=item B<CalcNavigation>( \%nav )

Use these keys from %nav (all values will be rounded by int())

=over 4

=item B<From>

Record which must be shown on current page.
First record number is 1.

=item B<Count>

Shown records per page.

=item B<Records>

Number of last record. 0 - no records.

=item B<DefaultCount>

Set Count to DefaultCount if Count <= 0.
Default value for DefaultCount is 20.
Count = DefaultCount = 1 if Count <= 0 and DefaultCount <= 0.

=item B<PrevPages>

=item B<NextPages>

Calculate per-page information for pages from Current-PrevPages to
Current+NextPages.
By default PrevPages and NextPages equal to 10.

=back

Records rounded to nearest non-negative integer.

From will be corrected by these rules:
From = 1 if From < 0;
From = Records if From > Records;
From = number of first records on current page.

Count rounded to nearest positive integer.

Return hashref to hash contains %nav keys plus these keys:

=over 4

=item B<To>

Number of last record on current page.
If Records = 0 then To = 0.

=item B<Prev>

Number of first record on previous page.
If currect page is first page then Prev = undef.

=item B<Next>

Number of first record on next page.
If current page is last page then Next = undef.

=item B<Page>

Number of current page.

=item B<Pages>

Arrayref to pages from Current-PrevPages to Current+NextPages.
Every page is a hashref with these keys:

=over 4

=item B<Page>

Number of this page.

=item B<From>

Number of first record on this page.

=item B<To>

Number of last record on this page.

=back

=back

=cut