#data: matrix of double or connection
serialize = function(data_ascii, data_bin_file, nb_per_chunk,
	sep=",", nbytes=4, endian=.Platform$endian)
{
	if (is.character(data_ascii))
		data_ascii = file(data_ascii, open="r")
	else if (is(data_ascii,"connection") && !isOpen(data_ascii))
		open(data_ascii)

	first_write = (!file.exists(data_bin_file) || file.info(data_bin_file)$size == 0)
	data_bin = file(data_bin_file, open=ifelse(first_write,"wb","ab"))

	#write data length on first call
	if (first_write)
	{
		#number of items always on 8 bytes
		writeBin(0L, data_bin, size=8) #,endian="little")
		if (is.matrix(data_ascii))
			data_length = ncol(data_ascii)
		else #if (is(data, "connection"))
		{
			data_line = scan(data_ascii, double(), sep=sep, nlines=1, quiet=TRUE)
			writeBin(data_line, data_bin, size=nbytes)
			data_length = length(data_line)
		}
	}

	if (is.matrix(data_ascii))
		index = 1
	repeat
	{
		if (is.matrix(data_ascii))
		{
			range = index:min(nrow(data_ascii),index+nb_per_chunk)
			data_chunk =
				if (range[1] <= nrow(data_ascii))
					as.double(t(data_ascii[range,]))
				else
					integer(0)
			index = index + nb_per_chunk
		}
		else
			data_chunk = scan(data_ascii, double(), sep=sep, nlines=nb_per_chunk, quiet=TRUE)
		if (length(data_chunk)==0)
			break
		writeBin(data_chunk, data_bin, size=nbytes)
	}

	if (first_write)
	{
		#ecrire file_size-1 / (nbytes*nbWritten) en 0 dans bin_data ! ignored == file_size
		ignored = seek(data_bin, 0)
		writeBin(data_length, data_bin, size=8)
	}
	close(data_bin)

	if (is(data_ascii,"connection"))
		close(data_ascii)
}

#read in binary file, always same structure
getDataInFile = function(indices, data_bin_file, nbytes=4, endian=.Platform$endian)
{
	data_bin = file(data_bin_file, "rb")
	data_length = readBin(data_bin, "integer", 1, 8, endian)
	#Ou t(sapply(...)) (+ rapide ?)
	data_ascii = do.call( rbind, lapply( indices, function(i) {
		ignored = seek(data_bin, 8+((i-1)*data_length*nbytes))
		readBin(data_bin, "double", n=data_length, size=nbytes)
	} ) )
	close(data_bin)
	data_ascii
}