#include "bitstream.h"


static const int BITS_PER_CHAR = 8;

// Return bit at position pos in a packed set of bits (pack)
int getBit( char pack, int pos )
{
    return ( pack & ( 1 << pos ) ) ? 1 : 0;
}

// Set bit at position pos in a packed set of bits (pack)
void setBit( char & pack, int pos, int val )
{
    if( val == 1 )
        pack |= ( val << pos );
}

// Construct the bit-input stream
ibstream::ibstream( istream & is )
  : bufferPos( BITS_PER_CHAR ), in( is )
{
}

// Read one bit
int ibstream::readBit( )
{
    if( bufferPos == BITS_PER_CHAR )
    {
        in.get( buffer );
        if( in.eof( ) )
            return EOF;
        bufferPos = 0;
    }

    return getBit( buffer, bufferPos++ );
}

// Return underlying input stream
istream & ibstream::getInputStream( ) const
{
    return in;
}


// Construct the bit-output stream
obstream::obstream( ostream & os ) 
  : bufferPos( 0 ), buffer( 0 ), out( os )
{
}

// Destructor (writes any bits left in the buffer)
obstream::~obstream( )
{
    flush( );
}

// If the buffer is non-empty, write one more char
void obstream::flush( )
{
    if( bufferPos == 0 )   // If buffer is empty
        return;            // Nothing to do
    out.put( buffer );     // Write the buffer
    bufferPos = 0;         // Reset the position
    buffer = 0;            // Clear the buffer

}

// Write one bit
void obstream::writeBit( int val )
{
    setBit( buffer, bufferPos++, val );
    if( bufferPos == BITS_PER_CHAR )
        flush( );
}

// Write a vector of bits
void obstream::writeBits( const vector<int> & val )
{
    for( int i = 0; i < val.size( ); i++ )
        writeBit( val[ i ] );
}

// Return underlying output stream
ostream & obstream::getOutputStream( ) const
{
    return out;
}