library md5hash;

{ Important note about DLL memory management: ShareMem must be the
  first unit in your library's USES clause AND your project's (select
  Project-View Source) USES clause if your DLL exports any procedures or
  functions that pass strings as parameters or function results. This
  applies to all strings passed to and from your DLL--even those that
  are nested in records and classes. ShareMem is the interface unit to
  the BORLNDMM.DLL shared memory manager, which must be deployed along
  with your DLL. To avoid using BORLNDMM.DLL, pass string information
  using PChar or ShortString parameters. }

uses
    SysUtils
  , Classes
  , Windows
  ;

{$R *.res}

type
 MD5Count = array[0..1] of DWORD;
 MD5State = array[0..3] of DWORD;
 MD5Block = array[0..15] of DWORD;
 MD5CBits = array[0..7] of byte;
 MD5Digest = array[0..15] of byte;
 MD5Buffer = array[0..63] of byte;
 MD5Context = record
   State: MD5State;
   Count: MD5Count;
   Buffer: MD5Buffer;
 end;

var
 PADDING: MD5Buffer = (
   $80, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00
 );

 function F(x, y, z: DWORD): DWORD;
begin
 Result := (x and y) or ((not x) and z);
end;

function G(x, y, z: DWORD): DWORD;
begin
 Result := (x and z) or (y and (not z));
end;

function H(x, y, z: DWORD): DWORD;
begin
 Result := x xor y xor z;
end;

function I(x, y, z: DWORD): DWORD;
begin
 Result := y xor (x or (not z));
end;

procedure rot(var x: DWORD; n: BYTE);
begin
 x := (x shl n) or (x shr (32 - n));
end;

procedure FF(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
 inc(a, F(b, c, d) + x + ac);
 rot(a, s);
 inc(a, b);
end;

procedure GG(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
 inc(a, G(b, c, d) + x + ac);
 rot(a, s);
 inc(a, b);
end;

procedure HH(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
 inc(a, H(b, c, d) + x + ac);
 rot(a, s);
 inc(a, b);
end;

procedure II(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
 inc(a, I(b, c, d) + x + ac);
 rot(a, s);
 inc(a, b);
end;

// ----------

// Encode Count bytes at Source into (Count / 4) DWORDs at Target
procedure Encode(Source, Target: pointer; Count: longword);
var
 S: PByte;
 T: PDWORD;
 I: longword;
begin
 S := Source;
 T := Target;
 for I := 1 to Count div 4 do begin
   T^ := S^;
   inc(S);
   T^ := T^ or (S^ shl 8);
   inc(S);
   T^ := T^ or (S^ shl 16);
   inc(S);
   T^ := T^ or (S^ shl 24);
   inc(S);
   inc(T);
 end;
end;

// Decode Count DWORDs at Source into (Count * 4) Bytes at Target
procedure Decode(Source, Target: pointer; Count: longword);
var
 S: PDWORD;
 T: PByte;
 I: longword;
begin
 S := Source;
 T := Target;
 for I := 1 to Count do begin
   T^ := S^ and $ff;
   inc(T);
   T^ := (S^ shr 8) and $ff;
   inc(T);
   T^ := (S^ shr 16) and $ff;
   inc(T);
   T^ := (S^ shr 24) and $ff;
   inc(T);
   inc(S);
 end;
end;

// Transform State according to first 64 bytes at Buffer
procedure Transform(Buffer: pointer; var State: MD5State);
var
 a, b, c, d: DWORD;
 Block: MD5Block;
begin
 Encode(Buffer, @Block, 64);
 a := State[0];
 b := State[1];
 c := State[2];
 d := State[3];
 FF (a, b, c, d, Block[ 0],  7, $d76aa478);
 FF (d, a, b, c, Block[ 1], 12, $e8c7b756);
 FF (c, d, a, b, Block[ 2], 17, $242070db);
 FF (b, c, d, a, Block[ 3], 22, $c1bdceee);
 FF (a, b, c, d, Block[ 4],  7, $f57c0faf);
 FF (d, a, b, c, Block[ 5], 12, $4787c62a);
 FF (c, d, a, b, Block[ 6], 17, $a8304613);
 FF (b, c, d, a, Block[ 7], 22, $fd469501);
 FF (a, b, c, d, Block[ 8],  7, $698098d8);
 FF (d, a, b, c, Block[ 9], 12, $8b44f7af);
 FF (c, d, a, b, Block[10], 17, $ffff5bb1);
 FF (b, c, d, a, Block[11], 22, $895cd7be);
 FF (a, b, c, d, Block[12],  7, $6b901122);
 FF (d, a, b, c, Block[13], 12, $fd987193);
 FF (c, d, a, b, Block[14], 17, $a679438e);
 FF (b, c, d, a, Block[15], 22, $49b40821);
 GG (a, b, c, d, Block[ 1],  5, $f61e2562);
 GG (d, a, b, c, Block[ 6],  9, $c040b340);
 GG (c, d, a, b, Block[11], 14, $265e5a51);
 GG (b, c, d, a, Block[ 0], 20, $e9b6c7aa);
 GG (a, b, c, d, Block[ 5],  5, $d62f105d);
 GG (d, a, b, c, Block[10],  9,  $2441453);
 GG (c, d, a, b, Block[15], 14, $d8a1e681);
 GG (b, c, d, a, Block[ 4], 20, $e7d3fbc8);
 GG (a, b, c, d, Block[ 9],  5, $21e1cde6);
 GG (d, a, b, c, Block[14],  9, $c33707d6);
 GG (c, d, a, b, Block[ 3], 14, $f4d50d87);
 GG (b, c, d, a, Block[ 8], 20, $455a14ed);
 GG (a, b, c, d, Block[13],  5, $a9e3e905);
 GG (d, a, b, c, Block[ 2],  9, $fcefa3f8);
 GG (c, d, a, b, Block[ 7], 14, $676f02d9);
 GG (b, c, d, a, Block[12], 20, $8d2a4c8a);
 HH (a, b, c, d, Block[ 5],  4, $fffa3942);
 HH (d, a, b, c, Block[ 8], 11, $8771f681);
 HH (c, d, a, b, Block[11], 16, $6d9d6122);
 HH (b, c, d, a, Block[14], 23, $fde5380c);
 HH (a, b, c, d, Block[ 1],  4, $a4beea44);
 HH (d, a, b, c, Block[ 4], 11, $4bdecfa9);
 HH (c, d, a, b, Block[ 7], 16, $f6bb4b60);
 HH (b, c, d, a, Block[10], 23, $bebfbc70);
 HH (a, b, c, d, Block[13],  4, $289b7ec6);
 HH (d, a, b, c, Block[ 0], 11, $eaa127fa);
 HH (c, d, a, b, Block[ 3], 16, $d4ef3085);
 HH (b, c, d, a, Block[ 6], 23,  $4881d05);
 HH (a, b, c, d, Block[ 9],  4, $d9d4d039);
 HH (d, a, b, c, Block[12], 11, $e6db99e5);
 HH (c, d, a, b, Block[15], 16, $1fa27cf8);
 HH (b, c, d, a, Block[ 2], 23, $c4ac5665);
 II (a, b, c, d, Block[ 0],  6, $f4292244);
 II (d, a, b, c, Block[ 7], 10, $432aff97);
 II (c, d, a, b, Block[14], 15, $ab9423a7);
 II (b, c, d, a, Block[ 5], 21, $fc93a039);
 II (a, b, c, d, Block[12],  6, $655b59c3);
 II (d, a, b, c, Block[ 3], 10, $8f0ccc92);
 II (c, d, a, b, Block[10], 15, $ffeff47d);
 II (b, c, d, a, Block[ 1], 21, $85845dd1);
 II (a, b, c, d, Block[ 8],  6, $6fa87e4f);
 II (d, a, b, c, Block[15], 10, $fe2ce6e0);
 II (c, d, a, b, Block[ 6], 15, $a3014314);
 II (b, c, d, a, Block[13], 21, $4e0811a1);
 II (a, b, c, d, Block[ 4],  6, $f7537e82);
 II (d, a, b, c, Block[11], 10, $bd3af235);
 II (c, d, a, b, Block[ 2], 15, $2ad7d2bb);
 II (b, c, d, a, Block[ 9], 21, $eb86d391);
 inc(State[0], a);
 inc(State[1], b);
 inc(State[2], c);
 inc(State[3], d);
end;

// ----------

// Initialize given Context
procedure MD5Init(var Context: MD5Context);
begin
 with Context do begin
   State[0] := $67452301;
   State[1] := $efcdab89;
   State[2] := $98badcfe;
   State[3] := $10325476;
   Count[0] := 0;
   Count[1] := 0;
   ZeroMemory(@Buffer, SizeOf(MD5Buffer));
 end;
end;

// Update given Context to include Length bytes of Input
procedure MD5Update(var Context: MD5Context; Input: pChar; Length: longword);
var
 Index: longword;
 PartLen: longword;
 I: longword;
begin
 with Context do begin
   Index := (Count[0] shr 3) and $3f;
   inc(Count[0], Length shl 3);
   if Count[0] < (Length shl 3) then inc(Count[1]);
   inc(Count[1], Length shr 29);
 end;
 PartLen := 64 - Index;
 if Length >= PartLen then begin
   CopyMemory(@Context.Buffer[Index], Input, PartLen);
   Transform(@Context.Buffer, Context.State);
   I := PartLen;
   while I + 63 < Length do begin
     Transform(@Input[I], Context.State);
     inc(I, 64);
   end;
   Index := 0;
 end else I := 0;
 CopyMemory(@Context.Buffer[Index], @Input[I], Length - I);
end;

// Finalize given Context, create Digest and zeroize Context
procedure MD5Final(var Context: MD5Context; var Digest: MD5Digest);
var
 Bits: MD5CBits;
 Index: longword;
 PadLen: longword;
begin
 Decode(@Context.Count, @Bits, 2);
 Index := (Context.Count[0] shr 3) and $3f;
 if Index < 56 then PadLen := 56 - Index else PadLen := 120 - Index;
 MD5Update(Context, @PADDING, PadLen);
 MD5Update(Context, @Bits, 8);
 Decode(@Context.State, @Digest, 4);
 ZeroMemory(@Context, SizeOf(MD5Context));
end;

// ----------

// Create digest of given Message
function MD5String(M: string): MD5Digest; stdcall;
var
 Context: MD5Context;
begin
 MD5Init(Context);
 MD5Update(Context, pChar(M), length(M));
 MD5Final(Context, Result);
end;

// Create digest of file with given Name
function MD5File(N: string): MD5Digest; stdcall;
var
 FileHandle: THandle;
 MapHandle: THandle;
 ViewPointer: pointer;
 Context: MD5Context;
begin
 MD5Init(Context);
 FileHandle := CreateFile(pChar(N), GENERIC_READ, FILE_SHARE_READ or FILE_SHARE_WRITE,
   nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL or FILE_FLAG_SEQUENTIAL_SCAN, 0);
 if FileHandle <> INVALID_HANDLE_VALUE then try
   MapHandle := CreateFileMapping(FileHandle, nil, PAGE_READONLY, 0, 0, nil);
   if MapHandle <> 0 then try
     ViewPointer := MapViewOfFile(MapHandle, FILE_MAP_READ, 0, 0, 0);
     if ViewPointer <> nil then try
       MD5Update(Context, ViewPointer, GetFileSize(FileHandle, nil));
     finally
       UnmapViewOfFile(ViewPointer);
     end;
   finally
     CloseHandle(MapHandle);
   end;
 finally
   CloseHandle(FileHandle);
 end;
 MD5Final(Context, Result);
end;

// Create hex representation of given Digest
function MD5Print(D: MD5Digest): string; stdcall;
var
 I: byte;
const
 Digits: array[0..15] of char =
   ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f');
begin
 Result := '';
 for I := 0 to 15 do
  begin
   Result := Result + Digits[(D[I] shr 4) and $0f] + Digits[D[I] and $0f];
  end;
end;

// ----------

// Compare two Digests
function MD5Match(D1, D2: MD5Digest): boolean;stdcall;
var
 I: byte;
begin
 I := 0;
 Result := TRUE;
 while Result and (I < 16) do begin
   Result := D1[I] = D2[I];
   inc(I);
 end;
end;


exports
    MD5Match
  , MD5String
  , MD5File
  , MD5Print
  ;

begin
end.