oracular (3) mtree_diff_map.3.gz

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)