150 lines
7.8 KiB
Ada
150 lines
7.8 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- I N T E R F A C E S . P A C K E D _ D E C I M A L --
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-- --
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-- S p e c --
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-- (Version for IBM Mainframe Packed Decimal Format) --
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-- --
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-- Copyright (C) 1992-2009, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This unit defines the packed decimal format used by GNAT in response to
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-- a specification of Machine_Radix 10 for a decimal fixed-point type. The
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-- format and operations are completely encapsulated in this unit, so all
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-- that is necessary to compile using different packed decimal formats is
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-- to replace this single unit.
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-- Note that the compiler access the spec of this unit during compilation
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-- to obtain the data length that needs allocating, so the correct version
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-- of the spec must be available to the compiler, and must correspond to
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-- the spec and body made available to the linker, and all units of a given
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-- program must be compiled with the same version of the spec and body.
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-- This consistency will be enforced automatically using the normal binder
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-- consistency checking, since any unit declaring Machine_Radix 10 types or
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-- containing operations on such data will implicitly with Packed_Decimal.
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with System;
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package Interfaces.Packed_Decimal is
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------------------------
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-- Format Description --
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------------------------
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-- IBM Mainframe packed decimal format uses a byte string of length one
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-- to 10 bytes, with the most significant byte first. Each byte contains
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-- two decimal digits (with the high order digit in the left nibble, and
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-- the low order four bits contain the sign, using the following code:
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-- 16#A# 2#1010# positive
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-- 16#B# 2#1011# negative
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-- 16#C# 2#1100# positive (preferred representation)
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-- 16#D# 2#1101# negative (preferred representation)
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-- 16#E# 2#1110# positive
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-- 16#F# 2#1011# positive
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-- In this package, all six sign representations are interpreted as
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-- shown above when an operand is read, when an operand is written,
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-- the preferred representations are always used. Constraint_Error
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-- is raised if any other bit pattern is found in the sign nibble,
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-- or if a digit nibble contains an invalid digit code.
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-- Some examples follow:
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-- 05 76 3C +5763
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-- 00 01 1D -11
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-- 00 04 4E +44 (non-standard sign)
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-- 00 00 00 invalid (incorrect sign nibble)
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-- 0A 01 1C invalid (bad digit)
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------------------
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-- Length Array --
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------------------
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-- The following array must be declared in exactly the form shown, since
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-- the compiler accesses the associated tree to determine the size to be
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-- allocated to a machine radix 10 type, depending on the number of digits.
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subtype Byte_Length is Positive range 1 .. 10;
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-- Range of possible byte lengths
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Packed_Size : constant array (1 .. 18) of Byte_Length :=
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(01 => 01, -- Length in bytes for digits 1
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02 => 02, -- Length in bytes for digits 2
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03 => 02, -- Length in bytes for digits 2
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04 => 03, -- Length in bytes for digits 2
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05 => 03, -- Length in bytes for digits 2
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06 => 04, -- Length in bytes for digits 2
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07 => 04, -- Length in bytes for digits 2
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08 => 05, -- Length in bytes for digits 2
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09 => 05, -- Length in bytes for digits 2
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10 => 06, -- Length in bytes for digits 2
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11 => 06, -- Length in bytes for digits 2
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12 => 07, -- Length in bytes for digits 2
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13 => 07, -- Length in bytes for digits 2
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14 => 08, -- Length in bytes for digits 2
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15 => 08, -- Length in bytes for digits 2
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16 => 09, -- Length in bytes for digits 2
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17 => 09, -- Length in bytes for digits 2
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18 => 10); -- Length in bytes for digits 2
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-------------------------
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-- Conversion Routines --
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-------------------------
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subtype D32 is Positive range 1 .. 9;
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-- Used to represent number of digits in a packed decimal value that
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-- can be represented in a 32-bit binary signed integer form.
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subtype D64 is Positive range 10 .. 18;
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-- Used to represent number of digits in a packed decimal value that
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-- requires a 64-bit signed binary integer for representing all values.
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function Packed_To_Int32 (P : System.Address; D : D32) return Integer_32;
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-- The argument P is the address of a packed decimal value and D is the
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-- number of digits (in the range 1 .. 9, as implied by the subtype).
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-- The returned result is the corresponding signed binary value. The
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-- exception Constraint_Error is raised if the input is invalid.
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function Packed_To_Int64 (P : System.Address; D : D64) return Integer_64;
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-- The argument P is the address of a packed decimal value and D is the
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-- number of digits (in the range 10 .. 18, as implied by the subtype).
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-- The returned result is the corresponding signed binary value. The
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-- exception Constraint_Error is raised if the input is invalid.
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procedure Int32_To_Packed (V : Integer_32; P : System.Address; D : D32);
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-- The argument V is a signed binary integer, which is converted to
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-- packed decimal format and stored using P, the address of a packed
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-- decimal item of D digits (D is in the range 1-9). Constraint_Error
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-- is raised if V is out of range of this number of digits.
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procedure Int64_To_Packed (V : Integer_64; P : System.Address; D : D64);
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-- The argument V is a signed binary integer, which is converted to
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-- packed decimal format and stored using P, the address of a packed
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-- decimal item of D digits (D is in the range 10-18). Constraint_Error
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-- is raised if V is out of range of this number of digits.
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end Interfaces.Packed_Decimal;
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