befs_iaddrs_per_block
indirblocks = dbl_bruns / befs_iaddrs_per_block(sb);
int arraylen = befs_iaddrs_per_block(sb);
size_t diblklen = iblklen * befs_iaddrs_per_block(sb)
dbl_which_block = dblindir_indx / befs_iaddrs_per_block(sb);
dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb));
which_block = indir_indx / befs_iaddrs_per_block(sb);
block_indx = indir_indx - (which_block * befs_iaddrs_per_block(sb));