tiny.sql.history.segment.manifest.PageRange

1pub const PageRange = struct {2    pub const Count = u64;3    pub const unit_precision_segments: Count = 1;4    pub const maximum_segments_per_second: Count =5        segment.SegmentRange.maximum_units_per_second;6    pub const maximum_seconds_per_year: Count =7        segment.SegmentRange.maximum_seconds_per_year;8    pub const service_lifetime_years: Count =9        segment.SegmentRange.service_lifetime_years;10    pub const service_lifetime_seconds: Count =11        segment.SegmentRange.service_lifetime_seconds;12    pub const segments_per_page: Count = entries_per_page;13    pub const maximum_increment_pages: Count = 1;14    pub const budget_pages: Count = total(15        maximum_segments_per_second,16        service_lifetime_seconds,17    ).?;1819    pub fn total(segments_per_second: Count, lifetime_seconds: Count) ?Count {20        const segment_count = @as(u128, unit_precision_segments) *21            @as(u128, segments_per_second) * @as(u128, lifetime_seconds);22        const page_count = if (segment_count == 0) 0 else (segment_count - 1) / @as(u128, segments_per_page) + 1;23        return std.math.cast(Count, page_count);24    }2526    pub fn advance(current: Count, increment: Count) ?Count {27        if (!containsCount(current) or increment > maximum_increment_pages) {28            return null;29        }30        const next = std.math.add(Count, current, increment) catch return null;31        return if (next <= budget_pages) next else null;32    }3334    pub fn containsCount(count: Count) bool {35        return count > 0 and count <= budget_pages;36    }37};