encfs/base/ConfigVar.cpp

/*****************************************************************************
 * Author:   Valient Gough <vgough@pobox.com>
 *
 *****************************************************************************
 * Copyright (c) 2004, Valient Gough
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "base/ConfigVar.h"
#include "base/Error.h"

#include <glog/logging.h>
#include <cstring>

namespace encfs {

#ifndef MIN
inline int MIN(int a, int b)
{
  return (a < b) ? a : b;
}
#endif


ConfigVar::ConfigVar()
    : pd( new ConfigVarData )
{
  pd->offset = 0;
}

ConfigVar::ConfigVar(const std::string &buf)
    : pd( new ConfigVarData )
{
  pd->buffer = buf;
  pd->offset = 0;
}

ConfigVar::ConfigVar(const ConfigVar &src)
{
  pd = src.pd;
}

ConfigVar::~ConfigVar()
{
  pd.reset();
}

ConfigVar & ConfigVar::operator = (const ConfigVar &src)
{
  if(src.pd == pd)
    return *this;
  else
    pd = src.pd;

  return *this;
}

void ConfigVar::resetOffset()
{
  pd->offset = 0;
}

int ConfigVar::read(byte *buffer_, int bytes) const
{
  int toCopy = MIN( bytes, pd->buffer.size() - pd->offset );

  if(toCopy > 0)
    memcpy( buffer_, pd->buffer.data() + pd->offset, toCopy );

  pd->offset += toCopy;

  return toCopy;
}

int ConfigVar::write(const byte *data, int bytes)
{
  if(pd->buffer.size() == (unsigned int)pd->offset)
  {
    pd->buffer.append( (const char *)data, bytes );
  } else
  {
    pd->buffer.insert( pd->offset, (const char *)data, bytes );
  }

  pd->offset += bytes;

  return bytes;
}

int ConfigVar::size() const
{
  return pd->buffer.size();
}

const char *ConfigVar::buffer() const
{
  return pd->buffer.data();
}

int ConfigVar::at() const
{
  return pd->offset;
}

void ConfigVar::writeString(const char *data, int bytes)
{
  writeInt( bytes );
  write( (const byte *)data, bytes );
}


// convert integer to BER encoded integer
void ConfigVar::writeInt(int val)
{
  // we can represent 7 bits per char output, so a 32bit number may take up
  // to 5 bytes.
  // first byte:    0x0000007f                                   0111,1111
  // second byte:   0x00003f80                         0011,1111 1000,0000
  // third byte:    0x001fb000     0000,0000 0001,1111 1100,0000 0000,0000
  // fourth byte:   0x0fe00000     0000,1111 1110,0000
  // fifth byte:    0xf0000000     1111,0000
  byte digit[5];

  digit[4] =        (byte)((val & 0x0000007f));
  digit[3] = 0x80 | (byte)((val & 0x00003f80) >> 7);
  digit[2] = 0x80 | (byte)((val & 0x001fc000) >> 14);
  digit[1] = 0x80 | (byte)((val & 0x0fe00000) >> 21);
  digit[0] = 0x80 | (byte)((val & 0xf0000000) >> 28);

  // find the starting point - we only need to output starting at the most
  // significant non-zero digit..
  int start = 0;
  while(digit[start] == 0x80)
    ++start;

  write( digit + start, 5-start );
}

int ConfigVar::readInt() const
{
  const byte * buf = (const byte *)buffer();
  int bytes = this->size();
  int offset = at();
  int value = 0;
  bool highBitSet;

  rAssert( offset < bytes );

  do
  {
    byte tmp = buf[offset++];
    highBitSet = tmp & 0x80;

    value = (value << 7) | (int)(tmp & 0x7f);
  } while(highBitSet && offset < bytes);

  pd->offset = offset;

  // should never end up with a negative number..
  rAssert( value >= 0 );

  return value;
}

int ConfigVar::readInt( int defaultValue ) const
{
  int bytes = this->size();
  int offset = at();

  if(offset >= bytes)
    return defaultValue;
  else
    return readInt();
}

bool ConfigVar::readBool( bool defaultValue ) const
{
  int tmp = readInt( defaultValue ? 1 : 0 );
  return (tmp != 0);
}

ConfigVar & operator << (ConfigVar &src, bool value)
{
  src.writeInt( value ? 1 : 0 );
  return src;
}

ConfigVar & operator << (ConfigVar &src, int var)
{
  src.writeInt( var );
  return src;
}

ConfigVar & operator << (ConfigVar &src, const std::string &str)
{
  src.writeString( str.data(), str.length() );
  return src;
}

const ConfigVar & operator >> (const ConfigVar &src, bool &result)
{
  int tmp = src.readInt();
  result = (tmp != 0);
  return src;
}

const ConfigVar & operator >> (const ConfigVar &src, int &result)
{
  result = src.readInt();
  return src;
}

const ConfigVar & operator >> (const ConfigVar &src, std::string &result)
{
  int length = src.readInt();
  LOG_IF(WARNING, length <= 0) << "Invalid config length " << length;

  int readLen;

  byte tmpBuf[32];
  if(length > (int)sizeof(tmpBuf))
  {
    byte *ptr = new byte[length];
    readLen = src.read( ptr, length );
    result.assign( (char*)ptr, length );
    delete[] ptr;
  } else
  {
    readLen = src.read( tmpBuf, length );
    result.assign( (char*)tmpBuf, length );
  }

  if(readLen != length)
  {
    VLOG(1) << "string encoded as size " << length 
        << " bytes, read " << readLen;
  }

  rAssert(readLen == length);

  return src;
}

}  // namespace encfs