Binary data frame file format about readr HOT 2 CLOSED

Again, lets think about this in the future.

from readr.

A binary data.frame file format where each column is represented as a contiguous file is already existing: ffdf in package ff does exactly this. The meta-data like column names, factor-levels etc. are not stored in the file(s) but in an R-object which points to the file(s). The meta-data can be saved in the usual way with save.image and loaded in a new session, provided automatic file removal has been switched-off appropriately. What ffdf doesnot support are strings (but factors). Furthermore factors with few levels and integers with few values can be represented with less bytes than 4 bytes (down to 2 bits), logicals with 2 bits, booleans with 1 bit. Current restriction: no long vectors, i.e. 2^31.

from readr.