fd.h

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/*-------------------------------------------------------------------------
 *
 * fd.h
 *    Virtual file descriptor definitions.
 *
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/fd.h
 *
 *-------------------------------------------------------------------------
 */

/*
 * calls:
 *
 *  File {Close, Read, Write, Size, 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);
 *
 *  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/CloseTransientFile for an
 * unbuffered file descriptor.
 *
 * If you really can't use any of the above, at least call AcquireExternalFD
 * or ReserveExternalFD to report any file descriptors that are held for any
 * length of time.  Failure to do so risks unnecessary EMFILE errors.
 */
#ifndef FD_H
#define FD_H

#include <dirent.h>


typedef int File;


/* GUC parameter */
extern PGDLLIMPORT int max_files_per_process;
extern PGDLLIMPORT bool data_sync_retry;

/*
 * This is private to fd.c, but exported for save/restore_backend_variables()
 */
extern int  max_safe_fds;

/*
 * On Windows, we have to interpret EACCES as possibly meaning the same as
 * ENOENT, because if a file is unlinked-but-not-yet-gone on that platform,
 * that's what you get.  Ugh.  This code is designed so that we don't
 * actually believe these cases are okay without further evidence (namely,
 * a pending fsync request getting canceled ... see ProcessSyncRequests).
 */
#ifndef WIN32
#define FILE_POSSIBLY_DELETED(err)  ((err) == ENOENT)
#else
#define FILE_POSSIBLY_DELETED(err)  ((err) == ENOENT || (err) == EACCES)
#endif

/*
 * prototypes for functions in fd.c
 */

/* Operations on virtual Files --- equivalent to Unix kernel file ops */
extern File PathNameOpenFile(const char *fileName, int fileFlags);
extern File PathNameOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode);
extern File OpenTemporaryFile(bool interXact);
extern void FileClose(File file);
extern int  FilePrefetch(File file, off_t offset, int amount, uint32 wait_event_info);
extern int  FileRead(File file, char *buffer, int amount, off_t offset, uint32 wait_event_info);
extern int  FileWrite(File file, char *buffer, int amount, off_t offset, uint32 wait_event_info);
extern int  FileSync(File file, uint32 wait_event_info);
extern off_t FileSize(File file);
extern int  FileTruncate(File file, off_t offset, uint32 wait_event_info);
extern void FileWriteback(File file, off_t offset, off_t nbytes, uint32 wait_event_info);
extern char *FilePathName(File file);
extern int  FileGetRawDesc(File file);
extern int  FileGetRawFlags(File file);
extern mode_t FileGetRawMode(File file);

/* Operations used for sharing named temporary files */
extern File PathNameCreateTemporaryFile(const char *name, bool error_on_failure);
extern File PathNameOpenTemporaryFile(const char *path, int mode);
extern bool PathNameDeleteTemporaryFile(const char *name, bool error_on_failure);
extern void PathNameCreateTemporaryDir(const char *base, const char *name);
extern void PathNameDeleteTemporaryDir(const char *name);
extern void TempTablespacePath(char *path, Oid tablespace);

/* 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 struct dirent *ReadDirExtended(DIR *dir, const char *dirname,
                                      int elevel);
extern int  FreeDir(DIR *dir);

/* Operations to allow use of a plain kernel FD, with automatic cleanup */
extern int  OpenTransientFile(const char *fileName, int fileFlags);
extern int  OpenTransientFilePerm(const char *fileName, int fileFlags, mode_t fileMode);
extern int  CloseTransientFile(int fd);

/* If you've really really gotta have a plain kernel FD, use this */
extern int  BasicOpenFile(const char *fileName, int fileFlags);
extern int  BasicOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode);

/* Use these for other cases, and also for long-lived BasicOpenFile FDs */
extern bool AcquireExternalFD(void);
extern void ReserveExternalFD(void);
extern void ReleaseExternalFD(void);

/* Make a directory with default permissions */
extern int  MakePGDirectory(const char *directoryName);

/* 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 int  GetTempTablespaces(Oid *tableSpaces, int numSpaces);
extern Oid  GetNextTempTableSpace(void);
extern void AtEOXact_Files(bool isCommit);
extern void AtEOSubXact_Files(bool isCommit, SubTransactionId mySubid,
                              SubTransactionId parentSubid);
extern void RemovePgTempFiles(void);
extern void RemovePgTempFilesInDir(const char *tmpdirname, bool missing_ok,
                                   bool unlink_all);
extern bool looks_like_temp_rel_name(const char *name);

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 void pg_flush_data(int fd, off_t offset, off_t amount);
extern int  pg_truncate(const char *path, off_t length);
extern void fsync_fname(const char *fname, bool isdir);
extern int  fsync_fname_ext(const char *fname, bool isdir, bool ignore_perm, int elevel);
extern int  durable_rename(const char *oldfile, const char *newfile, int loglevel);
extern int  durable_unlink(const char *fname, int loglevel);
extern int  durable_rename_excl(const char *oldfile, const char *newfile, int loglevel);
extern void SyncDataDirectory(void);
extern int  data_sync_elevel(int elevel);

/* Filename components */
#define PG_TEMP_FILES_DIR "pgsql_tmp"
#define PG_TEMP_FILE_PREFIX "pgsql_tmp"

#endif                          /* FD_H */