{*****************************************************************************
  The DEC team (see file NOTICE.txt) licenses this file
  to you under the Apache License, Version 2.0 (the
  "License"); you may not use this file except in compliance
  with the License. A copy of this licence is found in the root directory
  of this project in the file LICENCE.txt or alternatively at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing,
  software distributed under the License is distributed on an
  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  KIND, either express or implied.  See the License for the
  specific language governing permissions and limitations
  under the License.
*****************************************************************************}

/// <summary>
///   Utility functions
/// </summary>
unit DECUtil;

interface

{$INCLUDE DECOptions.inc}

uses
  {$IFDEF FPC}
  SysUtils, Classes;
  {$ELSE}
  System.SysUtils, System.Classes;
  {$ENDIF}

type
  // Exception Classes

  /// <summary>
  ///   Base exception class for all DEC specific exceptions,
  /// </summary>
  EDECException       = class(Exception)
  public
    {$IFDEF FMXTranslateableExceptions}
    /// <summary>
    ///   Creates the exception instance and makes the exception message translateable
    ///   via Firemonkey's TLang translation mechanism. Normal ressource strings
    ///   are not translated in the same way on mobile platforms as they are on
    ///   Win32/Win64.
    /// </summary>
    /// <param name="Msg">
    ///   String with a failure message to be output or logged
    /// </param>
    constructor Create(const Msg: string); reintroduce; overload;
    /// <summary>
    ///   Creates the exception instance and makes the exception message translateable
    ///   via Firemonkey's TLang translation mechanism. Normal ressource strings
    ///   are not translated in the same way on mobile platforms as they are on
    ///   Win32/Win64.
    /// </summary>
    /// <param name="Msg">
    ///   String with a failure message to be output or logged
    /// </param>
    /// <param name="Args">
    ///   Array with values for the parameters specified in the format string
    /// </param>
    constructor CreateFmt(const Msg: string;
                          const Args: array of const); reintroduce; overload;
    {$ENDIF}
  end;

  /// <summary>
  ///   Exception class used when reporting that a class searched in a list is
  ///   not contained in that list, e.g. when searching for a non existant
  ///   formatting class.
  /// </summary>
  EDECClassNotRegisteredException = class(EDECException);
  /// <summary>
  ///   Exception class for reporting formatting related exceptions
  /// </summary>
  EDECFormatException = class(EDECException);
  /// <summary>
  ///   Exception class for reporting exceptions related to hash functions
  /// </summary>
  EDECHashException   = class(EDECException);
  /// <summary>
  ///   Exception class for reporting encryption/decryption caused exceptions
  /// </summary>
  EDECCipherException = class(EDECException);

  /// <summary>
  ///   Exception class for reporting the use of abstract things which cannot
  ///   be called directly
  /// </summary>
  EDECAbstractError = class(EDECException)
    /// <summary>
    ///   Create the exception using a meaningfull error message
    /// </summary>
    constructor Create(ClassName: string); overload;
  end;

  /// <summary>
  ///   Reason for calling the progress event
  /// </summary>
  TDECProgressState = (Started, Processing, Finished {, Error});

  /// <summary>
  ///   Event type used by several hash- and cipher methods to display their
  ///   progress. It can be implemented as regular method, procedure and as
  ///   anonymous method, means: in place.
  /// </summary>
  /// <param name="Size">
  ///   Number of bytes to process. For files this is usually the file size. For
  ///   streams this can be less than the stream size if the stream is not being
  ///   processed from the beginning.
  /// </param>
  /// <param name="Pos">
  ///   Position within size in byte. For streams this may be a position
  ///   relative to the starting position for processing.
  /// </param>
  TDECProgressEvent = reference to procedure(Size, Pos: Int64; State: TDECProgressState);

// Byte Ordering

/// <summary>
///   Reverses all bits in the passed value, 1111 0000 will be 0000 1111 afterwards
/// </summary>
/// <param name="Source">
///   Value who's bits are to be reversed
/// </param>
/// <returns>
///   Representation of Source but with all bits reversed
/// </returns>
function ReverseBits(Source: UInt32): UInt32; overload;

/// <summary>
///   Reverses all bits in the passed value, 1111 0000 will be 0000 1111 afterwards
/// </summary>
/// <param name="Source">
///   Value who's bits are to be reversed
/// </param>
/// <returns>
///   Representation of Source but with all bits reversed
/// </returns>
function ReverseBits(Source: UInt8): UInt8; overload;

/// <summary>
///   Reverses the order of the bytes contained in the buffer passed in.
///   e.g. 1 2 3 will be 3 2 1 afterwards
/// </summary>
/// <param name="Buffer">
///   Buffer who's contents is to be reversed.
/// </param>
/// <param name="Size">
///   Size of the passed buffer in byte
/// </param>
procedure SwapBytes(var Buffer; Size: Integer);
/// <summary>
///   Reverses the byte order of the passed variable
/// </summary>
/// <param name="Source">
///   value who's byte order shall be reversed
/// </param>
/// <returns>
///   value of the passed vallue with reversed byte order
/// </returns>
function  SwapUInt32(Source: UInt32): UInt32;
/// <summary>
///   Reverses the byte order for all entries of a passed array of UInt32 values
/// </summary>
/// <param name="Source">
///   Data with a layout like an array of UInt32 values for which the byte order
///   of all entries shall be reversed
/// </param>
/// <param name="Dest">
///   In this variable the reversed values will be stored. Layout is like an
///   array of UInt32 values
/// </param>
/// <param name="Count">
///   Number of values to be reversed
/// </param>
procedure SwapUInt32Buffer(const Source; var Dest; Count: Integer);
/// <summary>
///   Reverses the byte order of an Int64 value
/// </summary>
/// <param name="Source">
///   Value who's byte order shall be reversed
/// </param>
/// <returns>
///   Representation of the passed value after reversing its byte order
/// </returns>
function  SwapInt64(Source: Int64): Int64;
/// <summary>
///   Reverses the byte order for all entries of a passed array of Int64 values
/// </summary>
/// <param name="Source">
///   Data with a layout like an array of Int64 values for which the byte order
///   of all entries shall be reversed
/// </param>
/// <param name="Dest">
///   In this variable the reversed values will be stored. Layout is like an
///   array of Int64 values
/// </param>
/// <param name="Count">
///   Number of values to be reversed
/// </param>
procedure SwapInt64Buffer(const Source; var Dest; Count: Integer);

/// <summary>
///   XORs the contents of two passed buffers and stores the result into a 3rd one
/// </summary>
/// <param name="Left">
///   One source buffer of bytes to be XORed
/// </param>
/// <param name="Right">
///   The other source buffer of bytes to be XORed. Buffer size must be equal
///   or bigger than Left
/// </param>
/// <param name="Size">
///   Buffer size in byte.
/// </param>
/// <param name="Dest">
///   Buffer where the result is to be stored in. Must be of equal or bigger
///   size than Left
/// </param>
procedure XORBuffers(const Left, Right; Size: Integer; var Dest);

// Buffer and Data Protection

/// <summary>
///   Fills a given buffer with zeros in a secure way
/// </summary>
/// <param name="Buffer">
///   Buffer to be zeroed. In case of TBytes to be passed as Buf[0]
/// </param>
/// <param name="Size">
///   Buffer size in byte
/// </param>
procedure ProtectBuffer(var Buffer; Size: NativeUInt);
/// <summary>
///   Fills a given stream with zeros in a secure way
/// </summary>
/// <param name="Stream">
///   Stream to be zeroed.
/// </param>
/// <param name="SizeToProtect">
///   Number of bytes of that stream to be zeroed. Starting point is Stream.Position
/// </param>
procedure ProtectStream(Stream: TStream; SizeToProtect: Int64 = 0);
/// <summary>
///   Fills a given byte array with zeros in a secure way and then empties the
///   buffer.
/// </summary>
/// <param name="Source">
///   Byte array to be zeroed. The length of the passed buffer is 0 afterwards!
/// </param>
procedure ProtectBytes(var Source: TBytes);

/// <summary>
///   Overwrites the string's contents in a secure way and returns an empty string.
/// </summary>
/// <param name="Source">
///   String to be safely overwritten
/// </param>
procedure ProtectString(var Source: string); overload;

/// <summary>
///   Overwrites the string's contents in a secure way and returns an empty string.
/// </summary>
/// <param name="Source">
///   String to be safely overwritten
/// </param>
procedure ProtectString(var Source: RawByteString); overload;

{$IFDEF ANSISTRINGSUPPORTED}
/// <summary>
///   Overwrites the string's contents in a secure way and returns an empty string.
/// </summary>
/// <param name="Source">
///   String to be safely overwritten
/// </param>
procedure ProtectString(var Source: AnsiString); overload;
{$ENDIF}

{$IFNDEF NEXTGEN}
/// <summary>
///   Overwrites the string's contents in a secure way and returns an empty string.
/// </summary>
/// <param name="Source">
///   String to be safely overwritten
/// </param>
procedure ProtectString(var Source: WideString); overload;
{$ENDIF}

// Byte/String conversion

/// <summary>
///   Converts a byte array to a RawByteString
/// </summary>
/// <param name="Source">
///   Byte array to be converted into a string. An empty byte array is allowed
///   and results in an empty string.
/// </param>
/// <returns>
///   RawByteString with the same length as Source and all bytes copied over.
///   No conversion of any sort is being applied to the bytes.
/// </returns>
/// <remarks>
///   Not easily replaced by some RTL function as none for TBytes to RawByteString
///   seems to exist
/// </remarks>
function BytesToRawString(const Source: TBytes): RawByteString;

implementation

{$IFDEF FMXTranslateableExceptions}
uses
  FMX.Types,
{$ELSE}
uses
{$ENDIF}
  DECUtilRawByteStringHelper, DECTypes;

const
{ TODO :
Prüfen warum das eine Konstante ist, die gleich vom Ressourcestring
benutzt wird. Weil es keine Ressorcestrings bei FMX gibt? }
  cAbstractError = 'Abstract Error: %s is not implemented';

resourcestring
  sAbstractError = cAbstractError;

const
  // Bit Lookup Table - see 'Bit Twiddling Hacks' by Sean Eron Anderson
  // http://graphics.stanford.edu/~seander/bithacks.html
  ReverseBitLookupTable256: array[0..255] of Byte = ($00, $80, $40, $C0,
   $20, $A0, $60, $E0, $10, $90, $50, $D0, $30, $B0, $70, $F0, $08, $88,
   $48, $C8, $28, $A8, $68, $E8, $18, $98, $58, $D8, $38, $B8, $78, $F8,
   $04, $84, $44, $C4, $24, $A4, $64, $E4, $14, $94, $54, $D4, $34, $B4,
   $74, $F4, $0C, $8C, $4C, $CC, $2C, $AC, $6C, $EC, $1C, $9C, $5C, $DC,
   $3C, $BC, $7C, $FC, $02, $82, $42, $C2, $22, $A2, $62, $E2, $12, $92,
   $52, $D2, $32, $B2, $72, $F2, $0A, $8A, $4A, $CA, $2A, $AA, $6A, $EA,
   $1A, $9A, $5A, $DA, $3A, $BA, $7A, $FA, $06, $86, $46, $C6, $26, $A6,
   $66, $E6, $16, $96, $56, $D6, $36, $B6, $76, $F6, $0E, $8E, $4E, $CE,
   $2E, $AE, $6E, $EE, $1E, $9E, $5E, $DE, $3E, $BE, $7E, $FE, $01, $81,
   $41, $C1, $21, $A1, $61, $E1, $11, $91, $51, $D1, $31, $B1, $71, $F1,
   $09, $89, $49, $C9, $29, $A9, $69, $E9, $19, $99, $59, $D9, $39, $B9,
   $79, $F9, $05, $85, $45, $C5, $25, $A5, $65, $E5, $15, $95, $55, $D5,
   $35, $B5, $75, $F5, $0D, $8D, $4D, $CD, $2D, $AD, $6D, $ED, $1D, $9D,
   $5D, $DD, $3D, $BD, $7D, $FD, $03, $83, $43, $C3, $23, $A3, $63, $E3,
   $13, $93, $53, $D3, $33, $B3, $73, $F3, $0B, $8B, $4B, $CB, $2B, $AB,
   $6B, $EB, $1B, $9B, $5B, $DB, $3B, $BB, $7B, $FB, $07, $87, $47, $C7,
   $27, $A7, $67, $E7, $17, $97, $57, $D7, $37, $B7, $77, $F7, $0F, $8F,
   $4F, $CF, $2F, $AF, $6F, $EF, $1F, $9F, $5F, $DF, $3F, $BF, $7F, $FF);

function ReverseBits(Source: UInt32): UInt32;
begin
  Result := (ReverseBitLookupTable256[Source and $FF] shl 24) or
            (ReverseBitLookupTable256[(Source shr 8) and $FF] shl 16) or
            (ReverseBitLookupTable256[(Source shr 16) and $FF] shl 8) or
            (ReverseBitLookupTable256[(Source shr 24) and $FF]);
end;

function ReverseBits(Source: UInt8): UInt8;
begin
  Result := ReverseBitLookupTable256[Source];
end;

procedure SwapBytes(var Buffer; Size: Integer);
{$IFDEF X86ASM}
asm
      CMP     EDX,1
      JLE     @@3
      AND     EAX,EAX
      JZ      @@3
      PUSH    EBX
      MOV     ECX,EDX
      LEA     EDX,[EAX + ECX - 1]
      SHR     ECX,1
@@1:  MOV     BL,[EAX]
      XCHG    BL,[EDX]
      DEC     EDX
      MOV     [EAX],BL
      INC     EAX
      DEC     ECX
      JNZ     @@1
@@2:  POP     EBX
@@3:
end;
{$ELSE !X86ASM}
var
  T: Byte;
  P, Q: PByte;
  i: Integer;
begin
  P := @Buffer;
  Inc(P, Size - 1);
  Q := @Buffer;
  for i := 0 to Size div 2 - 1 do // using P/Q comparison with 'while' breaks some compilers
  begin
    T := Q^;
    Q^ := P^;
    P^ := T;
    Dec(P);
    Inc(Q);
  end;
end;
{$ENDIF !X86ASM}

function SwapUInt32(Source: UInt32): UInt32;
{$IF defined(X86ASM) or defined(X64ASM)}
  asm
  {$IFDEF X64ASM}
    MOV   EAX, ECX
  {$ENDIF X64ASM}
    BSWAP EAX
  end;
{$ELSE PUREPASCAL}
begin
  Result := Source shl 24 or
            Source shr 24 or
            Source shl 8 and $00FF0000 or
            Source shr 8 and $0000FF00;
end;
{$IFEND PUREPASCAL}

procedure SwapUInt32Buffer(const Source; var Dest; Count: Integer);
{$IFDEF X86ASM}
asm
      TEST    ECX,ECX
      JLE     @Exit
      PUSH    EDI
      SUB     EAX,4
      SUB     EDX,4
@@1:  MOV     EDI,[EAX + ECX * 4]
      BSWAP   EDI
      MOV     [EDX + ECX * 4],EDI
      DEC     ECX
      JNZ     @@1
      POP     EDI
@Exit:
end;
{$ELSE !X86ASM}
var
  i: Integer;
  T: UInt32;
begin
  for i := 0 to Count - 1 do
  begin
    T := TUInt32Array(Source)[i];
    TUInt32Array(Dest)[i] := (T shl 24) or (T shr 24) or
                           ((T shl 8) and $00FF0000) or ((T shr 8) and $0000FF00);
  end;
end;
{$ENDIF !X86ASM}

function SwapInt64(Source: Int64): Int64;
{$IFDEF X86ASM}
asm
      MOV     EDX,Source.DWord[0]
      MOV     EAX,Source.DWord[4]
      BSWAP   EDX
      BSWAP   EAX
end;
{$ELSE !X86ASM}
var
  L, H: Cardinal;
begin
  L := Int64Rec(Source).Lo;
  H := Int64Rec(Source).Hi;
  L := L shl 24 or L shr 24 or L shl 8 and $00FF0000 or L shr 8 and $0000FF00;
  H := H shl 24 or H shr 24 or H shl 8 and $00FF0000 or H shr 8 and $0000FF00;
  Int64Rec(Result).Hi := L;
  Int64Rec(Result).Lo := H;
end;
{$ENDIF !X86ASM}

procedure SwapInt64Buffer(const Source; var Dest; Count: Integer);
{$IFDEF X86ASM}
asm
      TEST    ECX,ECX
      JLE     @Exit
      PUSH    ESI
      PUSH    EDI
      LEA     ESI,[EAX + ECX * 8]
      LEA     EDI,[EDX + ECX * 8]
      NEG     ECX
@@1:  MOV     EAX,[ESI + ECX * 8]
      MOV     EDX,[ESI + ECX * 8 + 4]
      BSWAP   EAX
      BSWAP   EDX
      MOV     [EDI + ECX * 8 + 4],EAX
      MOV     [EDI + ECX * 8],EDX
      INC     ECX
      JNZ     @@1
      POP     EDI
      POP     ESI
@Exit:
end;
{$ELSE !X86ASM}
var
  H, L: Cardinal;
  i: Integer;
begin
  for i := 0 to Count - 1 do
  begin
    H := TUInt32Array(Source)[i * 2    ];
    L := TUInt32Array(Source)[i * 2 + 1];
    TUInt32Array(Dest)[i * 2    ] := L shl 24 or L shr 24 or L shl 8 and $00FF0000 or L shr 8 and $0000FF00;
    TUInt32Array(Dest)[i * 2 + 1] := H shl 24 or H shr 24 or H shl 8 and $00FF0000 or H shr 8 and $0000FF00;
  end;
end;
{$ENDIF !X86ASM}

procedure XORBuffers(const Left, Right; Size: Integer; var Dest);
// Dest^ = Source1^ xor Source2^
// Buffers must have the same size!
{$IFDEF X86ASM}
asm
      AND     ECX,ECX
      JZ      @@5
      PUSH    ESI
      PUSH    EDI
      MOV     ESI,EAX
      MOV     EDI,Dest
@@1:  TEST    ECX,3
      JNZ     @@3
@@2:  SUB     ECX,4
      JL      @@4
      MOV     EAX,[ESI + ECX]
      XOR     EAX,[EDX + ECX]
      MOV     [EDI + ECX],EAX
      JMP     @@2
@@3:  DEC     ECX
      MOV     AL,[ESI + ECX]
      XOR     AL,[EDX + ECX]
      MOV     [EDI + ECX],AL
      JMP     @@1
@@4:  POP     EDI
      POP     ESI
@@5:
end;
{$ELSE !X86ASM}
var
  P, Q, D: PByte;
  i: Integer;
begin
  P := @Left;
  Q := @Right;
  D := @Dest;
  for i := 0 to Size - 1 do
  begin
    D^ := P^ xor Q^;
    Inc(P);
    Inc(Q);
    Inc(D);
  end;
end;
{$ENDIF !X86ASM}

const
  WipeCount = 4;
  WipeBytes: array[0..WipeCount - 1] of Byte = (
    $55, // 0101 0101
    $AA, // 1010 1010
    $FF, // 1111 1111
    $00  // 0000 0000
  );

procedure ProtectBuffer(var Buffer; Size: NativeUInt);
var
  Count: Integer;
begin
  if Size > 0 then
  begin
    for Count := 0 to WipeCount - 1 do
      FillChar(Buffer, Size, WipeBytes[Count]);
  end;
end;

procedure ProtectStream(Stream: TStream; SizeToProtect: Int64 = 0);
const
  BufferSize = 512;
var
  Buffer: string;
  Count, Bytes, Size: Integer;
  Position: Integer;
begin
  Position := Stream.Position;
  Size := Stream.Size;
  if SizeToProtect <= 0 then
  begin
    SizeToProtect := Size;
    Position := 0;
  end else
  begin
    Dec(Size, Position);
    if SizeToProtect > Size then
      SizeToProtect := Size;
  end;
  SetLength(Buffer, BufferSize);
  for Count := 0 to WipeCount -1 do
  begin
    Stream.Position := Position;
    Size := SizeToProtect;
    {$IF CompilerVersion >= 24.0}
    FillChar(Buffer[Low(Buffer)], BufferSize, WipeBytes[Count]);
    {$ELSE}
    FillChar(Buffer[1], BufferSize, WipeBytes[Count]);
    {$IFEND}
    while Size > 0 do
    begin
      Bytes := Size;
      if Bytes > BufferSize then
        Bytes := BufferSize;
      {$IF CompilerVersion >= 24.0}
      Stream.Write(Buffer[Low(Buffer)], Bytes);
      {$ELSE}
      Stream.Write(Buffer[1], Bytes);
      {$IFEND}
      Dec(Size, Bytes);
    end;
  end;
end;

procedure ProtectBytes(var Source: TBytes);
begin
  if (Source <> nil) and (Length(Source) > 0) then
  begin
    ProtectBuffer(Source[0], Length(Source));
    SetLength(Source, 0);
  end;
end;

procedure ProtectString(var Source: string);
begin
  if Length(Source) > 0 then
  begin
    System.UniqueString(Source);
    {$IF CompilerVersion >= 24.0}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[Low(Source)]));
    {$ELSE}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[1]));
    {$IFEND}
    Source := '';
  end;
end;

procedure ProtectString(var Source: RawByteString);
begin
  if Length(Source) > 0 then
  begin
    // UniqueString(Source); cannot be called with a RawByteString as there is
    // no overload for it, so we need to call our own one.
    DECUtilRawByteStringHelper.UniqueString(Source);
    {$IF CompilerVersion >= 24.0}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[Low(Source)]));
    {$ELSE}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[1]));
    {$IFEND}
    Source := '';
  end;
end;

{$IFNDEF NEXTGEN}
procedure ProtectString(var Source: AnsiString); overload;
begin
  if Length(Source) > 0 then
  begin
    System.UniqueString(Source);
    {$IF CompilerVersion >= 24.0}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[Low(Source)]));
    {$ELSE}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[1]));
    {$IFEND}
    Source := '';
  end;
end;

procedure ProtectString(var Source: WideString); overload;
begin
  if Length(Source) > 0 then
  begin
    System.UniqueString(Source); // for OS <> Win, WideString is not RefCounted on Win
    {$IF CompilerVersion >= 24.0}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[Low(Source)]));
    {$ELSE}
    ProtectBuffer(Pointer(Source)^, Length(Source) * SizeOf(Source[1]));
    {$IFEND}
    Source := '';
  end;
end;
{$ENDIF}

function BytesToRawString(const Source: TBytes): RawByteString;
begin
  SetLength(Result, Length(Source));
  if Length(Source) > 0 then
  begin
    // determine lowest string index for handling of ZeroBasedStrings
    {$IF CompilerVersion >= 24.0}
    Move(Source[0], Result[Low(result)], Length(Source));
    {$ELSE}
    Move(Source[0], Result[1], Length(Source));
    {$IFEND}
  end;
end;

{ EDECException }

{$IFDEF FMXTranslateableExceptions}
constructor EDECException.Create(const Msg: string);
begin
  inherited Create(Translate(msg));
end;

constructor EDECException.CreateFmt(const Msg: string;
                                    const Args: array of const);
begin
  inherited Create(Format(Translate(Msg), Args));
end;

constructor EDECAbstractError.Create(ClassName: string);
begin
  inherited Create(Format(Translate(sAbstractError), [ClassName]));
end;
{$ELSE}
constructor EDECAbstractError.Create(ClassName: string);
begin
  inherited CreateResFmt(@sAbstractError, [ClassName]);
end;
{$ENDIF}

end.