361 lines
11 KiB
Ada
361 lines
11 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- I N T E R F A C E S . C . S T R I N G S --
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-- --
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-- B o d y --
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-- --
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-- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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with System; use System;
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with System.Storage_Elements; use System.Storage_Elements;
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with Ada.Unchecked_Conversion;
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package body Interfaces.C.Strings is
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-- Note that the type chars_ptr has a pragma No_Strict_Aliasing in the
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-- spec, to prevent any assumptions about aliasing for values of this type,
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-- since arbitrary addresses can be converted, and it is quite likely that
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-- this type will in fact be used for aliasing values of other types.
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function To_chars_ptr is
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new Ada.Unchecked_Conversion (System.Parameters.C_Address, chars_ptr);
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function To_Address is
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new Ada.Unchecked_Conversion (chars_ptr, System.Parameters.C_Address);
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-----------------------
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-- Local Subprograms --
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-----------------------
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function Peek (From : chars_ptr) return char;
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pragma Inline (Peek);
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-- Given a chars_ptr value, obtain referenced character
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procedure Poke (Value : char; Into : chars_ptr);
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pragma Inline (Poke);
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-- Given a chars_ptr, modify referenced Character value
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function "+" (Left : chars_ptr; Right : size_t) return chars_ptr;
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pragma Inline ("+");
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-- Address arithmetic on chars_ptr value
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function Position_Of_Nul (Into : char_array) return size_t;
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-- Returns position of the first Nul in Into or Into'Last + 1 if none
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-- We can't use directly System.Memory because the categorization is not
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-- compatible, so we directly import here the malloc and free routines.
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function Memory_Alloc (Size : size_t) return chars_ptr;
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pragma Import (C, Memory_Alloc, System.Parameters.C_Malloc_Linkname);
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procedure Memory_Free (Address : chars_ptr);
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pragma Import (C, Memory_Free, "__gnat_free");
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---------
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-- "+" --
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---------
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function "+" (Left : chars_ptr; Right : size_t) return chars_ptr is
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begin
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return To_chars_ptr (To_Address (Left) + Storage_Offset (Right));
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end "+";
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----------
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-- Free --
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----------
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procedure Free (Item : in out chars_ptr) is
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begin
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if Item = Null_Ptr then
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return;
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end if;
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Memory_Free (Item);
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Item := Null_Ptr;
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end Free;
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--------------------
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-- New_Char_Array --
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--------------------
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function New_Char_Array (Chars : char_array) return chars_ptr is
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Index : size_t;
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Pointer : chars_ptr;
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begin
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-- Get index of position of null. If Index > Chars'Last,
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-- nul is absent and must be added explicitly.
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Index := Position_Of_Nul (Into => Chars);
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Pointer := Memory_Alloc ((Index - Chars'First + 1));
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-- If nul is present, transfer string up to and including nul
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if Index <= Chars'Last then
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Update (Item => Pointer,
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Offset => 0,
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Chars => Chars (Chars'First .. Index),
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Check => False);
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else
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-- If original string has no nul, transfer whole string and add
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-- terminator explicitly.
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Update (Item => Pointer,
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Offset => 0,
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Chars => Chars,
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Check => False);
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Poke (nul, Into => Pointer + size_t'(Chars'Length));
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end if;
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return Pointer;
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end New_Char_Array;
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----------------
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-- New_String --
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----------------
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function New_String (Str : String) return chars_ptr is
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-- It's important that this subprogram uses the heap directly to compute
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-- the result, and doesn't copy the string on the stack, otherwise its
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-- use is limited when used from tasks on large strings.
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Result : constant chars_ptr := Memory_Alloc (Str'Length + 1);
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Result_Array : char_array (1 .. Str'Length + 1);
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for Result_Array'Address use To_Address (Result);
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pragma Import (Ada, Result_Array);
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Count : size_t;
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begin
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To_C
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(Item => Str,
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Target => Result_Array,
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Count => Count,
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Append_Nul => True);
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return Result;
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end New_String;
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----------
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-- Peek --
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----------
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function Peek (From : chars_ptr) return char is
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begin
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return char (From.all);
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end Peek;
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----------
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-- Poke --
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----------
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procedure Poke (Value : char; Into : chars_ptr) is
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begin
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Into.all := Character (Value);
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end Poke;
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---------------------
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-- Position_Of_Nul --
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---------------------
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function Position_Of_Nul (Into : char_array) return size_t is
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begin
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for J in Into'Range loop
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if Into (J) = nul then
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return J;
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end if;
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end loop;
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return Into'Last + 1;
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end Position_Of_Nul;
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------------
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-- Strlen --
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------------
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function Strlen (Item : chars_ptr) return size_t is
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Item_Index : size_t := 0;
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begin
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if Item = Null_Ptr then
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raise Dereference_Error;
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end if;
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loop
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if Peek (Item + Item_Index) = nul then
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return Item_Index;
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end if;
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Item_Index := Item_Index + 1;
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end loop;
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end Strlen;
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------------------
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-- To_Chars_Ptr --
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------------------
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function To_Chars_Ptr
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(Item : char_array_access;
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Nul_Check : Boolean := False) return chars_ptr
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is
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begin
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if Item = null then
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return Null_Ptr;
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elsif Nul_Check
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and then Position_Of_Nul (Into => Item.all) > Item'Last
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then
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raise Terminator_Error;
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else
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return To_chars_ptr (Item (Item'First)'Address);
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end if;
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end To_Chars_Ptr;
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------------
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-- Update --
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------------
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procedure Update
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(Item : chars_ptr;
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Offset : size_t;
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Chars : char_array;
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Check : Boolean := True)
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is
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Index : chars_ptr := Item + Offset;
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begin
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if Check and then Offset + Chars'Length > Strlen (Item) then
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raise Update_Error;
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end if;
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for J in Chars'Range loop
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Poke (Chars (J), Into => Index);
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Index := Index + size_t'(1);
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end loop;
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end Update;
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procedure Update
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(Item : chars_ptr;
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Offset : size_t;
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Str : String;
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Check : Boolean := True)
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is
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begin
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-- Note: in RM 95, the Append_Nul => False parameter is omitted. But
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-- this has the unintended consequence of truncating the string after
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-- an update. As discussed in Ada 2005 AI-242, this was unintended,
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-- and should be corrected. Since this is a clear error, it seems
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-- appropriate to apply the correction in Ada 95 mode as well.
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Update (Item, Offset, To_C (Str, Append_Nul => False), Check);
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end Update;
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-----------
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-- Value --
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-----------
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function Value (Item : chars_ptr) return char_array is
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Result : char_array (0 .. Strlen (Item));
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begin
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if Item = Null_Ptr then
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raise Dereference_Error;
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end if;
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-- Note that the following loop will also copy the terminating Nul
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for J in Result'Range loop
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Result (J) := Peek (Item + J);
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end loop;
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return Result;
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end Value;
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function Value
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(Item : chars_ptr;
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Length : size_t) return char_array
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is
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begin
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if Item = Null_Ptr then
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raise Dereference_Error;
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end if;
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-- ACATS cxb3010 checks that Constraint_Error gets raised when Length
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-- is 0. Seems better to check that Length is not null before declaring
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-- an array with size_t bounds of 0 .. Length - 1 anyway.
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if Length = 0 then
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raise Constraint_Error;
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end if;
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declare
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Result : char_array (0 .. Length - 1);
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begin
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for J in Result'Range loop
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Result (J) := Peek (Item + J);
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if Result (J) = nul then
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return Result (0 .. J);
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end if;
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end loop;
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return Result;
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end;
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end Value;
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function Value (Item : chars_ptr) return String is
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begin
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return To_Ada (Value (Item));
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end Value;
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function Value (Item : chars_ptr; Length : size_t) return String is
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Result : char_array (0 .. Length);
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begin
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-- As per AI-00177, this is equivalent to:
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-- To_Ada (Value (Item, Length) & nul);
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if Item = Null_Ptr then
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raise Dereference_Error;
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end if;
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for J in 0 .. Length - 1 loop
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Result (J) := Peek (Item + J);
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if Result (J) = nul then
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return To_Ada (Result (0 .. J));
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end if;
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end loop;
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Result (Length) := nul;
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return To_Ada (Result);
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end Value;
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end Interfaces.C.Strings;
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