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 --          Copyright (C) 1992-2003 Free Software Foundation, Inc.          --
  11 --                                                                          --
  12 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  20 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  21 -- Boston, MA 02110-1301, USA.                                              --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNAT was originally developed  by the GNAT team at  New York University. --
  31 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 --  This unit defines the packed decimal format used by GNAT in response to
  36 --  a specification of Machine_Radix 10 for a decimal fixed-point type. The
  37 --  format and operations are completely encapsulated in this unit, so all
  38 --  that is necessary to compile using different packed decimal formats is
  39 --  to replace this single unit.
  40
  41 --  Note that the compiler access the spec of this unit during compilation
  42 --  to obtain the data length that needs allocating, so the correct version
  43 --  of the spec must be available to the compiler, and must correspond to
  44 --  the spec and body made available to the linker, and all units of a given
  45 --  program must be compiled with the same version of the spec and body.
  46 --  This consistency will be enforced automatically using the normal binder
  47 --  consistency checking, since any unit declaring Machine_Radix 10 types or
  48 --  containing operations on such data will implicitly with Packed_Decimal.
  49
  50 with System;
  51
  52 package Interfaces.Packed_Decimal is
  53
  54    ------------------------
  55    -- Format Description --
  56    ------------------------
  57
  58    --  IBM Mainframe packed decimal format uses a byte string of length one
  59    --  to 10 bytes, with the most significant byte first. Each byte contains
  60    --  two decimal digits (with the high order digit in the left nibble, and
  61    --  the low order four bits contain the sign, using the following code:
  62
  63    --     16#A#  2#1010#   positive
  64    --     16#B#  2#1011#   negative
  65    --     16#C#  2#1100#   positive (preferred representation)
  66    --     16#D#  2#1101#   negative (preferred representation)
  67    --     16#E#  2#1110#   positive
  68    --     16#F#  2#1011#   positive
  69
  70    --  In this package, all six sign representations are interpreted as
  71    --  shown above when an operand is read, when an operand is written,
  72    --  the preferred representations are always used. Constraint_Error
  73    --  is raised if any other bit pattern is found in the sign nibble,
  74    --  or if a digit nibble contains an invalid digit code.
  75
  76    --  Some examples follow:
  77
  78    --     05 76 3C      +5763
  79    --     00 01 1D        -11
  80    --     00 04 4E        +44 (non-standard sign)
  81    --     00 00 00      invalid (incorrect sign nibble)
  82    --     0A 01 1C      invalid (bad digit)
  83
  84    ------------------
  85    -- Length Array --
  86    ------------------
  87
  88    --  The following array must be declared in exactly the form shown, since
  89    --  the compiler accesses the associated tree to determine the size to be
  90    --  allocated to a machine radix 10 type, depending on the number of digits.
  91
  92    subtype Byte_Length is Positive range 1 .. 10;
  93    --  Range of possible byte lengths
  94
  95    Packed_Size : constant array (1 .. 18) of Byte_Length :=
  96       (01 => 01,    -- Length in bytes for digits 1
  97        02 => 02,    -- Length in bytes for digits 2
  98        03 => 02,    -- Length in bytes for digits 2
  99        04 => 03,    -- Length in bytes for digits 2
 100        05 => 03,    -- Length in bytes for digits 2
 101        06 => 04,    -- Length in bytes for digits 2
 102        07 => 04,    -- Length in bytes for digits 2
 103        08 => 05,    -- Length in bytes for digits 2
 104        09 => 05,    -- Length in bytes for digits 2
 105        10 => 06,    -- Length in bytes for digits 2
 106        11 => 06,    -- Length in bytes for digits 2
 107        12 => 07,    -- Length in bytes for digits 2
 108        13 => 07,    -- Length in bytes for digits 2
 109        14 => 08,    -- Length in bytes for digits 2
 110        15 => 08,    -- Length in bytes for digits 2
 111        16 => 09,    -- Length in bytes for digits 2
 112        17 => 09,    -- Length in bytes for digits 2
 113        18 => 10);   -- Length in bytes for digits 2
 114
 115    -------------------------
 116    -- Conversion Routines --
 117    -------------------------
 118
 119    subtype D32 is Positive range 1 .. 9;
 120    --  Used to represent number of digits in a packed decimal value that
 121    --  can be represented in a 32-bit binary signed integer form.
 122
 123    subtype D64 is Positive range 10 .. 18;
 124    --  Used to represent number of digits in a packed decimal value that
 125    --  requires a 64-bit signed binary integer for representing all values.
 126
 127    function Packed_To_Int32 (P : System.Address; D : D32) return Integer_32;
 128    --  The argument P is the address of a packed decimal value and D is the
 129    --  number of digits (in the range 1 .. 9, as implied by the subtype).
 130    --  The returned result is the corresponding signed binary value. The
 131    --  exception Constraint_Error is raised if the input is invalid.
 132
 133    function Packed_To_Int64 (P : System.Address; D : D64) return Integer_64;
 134    --  The argument P is the address of a packed decimal value and D is the
 135    --  number of digits (in the range 10 .. 18, as implied by the subtype).
 136    --  The returned result is the corresponding signed binary value. The
 137    --  exception Constraint_Error is raised if the input is invalid.
 138
 139    procedure Int32_To_Packed (V : Integer_32; P : System.Address; D : D32);
 140    --  The argument V is a signed binary integer, which is converted to
 141    --  packed decimal format and stored using P, the address of a packed
 142    --  decimal item of D digits (D is in the range 1-9). Constraint_Error
 143    --  is raised if V is out of range of this number of digits.
 144
 145    procedure Int64_To_Packed (V : Integer_64; P : System.Address; D : D64);
 146    --  The argument V is a signed binary integer, which is converted to
 147    --  packed decimal format and stored using P, the address of a packed
 148    --  decimal item of D digits (D is in the range 10-18). Constraint_Error
 149    --  is raised if V is out of range of this number of digits.
 150
 151 end Interfaces.Packed_Decimal;