text: /*-------------------------------------------------------------------------
   *
   * fd.h
   *	  Virtual file descriptor definitions.
   *
   *
   * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * src/include/storage/fd.h
   *
   *-------------------------------------------------------------------------
   */
  
  /*
   * calls:
   *
   *	File {Close, Read, Write, Seek, Tell, Sync}
   *	{Path Name Open, Allocate, Free} File
   *
   * These are NOT JUST RENAMINGS OF THE UNIX ROUTINES.
   * Use them for all file activity...
   *
   *	File fd;
   *	fd = PathNameOpenFile("foo", O_RDONLY, 0600);
   *
   *	AllocateFile();
   *	FreeFile();
   *
   * Use AllocateFile, not fopen, if you need a stdio file (FILE*); then
   * use FreeFile, not fclose, to close it.  AVOID using stdio for files
   * that you intend to hold open for any length of time, since there is
   * no way for them to share kernel file descriptors with other files.
   *
   * Likewise, use AllocateDir/FreeDir, not opendir/closedir, to allocate
   * open directories (DIR*), and OpenTransientFile/CloseTransient File for an
   * unbuffered file descriptor.
   */
  #ifndef FD_H
  #define FD_H
  
  #include <dirent.h>
  
  
  /*
   * FileSeek uses the standard UNIX lseek(2) flags.
   */
  
  typedef char *FileName;
  
  typedef int File;
  
  
  /* GUC parameter */
  extern int	max_files_per_process;
  
  /*
   * This is private to fd.c, but exported for save/restore_backend_variables()
   */
  extern int	max_safe_fds;
  
  
  /*
   * prototypes for functions in fd.c
   */
  
  /* Operations on virtual Files --- equivalent to Unix kernel file ops */
  extern File PathNameOpenFile(FileName fileName, int fileFlags, int fileMode);
  extern File OpenTemporaryFile(bool interXact);
  extern void FileClose(File file);
  extern int	FilePrefetch(File file, off_t offset, int amount);
  extern int	FileRead(File file, char *buffer, int amount);
  extern int	FileWrite(File file, char *buffer, int amount);
  extern int	FileSync(File file);
  extern off_t FileSeek(File file, off_t offset, int whence);
  extern int	FileTruncate(File file, off_t offset);
  extern char *FilePathName(File file);
  
  /* Operations that allow use of regular stdio --- USE WITH CAUTION */
  extern FILE *AllocateFile(const char *name, const char *mode);
  extern int	FreeFile(FILE *file);
  
  /* Operations that allow use of pipe streams (popen/pclose) */
  extern FILE *OpenPipeStream(const char *command, const char *mode);
  extern int	ClosePipeStream(FILE *file);
  
  /* Operations to allow use of the <dirent.h> library routines */
  extern DIR *AllocateDir(const char *dirname);
  extern struct dirent *ReadDir(DIR *dir, const char *dirname);
  extern int	FreeDir(DIR *dir);
  
  /* Operations to allow use of a plain kernel FD, with automatic cleanup */
  extern int	OpenTransientFile(FileName fileName, int fileFlags, int fileMode);
  extern int	CloseTransientFile(int fd);
  
  /* If you've really really gotta have a plain kernel FD, use this */
  extern int	BasicOpenFile(FileName fileName, int fileFlags, int fileMode);
  
  /* Miscellaneous support routines */
  extern void InitFileAccess(void);
  extern void set_max_safe_fds(void);
  extern void closeAllVfds(void);
  extern void SetTempTablespaces(Oid *tableSpaces, int numSpaces);
  extern bool TempTablespacesAreSet(void);
  extern Oid	GetNextTempTableSpace(void);
  extern void AtEOXact_Files(void);
  extern void AtEOSubXact_Files(bool isCommit, SubTransactionId mySubid,
  				  SubTransactionId parentSubid);
  extern void RemovePgTempFiles(void);
  
  extern int	pg_fsync(int fd);
  extern int	pg_fsync_no_writethrough(int fd);
  extern int	pg_fsync_writethrough(int fd);
  extern int	pg_fdatasync(int fd);
  extern int	pg_flush_data(int fd, off_t offset, off_t amount);
  extern void fsync_fname(const char *fname, bool isdir);
  extern int	durable_rename(const char *oldfile, const char *newfile, int loglevel);
  extern int	durable_link_or_rename(const char *oldfile, const char *newfile, int loglevel);
  extern void SyncDataDirectory(void);
  
  /* Filename components for OpenTemporaryFile */
  #define PG_TEMP_FILES_DIR "pgsql_tmp"
  #define PG_TEMP_FILE_PREFIX "pgsql_tmp"
  
  #endif   /* FD_H */
  