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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- 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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6 -- --
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7 -- S p e c --
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8 -- (Version for IBM Mainframe Packed Decimal Format) --
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9 -- --
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131
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10 -- Copyright (C) 1992-2018, Free Software Foundation, Inc. --
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111
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11 -- --
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12 -- GNAT is free software; you can redistribute it and/or modify it under --
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13 -- terms of the GNU General Public License as published by the Free Soft- --
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14 -- ware Foundation; either version 3, or (at your option) any later ver- --
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15 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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16 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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17 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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18 -- --
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19 -- As a special exception under Section 7 of GPL version 3, you are granted --
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20 -- additional permissions described in the GCC Runtime Library Exception, --
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21 -- version 3.1, as published by the Free Software Foundation. --
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22 -- --
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23 -- You should have received a copy of the GNU General Public License and --
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24 -- a copy of the GCC Runtime Library Exception along with this program; --
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25 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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26 -- <http://www.gnu.org/licenses/>. --
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27 -- --
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28 -- GNAT was originally developed by the GNAT team at New York University. --
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29 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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30 -- --
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31 ------------------------------------------------------------------------------
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32
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33 -- This unit defines the packed decimal format used by GNAT in response to
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34 -- a specification of Machine_Radix 10 for a decimal fixed-point type. The
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35 -- format and operations are completely encapsulated in this unit, so all
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36 -- that is necessary to compile using different packed decimal formats is
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37 -- to replace this single unit.
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38
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39 -- Note that the compiler access the spec of this unit during compilation
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40 -- to obtain the data length that needs allocating, so the correct version
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41 -- of the spec must be available to the compiler, and must correspond to
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42 -- the spec and body made available to the linker, and all units of a given
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43 -- program must be compiled with the same version of the spec and body.
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44 -- This consistency will be enforced automatically using the normal binder
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45 -- consistency checking, since any unit declaring Machine_Radix 10 types or
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46 -- containing operations on such data will implicitly with Packed_Decimal.
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47
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48 with System;
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49
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50 package Interfaces.Packed_Decimal is
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51
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52 ------------------------
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53 -- Format Description --
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54 ------------------------
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55
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56 -- IBM Mainframe packed decimal format uses a byte string of length one
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57 -- to 10 bytes, with the most significant byte first. Each byte contains
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58 -- two decimal digits (with the high order digit in the left nibble, and
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59 -- the low order four bits contain the sign, using the following code:
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60
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61 -- 16#A# 2#1010# positive
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62 -- 16#B# 2#1011# negative
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63 -- 16#C# 2#1100# positive (preferred representation)
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64 -- 16#D# 2#1101# negative (preferred representation)
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65 -- 16#E# 2#1110# positive
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66 -- 16#F# 2#1011# positive
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67
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68 -- In this package, all six sign representations are interpreted as
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69 -- shown above when an operand is read, when an operand is written,
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70 -- the preferred representations are always used. Constraint_Error
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71 -- is raised if any other bit pattern is found in the sign nibble,
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72 -- or if a digit nibble contains an invalid digit code.
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73
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74 -- Some examples follow:
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75
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76 -- 05 76 3C +5763
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77 -- 00 01 1D -11
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78 -- 00 04 4E +44 (non-standard sign)
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79 -- 00 00 00 invalid (incorrect sign nibble)
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80 -- 0A 01 1C invalid (bad digit)
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81
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82 ------------------
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83 -- Length Array --
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84 ------------------
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85
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86 -- The following array must be declared in exactly the form shown, since
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87 -- the compiler accesses the associated tree to determine the size to be
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88 -- allocated to a machine radix 10 type, depending on the number of digits.
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89
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90 subtype Byte_Length is Positive range 1 .. 10;
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91 -- Range of possible byte lengths
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92
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93 Packed_Size : constant array (1 .. 18) of Byte_Length :=
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94 (01 => 01, -- Length in bytes for digits 1
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95 02 => 02, -- Length in bytes for digits 2
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96 03 => 02, -- Length in bytes for digits 2
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97 04 => 03, -- Length in bytes for digits 2
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98 05 => 03, -- Length in bytes for digits 2
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99 06 => 04, -- Length in bytes for digits 2
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100 07 => 04, -- Length in bytes for digits 2
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101 08 => 05, -- Length in bytes for digits 2
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102 09 => 05, -- Length in bytes for digits 2
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103 10 => 06, -- Length in bytes for digits 2
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104 11 => 06, -- Length in bytes for digits 2
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105 12 => 07, -- Length in bytes for digits 2
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106 13 => 07, -- Length in bytes for digits 2
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107 14 => 08, -- Length in bytes for digits 2
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108 15 => 08, -- Length in bytes for digits 2
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109 16 => 09, -- Length in bytes for digits 2
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110 17 => 09, -- Length in bytes for digits 2
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111 18 => 10); -- Length in bytes for digits 2
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112
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113 -------------------------
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114 -- Conversion Routines --
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115 -------------------------
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116
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117 subtype D32 is Positive range 1 .. 9;
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118 -- Used to represent number of digits in a packed decimal value that
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119 -- can be represented in a 32-bit binary signed integer form.
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120
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121 subtype D64 is Positive range 10 .. 18;
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122 -- Used to represent number of digits in a packed decimal value that
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123 -- requires a 64-bit signed binary integer for representing all values.
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124
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125 function Packed_To_Int32 (P : System.Address; D : D32) return Integer_32;
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126 -- The argument P is the address of a packed decimal value and D is the
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127 -- number of digits (in the range 1 .. 9, as implied by the subtype).
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128 -- The returned result is the corresponding signed binary value. The
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129 -- exception Constraint_Error is raised if the input is invalid.
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130
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131 function Packed_To_Int64 (P : System.Address; D : D64) return Integer_64;
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132 -- The argument P is the address of a packed decimal value and D is the
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133 -- number of digits (in the range 10 .. 18, as implied by the subtype).
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134 -- The returned result is the corresponding signed binary value. The
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135 -- exception Constraint_Error is raised if the input is invalid.
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136
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137 procedure Int32_To_Packed (V : Integer_32; P : System.Address; D : D32);
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138 -- The argument V is a signed binary integer, which is converted to
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139 -- packed decimal format and stored using P, the address of a packed
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140 -- decimal item of D digits (D is in the range 1-9). Constraint_Error
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141 -- is raised if V is out of range of this number of digits.
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142
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143 procedure Int64_To_Packed (V : Integer_64; P : System.Address; D : D64);
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144 -- The argument V is a signed binary integer, which is converted to
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145 -- packed decimal format and stored using P, the address of a packed
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146 -- decimal item of D digits (D is in the range 10-18). Constraint_Error
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147 -- is raised if V is out of range of this number of digits.
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148
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149 end Interfaces.Packed_Decimal;
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