diffbits is an experimental library focused on providing and applying patches between sequences of
bytes that differ in relatively few bit positions. For example, this may be effective when used on
two related bloom filters. The diff output should be highly compressible in these situations.
Currently, diffbits cannot handle inputs larger than 536870911 bytes (4GB / 8 - 1). Additionally,
if given two inputs that differ more substantially than at a fraction of bit indices, diffbits is
unlikely to perform well.
diffbits runs in linear time with respect to the lengths of its inputs.
Given a left sequence of bytes and a right sequence of bytes (before/after,
current/next, etc.), diffbits expresses the difference between these inputs as a series of
4-byte big-endian integers (i.e. the bytes that appear earlier are more significant than the bytes
that appear later in each set of 4 bytes). The first integer is the byte length of the right
sequence of bytes. The second integer is the bit index of the first bit that differs in the inputs.
Every integer thereafter is the difference from the previous different bit index to the next
different bit index. Each 8-bit byte is treated as little-endian - bits that appear "earlier"
(starting from the right) in the byte have a lower index than bits that appear "later". For example,
in the byte 0b0010_0000, the set bit has index 5.
For example, consider the two byte sequences [0xff, 0xfa] and [0xff, 0xf8, 0x03]. The length of
the right is 3, or [0x00, 0x00, 0x00, 0x03] encoded as 4 big-endian bytes. The first differing
bit is at index 9. The next differing bit is 7 bits after that bit. The final differing bit is 1 bit
after that. The final output is [0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x09, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x01].
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