import logging, os
from cStringIO import StringIO

# Handle efficient operations on a non-fixed length buffer like appending,
# replacing, reading chunks, etc
class ChunkBufferStringIO:
    def __init__( self, data = '' ):
        logging.debug( "Creating chunkbuffer: %s" % data )
        self.io = StringIO();
        self.len = 0
        self.append( data )

    def append( self, s ):
        self.len += len( s )
        self.io.write( s )

    def replace( self, buf, start, end ):
        self.io.seek( start )
        self.io.write( buf[ end - start: ] )
        self.io.seek( 0, os.SEEK_END )

    def length( self ):
        return self.len

    def truncate( self, l ):
        self.len = l
        self.io.truncate( l )

    def string(self):
        return self.io.getvalue()