed | |

-- decimal item of D digits (D is in the range 1-9). Constraint_Error | |

-- is raised if V is out of range of this number of digits. | |

procedure Int64_To_Packed (V : Integer_64; P : System.Address; D : D64); | |

-- The argument V is a signed binary integer, which is converted to | |

-- packed decimal format and stored using P, the address of a packed | |

-- decimal item of D digits (D is in the range 10-18). Constraint_Error | |

-- is raised if V is out of range of this number of digits. | |

end Interfaces.Packed_Decimal; |