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.TH "GET_NR_FREE_CLUSTERS" "9" "09 October 2005" "" ""

.SH NAME
get_nr_free_clusters \- return the number of free clusters on a volume
.SH SYNOPSIS
"SYNOPSIS"
.sp
\fB
.sp
s64 get_nr_free_clusters  (ntfs_volume * \fIvol\fB);
\fR
.SH "ARGUMENTS"
.TP
\fB\fIvol\fB\fR
ntfs volume for which to obtain free cluster count
.SH "DESCRIPTION"
.PP
Calculate the number of free clusters on the mounted NTFS volume \fIvol\fR\&. We
actually calculate the number of clusters in use instead because this
allows us to not care about partial pages as these will be just zero filled
and hence not be counted as allocated clusters.
.PP
The only particularity is that clusters beyond the end of the logical ntfs
volume will be marked as allocated to prevent errors which means we have to
discount those at the end. This is important as the cluster bitmap always
has a size in multiples of 8 bytes, i.e. up to 63 clusters could be outside
the logical volume and marked in use when they are not as they do not exist.
.PP
If any pages cannot be read we assume all clusters in the erroring pages are
in use. This means we return an underestimate on errors which is better than
an overestimate.