Locker for files

为IPWorks做的一个HA方案，技术上打算用到锁文件，自己写了一个，参考了sourceforge上高手的代码。

似乎线程安全上还有点小问题，以后再考虑吧。

不过等到上到CBA了以后，HA由Core MW提供，就不需要了。

//

// Locking files

// LockFile.hh

//

#ifndef _MY_LOCKF_HH_

#define _MY_LOCKF_HH_

#include

extern "C" {

# include

# include

# include

# include

# include

# include

# include

};

#define LOCK_DIR      "/var/lock"

class LockFile {

private:

  bool isLocked;

  string name;

public:

  LockFile();

 ~LockFile();

  bool Lock(const char *fname);

  bool Lock(string fname)

    { Lock(fname.c_str()); }

  void UnLock();

};

#endif

========================================================================================

//

// Implementation of lock for files

// LockFile.cc

//

#include "LockFile.hh"

LockFile::LockFile()

{

  isLocked = false;

  name = "";

}

LockFile::~LockFile()

{

  UnLock();

}

bool LockFile::Lock(const char *fname)

{

  FILE *fp;

  const char *dn;

  int n;

  struct stat sbuf;

  printf("Locking file %s\n", fname);

  dn = fname;

  if (dn = strrchr(fname, '/'))

    dn++;

  name = LOCK_DIR;

  name += "/LCK..";

  name += dn;

  isLocked = false;

  if (stat(name.c_str(), &sbuf) != -1) {

    printf("Lock file exists.\n");

    if ((fp = fopen(name.c_str(), "r")) != NULL) {

      fscanf(fp, "%10d\n", &n);

      fclose(fp);

      if (n == getpid())

return true;

      printf("Device %s locked by process %d\n", dn, n);

    }

    return isLocked;

  }

  printf("Creating file lock %s\n", name.c_str());

  if ((fp = fopen(name.c_str(), "w")) == NULL)

    printf("Creating lock file %s\n", name.c_str());

  fprintf(fp, "%10d\n", getpid());

  fclose(fp);

  return isLocked = true;

}

void LockFile::UnLock()

{

  printf("Unlocking %s\n", name.c_str());

  if (isLocked) unlink(name.c_str());

}