int ntfs_get_size_for_mapping_pairs (const ntfs_volume * vol, const runlist_element * rl, const VCN first_vcn, const VCN last_vcn);
Walk the locked runlist rl and calculate the size in bytes of the mapping pairs array corresponding to the runlist rl, starting at vcn first_vcn and finishing with vcn last_vcn.
A last_vcn of -1 means end of runlist and in that case the size of the mapping pairs array corresponding to the runlist starting at vcn first_vcn and finishing at the end of the runlist is determined.
This for example allows us to allocate a buffer of the right size when building the mapping pairs array.
If rl is NULL, just return 1 (for the single terminator byte).
Return the calculated size in bytes on success. On error, return -errno.
-EINVAL - Run list contains unmapped elements. Make sure to only pass fully mapped runlists to this function. -EIO - The runlist is corrupt.
rl must be locked on entry (either for reading or writing), it remains locked throughout, and is left locked upon return.