FragmentedWindow::FragmentedWindow()
{
  memset(Mem,0,sizeof(Mem));
  memset(MemSize,0,sizeof(MemSize));
}


FragmentedWindow::~FragmentedWindow()
{
  for (uint I=0;I<ASIZE(Mem);I++)
    if (Mem[I]!=NULL)
      free(Mem[I]);
}


void FragmentedWindow::Init(size_t WinSize)
{
  uint BlockNum=0;
  size_t TotalSize=0; // Already allocated.
  while (TotalSize<WinSize && BlockNum<ASIZE(Mem))
  {
    size_t Size=WinSize-TotalSize; // Size needed to allocate.

    // Minimum still acceptable block size. Next allocations cannot be larger
    // than current, so we do not need blocks if they are smaller than
    // "size left / attempts left". Also we do not waste time to blocks
    // smaller than some arbitrary constant.
    size_t MinSize=Max(Size/(ASIZE(Mem)-BlockNum), 0x400000);

    byte *NewMem=NULL;
    while (Size>=MinSize)
    {
      NewMem=(byte *)malloc(Size);
      if (NewMem!=NULL)
        break;
      Size-=Size/32;
    }
    if (NewMem==NULL)
      throw std::bad_alloc();
    
    // Clean the window to generate the same output when unpacking corrupt
    // RAR files, which may access to unused areas of sliding dictionary.
    memset(NewMem,0,Size);

    Mem[BlockNum]=NewMem;
    TotalSize+=Size;
    MemSize[BlockNum]=TotalSize;
    BlockNum++;
  }
  if (TotalSize<WinSize) // Not found enough free blocks.
    throw std::bad_alloc();
}


byte& FragmentedWindow::operator [](size_t Item)
{
  if (Item<MemSize[0])
    return Mem[0][Item];
  for (uint I=1;I<ASIZE(MemSize);I++)
    if (Item<MemSize[I])
      return Mem[I][Item-MemSize[I-1]];
  return Mem[0][0]; // Must never happen;
}


void FragmentedWindow::CopyString(uint Length,uint Distance,size_t &UnpPtr,size_t MaxWinMask)
{
  size_t SrcPtr=UnpPtr-Distance;
  while (Length-- > 0)
  {
    (*this)[UnpPtr]=(*this)[SrcPtr++ & MaxWinMask];
    // We need to have masked UnpPtr after quit from loop, so it must not
    // be replaced with '(*this)[UnpPtr++ & MaxWinMask]'
    UnpPtr=(UnpPtr+1) & MaxWinMask;
  }
}


void FragmentedWindow::CopyData(byte *Dest,size_t WinPos,size_t Size)
{
  for (size_t I=0;I<Size;I++)
    Dest[I]=(*this)[WinPos+I];
}


size_t FragmentedWindow::GetBlockSize(size_t StartPos,size_t RequiredSize)
{
  for (uint I=0;I<ASIZE(MemSize);I++)
    if (StartPos<MemSize[I])
      return Min(MemSize[I]-StartPos,RequiredSize);
  return 0; // Must never be here.
}
