A computer implemented method of real-time index generation of data in a data stream during data stream recording to an archive, the method including: receiving a byte of the data stream; and adding an entry for the byte of the data stream to a bitmap index of bytes, the bitmap index indicating, for each possible byte value, a location in the archive of each of occurrences and non-occurrences of the byte value by a sequence of bit values in the bitmap index, wherein the bitmap index includes a count of a number of occurrences for each byte value, wherein a plurality of run length encoding (RLE) schemes are applied to sub-sequences of identical bit values for each byte value in the index, each RLE scheme having a different encoding type identified by an encoding type indicator and indicating a bit value and a number of bits in a sub-sequence, and wherein a pair of RLE encoded sub-sequences of indications of non-occurrence of a byte value implies a single indication of an occurrence of the byte value between the pair.