NAME

       mtree_diff_subtree - compare two subtrees and return bitmap

LIBRARY

       Librecast library (liblibrecast, -llibrecast)

SYNOPSIS

       #include <librecast/mtree.h>

       unsigned char *mtree_diff_subtree(mtree_t *t1, mtree_t *t2, size_t root, unsigned bits);
       unsigned char *mtree_diff_map(mtree_t *t1, mtree_t *t2);

       Compile and link with -llibrecast.

DESCRIPTION

       The  mtree_diff_subtree function performs a bredth-first comparison of the merkle trees t1
       and t2 and returns a pointer to a bitmap, setting bits bits for any  chunks  that  differ.
       bits should be set to the number of packets required to to transport each chunk. When bits
       > 1, chunks will be fragmented into multiple packets, and the bitmap  will  represent  the
       packets required.

       Checking  the popcount (Hamming Weight) of the returned bitmap gives the number of packets
       required to patch the differences.

       The returned bitmap must be freed by the caller  when  no  longer  needed  by  passing  to
       free(3).

       mtree_diff_map() is a convenience wrapper that is the same as calling mtree_diff_subtree()
       with root set to zero (whole tree) and bits set to one. Thus, it returns a bitmap  of  the
       entire tree with a single bit per chunk.

RETURN VALUE

       mtree_verify()  returns  zero  if  the  tree is valid, or NULL on error, with errno set to
       indicate the error.

ERRORS

       ENOMEM Not enough space/cannot allocate memory (POSIX.1-2001).

SEE ALSO

       mtree_init(3), mtree_free(3), mtree_build(3), free(3)