os_open.c
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上传日期:2022-05-23
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文件大小:6k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1997-2002
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: os_open.c,v 11.21 2002/07/12 18:56:55 bostic Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #include <fcntl.h>
- #include <signal.h>
- #include <string.h>
- #include <unistd.h>
- #endif
- #include "db_int.h"
- /*
- * __os_open --
- * Open a file descriptor.
- */
- int
- __os_open(dbenv, name, flags, mode, fhp)
- DB_ENV *dbenv;
- const char *name;
- u_int32_t flags;
- int mode;
- DB_FH *fhp;
- {
- DWORD bytesWritten;
- u_int32_t log_size, pagesize, sectorsize;
- int access, attr, oflags, share, createflag;
- int ret, nrepeat;
- char *drive, dbuf[4]; /* <letter><colon><slosh><nul> */
- #ifdef DIAGNOSTIC
- #define OKFLAGS
- (DB_OSO_CREATE | DB_OSO_DIRECT | DB_OSO_EXCL | DB_OSO_LOG |
- DB_OSO_RDONLY | DB_OSO_REGION | DB_OSO_SEQ | DB_OSO_TEMP |
- DB_OSO_TRUNC)
- if ((ret = __db_fchk(dbenv, "__os_open", flags, OKFLAGS)) != 0)
- return (ret);
- #endif
- /*
- * The "public" interface to the __os_open routine passes around POSIX
- * 1003.1 flags, not DB flags. If the user has defined their own open
- * interface, use the POSIX flags.
- */
- if (DB_GLOBAL(j_open) != NULL) {
- oflags = O_BINARY | O_NOINHERIT;
- if (LF_ISSET(DB_OSO_CREATE))
- oflags |= O_CREAT;
- if (LF_ISSET(DB_OSO_EXCL))
- oflags |= O_EXCL;
- if (LF_ISSET(DB_OSO_RDONLY))
- oflags |= O_RDONLY;
- else
- oflags |= O_RDWR;
- if (LF_ISSET(DB_OSO_SEQ))
- oflags |= _O_SEQUENTIAL;
- else
- oflags |= _O_RANDOM;
- if (LF_ISSET(DB_OSO_TEMP))
- oflags |= _O_TEMPORARY;
- if (LF_ISSET(DB_OSO_TRUNC))
- oflags |= O_TRUNC;
- return (__os_openhandle(dbenv, name, oflags, mode, fhp));
- }
- ret = 0;
- if (LF_ISSET(DB_OSO_LOG))
- log_size = fhp->log_size; /* XXX: Gag. */
- pagesize = fhp->pagesize;
- memset(fhp, 0, sizeof(*fhp));
- fhp->fd = -1;
- /*
- * Otherwise, use the Windows/32 CreateFile interface so that we can
- * play magic games with log files to get data flush effects similar
- * to the POSIX O_DSYNC flag.
- *
- * !!!
- * We currently ignore the 'mode' argument. It would be possible
- * to construct a set of security attributes that we could pass to
- * CreateFile that would accurately represents the mode. In worst
- * case, this would require looking up user and all group names and
- * creating an entry for each. Alternatively, we could call the
- * _chmod (partial emulation) function after file creation, although
- * this leaves us with an obvious race. However, these efforts are
- * largely meaningless on FAT, the most common file system, which
- * only has a "readable" and "writeable" flag, applying to all users.
- */
- access = GENERIC_READ;
- if (!LF_ISSET(DB_OSO_RDONLY))
- access |= GENERIC_WRITE;
- share = FILE_SHARE_READ | FILE_SHARE_WRITE;
- attr = FILE_ATTRIBUTE_NORMAL;
- /*
- * Reproduce POSIX 1003.1 semantics: if O_CREATE and O_EXCL are both
- * specified, fail, returning EEXIST, unless we create the file.
- */
- if (LF_ISSET(DB_OSO_CREATE) && LF_ISSET(DB_OSO_EXCL))
- createflag = CREATE_NEW; /* create only if !exist*/
- else if (!LF_ISSET(DB_OSO_CREATE) && LF_ISSET(DB_OSO_TRUNC))
- createflag = TRUNCATE_EXISTING; /* truncate, fail if !exist */
- else if (LF_ISSET(DB_OSO_TRUNC))
- createflag = CREATE_ALWAYS; /* create and truncate */
- else if (LF_ISSET(DB_OSO_CREATE))
- createflag = OPEN_ALWAYS; /* open or create */
- else
- createflag = OPEN_EXISTING; /* open only if existing */
- if (LF_ISSET(DB_OSO_LOG)) {
- F_SET(fhp, DB_FH_NOSYNC);
- attr |= FILE_FLAG_WRITE_THROUGH;
- }
- if (LF_ISSET(DB_OSO_SEQ))
- attr |= FILE_FLAG_SEQUENTIAL_SCAN;
- else
- attr |= FILE_FLAG_RANDOM_ACCESS;
- if (LF_ISSET(DB_OSO_TEMP))
- attr |= FILE_FLAG_DELETE_ON_CLOSE;
- /*
- * We can turn filesystem buffering off if the page size is a
- * multiple of the disk's sector size. To find the sector size,
- * we call GetDiskFreeSpace, which expects a drive name like "d:\"
- * or NULL for the current disk (i.e., a relative path)
- */
- if (LF_ISSET(DB_OSO_DIRECT) && pagesize != 0 && name[0] != ' ') {
- if (name[1] == ':') {
- drive = dbuf;
- snprintf(dbuf, sizeof(dbuf), "%c:\", name[0]);
- } else
- drive = NULL;
- if (GetDiskFreeSpace(drive, NULL, §orsize, NULL, NULL) &&
- pagesize % sectorsize == 0)
- attr |= FILE_FLAG_NO_BUFFERING;
- }
- for (nrepeat = 1;; ++nrepeat) {
- fhp->handle =
- CreateFile(name, access, share, NULL, createflag, attr, 0);
- if (fhp->handle == INVALID_HANDLE_VALUE) {
- /*
- * If it's a "temporary" error, we retry up to 3 times,
- * waiting up to 12 seconds. While it's not a problem
- * if we can't open a database, an inability to open a
- * log file is cause for serious dismay.
- */
- ret = __os_win32_errno();
- if ((ret != ENFILE && ret != EMFILE && ret != ENOSPC) ||
- nrepeat > 3)
- goto err;
- (void)__os_sleep(dbenv, nrepeat * 2, 0);
- } else
- break;
- }
- /*
- * Special handling needed for log files. To get Windows to not update
- * the MFT metadata on each write, extend the file to its maximum size.
- * Windows will allocate all the data blocks and store them in the MFT
- * (inode) area. In addition, flush the MFT area to disk.
- * This strategy only works for Win/NT; Win/9X does not
- * guarantee that the logs will be zero filled.
- */
- if (LF_ISSET(DB_OSO_LOG) && log_size != 0 && __os_is_winnt()) {
- if (SetFilePointer(fhp->handle,
- log_size - 1, NULL, FILE_BEGIN) == (DWORD)-1)
- goto err;
- if (WriteFile(fhp->handle, "x00", 1, &bytesWritten, NULL) == 0)
- goto err;
- if (bytesWritten != 1)
- goto err;
- if (SetEndOfFile(fhp->handle) == 0)
- goto err;
- if (SetFilePointer(
- fhp->handle, 0, NULL, FILE_BEGIN) == (DWORD)-1)
- goto err;
- if (FlushFileBuffers(fhp->handle) == 0)
- goto err;
- }
- F_SET(fhp, DB_FH_VALID);
- return (0);
- err: if (ret == 0)
- ret = __os_win32_errno();
- if (fhp->handle != INVALID_HANDLE_VALUE)
- (void)CloseHandle(fhp->handle);
- return (ret);
- }