@
SILdoc(`Calculate a size of data referenced by snapshots in the inclusive range between the firstsnap and the lastsnap and not shared with any other datasets.
Params:
string firstSnap: the name of the first snapshot in the range.
string lastSnap: the name of the last snapshot in the range.
Returns:
ulong: the calculated stream size, in bytes.
Errors:
SnapshotNotFound: if either of the snapshots does not exist.
NameInvalid: if the name of either snapshot is invalid.
NameTooLong: if the name of either snapshot is too long.
SnapshotMismatch: if fromsnap is not an ancestor snapshot of snapname
PoolsDiffer: if the snapshots belong to different pools.
snapRangeSpace calculates total size of blocks that exist because they are referenced only by one or more snapshots in the given range but no other dataset. In other words, this is the set of blocks that were born after the snap before firstsnap, and died before the snap after the last snap. Yet another interpretation is that the result of snapRangeSpace is the size of the space that would be freed if the snapshots in the range are destroyed. If the same snapshot is given as both the firstSnap and the lastSnap then snapRangeSpace calculates space used by the snapshot.
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