// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// Mobius Forensic Toolkit
// Copyright (C) 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019 Eduardo Aguiar
//
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option) any later
// version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
// Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
#include "reader_impl.h"
#include "exception.h"
#include <mobius/exception.inc>
#include <stdexcept>

namespace mobius
{
namespace filesystem
{
namespace tsk
{
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief constructor
//! \param path path to local file
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
reader_impl::reader_impl (const TSK_FS_ATTR *fs_attr)
  : fs_attr_ (fs_attr), size_ (fs_attr->size)
{
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief set read position
//! \param offset offset in bytes
//! \param w either beginning, current or end
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
reader_impl::seek (offset_type offset, whence_type w)
{
  // calculate offset from the beginning of data
  offset_type abs_offset;

  if (w == whence_type::beginning)
    abs_offset = offset;

  else if (w == whence_type::current)
    abs_offset = pos_ + offset;

  else if (w == whence_type::end)
    abs_offset = size_ - 1 + offset;

  else
    throw std::invalid_argument (mobius::MOBIUS_EXCEPTION_MSG ("invalid whence_type"));

  // update current pos, if possible
  if (abs_offset >= 0 && size_type (abs_offset) < size_)
    pos_ = abs_offset;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief read bytes from reader
//! \param size size in bytes
//! \return bytearray containing data
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::bytearray
reader_impl::read (size_type size)
{
  if (pos_ + size > size_)
    size = size_ - pos_;

  mobius::bytearray data (size);

  if (size > 0)
    {
      ssize_t count = tsk_fs_file_read_type (
                        fs_attr_->fs_file,
                        fs_attr_->type,
                        fs_attr_->id,
                        pos_,
                        reinterpret_cast <char *>(data.data ()),
                        size,
                        TSK_FS_FILE_READ_FLAG_NONE);

      if (count < 0)
        throw MOBIUS_TSK_EXCEPTION;

      if (size_type (count) < size)
        data.resize (count);

      pos_ += count;
    }

  return data;
}

} // namespace tsk
} // namespace filesystem
} // namespace mobius
