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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT LIBRARY COMPONENTS --
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4 -- --
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5 -- A D A . C O N T A I N E R S . H E L P E R S --
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6 -- --
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7 -- S p e c --
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8 -- --
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131
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9 -- Copyright (C) 2015-2018, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 ------------------------------------------------------------------------------
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27
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28 with Ada.Finalization;
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29 with System.Atomic_Counters;
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30
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31 package Ada.Containers.Helpers is
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32 pragma Annotate (CodePeer, Skip_Analysis);
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33 pragma Pure;
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34
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35 -- Miscellaneous helpers shared among various containers
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36
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37 package SAC renames System.Atomic_Counters;
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38
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39 Count_Type_Last : constant := Count_Type'Last;
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40 -- Count_Type'Last as a universal_integer, so we can compare Index_Type
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41 -- values against this without type conversions that might overflow.
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42
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43 type Tamper_Counts is record
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44 Busy : aliased SAC.Atomic_Unsigned := 0;
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45 Lock : aliased SAC.Atomic_Unsigned := 0;
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46 end record;
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47
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48 -- Busy is positive when tampering with cursors is prohibited. Busy and
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49 -- Lock are both positive when tampering with elements is prohibited.
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50
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51 type Tamper_Counts_Access is access all Tamper_Counts;
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52 for Tamper_Counts_Access'Storage_Size use 0;
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53
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54 generic
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55 package Generic_Implementation is
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56
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57 -- Generic package used in the implementation of containers.
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58
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59 -- This needs to be generic so that the 'Enabled attribute will return
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60 -- the value that is relevant at the point where a container generic is
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61 -- instantiated. For example:
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62 --
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63 -- pragma Suppress (Container_Checks);
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64 -- package My_Vectors is new Ada.Containers.Vectors (...);
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65 --
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66 -- should suppress all container-related checks within the instance
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67 -- My_Vectors.
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68
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69 -- Shorthands for "checks enabled" and "tampering checks enabled". Note
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70 -- that suppressing either Container_Checks or Tampering_Check disables
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71 -- tampering checks. Note that this code needs to be in a generic
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72 -- package, because we want to take account of check suppressions at the
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73 -- instance. We use these flags, along with pragma Inline, to ensure
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74 -- that the compiler can optimize away the checks, as well as the
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75 -- tampering check machinery, when checks are suppressed.
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76
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77 Checks : constant Boolean := Container_Checks'Enabled;
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78 T_Check : constant Boolean :=
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79 Container_Checks'Enabled and Tampering_Check'Enabled;
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80
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81 -- Reference_Control_Type is used as a component of reference types, to
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82 -- prohibit tampering with elements so long as references exist.
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83
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84 type Reference_Control_Type is
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85 new Finalization.Controlled with record
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86 T_Counts : Tamper_Counts_Access;
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87 end record
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88 with Disable_Controlled => not T_Check;
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89
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90 overriding procedure Adjust (Control : in out Reference_Control_Type);
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91 pragma Inline (Adjust);
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92
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93 overriding procedure Finalize (Control : in out Reference_Control_Type);
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94 pragma Inline (Finalize);
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95
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96 procedure Zero_Counts (T_Counts : out Tamper_Counts);
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97 pragma Inline (Zero_Counts);
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98 -- Set Busy and Lock to zero
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99
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100 procedure Busy (T_Counts : in out Tamper_Counts);
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101 pragma Inline (Busy);
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102 -- Prohibit tampering with cursors
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103
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104 procedure Unbusy (T_Counts : in out Tamper_Counts);
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105 pragma Inline (Unbusy);
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106 -- Allow tampering with cursors
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107
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108 procedure Lock (T_Counts : in out Tamper_Counts);
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109 pragma Inline (Lock);
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110 -- Prohibit tampering with elements
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111
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112 procedure Unlock (T_Counts : in out Tamper_Counts);
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113 pragma Inline (Unlock);
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114 -- Allow tampering with elements
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115
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116 procedure TC_Check (T_Counts : Tamper_Counts);
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117 pragma Inline (TC_Check);
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118 -- Tampering-with-cursors check
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119
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120 procedure TE_Check (T_Counts : Tamper_Counts);
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121 pragma Inline (TE_Check);
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122 -- Tampering-with-elements check
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123
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124 -----------------
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125 -- RAII Types --
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126 -----------------
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127
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128 -- Initialize of With_Busy increments the Busy count, and Finalize
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129 -- decrements it. Thus, to prohibit tampering with elements within a
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130 -- given scope, declare an object of type With_Busy. The Busy count
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131 -- will be correctly decremented in case of exception or abort.
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132
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133 -- With_Lock is the same as With_Busy, except it increments/decrements
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134 -- BOTH Busy and Lock, thus prohibiting tampering with cursors.
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135
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136 type With_Busy (T_Counts : not null access Tamper_Counts) is
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137 new Finalization.Limited_Controlled with null record
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138 with Disable_Controlled => not T_Check;
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139 overriding procedure Initialize (Busy : in out With_Busy);
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140 overriding procedure Finalize (Busy : in out With_Busy);
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141
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142 type With_Lock (T_Counts : not null access Tamper_Counts) is
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143 new Finalization.Limited_Controlled with null record
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144 with Disable_Controlled => not T_Check;
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145 overriding procedure Initialize (Lock : in out With_Lock);
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146 overriding procedure Finalize (Lock : in out With_Lock);
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147
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148 -- Variables of type With_Busy and With_Lock are declared only for the
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149 -- effects of Initialize and Finalize, so they are not referenced;
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150 -- disable warnings about that. Note that all variables of these types
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151 -- have names starting with "Busy" or "Lock". These pragmas need to be
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152 -- present wherever these types are used.
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153
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154 pragma Warnings (Off, "variable ""Busy*"" is not referenced");
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155 pragma Warnings (Off, "variable ""Lock*"" is not referenced");
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156
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157 end Generic_Implementation;
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158
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159 end Ada.Containers.Helpers;
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