fd.h

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/*-------------------------------------------------------------------------
 *
 * fd.h
 *    Virtual file descriptor definitions.
 *
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/fd.h
 *
 *-------------------------------------------------------------------------
 */
 
/*
 * calls:
 *
 *  File {Close, Read, ReadV, Write, WriteV, 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 "port/pg_iovec.h"
 
#include <dirent.h>
#include <fcntl.h>
 
typedef int File;
 
 
#define IO_DIRECT_DATA          0x01
#define IO_DIRECT_WAL           0x02
#define IO_DIRECT_WAL_INIT      0x04
 
enum FileExtendMethod
{
#ifdef HAVE_POSIX_FALLOCATE
    FILE_EXTEND_METHOD_POSIX_FALLOCATE,
#endif
    FILE_EXTEND_METHOD_WRITE_ZEROS,
};
 
/* Default to the first available file_extend_method. */
#define DEFAULT_FILE_EXTEND_METHOD 0
 
/* GUC parameter */
extern PGDLLIMPORT int max_files_per_process;
extern PGDLLIMPORT bool data_sync_retry;
extern PGDLLIMPORT int recovery_init_sync_method;
extern PGDLLIMPORT int io_direct_flags;
extern PGDLLIMPORT int file_extend_method;
 
/*
 * This is private to fd.c, but exported for save/restore_backend_variables()
 */
extern PGDLLIMPORT 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
 
/*
 * O_DIRECT is not standard, but almost every Unix has it.  We translate it
 * to the appropriate Windows flag in src/port/open.c.  We simulate it with
 * fcntl(F_NOCACHE) on macOS inside fd.c's open() wrapper.  We use the name
 * PG_O_DIRECT rather than defining O_DIRECT in that case (probably not a good
 * idea on a Unix).
 */
#if defined(O_DIRECT)
#define     PG_O_DIRECT O_DIRECT
#elif defined(F_NOCACHE)
#define     PG_O_DIRECT 0x80000000
#define     PG_O_DIRECT_USE_F_NOCACHE
/*
 * The value we defined to stand in for O_DIRECT when simulating it with
 * F_NOCACHE had better not collide with any of the standard flags.
 */
StaticAssertDecl((PG_O_DIRECT &
                  (O_APPEND |
                   O_CLOEXEC |
                   O_CREAT |
                   O_DSYNC |
                   O_EXCL |
                   O_RDWR |
                   O_RDONLY |
                   O_SYNC |
                   O_TRUNC |
                   O_WRONLY)) == 0,
                 "PG_O_DIRECT value collides with standard flag");
#else
#define     PG_O_DIRECT 0
#endif
 
/*
 * prototypes for functions in fd.c
 */
 
struct PgAioHandle;
 
/* 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, pgoff_t offset, pgoff_t amount, uint32 wait_event_info);
extern ssize_t FileReadV(File file, const struct iovec *iov, int iovcnt, pgoff_t offset, uint32 wait_event_info);
extern ssize_t FileWriteV(File file, const struct iovec *iov, int iovcnt, pgoff_t offset, uint32 wait_event_info);
extern int  FileStartReadV(struct PgAioHandle *ioh, File file, int iovcnt, pgoff_t offset, uint32 wait_event_info);
extern int  FileSync(File file, uint32 wait_event_info);
extern int  FileZero(File file, pgoff_t offset, pgoff_t amount, uint32 wait_event_info);
extern int  FileFallocate(File file, pgoff_t offset, pgoff_t amount, uint32 wait_event_info);
 
extern pgoff_t FileSize(File file);
extern int  FileTruncate(File file, pgoff_t offset, uint32 wait_event_info);
extern void FileWriteback(File file, pgoff_t offset, pgoff_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 *path, bool error_on_failure);
extern File PathNameOpenTemporaryFile(const char *path, int mode);
extern bool PathNameDeleteTemporaryFile(const char *path, bool error_on_failure);
extern void PathNameCreateTemporaryDir(const char *basedir, const char *directory);
extern void PathNameDeleteTemporaryDir(const char *dirname);
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 InitTemporaryFileAccess(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 bool pg_file_exists(const char *name);
extern void pg_flush_data(int fd, pgoff_t offset, pgoff_t nbytes);
extern int  pg_truncate(const char *path, pgoff_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 elevel);
extern int  durable_unlink(const char *fname, int elevel);
extern void SyncDataDirectory(void);
extern int  data_sync_elevel(int elevel);
 
static inline ssize_t
FileRead(File file, void *buffer, size_t amount, pgoff_t offset,
         uint32 wait_event_info)
{
    struct iovec iov = {
        .iov_base = buffer,
        .iov_len = amount
    };
 
    return FileReadV(file, &iov, 1, offset, wait_event_info);
}
 
static inline ssize_t
FileWrite(File file, const void *buffer, size_t amount, pgoff_t offset,
          uint32 wait_event_info)
{
    struct iovec iov = {
        .iov_base = unconstify(void *, buffer),
        .iov_len = amount
    };
 
    return FileWriteV(file, &iov, 1, offset, wait_event_info);
}
 
#endif                          /* FD_H */