open.c

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/*-------------------------------------------------------------------------
 *
 * open.c
 *     Win32 open() replacement
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 *
 * src/port/open.c
 *
 *-------------------------------------------------------------------------
 */
 
#ifdef WIN32
 
#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif
 
#include "port/win32ntdll.h"
 
#include <fcntl.h>
#include <assert.h>
#include <sys/stat.h>
 
static int
openFlagsToCreateFileFlags(int openFlags)
{
    switch (openFlags & (O_CREAT | O_TRUNC | O_EXCL))
    {
            /* O_EXCL is meaningless without O_CREAT */
        case 0:
        case O_EXCL:
            return OPEN_EXISTING;
 
        case O_CREAT:
            return OPEN_ALWAYS;
 
            /* O_EXCL is meaningless without O_CREAT */
        case O_TRUNC:
        case O_TRUNC | O_EXCL:
            return TRUNCATE_EXISTING;
 
        case O_CREAT | O_TRUNC:
            return CREATE_ALWAYS;
 
            /* O_TRUNC is meaningless with O_CREAT */
        case O_CREAT | O_EXCL:
        case O_CREAT | O_TRUNC | O_EXCL:
            return CREATE_NEW;
    }
 
    /* will never get here */
    return 0;
}
 
/*
 * Internal function used by pgwin32_open() and _pgstat64().  When
 * backup_semantics is true, directories may be opened (for limited uses).  On
 * failure, INVALID_HANDLE_VALUE is returned and errno is set.
 */
HANDLE
pgwin32_open_handle(const char *fileName, int fileFlags, bool backup_semantics)
{
    HANDLE      h;
    SECURITY_ATTRIBUTES sa;
    int         loops = 0;
 
    if (initialize_ntdll() < 0)
        return INVALID_HANDLE_VALUE;
 
    /* Check that we can handle the request */
    assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
                         (O_RANDOM | O_SEQUENTIAL | O_TEMPORARY) |
                         _O_SHORT_LIVED | O_DSYNC | O_DIRECT | O_CLOEXEC |
                         (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
 
    sa.nLength = sizeof(sa);
    sa.lpSecurityDescriptor = NULL;
 
    /*
     * If O_CLOEXEC is specified, create a non-inheritable handle.  Otherwise,
     * create an inheritable handle (the default Windows behavior).
     *
     * Note: We could instead use SetHandleInformation() after CreateFile() to
     * clear HANDLE_FLAG_INHERIT, but this way avoids rare leaks in
     * multi-threaded programs that create processes, just like POSIX
     * O_CLOEXEC.
     */
    sa.bInheritHandle = !(fileFlags & O_CLOEXEC);
 
    while ((h = CreateFile(fileName,
    /* cannot use O_RDONLY, as it == 0 */
                           (fileFlags & O_RDWR) ? (GENERIC_WRITE | GENERIC_READ) :
                           ((fileFlags & O_WRONLY) ? GENERIC_WRITE : GENERIC_READ),
    /* These flags allow concurrent rename/unlink */
                           (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
                           &sa,
                           openFlagsToCreateFileFlags(fileFlags),
                           FILE_ATTRIBUTE_NORMAL |
                           (backup_semantics ? FILE_FLAG_BACKUP_SEMANTICS : 0) |
                           ((fileFlags & O_RANDOM) ? FILE_FLAG_RANDOM_ACCESS : 0) |
                           ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
                           ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
                           ((fileFlags & O_TEMPORARY) ? FILE_FLAG_DELETE_ON_CLOSE : 0) |
                           ((fileFlags & O_DIRECT) ? FILE_FLAG_NO_BUFFERING : 0) |
                           ((fileFlags & O_DSYNC) ? FILE_FLAG_WRITE_THROUGH : 0),
                           NULL)) == INVALID_HANDLE_VALUE)
    {
        /*
         * Sharing violation or locking error can indicate antivirus, backup
         * or similar software that's locking the file.  Wait a bit and try
         * again, giving up after 30 seconds.
         */
        DWORD       err = GetLastError();
 
        if (err == ERROR_SHARING_VIOLATION ||
            err == ERROR_LOCK_VIOLATION)
        {
#ifndef FRONTEND
            if (loops == 50)
                ereport(LOG,
                        (errmsg("could not open file \"%s\": %s", fileName,
                                (err == ERROR_SHARING_VIOLATION) ? _("sharing violation") : _("lock violation")),
                         errdetail("Continuing to retry for 30 seconds."),
                         errhint("You might have antivirus, backup, or similar software interfering with the database system.")));
#endif
 
            if (loops < 300)
            {
                pg_usleep(100000);
                loops++;
                continue;
            }
        }
 
        /*
         * ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
         * gone (Windows NT status code is STATUS_DELETE_PENDING).  In that
         * case, we'd better ask for the NT status too so we can translate it
         * to a more Unix-like error.  We hope that nothing clobbers the NT
         * status in between the internal NtCreateFile() call and CreateFile()
         * returning.
         *
         * If there's no O_CREAT flag, then we'll pretend the file is
         * invisible.  With O_CREAT, we have no choice but to report that
         * there's a file in the way (which wouldn't happen on Unix).
         */
        if (err == ERROR_ACCESS_DENIED &&
            pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
        {
            if (fileFlags & O_CREAT)
                err = ERROR_FILE_EXISTS;
            else
                err = ERROR_FILE_NOT_FOUND;
        }
 
        _dosmaperr(err);
        return INVALID_HANDLE_VALUE;
    }
 
    return h;
}
 
int
pgwin32_open(const char *fileName, int fileFlags,...)
{
    HANDLE      h;
    int         fd;
 
    h = pgwin32_open_handle(fileName, fileFlags, false);
    if (h == INVALID_HANDLE_VALUE)
        return -1;
 
#ifdef FRONTEND
 
    /*
     * Since PostgreSQL 12, those concurrent-safe versions of open() and
     * fopen() can be used by frontends, having as side-effect to switch the
     * file-translation mode from O_TEXT to O_BINARY if none is specified.
     * Caller may want to enforce the binary or text mode, but if nothing is
     * defined make sure that the default mode maps with what versions older
     * than 12 have been doing.
     */
    if ((fileFlags & O_BINARY) == 0)
        fileFlags |= O_TEXT;
#endif
 
    /* _open_osfhandle will, on error, set errno accordingly */
    if ((fd = _open_osfhandle((intptr_t) h, fileFlags & O_APPEND)) < 0)
        CloseHandle(h);         /* will not affect errno */
    else if (fileFlags & (O_TEXT | O_BINARY) &&
             _setmode(fd, fileFlags & (O_TEXT | O_BINARY)) < 0)
    {
        _close(fd);
        return -1;
    }
 
    return fd;
}
 
FILE *
pgwin32_fopen(const char *fileName, const char *mode)
{
    int         openmode = 0;
    int         fd;
 
    if (strstr(mode, "r+"))
        openmode |= O_RDWR;
    else if (strchr(mode, 'r'))
        openmode |= O_RDONLY;
    if (strstr(mode, "w+"))
        openmode |= O_RDWR | O_CREAT | O_TRUNC;
    else if (strchr(mode, 'w'))
        openmode |= O_WRONLY | O_CREAT | O_TRUNC;
    if (strchr(mode, 'a'))
        openmode |= O_WRONLY | O_CREAT | O_APPEND;
 
    if (strchr(mode, 'b'))
        openmode |= O_BINARY;
    if (strchr(mode, 't'))
        openmode |= O_TEXT;
 
    fd = pgwin32_open(fileName, openmode);
    if (fd == -1)
        return NULL;
    return _fdopen(fd, mode);
}
 
#endif