46 lines
1.2 KiB
Java
46 lines
1.2 KiB
Java
package it.cavallium.dbengine.lucene;
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/**
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* <pre>y = 2 ^ (x + pageIndexOffset) + firstPageLimit</pre>
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*/
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public class ExponentialPageLimits implements PageLimits {
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private static final int DEFAULT_PAGE_INDEX_OFFSET = 0;
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private final int pageIndexOffset;
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private final int firstPageLimit;
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private final int maxItemsPerPage;
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public ExponentialPageLimits() {
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this(DEFAULT_PAGE_INDEX_OFFSET);
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}
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public ExponentialPageLimits(int pageIndexOffset) {
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this(pageIndexOffset, DEFAULT_MIN_ITEMS_PER_PAGE);
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}
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public ExponentialPageLimits(int pageIndexOffset, int firstPageLimit) {
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this(pageIndexOffset, firstPageLimit, DEFAULT_MAX_ITEMS_PER_PAGE);
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}
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public ExponentialPageLimits(int pageIndexOffset, int firstPageLimit, int maxItemsPerPage) {
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this.pageIndexOffset = pageIndexOffset;
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this.firstPageLimit = firstPageLimit;
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this.maxItemsPerPage = maxItemsPerPage;
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}
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@Override
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public int getPageLimit(int pageIndex) {
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var offsetedIndex = pageIndex + pageIndexOffset;
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var power = 0b1L << offsetedIndex;
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if (offsetedIndex >= 30) { // safety
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return maxItemsPerPage;
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}
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var min = Math.max(firstPageLimit, Math.min(maxItemsPerPage, firstPageLimit + power));
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assert min > 0;
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return LuceneUtils.safeLongToInt(min);
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}
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}
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