Unit OS8: File System Unit OS8: File System

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Unit OS8: File System Unit OS8: File System

8.5. Windows File and Directory Management

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Copyright Notice Copyright Notice

These materials are part of the

These materials are part of the Windows Operating Windows Operating System Internals Curriculum Development Kit,

System Internals Curriculum Development Kit, developed by David A. Solomon and Mark E.

developed by David A. Solomon and Mark E.

Russinovich with Andreas Polze Russinovich with Andreas Polze

Microsoft has licensed these materials from David Microsoft has licensed these materials from David Solomon Expert Seminars, Inc. for distribution to Solomon Expert Seminars, Inc. for distribution to academic organizations solely for use in academic academic organizations solely for use in academic environments (and not for commercial use)

environments (and not for commercial use)

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Roadmap for Section 8.5 Roadmap for Section 8.5

Windows File I/O API - General Principles Windows File I/O API - General Principles

Moving and Copying Files Moving and Copying Files

Directory Management Directory Management

Directory Searching Directory Searching

File and Directory Attributes

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Windows API I/O:

File and Directory Management File and Directory Management

Windows API provides a number of straightforward Windows API provides a number of straightforward functions to manage files

functions to manage files

Delete, copy, rename files Delete, copy, rename files Create temporary file names Create temporary file names

Absolute pathnames start with drive letter or Absolute pathnames start with drive letter or server name!

server name!

It is not possible to delete an open file in Windows It is not possible to delete an open file in Windows

(but it is possible in Windows9X) (but it is possible in Windows9X)

UNIX unlink() decrements link count UNIX unlink() decrements link count

(but does not necessarily delete file) (but does not necessarily delete file)

BOOL DeleteFile (LPCTSTR lpszFileName)

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Moving files Moving files

Copies the named existing file and assigns new name Copies the named existing file and assigns new name An existing file will be replaced only if

An existing file will be replaced only if

fFailIfExists == FALSE fFailIfExists == FALSE

DeleteFile() and CopyFile do not work for directories DeleteFile() and CopyFile do not work for directories Win32 does not support any file linking

Win32 does not support any file linking

(but NTFS and POSIX subsystem do) (but NTFS and POSIX subsystem do)

BOOL CopyFile( LPCTSTR lpszExistingFile, LPCTSTR lpszNewFile,

BOOL fFailIfExists );

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Moving Files (contd.) Moving Files (contd.)

MoveFile() fails if the new file already exists MoveFile() fails if the new file already exists (use MoveFileEx() for existing files)

(use MoveFileEx() for existing files)

Windows 9X does not implement MoveFileEx() Windows 9X does not implement MoveFileEx() New files can be on different drives / directories New files can be on different drives / directories New directories must be on same drive

New directories must be on same drive lpszNew == NULL : existing file is deleted lpszNew == NULL : existing file is deleted fdwFlags:

fdwFlags:

MOVEFILE_REPLACE_EXISTING – replace existing destination file MOVEFILE_REPLACE_EXISTING – replace existing destination file

MOVEFILE_COPY_ALLOWED – destination may be on different volume MOVEFILE_COPY_ALLOWED – destination may be on different volume

BOOL MoveFile (LPCTSTR lpszExisting, LPCTSTR lpszNew);

BOOL MoveFileEx( LPCTSTR lpszExisting,

LPCTSTR lpszNew, DWORD fdwFlags);

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Directory Management Directory Management

lpszPath points to null-terminated string with the lpszPath points to null-terminated string with the

name of the target directory name of the target directory

Only an empty directory can be rmoved Only an empty directory can be rmoved

lpsa == NULL will create a null-ACL for the new lpsa == NULL will create a null-ACL for the new

BOOL CreateDirectory( LPCTSTR lpszPath, LPSECURITY_ATTRIBUTES lpsa );

BOOL RemoveDirectory( LPCTSTR lpszPath );

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Directory Management (contd.) Directory Management (contd.)

Each process has current working directory Each process has current working directory

Each individual drive keeps working directory Each individual drive keeps working directory

GetCurrentDirectory:

ccCurDir is size of buffer in characters (!) ccCurDir is size of buffer in characters (!)

Buffer to small: GetCurrentDirectory() returns required size (!) or Buffer to small: GetCurrentDirectory() returns required size (!) or zero on failure

zero on failure

Call GetCurrentDirectory twice: first to obtain size of buffer, next to Call GetCurrentDirectory twice: first to obtain size of buffer, next to obtain value

obtain value

(or use MAX_PATH constant) (or use MAX_PATH constant)

BOOL SetCurrentDirectory( LPCTSTR lpszCurDir );

DWORD GetCurrentDirectory( DWORD cchCurDir, LPTSTR lpszCurDir );

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Directory Searching Directory Searching

Search a directory for files that satisfy a specified name pattern Search a directory for files that satisfy a specified name pattern

Search handles must be obtained via FindFirstFile() and closed via Search handles must be obtained via FindFirstFile() and closed via FindClose()

FindClose() FindFirstFile

FindFirstFile() examines subdirectories and file names() examines subdirectories and file names Return of INVALID_HANDLE_VALUE indicates failure Return of INVALID_HANDLE_VALUE indicates failure

Parameters:

lpszSearchFile points to directory/pathname that can contain wildcard lpszSearchFile points to directory/pathname that can contain wildcard characters (? and *; no regular expressions)

characters (? and *; no regular expressions)

lpffd points to data structure with access informationlpffd points to data structure with access information HANDLE FindFirstFile( LPCTSTR lpszSearchFile,

LPWIN32_FIND_DATA lpffd );

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WIN32_FIND_DATA structure WIN32_FIND_DATA structure

typedef struct _WIN32_FIND_DATA { // wfd DWORD dwFileAttributes;

FILETIME ftCreationTime;

FILETIME ftLastAccessTime;

FILETIME ftLastWriteTime;

DWORD nFileSizeHigh;

DWORD nFileSizeLow;

DWORD dwReserved0;

DWORD dwReserved1;

TCHAR cFileName[ MAX_PATH ];

TCHAR cAlternateFileName[ 14 ];

Does not contain path- portion of name

DOS 8.3 name

FILE_ATTRIBUTE_ARCHIVE, FILE_ATTRIBUTE_COMPRESSED, FILE_ATTRIBUTE_DIRECTORY, FILE_ATTRIBUTE_ENCRYPTED, FILE_ATTRIBUTE_HIDDEN,.FILE_ATTRIBUTE_NORMAL, FILE_ATTRIBUTE_OFFLINE, FILE_ATTRIBUTE_READONLY, FILE_ATTRIBUTE_REPARSE_POINT, FILE_ATTRIBUTE_SPARSE_FILE, FILE_ATTRIBUTE_SYSTEM, FILE_ATTRIBUTE_TEMPORARY

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Directory Searching (contd.) Directory Searching (contd.)

FindNextFile() returns FALSE in case of invalid arguments or if no FindNextFile() returns FALSE in case of invalid arguments or if no more matching files are found

more matching files are found

GetLastError() returns ERROR_NO_MORE_FILES GetLastError() returns ERROR_NO_MORE_FILES

Use FindClose() to close search handle Use FindClose() to close search handle

CloseHandle() will raise an exception CloseHandle() will raise an exception

GetFileInformationByHandle() obtains same info...

Programs must do wildcard expansion on their own Programs must do wildcard expansion on their own

BOOL FindNextFile( HANDLE hFindFile, LPWIN32_FIND_DATA lpffd );

BOOL FindClose( HANDLE hFindFile );

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More File and Directory Attributes More File and Directory Attributes

File times are 64-bit unsigned integers File times are 64-bit unsigned integers

(time in 100 ns units (10

(time in 100 ns units (10⁷⁷ / s) since January 1, 1601) / s) since January 1, 1601)

FileTimeToSystemTime()/SystemTimeToFileTime() convert into FileTimeToSystemTime()/SystemTimeToFileTime() convert into years down to milliseconds

years down to milliseconds

(and vice versa)(and vice versa)

CompareFileTime(), SetFileTime() CompareFileTime(), SetFileTime() NTFS supports all three file times NTFS supports all three file times

FAT is accurate only for LastAccess-time FAT is accurate only for LastAccess-time

BOOL GetFileTime( HANDLE hFiles, LPFILETIME lpftCreation, LPFILETIME lpftLastAccess, LPFILETIME lpftLastWrite );

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File Attributes (contd.) File Attributes (contd.)

Returns file attribute or 0xFFFFFFFF in case of failure Returns file attribute or 0xFFFFFFFF in case of failure Attributes include:

Attributes include:

FILE_ATTRIBUTE_DIRECTORY FILE_ATTRIBUTE_DIRECTORY FILE_ATTRIBUTE_NORMAL FILE_ATTRIBUTE_NORMAL FILE_ATTRIBUTE_READONLY FILE_ATTRIBUTE_READONLY FILE_ATTRIBUTE_TEMPORARY FILE_ATTRIBUTE_TEMPORARY

SetFileAttribute() changes those attributes for a file SetFileAttribute() changes those attributes for a file

DWORD GetFileAttributes( LPCTSTR lpszFileName )

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File Flags - controlling read-ahead File Flags - controlling read-ahead

Cache Manager (CM) performs read-ahead and write-back Cache Manager (CM) performs read-ahead and write-back

Reading the next block during sequential access Reading the next block during sequential access Asynch. read-ahead with history for strided access Asynch. read-ahead with history for strided access

history of the last two read requests history of the last two read requests

If a pattern can be determined, cache manager extrapolates it If a pattern can be determined, cache manager extrapolates it

Cache Manager un-maps cached data according to access scheme Cache Manager un-maps cached data according to access scheme

File flags can be specified when opening a file with CreateFile() File flags can be specified when opening a file with CreateFile()

FILE_FLAG_SEQUENTIAL_SCAN FILE_FLAG_SEQUENTIAL_SCAN

Instructs Cache Manager to perform sequential read-ahead Instructs Cache Manager to perform sequential read-ahead

FILE_FLAG_ RANDOM_ACCESS FILE_FLAG_ RANDOM_ACCESS

Instructs Cache Manager not to perform read-ahead Instructs Cache Manager not to perform read-ahead

FILE_FLAG_NO_BUFFERING FILE_FLAG_NO_BUFFERING

Cache Manager shall not be involved with I/O on this file Cache Manager shall not be involved with I/O on this file

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Unit OS8: File System Unit OS8: File System