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 * Copyright (C) 1990-2007, Condor Team, Computer Sciences Department,
 * University of Wisconsin-Madison, WI.
 * Licensed under the Apache License, Version 2.0 (the "License"); you
 * may not use this file except in compliance with the License.  You may
 * obtain a copy of the License at
 *    http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.


#ifndef _FILE_STATE_H
#define _FILE_STATE_H

#include "condor_common.h"
#include "condor_file.h"
#include "syscall_numbers.h"
#include "condor_syscall_mode.h"

class CondorFileInfo;
class CondorFilePointer;

This class multiplexes number of UNIX file system calls.
The fd's used to index this table are "virtual file descriptors",
and could refer to real local fds, remote fds, ioservers, sockets,
or who knows what.  It only makes sense to use this table when
MappingFileDescriptors() is in effect.
This class does several things:
      <li> checks validity of fds  
      <li> multiplexes fds to file objects
      <li> keeps I/O summaries
      <li> manages checkpoint and restore

This class does _not_:
      <li> Decide whether mapping is in effect.
           The system call stubs do that.
      <li> Implement read, write, ioctl, etc. for _any_ file.
           Subclasses of CondorFile do that (condor_file_*.h)
      <li> Implement buffering.
           A CondorFileBuffer wrapped around a file object does that.
      <li> Perform operations on names (i.e. stat()).
           Those are handled transparently by the syscall switches.

This file table is similar to an in-kernel file table.
It has several sub-structures:
<li> CondorFile -- represents a truly-opened file
<li> CondorFilePointer -- represents a seek pointer
<li> CondorFileInfo -- records I/O summares for a file.
Each integer file descriptor (fd) indexes a CondorFilePointer (CFP) in
the open file table.  Each CFP stores a current seek pointer and a 
pointer to a CondorFile (CF) and CondorFileInfo (CFI).
An open() causes a new CFP, CFI, and CF to be created.  The CFP is installed
in the file table, and the index is returned as a file descriptor.
open("words") would create this:

    / \

Suppose that another open() is performed on the same file.  This requires
a separate seek pointer be managed, and a new fd be allocated, but the
same file must be manipulated.

   fd=3  fd=4
     |     |
    CFP   CFP
     \ \ / /
      \ X /
      CF CFI

Suppose that a dup is performed on fd 4.  A new fd must be allocated, but
it will share the same seek pointer as fd 4.

   fd=3  fd=4 fd=5
     |     | /
    CFP   CFP
     \ \ / /
      \ X /
      CF CFI

A close() on an fd causes the fd to be de-allocated.  It it is the last
reference to a CFP, that is also de-allocated.  If the last CFP to a CF
is de-allocated, the file is closed, and the CF de-allocated.  However,
the CFI is saved and kept in a list.  If the file is opened again, the
same CFI is used for keeping summaries.  CFIs are reported to the
shadow whenever a file is closed or the job terminates.
When in standalone checkpointing mode, the structure above is
maintained so that we can use the same object and caching sceme.
However, because stubs are not generated for remapping fds, we try
hard to keep the real fds synchronized with the virtual fds.

00123 class CondorFileTable {

      /** Prepare the table for use */
      void  init();

      /** Write out any buffered data */
      void  flush();

      /** Report all cached I/O summaries */
      void  report_all();

      /** Close all files */
      void  close_all();

      /** If aggravation is enabled, virtual fds will never match real fds. */
      void  set_aggravate_mode( int on_off );

      /** Display debug info */
      void  dump();

      /** If in LocalSyscalls, just perform a UNIX open.  If in
          RemoteSyscalls, ask the shadow for the appropriate 
          access method, and then use that method for the open. */
      int   open( const char *path, int flags, int mode );

      /** Pipe with UNIX semantics.
          While a pipe is open, checkpointing is disabled.  */
      int   pipe(int fds[]);

      /** Socket with UNIX semantics.
          While a socket is open, checkpointing is disabled. */
      int   socket( int domain, int type, int prototcol );
      /** Close this file with UNIX semantics */
      int   close( int fd );

      /** Read with UNIX semantics */
      ssize_t     read( int fd, void *data, size_t length );

      /** Write with UNIX semantics */
      ssize_t     write( int fd, const void *data, size_t length );

      /** Seek with UNIX semantics */
      off_t lseek( int fd, off_t offset, int whence );

      /** Dup with UNIX semantics */
      int   dup( int old );

      /** Dup2 with UNIX semantics, even if dup2 is not supported
          on this platform. */
      int   dup2( int old, int nfd );

      /** Similar to dup2, but will dup to any free fd >= search */
      int   search_dup2( int old, int search );

      /** Find the name of this file, and then chdir() to that
          name.  This is not exactly UNIX semantics. */
      int   fchdir( int fd );

      /** Change the working directory with UNIX semantics. */
      int   chdir( const char *path );

      /** Handle known fcntl values by modifying the table, or passing
          the value to the appropriate file object.  Unknown fcntls
          or those with non-integer third arguments fail with a 
          warning message and EINVAL. */
      int   fcntl( int fd, int cmd, int arg );

      /** See comments for fcntl. */
      int   ioctl( int fd, int cmd, long arg );

      /** This poll() will only work on certain kinds of files.
          An error is caused if you poll on an unsupported kind. */
      int   poll( struct pollfd fds[], int count, int timeout );

      /** This select() will only work on certain kinds of files.
          An error is caused if you poll on an unsupported kind. */
      int   select( int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout );

      /** Truncate with UNIX semantics */
      int   ftruncate( int fd, size_t length );

      /** Flush any Condor-buffered data on this file, then
          perform a UNIX fsync/fdsync/fdatasync as appropriate. */
      int   fsync( int fd );

      /** Do a UNIX fstat() */
      int fstat( int fd, struct stat *buf);

      /** Do a UNIX stat() */
      int stat( const char *name, struct stat *buf);

      /** Do a UNIX lstat() */
      int lstat( const char *name, struct stat *buf);

      /** Return the max number of bytes to buffer per file */
      int   get_buffer_size();

      /** Return the approximate buffer block size to use */
      int   get_buffer_block_size();

      /** Save the state of all open files */
      void  checkpoint();

      /** A checkpoint has resumed, so open everything up again. */
      void  resume();

      /** Converts a mapped fd into an unmapped fd.
          If the mapping is non-trivial, -1 is returned. */
      int   get_unmapped_fd( int fd );

      /** Returns true if this fd should be access local */
      int   is_fd_local( int fd );

      /** Returns true if this file name should be accessed locally */
      int   is_file_name_local( const char *name, char **local_name );

      int   resume( int fd );
      int   install_special( int real_fd, char *kind );
      int   find_empty();
      int   count_file_uses( CondorFile *f );
      int   count_pointer_uses( CondorFilePointer *f );
      void  check_safety( CondorFilePointer *f );
      int   find_url( char *url );
      int   find_logical_name( const char *logical_name );
      void  complete_path( const char *short_path, char **long_path );
      void  lookup_url( char *logical_name, char **url );
      void  replace_file( CondorFile *o, CondorFile *n );

      CondorFile * create_url_chain( char const *url );
      CondorFile * create_url_chain( char const *url, char *method, char *rest );
      CondorFile * open_url( char const *url, int flags, int mode );
      CondorFile * open_url_retry( char const *url, int flags, int mode );
      CondorFile * open_file_unique( char *logical_name, int flags, int mode );
      CondorFileInfo    * make_info( char *logical_name );

      CondorFilePointer **pointers;
      CondorFileInfo          *info_head;

      int   length;
      char  *working_dir;
      int   buffer_size;
      int   buffer_block_size;
      int   got_buffer_info;
      int   aggravate_mode;
      int   info_count;

This is a pointer to the single global instance of the file
table.  The only user of this pointer should be the system call
switches, who need to send some syscalls to the open file table.

extern CondorFileTable *FileTab;


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