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--                                                                          --

--                         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) 1992-2009, 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.      --

--                                                                          --

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--  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;