gcc/ada/i-pacdec.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --            I N T E R F A C E S . P A C K E D _ D E C I M A L             --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --            (Version for IBM Mainframe Packed Decimal Format)             --
   9 --                                                                          --
  10 --                            $Revision: 1.1.16.1 $
  11 --                                                                          --
  12 --     Copyright (C) 1992,1993,1994,1995 Free Software Foundation, Inc.     --
  13 --                                                                          --
  14 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  15 -- terms of the  GNU General Public License as published  by the Free Soft- --
  16 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  17 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  18 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  19 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  20 -- for  more details.  You should have  received  a copy of the GNU General --
  21 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  22 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  23 -- MA 02111-1307, USA.                                                      --
  24 --                                                                          --
  25 -- As a special exception,  if other files  instantiate  generics from this --
  26 -- unit, or you link  this unit with other files  to produce an executable, --
  27 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  28 -- covered  by the  GNU  General  Public  License.  This exception does not --
  29 -- however invalidate  any other reasons why  the executable file  might be --
  30 -- covered by the  GNU Public License.                                      --
  31 --                                                                          --
  32 -- GNAT was originally developed  by the GNAT team at  New York University. --
  33 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  34 --                                                                          --
  35
  36 --  This unit defines the packed decimal format used by GNAT in response to
  37 --  a specication of Machine_Radix 10 for a decimal fixed-point type. The
  38 --  format and operations are completely encapsulated in this unit, so all
  39 --  that is necessary to compile using different packed decimal formats is
  40 --  to replace this single unit.
  41
  42 --  Note that the compiler access the spec of this unit during compilation
  43 --  to obtain the data length that needs allocating, so the correct version
  44 --  of the spec must be available to the compiler, and must correspond to
  45 --  the spec and body made available to the linker, and all units of a given
  46 --  program must be compiled with the same version of the spec and body.
  47 --  This consistency will be enforced automatically using the normal binder
  48 --  consistency checking, since any unit declaring Machine_Radix 10 types or
  49 --  containing operations on such data will implicitly with Packed_Decimal.
  50
  51 with System;
  52
  53 package Interfaces.Packed_Decimal is
  54
  55    ------------------------
  56    -- Format Description --
  57    ------------------------
  58
  59    --  IBM Mainframe packed decimal format uses a byte string of length one
  60    --  to 10 bytes, with the most significant byte first. Each byte contains
  61    --  two decimal digits (with the high order digit in the left nibble, and
  62    --  the low order four bits contain the sign, using the following code:
  63
  64    --     16#A#  2#1010#   positive
  65    --     16#B#  2#1011#   negative
  66    --     16#C#  2#1100#   positive (preferred representation)
  67    --     16#D#  2#1101#   negative (preferred representation)
  68    --     16#E#  2#1110#   positive
  69    --     16#F#  2#1011#   positive
  70
  71    --  In this package, all six sign representations are interpreted as
  72    --  shown above when an operand is read, when an operand is written,
  73    --  the preferred representations are always used. Constraint_Error
  74    --  is raised if any other bit pattern is found in the sign nibble,
  75    --  or if a digit nibble contains an invalid digit code.
  76
  77    --  Some examples follow:
  78
  79    --     05 76 3C      +5763
  80    --     00 01 1D        -11
  81    --     00 04 4E        +44 (non-standard sign)
  82    --     00 00 00      invalid (incorrect sign nibble)
  83    --     0A 01 1C      invalid (bad digit)
  84
  85    ------------------
  86    -- Length Array --
  87    ------------------
  88
  89    --  The following array must be declared in exactly the form shown, since
  90    --  the compiler accesses the associated tree to determine the size to be
  91    --  allocated to a machine radix 10 type, depending on the number of digits.
  92
  93    subtype Byte_Length is Positive range 1 .. 10;
  94    --  Range of possible byte lengths
  95
  96    Packed_Size : constant array (1 .. 18) of Byte_Length :=
  97       (01 => 01,    -- Length in bytes for digits 1
  98        02 => 02,    -- Length in bytes for digits 2
  99        03 => 02,    -- Length in bytes for digits 2
 100        04 => 03,    -- Length in bytes for digits 2
 101        05 => 03,    -- Length in bytes for digits 2
 102        06 => 04,    -- Length in bytes for digits 2
 103        07 => 04,    -- Length in bytes for digits 2
 104        08 => 05,    -- Length in bytes for digits 2
 105        09 => 05,    -- Length in bytes for digits 2
 106        10 => 06,    -- Length in bytes for digits 2
 107        11 => 06,    -- Length in bytes for digits 2
 108        12 => 07,    -- Length in bytes for digits 2
 109        13 => 07,    -- Length in bytes for digits 2
 110        14 => 08,    -- Length in bytes for digits 2
 111        15 => 08,    -- Length in bytes for digits 2
 112        16 => 09,    -- Length in bytes for digits 2
 113        17 => 09,    -- Length in bytes for digits 2
 114        18 => 10);   -- Length in bytes for digits 2
 115
 116    -------------------------
 117    -- Conversion Routines --
 118    -------------------------
 119
 120    subtype D32 is Positive range 1 .. 9;
 121    --  Used to represent number of digits in a packed decimal value that
 122    --  can be represented in a 32-bit binary signed integer form.
 123
 124    subtype D64 is Positive range 10 .. 18;
 125    --  Used to represent number of digits in a packed decimal value that
 126    --  requires a 64-bit signed binary integer for representing all values.
 127
 128    function Packed_To_Int32 (P : System.Address; D : D32) return Integer_32;
 129    --  The argument P is the address of a packed decimal value and D is the
 130    --  number of digits (in the range 1 .. 9, as implied by the subtype).
 131    --  The returned result is the corresponding signed binary value. The
 132    --  exception Constraint_Error is raised if the input is invalid.
 133
 134    function Packed_To_Int64 (P : System.Address; D : D64) return Integer_64;
 135    --  The argument P is the address of a packed decimal value and D is the
 136    --  number of digits (in the range 10 .. 18, as implied by the subtype).
 137    --  The returned result is the corresponding signed binary value. The
 138    --  exception Constraint_Error is raised if the input is invalid.
 139
 140    procedure Int32_To_Packed (V : Integer_32; P : System.Address; D : D32);
 141    --  The argument V is a signed binary integer, which is converted to
 142    --  packed decimal format and stored using P, the address of a packed
 143    --  decimal item of D digits (D is in the range 1-9). Constraint_Error
 144    --  is raised if V is out of range of this number of digits.
 145
 146    procedure Int64_To_Packed (V : Integer_64; P : System.Address; D : D64);
 147    --  The argument V is a signed binary integer, which is converted to
 148    --  packed decimal format and stored using P, the address of a packed
 149    --  decimal item of D digits (D is in the range 10-18). Constraint_Error
 150    --  is raised if V is out of range of this number of digits.
 151
 152 end Interfaces.Packed_Decimal;