gcc/ada/i-cpoint.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                I N T E R F A C E S . C . P O I N T E R S                 --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2015, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with Interfaces.C.Strings; use Interfaces.C.Strings;
  33 with System;               use System;
  34
  35 with Ada.Unchecked_Conversion;
  36
  37 package body Interfaces.C.Pointers is
  38
  39    type Addr is mod 2 ** System.Parameters.ptr_bits;
  40
  41    function To_Pointer is new Ada.Unchecked_Conversion (Addr,      Pointer);
  42    function To_Addr    is new Ada.Unchecked_Conversion (Pointer,   Addr);
  43    function To_Addr    is new Ada.Unchecked_Conversion (ptrdiff_t, Addr);
  44    function To_Ptrdiff is new Ada.Unchecked_Conversion (Addr,      ptrdiff_t);
  45
  46    Elmt_Size : constant ptrdiff_t :=
  47                  (Element_Array'Component_Size
  48                    + Storage_Unit - 1) / Storage_Unit;
  49
  50    subtype Index_Base is Index'Base;
  51
  52    ---------
  53    -- "+" --
  54    ---------
  55
  56    function "+" (Left : Pointer; Right : ptrdiff_t) return Pointer is
  57    begin
  58       if Left = null then
  59          raise Pointer_Error;
  60       end if;
  61
  62       return To_Pointer (To_Addr (Left) + To_Addr (Elmt_Size * Right));
  63    end "+";
  64
  65    function "+" (Left : ptrdiff_t; Right : Pointer) return Pointer is
  66    begin
  67       if Right = null then
  68          raise Pointer_Error;
  69       end if;
  70
  71       return To_Pointer (To_Addr (Elmt_Size * Left) + To_Addr (Right));
  72    end "+";
  73
  74    ---------
  75    -- "-" --
  76    ---------
  77
  78    function "-" (Left : Pointer; Right : ptrdiff_t) return Pointer is
  79    begin
  80       if Left = null then
  81          raise Pointer_Error;
  82       end if;
  83
  84       return To_Pointer (To_Addr (Left) - To_Addr (Right * Elmt_Size));
  85    end "-";
  86
  87    function "-" (Left : Pointer; Right : Pointer) return ptrdiff_t is
  88    begin
  89       if Left = null or else Right = null then
  90          raise Pointer_Error;
  91       end if;
  92
  93       return To_Ptrdiff (To_Addr (Left) - To_Addr (Right)) / Elmt_Size;
  94    end "-";
  95
  96    ----------------
  97    -- Copy_Array --
  98    ----------------
  99
 100    procedure Copy_Array
 101      (Source  : Pointer;
 102       Target  : Pointer;
 103       Length  : ptrdiff_t)
 104    is
 105       T : Pointer;
 106       S : Pointer;
 107
 108    begin
 109       if Source = null or else Target = null then
 110          raise Dereference_Error;
 111
 112       --  Forward copy
 113
 114       elsif To_Addr (Target) <= To_Addr (Source) then
 115          T := Target;
 116          S := Source;
 117          for J in 1 .. Length loop
 118             T.all := S.all;
 119             Increment (T);
 120             Increment (S);
 121          end loop;
 122
 123       --  Backward copy
 124
 125       else
 126          T := Target + Length;
 127          S := Source + Length;
 128          for J in 1 .. Length loop
 129             Decrement (T);
 130             Decrement (S);
 131             T.all := S.all;
 132          end loop;
 133       end if;
 134    end Copy_Array;
 135
 136    ---------------------------
 137    -- Copy_Terminated_Array --
 138    ---------------------------
 139
 140    procedure Copy_Terminated_Array
 141      (Source     : Pointer;
 142       Target     : Pointer;
 143       Limit      : ptrdiff_t := ptrdiff_t'Last;
 144       Terminator : Element := Default_Terminator)
 145    is
 146       L : ptrdiff_t;
 147       S : Pointer := Source;
 148
 149    begin
 150       if Source = null or Target = null then
 151          raise Dereference_Error;
 152       end if;
 153
 154       --  Compute array limited length (including the terminator)
 155
 156       L := 0;
 157       while L < Limit loop
 158          L := L + 1;
 159          exit when S.all = Terminator;
 160          Increment (S);
 161       end loop;
 162
 163       Copy_Array (Source, Target, L);
 164    end Copy_Terminated_Array;
 165
 166    ---------------
 167    -- Decrement --
 168    ---------------
 169
 170    procedure Decrement (Ref : in out Pointer) is
 171    begin
 172       Ref := Ref - 1;
 173    end Decrement;
 174
 175    ---------------
 176    -- Increment --
 177    ---------------
 178
 179    procedure Increment (Ref : in out Pointer) is
 180    begin
 181       Ref := Ref + 1;
 182    end Increment;
 183
 184    -----------
 185    -- Value --
 186    -----------
 187
 188    function Value
 189      (Ref        : Pointer;
 190       Terminator : Element := Default_Terminator) return Element_Array
 191    is
 192       P : Pointer;
 193       L : constant Index_Base := Index'First;
 194       H : Index_Base;
 195
 196    begin
 197       if Ref = null then
 198          raise Dereference_Error;
 199
 200       else
 201          H := L;
 202          P := Ref;
 203
 204          loop
 205             exit when P.all = Terminator;
 206             H := Index_Base'Succ (H);
 207             Increment (P);
 208          end loop;
 209
 210          declare
 211             subtype A is Element_Array (L .. H);
 212
 213             type PA is access A;
 214             for PA'Size use System.Parameters.ptr_bits;
 215             function To_PA is new Ada.Unchecked_Conversion (Pointer, PA);
 216
 217          begin
 218             return To_PA (Ref).all;
 219          end;
 220       end if;
 221    end Value;
 222
 223    function Value
 224      (Ref    : Pointer;
 225       Length : ptrdiff_t) return Element_Array
 226    is
 227       L : Index_Base;
 228       H : Index_Base;
 229
 230    begin
 231       if Ref = null then
 232          raise Dereference_Error;
 233
 234       --  For length zero, we need to return a null slice, but we can't make
 235       --  the bounds of this slice Index'First, since this could cause a
 236       --  Constraint_Error if Index'First = Index'Base'First.
 237
 238       elsif Length <= 0 then
 239          declare
 240             pragma Warnings (Off); -- kill warnings since X not assigned
 241             X : Element_Array (Index'Succ (Index'First) .. Index'First);
 242             pragma Warnings (On);
 243
 244          begin
 245             return X;
 246          end;
 247
 248       --  Normal case (length non-zero)
 249
 250       else
 251          L := Index'First;
 252          H := Index'Val (Index'Pos (Index'First) + Length - 1);
 253
 254          declare
 255             subtype A is Element_Array (L .. H);
 256
 257             type PA is access A;
 258             for PA'Size use System.Parameters.ptr_bits;
 259             function To_PA is new Ada.Unchecked_Conversion (Pointer, PA);
 260
 261          begin
 262             return To_PA (Ref).all;
 263          end;
 264       end if;
 265    end Value;
 266
 267    --------------------
 268    -- Virtual_Length --
 269    --------------------
 270
 271    function Virtual_Length
 272      (Ref        : Pointer;
 273       Terminator : Element := Default_Terminator) return ptrdiff_t
 274    is
 275       P : Pointer;
 276       C : ptrdiff_t;
 277
 278    begin
 279       if Ref = null then
 280          raise Dereference_Error;
 281
 282       else
 283          C := 0;
 284          P := Ref;
 285
 286          while P.all /= Terminator loop
 287             C := C + 1;
 288             Increment (P);
 289          end loop;
 290
 291          return C;
 292       end if;
 293    end Virtual_Length;
 294
 295 end Interfaces.C.Pointers;