// extent_manager.cpp

/**
*    Copyright (C) 2013 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/>.
*
*    As a special exception, the copyright holders give permission to link the
*    code of portions of this program with the OpenSSL library under certain
*    conditions as described in each individual source file and distribute
*    linked combinations including the program with the OpenSSL library. You
*    must comply with the GNU Affero General Public License in all respects for
*    all of the code used other than as permitted herein. If you modify file(s)
*    with this exception, you may extend this exception to your version of the
*    file(s), but you are not obligated to do so. If you do not wish to do so,
*    delete this exception statement from your version. If you delete this
*    exception statement from all source files in the program, then also delete
*    it in the license file.
*/

#include "mongo/db/storage/extent_manager.h"

#include "mongo/db/storage/extent.h"

namespace mongo {

    int ExtentManager::quantizeExtentSize( int size ) const {

        if ( size == maxSize() ) {
            // no point doing quantizing for the entire file
            return size;
        }

        invariant( size <= maxSize() );

        // make sizes align with VM page size
        int newSize = (size + 0xfff) & 0xfffff000;

        if ( newSize > maxSize() ) {
            return maxSize();
        }

        if ( newSize < minSize() ) {
            return minSize();
        }

        return newSize;
    }

    int ExtentManager::followupSize( int len, int lastExtentLen ) const {
        invariant( len < maxSize() );
        int x = initialSize(len);
        // changed from 1.20 to 1.35 in v2.1.x to get to larger extent size faster
        int y = (int) (lastExtentLen < 4000000 ? lastExtentLen * 4.0 : lastExtentLen * 1.35);
        int sz = y > x ? y : x;

        if ( sz < lastExtentLen ) {
            // this means there was an int overflow
            // so we should turn it into maxSize
            return maxSize();
        }
        else if ( sz > maxSize() ) {
            return maxSize();
        }

        sz = quantizeExtentSize( sz );
        verify( sz >= len );

        return sz;
    }

    int ExtentManager::initialSize( int len ) const {
        invariant( len <= maxSize() );

        long long sz = len * 16;
        if ( len < 1000 )
            sz = len * 64;

        if ( sz >= maxSize() )
            return maxSize();

        if ( sz <= minSize() )
            return minSize();

        int z = ExtentManager::quantizeExtentSize( sz );
        verify( z >= len );
        return z;
    }
}
