/**
*    Copyright (C) 2008 10gen Inc.
*
*    This program is free software: you can redistribute it and/or  modify
*    it under the terms of the GNU Affero General Public License, version 3,
*    as published by the Free Software Foundation.
*
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU Affero General Public License for more details.
*
*    You should have received a copy of the GNU Affero General Public License
*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/* storage.h

   Storage subsystem management.
   Lays out our datafiles on disk, manages disk space.
*/

#pragma once

#pragma pack(push,1)

class Record;
class DeletedRecord;
class Extent;
class BtreeBucket;
class BSONObj;
class PhysicalDataFile;

class DiskLoc {
    int fileNo; /* this will be volume, file #, etc. */
    int ofs;
public:
    enum { NullOfs = -1, MaxFiles=4000 };
    int a() const {
        return fileNo;
    }
    DiskLoc(int a, int b) : fileNo(a), ofs(b) {
        assert(ofs!=0);
    }
    DiskLoc() {
        fileNo = -1;
        ofs = NullOfs;
    }

    DiskLoc(const DiskLoc& l) {
        fileNo=l.fileNo;
        ofs=l.ofs;
    }

    bool questionable() {
        return ofs < -1 ||
               fileNo < -1 ||
               fileNo > 20;
    }

    bool isNull() const {
        return ofs == NullOfs;
    }
    void Null() {
        fileNo = -1;
        ofs = NullOfs;
    }
    void assertOk() {
        assert(!isNull());
    }
    void setInvalid() {
        fileNo = -2;
    }
    bool isValid() const {
        return fileNo != -2;
    }

    string toString() const {
        if ( isNull() )
            return "null";
        stringstream ss;
        ss << hex << fileNo << ':' << ofs;
        return ss.str();
    }

    int& GETOFS() {
        return ofs;
    }
    int getOfs() const {
        return ofs;
    }
    void set(int a, int b) {
        fileNo=a;
        ofs=b;
    }
    void setOfs(int _fileNo, int _ofs) {
        fileNo = _fileNo;
        ofs = _ofs;
    }

    void inc(int amt) {
        assert( !isNull() );
        ofs += amt;
    }

    bool sameFile(DiskLoc b) {
        return fileNo == b.fileNo;
    }

    bool operator==(const DiskLoc& b) const {
        return fileNo==b.fileNo && ofs == b.ofs;
    }
    bool operator!=(const DiskLoc& b) const {
        return !(*this==b);
    }
    const DiskLoc& operator=(const DiskLoc& b) {
        fileNo=b.fileNo;
        ofs = b.ofs;
        assert(ofs!=0);
        return *this;
    }
    int compare(const DiskLoc& b) const {
        int x = fileNo - b.fileNo;
        if ( x )
            return x;
        return ofs - b.ofs;
    }
    bool operator<(const DiskLoc& b) const {
        return compare(b) < 0;
    }

    /* get the "thing" associated with this disk location.
       it is assumed the object is what it is -- you must asure that:
       think of this as an unchecked type cast.
    */
    BSONObj obj() const;
    Record* rec() const;
    DeletedRecord* drec() const;
    Extent* ext() const;
    BtreeBucket* btree() const;

    PhysicalDataFile& pdf() const;
};

#pragma pack(pop)