bitmapcustomallocator.java

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package org.garret.perst.impl;

import org.garret.perst.*;
import java.util.*;

public class BitmapCustomAllocator extends Persistent implements CustomAllocator { 
    protected int  quantum;
    protected int  quantumBits;
    protected long base;
    protected long limit;
    protected Link pages;
    protected int  extensionPages;

    transient int  currPage;
    transient int  currOffs;
    transient TreeMap reserved = new TreeMap();

    static final int BITMAP_PAGE_SIZE = Page.pageSize - ObjectHeader.sizeof - 4;
    static final int BITMAP_PAGE_BITS = BITMAP_PAGE_SIZE*8;
    
    static class BitmapPage extends Persistent { 
        byte[] data;
    }

    public BitmapCustomAllocator(Storage storage, int quantum, long base, long extension, long limit) {
        super(storage);
        this.quantum = quantum;
        this.base = base;
        this.limit = limit;
        int bits = 0;
        for (int q = quantum; q != 1; q >>>= 1) { 
            bits += 1;
        }
        quantumBits = bits;
        Assert.that((1 << bits) == quantum);
        extensionPages = (int)((extension + ((long)BITMAP_PAGE_BITS << quantumBits) - 1) / ((long)BITMAP_PAGE_BITS << quantumBits));
        pages = storage.createLink();
    }
    
    protected BitmapCustomAllocator() {}

    public long allocate(long size) { 
        size = (size + quantum-1) & ~(quantum-1);
        long objBitSize = size >> quantumBits;
        long pos;    
        long holeBitSize = 0;
        int  firstPage = currPage;
        int  lastPage = pages.size();
        int  offs = currOffs;
        long lastHoleSize = 0;

        while (true) { 
            for (int i = firstPage; i < lastPage; i++) {
                BitmapPage pg = (BitmapPage)pages.get(i);
                while (offs < BITMAP_PAGE_SIZE) { 
                    int mask = pg.data[offs] & 0xFF; 
                    if (holeBitSize + StorageImpl.firstHoleSize[mask] >= objBitSize) { 
                        pos = base + ((((long)i*BITMAP_PAGE_SIZE + offs)*8 - holeBitSize) << quantumBits);
                        long nextPos = wasReserved(pos, size);
                        if (nextPos != 0) {
                            long quantNo = ((nextPos - base) >>> quantumBits) + 7;
                            i = (int)(quantNo / BITMAP_PAGE_BITS);
                            offs = (int)(quantNo - (long)i*BITMAP_PAGE_BITS) >> 3;
                            holeBitSize = 0;
                            continue;
                        }       
                        currPage = i;
                        currOffs = offs;
                        pg.data[offs] |= (byte)((1 << (int)(objBitSize - holeBitSize)) - 1); 
                        pg.modify();
                        if (holeBitSize != 0) { 
                            if (holeBitSize > offs*8) { 
                                memset(pg, 0, 0xFF, offs);
                                holeBitSize -= offs*8;
                                pg = (BitmapPage)pages.get(--i);
                                offs = Page.pageSize;
                            }
                            while (holeBitSize > BITMAP_PAGE_BITS) { 
                                memset(pg, 0, 0xFF, BITMAP_PAGE_SIZE);
                                holeBitSize -= BITMAP_PAGE_BITS;
                                pg = (BitmapPage)pages.get(--i);
                            }
                            while ((holeBitSize -= 8) > 0) { 
                                pg.data[--offs] = (byte)0xFF; 
                            }
                            pg.data[offs-1] |= (byte)~((1 << -(int)holeBitSize) - 1);
                            pg.modify();
                        }
                        return pos;
                    } else if (StorageImpl.maxHoleSize[mask] >= objBitSize) { 
                        int holeBitOffset = StorageImpl.maxHoleOffset[mask];
                        pos = base + ((((long)i*BITMAP_PAGE_SIZE + offs)*8 + holeBitOffset) << quantumBits);
                        long nextPos = wasReserved(pos, size);
                        if (nextPos != 0) {
                            long quantNo = ((nextPos - base) >>> quantumBits) + 7;
                            i = (int)(quantNo / BITMAP_PAGE_BITS);
                            offs = (int)(quantNo - (long)i*BITMAP_PAGE_BITS) >> 3;
                            holeBitSize = 0;
                            continue;
                        }       
                        currPage = i;
                        currOffs = offs;
                        pg.data[offs] |= (byte)(((1<<(int)objBitSize) - 1) << holeBitOffset);
                        pg.modify();
                        return pos;
                    }
                    offs += 1;
                    if (StorageImpl.lastHoleSize[mask] == 8) { 
                        holeBitSize += 8;
                    } else { 
                        holeBitSize = StorageImpl.lastHoleSize[mask];
                    }
                }
                offs = 0;
            }
            if (firstPage == 0) {
                firstPage = pages.size();
                int nPages = (int)(size / (BITMAP_PAGE_BITS*quantum));
                lastPage = firstPage + (nPages > extensionPages ? nPages : extensionPages);
                if ((long)lastPage*BITMAP_PAGE_BITS*quantum > limit) {
                    throw new StorageError(StorageError.NOT_ENOUGH_SPACE);
                }
                pages.setSize(lastPage);
                for (int i = firstPage; i < lastPage; i++) { 
                    BitmapPage pg = new BitmapPage();
                    pg.data = new byte[BITMAP_PAGE_SIZE];
                    pages.setObject(i, pg);
                }
                holeBitSize = lastHoleSize;
            } else {
                lastHoleSize = holeBitSize;
                holeBitSize = 0;
                lastPage = firstPage + 1;
                firstPage = 0;
            }
        }
    }


    public long reallocate(long pos, long oldSize, long newSize) {
        StorageImpl db = (StorageImpl)getStorage();
        if (((newSize + quantum - 1) & ~(quantum-1)) > ((oldSize + quantum - 1) & ~(quantum-1))) { 
            long newPos = allocate(newSize);
            free0(pos, oldSize);
            pos = newPos;
        }
        return pos;
    }

    public void free(long pos, long size) { 
        reserve(pos, size);
        free0(pos, size);
    }


    static class Location implements Comparable { 
        long pos;
        long size;
        
        Location(long pos, long size) { 
            this.pos = pos;
            this.size = size;
        }

        public int compareTo(Object o) { 
            Location loc = (Location)o;
            return pos + size <= loc.pos ? -1 : loc.pos + loc.size <= pos ? 1 : 0;
        }
    }

    private long wasReserved(long pos, long size) { 
        Location loc = new Location(pos, size);
        Location r = (Location)reserved.get(loc);
        if (r != null) { 
            return Math.max(pos + size, r.pos + r.size);
        }
        return 0;
    }

    private void reserve(long pos, long size) { 
        Location loc = new Location(pos, size);
        reserved.put(loc, loc);
    }
    

            
    private void free0(long pos, long size) { 
        long quantNo = (pos - base) >>> quantumBits;
        long objBitSize = (size+quantum-1) >>> quantumBits;
        int  pageId = (int)(quantNo / BITMAP_PAGE_BITS);
        int  offs = (int)(quantNo - (long)pageId*BITMAP_PAGE_BITS) >> 3;
        BitmapPage pg = (BitmapPage)pages.get(pageId);
        int  bitOffs = (int)quantNo & 7;
        
        if (objBitSize > 8 - bitOffs) { 
            objBitSize -= 8 - bitOffs;
            pg.data[offs++] &= (1 << bitOffs) - 1;
            while (objBitSize + offs*8 > BITMAP_PAGE_BITS) { 
                memset(pg, offs, 0, BITMAP_PAGE_SIZE - offs);
                pg = (BitmapPage)pages.get(++pageId);
                objBitSize -= (BITMAP_PAGE_SIZE - offs)*8;
                offs = 0;
            }
            while ((objBitSize -= 8) > 0) { 
                pg.data[offs++] = (byte)0;
            }
            pg.data[offs] &= (byte)~((1 << ((int)objBitSize + 8)) - 1);
        } else { 
            pg.data[offs] &= (byte)~(((1 << (int)objBitSize) - 1) << bitOffs); 
        }
        pg.modify();
    }

    static final void memset(BitmapPage pg, int offs, int pattern, int len) { 
        byte[] arr = pg.data;
        byte pat = (byte)pattern;
        while (--len >= 0) { 
            arr[offs++] = pat;
        }
        pg.modify();
    }


    public void commit() {
        reserved.clear();
    }
}