gcc/ada/libgnat/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) 1992-2024, 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 3,  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.                                     --
  18 --                                                                          --
  19 -- As a special exception under Section 7 of GPL version 3, you are granted --
  20 -- additional permissions described in the GCC Runtime Library Exception,   --
  21 -- version 3.1, as published by the Free Software Foundation.               --
  22 --                                                                          --
  23 -- You should have received a copy of the GNU General Public License and    --
  24 -- a copy of the GCC Runtime Library Exception along with this program;     --
  25 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  26 -- <http://www.gnu.org/licenses/>.                                          --
  27 --                                                                          --
  28 -- GNAT was originally developed  by the GNAT team at  New York University. --
  29 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  30 --                                                                          --
  31 ------------------------------------------------------------------------------
  32
  33 --  This unit defines the packed decimal format used by GNAT in response to
  34 --  a specification of Machine_Radix 10 for a decimal fixed-point type. The
  35 --  format and operations are completely encapsulated in this unit, so all
  36 --  that is necessary to compile using different packed decimal formats is
  37 --  to replace this single unit.
  38
  39 --  Note that the compiler access the spec of this unit during compilation
  40 --  to obtain the data length that needs allocating, so the correct version
  41 --  of the spec must be available to the compiler, and must correspond to
  42 --  the spec and body made available to the linker, and all units of a given
  43 --  program must be compiled with the same version of the spec and body.
  44 --  This consistency will be enforced automatically using the normal binder
  45 --  consistency checking, since any unit declaring Machine_Radix 10 types or
  46 --  containing operations on such data will implicitly with Packed_Decimal.
  47
  48 with System;
  49
  50 package Interfaces.Packed_Decimal is
  51
  52    ------------------------
  53    -- Format Description --
  54    ------------------------
  55
  56    --  IBM Mainframe packed decimal format uses a byte string of length one
  57    --  to 10 bytes, with the most significant byte first. Each byte contains
  58    --  two decimal digits (with the high order digit in the left nibble, and
  59    --  the low order four bits contain the sign, using the following code:
  60
  61    --     16#A#  2#1010#   positive
  62    --     16#B#  2#1011#   negative
  63    --     16#C#  2#1100#   positive (preferred representation)
  64    --     16#D#  2#1101#   negative (preferred representation)
  65    --     16#E#  2#1110#   positive
  66    --     16#F#  2#1011#   positive
  67
  68    --  In this package, all six sign representations are interpreted as
  69    --  shown above when an operand is read, when an operand is written,
  70    --  the preferred representations are always used. Constraint_Error
  71    --  is raised if any other bit pattern is found in the sign nibble,
  72    --  or if a digit nibble contains an invalid digit code.
  73
  74    --  Some examples follow:
  75
  76    --     05 76 3C      +5763
  77    --     00 01 1D        -11
  78    --     00 04 4E        +44 (non-standard sign)
  79    --     00 00 00      invalid (incorrect sign nibble)
  80    --     0A 01 1C      invalid (bad digit)
  81
  82    ------------------
  83    -- Length Array --
  84    ------------------
  85
  86    --  The following array must be declared in exactly the form shown, since
  87    --  the compiler accesses the associated tree to determine the size to be
  88    --  allocated to a machine radix 10 type, depending on the number of digits.
  89
  90    subtype Byte_Length is Positive range 1 .. 10;
  91    --  Range of possible byte lengths
  92
  93    Packed_Size : constant array (1 .. 18) of Byte_Length :=
  94       [01 => 01,    -- Length in bytes for digits 1
  95        02 => 02,    -- Length in bytes for digits 2
  96        03 => 02,    -- Length in bytes for digits 2
  97        04 => 03,    -- Length in bytes for digits 2
  98        05 => 03,    -- Length in bytes for digits 2
  99        06 => 04,    -- Length in bytes for digits 2
 100        07 => 04,    -- Length in bytes for digits 2
 101        08 => 05,    -- Length in bytes for digits 2
 102        09 => 05,    -- Length in bytes for digits 2
 103        10 => 06,    -- Length in bytes for digits 2
 104        11 => 06,    -- Length in bytes for digits 2
 105        12 => 07,    -- Length in bytes for digits 2
 106        13 => 07,    -- Length in bytes for digits 2
 107        14 => 08,    -- Length in bytes for digits 2
 108        15 => 08,    -- Length in bytes for digits 2
 109        16 => 09,    -- Length in bytes for digits 2
 110        17 => 09,    -- Length in bytes for digits 2
 111        18 => 10];   -- Length in bytes for digits 2
 112
 113    -------------------------
 114    -- Conversion Routines --
 115    -------------------------
 116
 117    subtype D32 is Positive range 1 .. 9;
 118    --  Used to represent number of digits in a packed decimal value that
 119    --  can be represented in a 32-bit binary signed integer form.
 120
 121    subtype D64 is Positive range 10 .. 18;
 122    --  Used to represent number of digits in a packed decimal value that
 123    --  requires a 64-bit signed binary integer for representing all values.
 124
 125    function Packed_To_Int32 (P : System.Address; D : D32) return Integer_32;
 126    --  The argument P is the address of a packed decimal value and D is the
 127    --  number of digits (in the range 1 .. 9, as implied by the subtype).
 128    --  The returned result is the corresponding signed binary value. The
 129    --  exception Constraint_Error is raised if the input is invalid.
 130
 131    function Packed_To_Int64 (P : System.Address; D : D64) return Integer_64;
 132    --  The argument P is the address of a packed decimal value and D is the
 133    --  number of digits (in the range 10 .. 18, as implied by the subtype).
 134    --  The returned result is the corresponding signed binary value. The
 135    --  exception Constraint_Error is raised if the input is invalid.
 136
 137    procedure Int32_To_Packed (V : Integer_32; P : System.Address; D : D32);
 138    --  The argument V is a signed binary integer, which is converted to
 139    --  packed decimal format and stored using P, the address of a packed
 140    --  decimal item of D digits (D is in the range 1-9). Constraint_Error
 141    --  is raised if V is out of range of this number of digits.
 142
 143    procedure Int64_To_Packed (V : Integer_64; P : System.Address; D : D64);
 144    --  The argument V is a signed binary integer, which is converted to
 145    --  packed decimal format and stored using P, the address of a packed
 146    --  decimal item of D digits (D is in the range 10-18). Constraint_Error
 147    --  is raised if V is out of range of this number of digits.
 148
 149 end Interfaces.Packed_Decimal;