標(biāo)題: 從一個已經(jīng)打開的文件句柄中取得文件名 [打印本頁] 作者: jialinx 時間: 2015-9-13 16:47 標(biāo)題: 從一個已經(jīng)打開的文件句柄中取得文件名 采用CopyFileEx這個API進(jìn)行文件復(fù)制時，為了能夠動態(tài)的顯示文件的復(fù)制進(jìn)度百分比，用戶可以自定義回調(diào)函數(shù)，采用進(jìn)度條和標(biāo)簽來顯示復(fù)制進(jìn)度。這2個回調(diào)函數(shù)的格式如下：
Declare Function CopyFileEx Lib "kernel32.dll" Alias "CopyFileExA" (ByVal lpExistingFileName As String, _
ByVal lpNewFileName As String, ByVal lpProgressRoutine As Long, _
lpData As Any, ByRef pbCancel As Long, ByVal dwCopyFlags As Long) As Long
其中，現(xiàn)有文件名lpExistingFileName，新建的文件名lpNewFileName。而lpProgressRoutine則是系統(tǒng)的回調(diào)函數(shù)指針。其定義如下：
Public Function CopyProgressRoutine(ByVal TotalFileSize As Currency, ByVal TotalBytesTransferred As Currency, ByVal StreamSize As Currency, ByVal StreamBytesTransferred As Currency, _
ByVal dwStreamNumber As Long, ByVal dwCallbackReason As Long, _
ByVal hSourceFile As Long, ByVal hDestinationFile As Long, ByVal lpData As Long) As Long
可以看出這個回調(diào)函數(shù)的格式很復(fù)雜，好處是其中的大部分參數(shù)都是由Windows提供給用戶使用的，如TotalFileSize 為文件的大小, TotalBytesTransferred 為已經(jīng)傳送的大小，這樣用戶就可以計算出實際進(jìn)度，從而用控件在用戶界面中反映出來。
但是可以看出，這里面沒有給出文件名稱，而是給了源文件和目標(biāo)文件的文件句柄指針，不便在用戶控件中給出“正在復(fù)制xxx文件，進(jìn)度 25%”類似的信息，因此就涉及到了怎樣從文件句柄反查實際文件路徑的問題。
從網(wǎng)上的開發(fā)者的反饋來看，微軟并沒有直接提供能夠從文件句柄獲得文件名稱的開發(fā)接口，只是在核心態(tài)的操作中，有一個NTQueryObject的函數(shù)，可以取得NT物理路徑名，即\DEVICE\HARDDISK0\Test\myfile.dat這樣的名稱。而如何將NT物理設(shè)備路徑與DOS路徑名對應(yīng)起來，只有再次采用QueryDosDevice這樣的函數(shù)，將系統(tǒng)中所有的可能驅(qū)動器的NT物理設(shè)備路徑列舉出來進(jìn)行比對，將能夠匹配的設(shè)備進(jìn)行匹配替換，從而獲得Dos路徑。
因為NTQueryObject函數(shù)屬于系統(tǒng)核心操作函數(shù)，需要有管理員權(quán)限才能運行，因此這樣的做法并不很好用。但是目前未看到更好的做法，暫時這樣處理。
下面是具體的實現(xiàn)過程：
' 主要操作過程, hFile是要查找的文件句柄
Private Function GetFileNameFromHandle(ByVal hFile As Long) As String
Dim hFileMapping As Long, pMemMap As Long
'這個操作過程有點煩雜。因為NTQueryObject屬于核心函數(shù)，而FileObject是NT系統(tǒng)的核心構(gòu)建，對其直接訪問會導(dǎo)致系統(tǒng)不穩(wěn)定，死機的機會很大。因此只有建立要訪問的對象的映像后，對映像進(jìn)行訪問，確保安全性。
' hFileMapping，pMemeMap都是內(nèi)存映像句柄
Dim sFilename As String
Dim sa As SECURITY_Attributes '這是文件訪問的安全屬性結(jié)構(gòu)，后面介紹
'對安全訪問作初始設(shè)置，一般可以使用 ByVal 0&的方式提供Null指針，但是這里VB編譯器一直報告錯誤，只好設(shè)置一個初始值后，直接提供給函數(shù)使用。
sa.bInheritHandle = 1
sa.lpSecurityDescriptor = 0
sa.nLength = Len(sa)
'將 NT 路徑替換為DOS設(shè)備路徑，邏輯盤符
' 此處是開始創(chuàng)建了一個從 A-Z的NT路徑表 NTDriverNames(0 to 25)，全局變量
' 并使用 InitDosName 對其進(jìn)行初始化。
Function FindDosName(lpNTDevice As String) As String
Dim i As Integer
Dim lpName As String
'Dim sC As String
Dim sBuffer As String * 520
Dim ret As Long
For i = 0 To 25
lpName = NTDriverNames(i)
If Len(lpName) > 0 Then
sBuffer = Mid(lpNTDevice, Len(lpName) + 1)
If Left(lpNTDevice, Len(lpName)) = lpName And Left(sBuffer, 1) = "\" Then
FindDosName = Chr(&H41 + i) & sBuffer
Exit For
End If
End If
Next
'If sC > "Z" Then FindDosName = vbNullString
End Function
'從 0 -25 一次對應(yīng)每個設(shè)備的NTDriverName: \DEVICE\HARDDISKVOLUME7-->DOSName E:\
Sub InitDosName()
Dim i As Integer
Dim sC As String
Dim sBuffer As String * 520
Dim ret As Long
For i = 0 To 25
sBuffer = String$(520, 0)
sC = Chr(&H41 + i) & ":" '形成DOS設(shè)備名， 如C：
ret = QueryDosDeviceA(sC, sBuffer, 520) '查詢設(shè)備名
'If ret = 0 Then
' MsgBox GetLastError
'End If
ret = InStr(sBuffer, Chr$(0))
NTDriverNames(i) = Trim(IIf(ret > 0, Left(sBuffer, ret - 1), sBuffer))
Next
End Sub
'完成 ASCIIZ 到 DOS String的轉(zhuǎn)換
Private Function TrimNull(item As String) As String
Dim pos As Integer
pos = InStr(item, Chr$(0))
If pos Then
TrimNull = Left$(item, pos - 1)
Else
TrimNull = item
End If
End Function
' 前面的操作中所涉及到的 API 及 Types。
Type SECURITY_Attributes
nLength As Long
lpSecurityDescriptor As Long
bInheritHandle As Long
End Type
Const PAGE_READWRITE = 1
'以可讀?可寫方式打開映射
Const ERROR_ALREADY_EXISTS = 183
Private Const FILE_ATTRIBUTE_NORMAL As Long = &H80
Private Const SECTION_MAP_READ As Long = &H4
Private Const FILE_MAP_READ As Long = SECTION_MAP_READ
Private Const FILE_SHARE_READ As Long = &H1
Private Const GENERIC_READ As Long = &H80000000
Private Const OPEN_EXISTING As Long = 3
Private Const PAGE_EXECUTE_READWRITE As Long = &H40
Private Const PAGE_READONLY As Long = &H2
Private Const SEC_IMAGE As Long = &H1000000
Private Const INVALID_HANDLE_VALUE As Long = -1
Private Declare Function CreateFileMapping Lib "kernel32 " Alias "CreateFileMappingA" (ByVal hFile As Long, lpFileMappingAttributes As SECURITY_Attributes, ByVal flProtect As Long, ByVal dwMaximumSizeHigh As Long, ByVal dwMaximumSizeLow As Long, ByVal lpName As String) As Long
'創(chuàng)建一個文件映射對象
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
Private Declare Function GetMappedFileName Lib "psapi" Alias "GetMappedFileNameA" (ByVal hProcess As Long, lpv As Any, ByVal lpFileName As String, ByVal nSize As Long) As Long
Private Declare Function QueryDosDevice Lib "kernel32" Alias "QueryDosDeviceA" (ByVal lpDeviceName As String, ByVal lpTargetPath As String, ByVal ucchMax As Long) As Long
Private Declare Function MapViewOfFile Lib "kernel32.dll" (ByVal hFileMappingObject As Long, ByVal dwDesiredAccess As Long, ByVal dwFileOffsetHigh As Long, ByVal dwFileOffsetLow As Long, ByVal dwNumberOfBytesToMap As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (ByRef Destination As Any, ByRef Source As Any, ByVal Length As Long)
Private Declare Function UnmapViewOfFile Lib "kernel32.dll" (ByRef lpBaseAddress As Any) As Long