355 lines
13 KiB
Java
355 lines
13 KiB
Java
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/*******************************************************************************
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* Copyright 2010 Cees De Groot, Alex Boisvert, Jan Kotek
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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******************************************************************************/
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package org.apache.jdbm;
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import java.io.IOException;
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import static org.apache.jdbm.Storage.*;
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/**
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* This class manages physical row ids, and their data.
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*/
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final class PhysicalRowIdManager {
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// The file we're talking to and the associated page manager.
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final private PageFile file;
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final private PageManager pageman;
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final PhysicalFreeRowIdManager freeman;
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static final private short DATA_PER_PAGE = (short) (PAGE_SIZE - Magic.DATA_PAGE_O_DATA);
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//caches offset after last allocation. So we dont have to iterate throw page every allocation
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private long cachedLastAllocatedRecordPage = Long.MIN_VALUE;
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private short cachedLastAllocatedRecordOffset = Short.MIN_VALUE;
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/**
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* Creates a new rowid manager using the indicated record file. and page manager.
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*/
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PhysicalRowIdManager(PageFile file, PageManager pageManager) throws IOException {
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this.file = file;
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this.pageman = pageManager;
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this.freeman = new PhysicalFreeRowIdManager(file, pageManager);
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}
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/**
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* Inserts a new record. Returns the new physical rowid.
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*/
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long insert(final byte[] data, final int start, final int length) throws IOException {
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if (length < 1)
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throw new IllegalArgumentException("Length is <1");
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if (start < 0)
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throw new IllegalArgumentException("negative start");
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long retval = alloc(length);
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write(retval, data, start, length);
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return retval;
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}
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/**
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* Updates an existing record. Returns the possibly changed physical rowid.
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*/
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long update(long rowid, final byte[] data, final int start, final int length) throws IOException {
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// fetch the record header
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PageIo page = file.get(rowid>>> Storage.PAGE_SIZE_SHIFT);
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short head = (short) (rowid & Storage.OFFSET_MASK);
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int availSize = RecordHeader.getAvailableSize(page, head);
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if (length > availSize ||
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//difference between free and available space can be only 254.
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//if bigger, need to realocate and free page
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availSize - length > RecordHeader.MAX_SIZE_SPACE
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) {
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// not enough space - we need to copy to a new rowid.
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file.release(page);
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free(rowid);
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rowid = alloc(length);
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} else {
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file.release(page);
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}
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// 'nuff space, write it in and return the rowid.
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write(rowid, data, start, length);
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return rowid;
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}
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void fetch(final DataInputOutput out, final long rowid) throws IOException {
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// fetch the record header
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long current = rowid >>> Storage.PAGE_SIZE_SHIFT;
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PageIo page = file.get(current);
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final short head = (short) (rowid & Storage.OFFSET_MASK);
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// allocate a return buffer
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// byte[] retval = new byte[ head.getCurrentSize() ];
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final int size = RecordHeader.getCurrentSize(page, head);
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if (size == 0) {
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file.release(current, false);
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return;
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}
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// copy bytes in
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int leftToRead = size;
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short dataOffset = (short) ( head + RecordHeader.SIZE);
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while (leftToRead > 0) {
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// copy current page's data to return buffer
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int toCopy = PAGE_SIZE - dataOffset;
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if (leftToRead < toCopy) {
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toCopy = leftToRead;
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}
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out.writeFromByteBuffer(page.getData(), dataOffset, toCopy);
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// Go to the next page
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leftToRead -= toCopy;
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// out.flush();
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file.release(page);
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if (leftToRead > 0) {
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current = pageman.getNext(current);
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page = file.get(current);
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dataOffset = Magic.DATA_PAGE_O_DATA;
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}
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}
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// return retval;
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}
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/**
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* Allocate a new rowid with the indicated size.
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*/
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private long alloc(int size) throws IOException {
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size = RecordHeader.roundAvailableSize(size);
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long retval = freeman.getFreeRecord(size);
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if (retval == 0) {
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retval = allocNew(size, pageman.getLast(Magic.USED_PAGE));
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}
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return retval;
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}
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/**
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* Allocates a new rowid. The second parameter is there to allow for a recursive call - it indicates where the
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* search should start.
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*/
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private long allocNew(int size, long start) throws IOException {
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PageIo curPage;
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if (start == 0 ||
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//last page was completely filled?
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cachedLastAllocatedRecordPage == start && cachedLastAllocatedRecordOffset == PAGE_SIZE
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) {
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// we need to create a new page.
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start = pageman.allocate(Magic.USED_PAGE);
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curPage = file.get(start);
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curPage.dataPageSetFirst(Magic.DATA_PAGE_O_DATA);
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cachedLastAllocatedRecordOffset = Magic.DATA_PAGE_O_DATA;
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cachedLastAllocatedRecordPage = curPage.getPageId();
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RecordHeader.setAvailableSize(curPage, Magic.DATA_PAGE_O_DATA, 0);
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RecordHeader.setCurrentSize(curPage, Magic.DATA_PAGE_O_DATA, 0);
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} else {
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curPage = file.get(start);
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}
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// follow the rowids on this page to get to the last one. We don't
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// fall off, because this is the last page, remember?
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short pos = curPage.dataPageGetFirst();
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if (pos == 0) {
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// page is exactly filled by the last page of a record
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file.release(curPage);
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return allocNew(size, 0);
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}
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short hdr = pos;
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if (cachedLastAllocatedRecordPage != curPage.getPageId() ) {
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//position was not cached, have to find it again
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int availSize = RecordHeader.getAvailableSize(curPage, hdr);
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while (availSize != 0 && pos < PAGE_SIZE) {
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pos += availSize + RecordHeader.SIZE;
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if (pos == PAGE_SIZE) {
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// Again, a filled page.
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file.release(curPage);
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return allocNew(size, 0);
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}
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hdr = pos;
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availSize = RecordHeader.getAvailableSize(curPage, hdr);
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}
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} else {
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hdr = cachedLastAllocatedRecordOffset;
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pos = cachedLastAllocatedRecordOffset;
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}
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if (pos == RecordHeader.SIZE) { //TODO why is this here?
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// the last record exactly filled the page. Restart forcing
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// a new page.
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file.release(curPage);
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}
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if(hdr>Storage.PAGE_SIZE - 16){
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file.release(curPage);
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//there is not enought space on current page, so force new page
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return allocNew(size,0);
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}
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// we have the position, now tack on extra pages until we've got
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// enough space.
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long retval =(start << Storage.PAGE_SIZE_SHIFT) + (long) pos;
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int freeHere = PAGE_SIZE - pos - RecordHeader.SIZE;
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if (freeHere < size) {
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// check whether the last page would have only a small bit left.
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// if yes, increase the allocation. A small bit is a record
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// header plus 16 bytes.
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int lastSize = (size - freeHere) % DATA_PER_PAGE;
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if (size <DATA_PER_PAGE && (DATA_PER_PAGE - lastSize) < (RecordHeader.SIZE + 16)) {
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size += (DATA_PER_PAGE - lastSize);
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size = RecordHeader.roundAvailableSize(size);
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}
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// write out the header now so we don't have to come back.
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RecordHeader.setAvailableSize(curPage, hdr, size);
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file.release(start, true);
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int neededLeft = size - freeHere;
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// Refactor these two pages!
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while (neededLeft >= DATA_PER_PAGE) {
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start = pageman.allocate(Magic.USED_PAGE);
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curPage = file.get(start);
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curPage.dataPageSetFirst((short) 0); // no rowids, just data
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file.release(start, true);
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neededLeft -= DATA_PER_PAGE;
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}
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if (neededLeft > 0) {
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// done with whole chunks, allocate last fragment.
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start = pageman.allocate(Magic.USED_PAGE);
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curPage = file.get(start);
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curPage.dataPageSetFirst((short) (Magic.DATA_PAGE_O_DATA + neededLeft));
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file.release(start, true);
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cachedLastAllocatedRecordOffset = (short) (Magic.DATA_PAGE_O_DATA + neededLeft);
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cachedLastAllocatedRecordPage = curPage.getPageId();
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}
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} else {
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// just update the current page. If there's less than 16 bytes
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// left, we increase the allocation (16 bytes is an arbitrary
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// number).
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if (freeHere - size <= (16 + RecordHeader.SIZE)) {
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size = freeHere;
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}
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RecordHeader.setAvailableSize(curPage, hdr, size);
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file.release(start, true);
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cachedLastAllocatedRecordOffset = (short) (hdr + RecordHeader.SIZE + size);
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cachedLastAllocatedRecordPage = curPage.getPageId();
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}
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return retval;
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}
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void free(final long id) throws IOException {
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// get the rowid, and write a zero current size into it.
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final long curPageId = id >>> Storage.PAGE_SIZE_SHIFT;
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final PageIo curPage = file.get(curPageId);
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final short offset = (short) (id & Storage.OFFSET_MASK);
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RecordHeader.setCurrentSize(curPage, offset, 0);
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int size = RecordHeader.getAvailableSize(curPage, offset);
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//trim size if spreads across multiple pages
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if(offset + RecordHeader.SIZE + size >PAGE_SIZE + (PAGE_SIZE-Magic.DATA_PAGE_O_DATA)){
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int numOfPagesToSkip = (size -
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(Storage.PAGE_SIZE-(offset - RecordHeader.SIZE)) //minus data remaining on this page
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)/(PAGE_SIZE-Magic.DATA_PAGE_O_DATA);
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size = size - numOfPagesToSkip * (PAGE_SIZE-Magic.DATA_PAGE_O_DATA);
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RecordHeader.setAvailableSize(curPage, offset,size);
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//get next page
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long nextPage = curPage.pageHeaderGetNext();
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file.release(curPage);
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//release pages
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for(int i = 0;i<numOfPagesToSkip;i++){
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PageIo page = file.get(nextPage);
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long nextPage2 = page.pageHeaderGetNext();
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file.release(page);
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pageman.free(Magic.USED_PAGE,nextPage);
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nextPage = nextPage2;
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}
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}else{
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file.release(curPage);
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}
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// write the rowid to the free list
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freeman.putFreeRecord(id, size);
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}
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/**
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* Writes out data to a rowid. Assumes that any resizing has been done.
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*/
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private void write(final long rowid, final byte[] data,final int start, final int length) throws IOException {
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long current = rowid >>> Storage.PAGE_SIZE_SHIFT;
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PageIo page = file.get(current);
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final short hdr = (short) (rowid & Storage.OFFSET_MASK);
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RecordHeader.setCurrentSize(page, hdr, length);
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if (length == 0) {
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file.release(current, true);
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return;
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}
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// copy bytes in
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int offsetInBuffer = start;
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int leftToWrite = length;
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short dataOffset = (short) (hdr + RecordHeader.SIZE);
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while (leftToWrite > 0) {
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// copy current page's data to return buffer
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int toCopy = PAGE_SIZE - dataOffset;
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if (leftToWrite < toCopy) {
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toCopy = leftToWrite;
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}
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page.writeByteArray(data, offsetInBuffer, dataOffset, toCopy);
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// Go to the next page
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leftToWrite -= toCopy;
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offsetInBuffer += toCopy;
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file.release(current, true);
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if (leftToWrite > 0) {
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current = pageman.getNext(current);
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page = file.get(current);
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dataOffset = Magic.DATA_PAGE_O_DATA;
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}
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}
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}
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void rollback() throws IOException {
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cachedLastAllocatedRecordPage = Long.MIN_VALUE;
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cachedLastAllocatedRecordOffset = Short.MIN_VALUE;
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freeman.rollback();
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}
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void commit() throws IOException {
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freeman.commit();
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}
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}
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