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分享VB CreateFile不能写string类型数据
各位高手，用VB做数据保存和读取，定义的数据只要不是string类型的，使用CreateFile，write file ,read file都正常。如果要写入的数据包含strin类型的数据，读写就出现乱码。
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舉杯邀明月 2018-05-02
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谢谢，之前我采用的方法是OPEN INOUT或者write方法，但是发现在断电时会丢失数据。API这个函数支持无缓存直接写入，防止出现数据先被擦出还没来得及写入的情况。[/quote]
直接用VB6的文件操作语句，你写完后“Close”时，它也应该是会从缓冲区执行“写盘”的吧！
你说的“断电时会丢失数据”，
其一，估计是你没有及时“关闭文件”，造成缓存数据延后更新；
其二，如果是你正好在“写入磁盘”时断电，恐怕什么方法都无法保证“数据有效”的吧！
sandjuanjuan 2018-05-02
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谢谢，之前我采用的方法是OPEN INOUT或者write方法，但是发现在断电时会丢失数据。API这个函数支持无缓存直接写入，防止出现数据先被擦出还没来得及写入的情况。
sandjuanjuan 2018-05-02
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[quote=引用 11 楼 Chen8013 的回复:]
给你段代码，参考一下。
非常感谢，学习了。
非常感谢，学习了。
脆皮大雪糕 2018-05-02
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其实你的这段代码太偷懒了，你应该定义数据格式，比如固定每条记录的长度，或者记录之间要有分割标志。否则只管写不管读，即使写正常了，读的时候也是一片混乱。
脆皮大雪糕 2018-05-02
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谢谢，之前我采用的方法是OPEN INOUT或者write方法，但是发现在断电时会丢失数据。API这个函数支持无缓存直接写入，防止出现数据先被擦出还没来得及写入的情况。[/quote]
文件open写完及时close。
你调用API的这段代码，并不是因为它不缓存，而是你调用的WriteArray在函数的最后及时close handle了
脆皮大雪糕 2018-04-29
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貌似就是普通的读写文件嘛，VB有完整的一套文件操作指令，为啥要全API操作？
问度娘：“VB6 文件操作” 遍地都是结果
推荐看看
https://blog.csdn.net/ben1978/article/details/751498
舉杯邀明月 2018-04-28
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给你段代码，参考一下。
' 窗体代码：
Option Explicit
Private strFileName As String
Private Sub Form_Load()
'strFileName = "E:\CESHI.TXT"
strFileName = "E:\Temp\TestA.txt"
End Sub
Private Sub Command1_Click()
Dim arrTest(1) As MyType
arrTest(0).banci = 12345
arrTest(0).xingming = "张三李四"
arrTest(1).banci = 789
arrTest(1).xingming = "吕洞宾"
WriteArray strFileName, arrTest
End Sub
Private Sub Command2_Click()
Dim arrTemp(1) As MyType
Dim i As Long
Call ReadArray(strFileName, arrTemp())
Me.Cls
For i = 0& To 1&
' 加个“<”符号，让你可以看到读出来的文本没有“多余的东西”
Me.Print arrTemp(i).banci, arrTemp(i).xingming & "<"
Next
'Text1.Text = S(0).xingming
End Sub' 标准模块代码：
Option Explicit
Private Declare Sub CopyMemory Lib "Kernel32" Alias "RtlMoveMemory" ( _
ByRef Destination As Any, _
ByRef Source As Any, _
ByVal Length As Long)
Private Declare Function ReadFile Lib "Kernel32" ( _
ByVal hFile As Long, _
ByRef lpBuffer As Any, _
ByVal nNumberOfBytesToRead As Long, _
ByRef lpNumberOfBytesRead As Long, _
ByVal lpOverlapped As Long) As Long
Private Declare Function CloseHandle Lib "Kernel32" ( _
ByVal hObject As Long) As Long
Private Declare Function WriteFile Lib "Kernel32" ( _
ByVal hFile As Long, _
ByRef lpBuffer As Any, _
ByVal nNumberOfBytesToWrite As Long, _
ByRef lpNumberOfBytesWritten As Long, _
ByVal lpOverlapped As Long) As Long
Private Declare Function CreateFile Lib "Kernel32" _
Alias "CreateFileA" (ByVal lpFileName As String, _
ByVal dwDesiredAccess As Long, _
ByVal dwShareMode As Long, _
ByVal lpSecurityAttributes As Long, _
ByVal dwCreationDisposition As Long, _
ByVal dwFlagsAndAttributes As Long, _
ByVal hTemplateFile As Long) As Long
Private Declare Function FlushFileBuffers Lib "Kernel32" (ByVal hFile As Long) As Long
Public Type MyType
banci As Integer
xingming As String
End Type
Private Type MyType_IO
banci As Integer
data(9) As Byte
End Type
Private Const GENERIC_WRITE As Long = &H40000000
Private Const GENERIC_READ As Long = &H80000000
Private Const FILE_ATTRIBUTE_NORMAL As Long = &H80
Private Const CREATE_ALWAYS As Long = 2
Private Const OPEN_ALWAYS As Long = 4
Private Const INVALID_HANDLE_VALUE As Long = -1
Public Sub ReadArray(ByVal Fname As String, anArray() As MyType)
Dim arrBuff() As MyType_IO
Dim strTemp As String
Dim fHandle As Long
Dim fSuccess As Long
Dim lBytesRead As Long
Dim BytesToRead As Long
Dim i%, m As Integer
m = UBound(anArray)
ReDim arrBuff(m)
BytesToRead = (m + 1) * LenB(arrBuff(0))
fHandle = CreateFile(Fname, GENERIC_WRITE Or GENERIC_READ, _
0&, 0&, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0&)
If (INVALID_HANDLE_VALUE = fHandle) Then Exit Sub
fSuccess = ReadFile(fHandle, arrBuff(0), BytesToRead, lBytesRead, 0&)
Call CloseHandle(fHandle)
If (fSuccess) Then
For i = 0 To m
anArray(i).banci = arrBuff(i).banci
strTemp = StrConv(arrBuff(i).data(), vbUnicode)
m = InStr(1&, strTemp, vbNullChar)
If (m) Then strTemp = Left$(strTemp, m - 1&)
anArray(i).xingming = strTemp
Next
End If
End Sub
Public Sub WriteArray(Fname As String, anArray() As MyType)
Dim arrBuff() As MyType_IO
Dim arrTemp() As Byte
Dim fHandle As Long
Dim fSuccess As Long
Dim lBytesWritten As Long
Dim BytesToWrite As Long
Dim i%, m As Integer
m = UBound(anArray)
ReDim arrBuff(m)
For i = 0 To m
arrBuff(i).banci = anArray(i).banci
arrTemp() = StrConv(anArray(i).xingming, vbFromUnicode)
m = 1& + UBound(arrTemp())
If (10 < m) Then m = 10 ' 文本限制最多10字节
If (m) Then Call CopyMemory(arrBuff(i).data(0), arrTemp(0), m)
Next
BytesToWrite = i * LenB(arrBuff(0))
fHandle = CreateFile(Fname, GENERIC_WRITE Or GENERIC_READ, _
0&, 0&, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0&)
If (INVALID_HANDLE_VALUE = fHandle) Then Exit Sub
fSuccess = WriteFile(fHandle, arrBuff(0), BytesToWrite, lBytesWritten, 0&)
If (fSuccess) Then Call FlushFileBuffers(fHandle)
Call CloseHandle(fHandle)
End Sub舉杯邀明月 2018-04-28
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我觉得，你这种“结构体”（自定义数据类型），恐怕只有用“定长记录格式”进行磁盘I/O操作，才能保证数据的正确性。
否则，你那其中的一个“字符串数据”长度是不确定的，你怎么知道“某条数据”究竟是占用了多少字节呢！
sandjuanjuan 2018-04-28
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非常感谢！
我根据老弟给的建议重新写的程序，计算了写的字节数，运行程序发现，有一半的机率可以读出字符，另一半读出来是E盘符，不知道为啥？
模块程序：
Public FILE_NAME As String
Public Const GENERIC_WRITE = &H40000000
Const GENERIC_READ = &H80000000
Const FILE_ATTRIBUTE_NORMAL = &H80
Const CREATE_ALWAYS = 2
Const OPEN_ALWAYS = 4
Const INVALID_HANDLE_VALUE = -1
Public Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, _
lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, _
lpNumberOfBytesRead As Long, ByVal lpOverlapped As Long) As Long
Public Declare Function CloseHandle Lib "kernel32" ( _
ByVal hObject As Long) As Long
Public Declare Function WriteFile Lib "kernel32" ( _
ByVal hFile As Long, lpBuffer As Any, _
ByVal nNumberOfBytesToWrite As Long, _
lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Long) As Long
Public Declare Function CreateFile Lib "kernel32" _
Alias "CreateFileA" (ByVal lpFileName As String, _
ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, _
ByVal lpSecurityAttributes As Long, _
ByVal dwCreationDisposition As Long, _
ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) _
As Long
Public Declare Function FlushFileBuffers Lib "kernel32" ( _
ByVal hFile As Long) As Long
Declare Function GetLastError Lib "kernel32" () As Long
Type MyType
banci As Integer
xingming As String
End Type
Public T(0) As MyType
Public S(0) As MyType
Public Sub readArray(Fname As String, anArray() As MyType)
Dim fHandle As Long
Dim fSuccess As Long
Dim lBytesRead As Long
Dim BytesToRead As Long
' 'Get size of data to write
Dim i As Integer
i = UBound(anArray)
BytesToRead = (UBound(anArray) + 1) * (LenB(Str((anArray(i).banci))) + LenB(anArray(i).xingming))
' 'Get a handle to a file Fname.
fHandle = CreateFile(Fname, GENERIC_WRITE Or GENERIC_READ, _
0, 0, OPEN_ALWAYS, FILE_FLAG_WRITE_THROUGH, 0)
'Here you should test to see if you get a file handle or not.
'CreateFile returns INVALID_HANDLE_VALUE if it fails.
If fHandle <> INVALID_HANDLE_VALUE Then
Dim j As Integer
j = 0
fSuccess = ReadFile(fHandle, anArray(j), _
BytesToRead, lBytesRead, 0)
'ReadFile returns a non-zero value if it is successful.
'Now you just close the file.
fSuccess = CloseHandle(fHandle)
End If
End Sub
Public Sub writearray(Fname As String, anArray() As MyType)
Dim fHandle As Long
Dim fSuccess As Long
Dim lBytesWritten As Long
Dim BytesToWrite As Long
'Get the length of data to write
Dim i As Integer
i = UBound(anArray)
BytesToWrite = (UBound(anArray) + 1) * (LenB(Str((anArray(i).banci))) + LenB(anArray(i).xingming))
'Get a handle to a file Fname.
fHandle = CreateFile(Fname, GENERIC_WRITE Or GENERIC_READ, _
0, 0, OPEN_ALWAYS, FILE_FLAG_WRITE_THROUGH, 0)
'Here you should test to see if you get a file handle or not.
'CreateFile returns INVALID_HANDLE_VALUE if it fails.
If fHandle <> INVALID_HANDLE_VALUE Then
Dim j As Integer
j = 0
fSuccess = WriteFile(fHandle, anArray(j), _
BytesToWrite, lBytesWritten, 0)
'Check to see if you were successful writing the data
If fSuccess <> INVALID_HANDLE_VALUE Then
' 'Flush the file buffers to force writing of the data.
fSuccess = FlushFileBuffers(fHandle)
'Close the file.
fSuccess = CloseHandle(fHandle)
End If
End If
End Sub
FORM1：
Private Sub Form_Load()
FILE_NAME = "E:\CESHI.TXT"
End Sub
Private Sub Command1_Click() '写按钮
T(0).banci = 12345
T(0).xingming = "张三李四"
writearray FILE_NAME, T 'Write the entire array to disk
End Sub
Private Sub Command2_Click() 'Define another large array
' S(0).xingming = ""
readArray FILE_NAME, S 'Read into a different array
Text1.Text = S(0).xingming
End Sub
舉杯邀明月 2018-04-28
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如果你有简单的实例，能不能发个看一下。我并不是专业程序员，我是做工控的，有客户有这个需求了，我才接触了VB语言。都是百度出来了………………[/quote]
刚才看一下，你的“代码”根本不能运行吧！
在 Command1_Click() 中，调用： writearray FILE_NAME, T
按 Sub writearray( )的定义，这儿的第2个参数，要求是“字符串数组”；
而你的变量 T ，类型是 MyType 。 根本就是“类型不匹配”的。
在 Command2_Click() 中，调用 readArray FILE_NAME, S 也是同样的错误！
另外再说一点：
即使把 writearray( ) 、readArray( ) 的第2个参数类型改为“MyType”，也不能保证正常的数据 读/写，
因为“直接”以你这种方式传递 MyType类型的数据给API，无法保证 读/写的长度（字节数）。
在 Command2_Click() 中，调用 readArray FILE_NAME, S 也是同样的错误！
另外再说一点：
即使把 writearray( ) 、readArray( ) 的第2个参数类型改为“MyType”，也不能保证正常的数据 读/写，
因为“直接”以你这种方式传递 MyType类型的数据给API，无法保证 读/写的长度（字节数）。
sandjuanjuan 2018-04-28
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请问是不是这样赋值：T(0).xingming=StrConv("张三", vbFromUnicode)？
sandjuanjuan 2018-04-28
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谢谢各位的回复，我把代码贴出来，请参阅。
模块里的代码如下：
Public FILE_NAME As String
Public Const GENERIC_WRITE = &H40000000
Const GENERIC_READ = &H80000000
Const FILE_ATTRIBUTE_NORMAL = &H80
Const CREATE_ALWAYS = 2
Const OPEN_ALWAYS = 4
Const INVALID_HANDLE_VALUE = -1
Private Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, _
lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, _
lpNumberOfBytesRead As Long, ByVal lpOverlapped As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" ( _
ByVal hObject As Long) As Long
Private Declare Function WriteFile Lib "kernel32" ( _
ByVal hFile As Long, lpBuffer As Any, _
ByVal nNumberOfBytesToWrite As Long, _
lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Long) As Long
Private Declare Function CreateFile Lib "kernel32" _
Alias "CreateFileA" (ByVal lpFileName As String, _
ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, _
ByVal lpSecurityAttributes As Long, _
ByVal dwCreationDisposition As Long, _
ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) _
As Long
Private Declare Function FlushFileBuffers Lib "kernel32" ( _
ByVal hFile As Long) As Long
Type MyType
banci As Integer
xingming As String
End Type
Public T(0) As MyType
Public S(0) As MyType
Public Sub readArray(Fname As String, anArray() As String)
Dim fHandle As Long
Dim fSuccess As Long
Dim lBytesRead As Long
Dim BytesToRead As Long
' 'Get size of data to write
BytesToRead = (UBound(anArray) + 1) * LenB(anArray(0))
' 'Get a handle to a file Fname.
fHandle = CreateFile(Fname, GENERIC_WRITE Or GENERIC_READ, _
0, 0, OPEN_ALWAYS, FILE_FLAG_WRITE_THROUGH, 0)
'Here you should test to see if you get a file handle or not.
'CreateFile returns INVALID_HANDLE_VALUE if it fails.
If fHandle <> INVALID_HANDLE_VALUE Then
fSuccess = ReadFile(fHandle, anArray(0), _
BytesToRead, lBytesRead, 0)
'ReadFile returns a non-zero value if it is successful.
'Now you just close the file.
fSuccess = CloseHandle(fHandle)
End If
End Sub
Public Sub writearray(Fname As String, anArray() As String)
Dim fHandle As Long
Dim fSuccess As Long
Dim lBytesWritten As Long
Dim BytesToWrite As Long
'Get the length of data to write
BytesToWrite = LenB(anArray(iii)) + BytesToWrite
'Get a handle to a file Fname.
fHandle = CreateFile(Fname, GENERIC_WRITE Or GENERIC_READ, _
0, 0, OPEN_ALWAYS, FILE_FLAG_WRITE_THROUGH, 0)
'Here you should test to see if you get a file handle or not.
'CreateFile returns INVALID_HANDLE_VALUE if it fails.
If fHandle <> INVALID_HANDLE_VALUE Then
fSuccess = WriteFile(fHandle, anArray(0), _
BytesToWrite, lBytesWritten, 0)
'Check to see if you were successful writing the data
If fSuccess <> INVALID_HANDLE_VALUE Then
' 'Flush the file buffers to force writing of the data.
fSuccess = FlushFileBuffers(fHandle)
'Close the file.
fSuccess = CloseHandle(fHandle)
End If
End If
End Sub
窗口FORM1里的代码如下：
Private Sub Form_Load()
FILE_NAME = "E：\CESHI.TXT"
End Sub
Private Sub Command1_Click() '写按钮
T(0).banci = 1
T(0).xingming = "张三"
writearray FILE_NAME, T 'Write the entire array to disk
End Sub
Private Sub Command2_Click() 'Define another large array
readArray FILE_NAME, S 'Read into a different array
Text1.Text = S(0).xingming
End Sub
FORM1里有三个控件：一个写按钮，一个读按钮，一个显示。
sandjuanjuan 2018-04-28
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如果你有简单的实例，能不能发个看一下。我并不是专业程序员，我是做工控的，有客户有这个需求了，我才接触了VB语言。都是百度出来了………………
xzjxucxx 2018-04-25
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代码贴出来。。。。。。。。。。
vansoft 2018-04-24
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文件编码格式。
赵4老师 2018-04-24
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strconv
舉杯邀明月 2018-04-23
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你的API声明 or 使用不恰当。
把你的代码贴出来…………
一般来说，你要处理“String数据”的话，那个“缓冲区”你得用字节数组中转一下。
把你的代码贴出来…………
一般来说，你要处理“String数据”的话，那个“缓冲区”你得用字节数组中转一下。
