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shadowsegment.h

#ifndef SHADOW_SEGMENT_H
#define SHADOW_SEGMENT_H

#include"errorclass.h"
#include"pmseg.h"
#include"rpointer.h"
#include"bitmap.h"
#include"reliable.h"

#ifndef PAGESIZE
#define PAGESIZE 4096
#endif


#define MAXPAGES 1024
/*--------- Speicherlayout ----------------------*/
typedef unsigned long Pageno;
typedef unsigned long index_t;
struct Pageentry
{
  unsigned long shadowbit:1;
  unsigned long pageno:31;
};
 
const unsigned long UNDEFINED_PAGE=0x7fffffff;

// PAGESIZE 4096 = 2^12 
inline off_t index2offset(index_t in) { return in<<12; }
inline index_t offset2index(off_t o)  { return o>>12;  }

class SegmentVersion
{
  size_t count_;
  Pageentry entry[1];
public:
  size_t maxcount() { return (PAGESIZE-sizeof(size_t))/sizeof(Pageentry); }
  Pageentry &operator[](index_t i) { return entry[i]; }
  size_t rsize() { return sizeof(size_t)+count_*sizeof(Pageentry); }
  size_t size() { return PAGESIZE; }
  size_t count() { return count_; }
  void grow(int anz) { assert(count_+anz <= maxcount()); count_+=anz; }
  int clearallshadowbits();
  static SegmentVersion *init(char *puffer,int len);
  
  void print(ostream& str);
};

struct MasterLayout 
{
  off_t mc;     // Offset Aktuelle Freispeicherbitmap
  off_t m0;     // Offset erste Freispeicherbitmap
  off_t m1;     // Offset zweite Freispeicherbitmap
  long  status; // Status des Segmente / eventuell spaeter Array
  // erste Freispeicherbitmap
  // zweite Freispeicherbitmap
};

class ShadowSegMaster
{
  TwinblockStrategy tws;
  ReliableSegment rseg;
  RAMS::RPointer<BitMap> mc,m0,m1;
  // mc bzw. dessen offset ist der mapswitch
 public:
  ShadowSegMaster();
  int open(char *name);
  BitMap& CurrentM() { return *(mc.ptr()); }
  BitMap& M0() { return *(m0.ptr()); }
  BitMap& M1() { return *(m1.ptr()); }
  void save();
  int getstatus() { return ((MasterLayout *)rseg.begin())->status; }
  void setstatus(int s) { ((MasterLayout *)rseg.begin())->status=s; }
  void copyandswitchm();
  void druckebelegtliste();
};

class ShadowSegment : public PMSeg
{
  char svpuffer[2*PAGESIZE];
  SegmentVersion *vw[2];
  ShadowSegMaster ssm;
  int sfd;
  int vfd;
  SegmentVersion &Vwork() { return *vw[0]; } 
  SegmentVersion &Vold() { return *vw[1]; } 
  void readsegversions() throw(Systemerror);
  void savesegversion(int nr,int snr) throw(Systemerror);
  void save();
  void reopen();
  void clearshadowbitsandfree();
  
  void recover();

 public:
  ShadowSegment() { sfd=-1; vfd=-1; }
  void init();
  void open(const char *name) throw(Systemerror);

  void close()      { save(); }
  void checkpoint() { save(); reopen(); }
  void rollback();

  void handle(void *page,void *addr);
};
#endif

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