os_seek.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:2k
- /*-
- * 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_seek.c,v 11.17 2002/08/06 04:56:20 bostic Exp $";
- #endif /* not lint */
- #include "db_int.h"
- /*
- * __os_seek --
- * Seek to a page/byte offset in the file.
- */
- int
- __os_seek(dbenv, fhp, pgsize, pageno, relative, isrewind, db_whence)
- DB_ENV *dbenv;
- DB_FH *fhp;
- size_t pgsize;
- db_pgno_t pageno;
- u_int32_t relative;
- int isrewind;
- DB_OS_SEEK db_whence;
- {
- /* Yes, this really is how Microsoft have designed their API */
- union {
- __int64 bigint;
- struct {
- unsigned long low;
- long high;
- };
- } offset;
- int ret, whence;
- DWORD from;
- if (DB_GLOBAL(j_seek) != NULL) {
- switch (db_whence) {
- case DB_OS_SEEK_CUR:
- whence = SEEK_CUR;
- break;
- case DB_OS_SEEK_END:
- whence = SEEK_END;
- break;
- case DB_OS_SEEK_SET:
- whence = SEEK_SET;
- break;
- default:
- return (EINVAL);
- }
- ret = DB_GLOBAL(j_seek)(fhp->fd, pgsize, pageno,
- relative, isrewind, whence);
- } else {
- switch (db_whence) {
- case DB_OS_SEEK_CUR:
- from = FILE_CURRENT;
- break;
- case DB_OS_SEEK_END:
- from = FILE_END;
- break;
- case DB_OS_SEEK_SET:
- from = FILE_BEGIN;
- break;
- default:
- return (EINVAL);
- }
- offset.bigint = (__int64)pgsize * pageno + relative;
- if (isrewind)
- offset.bigint = -offset.bigint;
- ret = (SetFilePointer(fhp->handle,
- offset.low, &offset.high, from) == (DWORD) - 1) ?
- __os_win32_errno() : 0;
- }
- if (ret != 0)
- __db_err(dbenv, "seek: %lu %d %d: %s",
- (u_long)pgsize * pageno + relative,
- isrewind, db_whence, strerror(ret));
- return (ret);
- }