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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT LIBRARY COMPONENTS                          --

--                                                                          --

--              G N A T . S E C U R E _ H A S H E S . S H A 1               --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--         Copyright (C) 2002-2009, Free Software Foundation, Inc.          --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

package body GNAT.Secure_Hashes.SHA1 is

   use Interfaces;

   use GNAT.Byte_Swapping;

   --  The following functions are the four elementary components of each

   --  of the four round groups (0 .. 19, 20 .. 39, 40 .. 59, and 60 .. 79)

   --  defined in RFC 3174.

   function F0 (B, C, D : Unsigned_32) return Unsigned_32;

   pragma Inline (F0);

   function F1 (B, C, D : Unsigned_32) return Unsigned_32;

   pragma Inline (F1);

   function F2 (B, C, D : Unsigned_32) return Unsigned_32;

   pragma Inline (F2);

   function F3 (B, C, D : Unsigned_32) return Unsigned_32;

   pragma Inline (F3);

   --------

   -- F0 --

   --------

   function F0

     (B, C, D : Interfaces.Unsigned_32) return Interfaces.Unsigned_32

   is

   begin

      return (B and C) or ((not B) and D);

   end F0;

   --------

   -- F1 --

   --------

   function F1

     (B, C, D : Interfaces.Unsigned_32) return Interfaces.Unsigned_32

   is

   begin

      return B xor C xor D;

   end F1;

   --------

   -- F2 --

   --------

   function F2

     (B, C, D : Interfaces.Unsigned_32) return Interfaces.Unsigned_32

   is

   begin

      return (B and C) or (B and D) or (C and D);

   end F2;

   --------

   -- F3 --

   --------

   function F3

     (B, C, D : Interfaces.Unsigned_32) return Interfaces.Unsigned_32

     renames F1;

   ---------------

   -- Transform --

   ---------------

   procedure Transform

     (H : in out Hash_State.State;

      M : in out Message_State)

   is

      use System;

      type Words is array (Natural range <>) of Interfaces.Unsigned_32;

      X : Words (0 .. 15);

      for X'Address use M.Buffer'Address;

      pragma Import (Ada, X);

      W : Words (0 .. 79);

      A, B, C, D, E, Temp : Interfaces.Unsigned_32;

   begin

      if Default_Bit_Order /= High_Order_First then

         for J in X'Range loop

            Swap4 (X (J)'Address);

         end loop;

      end if;

      --  a. Divide data block into sixteen words

      W (0 .. 15) := X;

      --  b. Prepare working block of 80 words

      for T in 16 .. 79 loop

         --  W(t) = S^1(W(t-3) XOR W(t-8) XOR W(t-14) XOR W(t-16))

         W (T) := Rotate_Left

           (W (T - 3) xor W (T - 8) xor W (T - 14) xor W (T - 16), 1);

      end loop;

      --  c. Set up transformation variables

      A := H (0);

      B := H (1);

      C := H (2);

      D := H (3);

      E := H (4);

      --  d. For each of the 80 rounds, compute:

      --  TEMP = S^5(A) + f(t;B,C,D) + E + W(t) + K(t);

      --  E = D;  D = C;  C = S^30(B);  B = A; A = TEMP;

      for T in 0 .. 19 loop

         Temp := Rotate_Left (A, 5) + F0 (B, C, D) + E + W (T) + 16#5A827999#;

         E := D; D := C; C := Rotate_Left (B, 30); B := A; A := Temp;

      end loop;

      for T in 20 .. 39 loop

         Temp := Rotate_Left (A, 5) + F1 (B, C, D) + E + W (T) + 16#6ED9EBA1#;

         E := D; D := C; C := Rotate_Left (B, 30); B := A; A := Temp;

      end loop;

      for T in 40 .. 59 loop

         Temp := Rotate_Left (A, 5) + F2 (B, C, D) + E + W (T) + 16#8F1BBCDC#;

         E := D; D := C; C := Rotate_Left (B, 30); B := A; A := Temp;

      end loop;

      for T in 60 .. 79 loop

         Temp := Rotate_Left (A, 5) + F3 (B, C, D) + E + W (T) + 16#CA62C1D6#;

         E := D; D := C; C := Rotate_Left (B, 30); B := A; A := Temp;

      end loop;

      --  e. Update context:

      --  H0 = H0 + A, H1 = H1 + B, H2 = H2 + C, H3 = H3 + D, H4 = H4 + E

      H (0) := H (0) + A;

      H (1) := H (1) + B;

      H (2) := H (2) + C;

      H (3) := H (3) + D;

      H (4) := H (4) + E;

   end Transform;

end GNAT.Secure_Hashes.SHA1;