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) 1992,1993,1994,1995 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,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, 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 --  This unit defines the packed decimal format used by GNAT in response to
  35 --  a specication of Machine_Radix 10 for a decimal fixed-point type. The
  36 --  format and operations are completely encapsulated in this unit, so all
  37 --  that is necessary to compile using different packed decimal formats is
  38 --  to replace this single unit.
  39
  40 --  Note that the compiler access the spec of this unit during compilation
  41 --  to obtain the data length that needs allocating, so the correct version
  42 --  of the spec must be available to the compiler, and must correspond to
  43 --  the spec and body made available to the linker, and all units of a given
  44 --  program must be compiled with the same version of the spec and body.
  45 --  This consistency will be enforced automatically using the normal binder
  46 --  consistency checking, since any unit declaring Machine_Radix 10 types or
  47 --  containing operations on such data will implicitly with Packed_Decimal.
  48
  49 with System;
  50
  51 package Interfaces.Packed_Decimal is
  52
  53    ------------------------
  54    -- Format Description --
  55    ------------------------
  56
  57    --  IBM Mainframe packed decimal format uses a byte string of length one
  58    --  to 10 bytes, with the most significant byte first. Each byte contains
  59    --  two decimal digits (with the high order digit in the left nibble, and
  60    --  the low order four bits contain the sign, using the following code:
  61
  62    --     16#A#  2#1010#   positive
  63    --     16#B#  2#1011#   negative
  64    --     16#C#  2#1100#   positive (preferred representation)
  65    --     16#D#  2#1101#   negative (preferred representation)
  66    --     16#E#  2#1110#   positive
  67    --     16#F#  2#1011#   positive
  68
  69    --  In this package, all six sign representations are interpreted as
  70    --  shown above when an operand is read, when an operand is written,
  71    --  the preferred representations are always used. Constraint_Error
  72    --  is raised if any other bit pattern is found in the sign nibble,
  73    --  or if a digit nibble contains an invalid digit code.
  74
  75    --  Some examples follow:
  76
  77    --     05 76 3C      +5763
  78    --     00 01 1D        -11
  79    --     00 04 4E        +44 (non-standard sign)
  80    --     00 00 00      invalid (incorrect sign nibble)
  81    --     0A 01 1C      invalid (bad digit)
  82
  83    ------------------
  84    -- Length Array --
  85    ------------------
  86
  87    --  The following array must be declared in exactly the form shown, since
  88    --  the compiler accesses the associated tree to determine the size to be
  89    --  allocated to a machine radix 10 type, depending on the number of digits.
  90
  91    subtype Byte_Length is Positive range 1 .. 10;
  92    --  Range of possible byte lengths
  93
  94    Packed_Size : constant array (1 .. 18) of Byte_Length :=
  95       (01 => 01,    -- Length in bytes for digits 1
  96        02 => 02,    -- Length in bytes for digits 2
  97        03 => 02,    -- Length in bytes for digits 2
  98        04 => 03,    -- Length in bytes for digits 2
  99        05 => 03,    -- Length in bytes for digits 2
 100        06 => 04,    -- Length in bytes for digits 2
 101        07 => 04,    -- Length in bytes for digits 2
 102        08 => 05,    -- Length in bytes for digits 2
 103        09 => 05,    -- Length in bytes for digits 2
 104        10 => 06,    -- Length in bytes for digits 2
 105        11 => 06,    -- Length in bytes for digits 2
 106        12 => 07,    -- Length in bytes for digits 2
 107        13 => 07,    -- Length in bytes for digits 2
 108        14 => 08,    -- Length in bytes for digits 2
 109        15 => 08,    -- Length in bytes for digits 2
 110        16 => 09,    -- Length in bytes for digits 2
 111        17 => 09,    -- Length in bytes for digits 2
 112        18 => 10);   -- Length in bytes for digits 2
 113
 114    -------------------------
 115    -- Conversion Routines --
 116    -------------------------
 117
 118    subtype D32 is Positive range 1 .. 9;
 119    --  Used to represent number of digits in a packed decimal value that
 120    --  can be represented in a 32-bit binary signed integer form.
 121
 122    subtype D64 is Positive range 10 .. 18;
 123    --  Used to represent number of digits in a packed decimal value that
 124    --  requires a 64-bit signed binary integer for representing all values.
 125
 126    function Packed_To_Int32 (P : System.Address; D : D32) return Integer_32;
 127    --  The argument P is the address of a packed decimal value and D is the
 128    --  number of digits (in the range 1 .. 9, as implied by the subtype).
 129    --  The returned result is the corresponding signed binary value. The
 130    --  exception Constraint_Error is raised if the input is invalid.
 131
 132    function Packed_To_Int64 (P : System.Address; D : D64) return Integer_64;
 133    --  The argument P is the address of a packed decimal value and D is the
 134    --  number of digits (in the range 10 .. 18, as implied by the subtype).
 135    --  The returned result is the corresponding signed binary value. The
 136    --  exception Constraint_Error is raised if the input is invalid.
 137
 138    procedure Int32_To_Packed (V : Integer_32; P : System.Address; D : D32);
 139    --  The argument V is a signed binary integer, which is converted to
 140    --  packed decimal format and stored using P, the address of a packed
 141    --  decimal item of D digits (D is in the range 1-9). Constraint_Error
 142    --  is raised if V is out of range of this number of digits.
 143
 144    procedure Int64_To_Packed (V : Integer_64; P : System.Address; D : D64);
 145    --  The argument V is a signed binary integer, which is converted to
 146    --  packed decimal format and stored using P, the address of a packed
 147    --  decimal item of D digits (D is in the range 10-18). Constraint_Error
 148    --  is raised if V is out of range of this number of digits.
 149
 150 end Interfaces.Packed_Decimal;