手上的一个VB项目(过程中发现，.Net果然是好啊)，需要在一个ActiveX中实现HTTP下载功能，我是采用InternetreadFile这个API来实现，一开始的代码我是这么写的
Function
Gethttpdownload(sUrl
As
String
)
As
boolen
Dim
s
As
String
Dim
hOpen
As
Long
Dim
hOpenUrl
As
Long
Dim
bDoLoop
As
Boolean
Dim
bRet
As
Boolean
Dim
sReadBuffer
As
String
*
2048
Dim
lNumberOfBytesRead
As
Long
hOpen
=
InternetOpen(scUserAgent, INTERNET_OPEN_TYPE_PRECONFIG, vbNullString, vbNullString,
0
)hOpenUrl
=
InternetOpenUrl(hOpen, sUrl, vbNullString,
0
, INTERNET_FLAG_RELOAD,
0
) bDoLoop
=
True
Do
While
bDoLoop sReadBuffer
=
vbNullString bRet
=
InternetReadFile(hOpenUrl, sReadBuffer,
Len
(sReadBuffer), lNumberOfBytesRead) s
=
s
&
Left
$(sReadBuffer, lNumberOfBytesRead)
If
Not
CBool
(lNumberOfBytesRead)
Then
bDoLoop
=
False
Loop
FileName
=
"
E:\BitSpirit\Torrent\121212.torrent"
F1
=
FreeFileOpen FileName
For
Binary
As
F1Put F1, , sClose F1
If
hOpen
<>
0
Then
InternetCloseHandle (hOpen) Gethttpdownload
=
true
End Function
上面方法，用来获取服务器上的文本类型的文件一点问题，都没有，但是用来下载二进制文件的时候 就出现问题了，里面的数据怎么也不对，研究了下载下来的文件后发现，问题外话应该是在接收数据的变量是个STRING的定长字符串上。但是在网上查了好久，甚至M$ MSDN上的一个用VB来实现下载的程也是用 string类型来接收数据的而且网上的代码写法，基本上也都是这个样，好来才好现，都是从MSDN上的哪个例程上演变过来的.
我想如果能用一个byte数组来代替定长字符串，哪可能就没有问题了，但是查看了一个VB 对Internetreadfile的申明
Public Declare Function InternetReadFile Lib "wininet.dll" (ByVal hFile As Long, ByVal sBuffer As String, ByVal lNumBytesToRead As Long, lNumberOfBytesRead As Long) As Integer
发现其定义
ByVal sBuffer As String 看来只能用String了，在网上查找过程中，发现人家用VC写的程序中这人参数可以是其它的，所以查看了一下Internetreadfile的原型。发现的确可以， 所以我把internetreadfile的定义修改了一下，为了通用，我为新的internetreadfile定义了一个别名。Internetreadfilebyte申明如下:
Public Declare Function InternetReadFileByte Lib "wininet.dll" Alias "InternetReadFile" (ByVal hFile As Long, ByRef sBuffer As Byte, ByVal lNumBytesToRead As Long, lNumberOfBytesRead As Long) As Integer
试了一下的确可以，重新修改函数，（在这过程中发现，如果要取到正确数据，还必须取得文件大小。所以增加了HttpQueryInfo的定义）最后完整的函数
Function
FileDownload(sUrl
As
Variant)
As
Boolean
Dim
b(
99
)
As
Byte
Dim
EndByte()
As
Byte
Dim
s
As
String
Dim
hOpen
As
Long
Dim
hOpenUrl
As
Long
Dim
bDoLoop
As
Boolean
Dim
bRet
As
Boolean
Dim
bbuffer
As
Byte
Dim
sReadBuffer
As
String
Dim
FileName
As
String
Dim
lNumberOfBytesRead
As
Long
Dim
F1
As
Integer
Dim
strsize
As
String
Dim
size
As
Long
strsize
=
String
$(
1024
,
"
"
) F1
=
FreeFile stTotal
=
vbNullString FileName
=
"
E:\BitSpirit\Torrent\121212.torrent"
Open FileName
For
Binary
As
F1 hOpen
=
InternetOpen(scUserAgent, INTERNET_OPEN_TYPE_PRECONFIG, vbNullString, vbNullString,
0
) hOpenUrl
=
InternetOpenUrl(hOpen, sUrl, vbNullString,
0
, INTERNET_FLAG_RELOAD,
0
) bDoLoop
=
True
HttpQueryInfo hOpenUrl, HTTP_QUERY_CONTENT_LENGTH
Or
HTTP_QUERY_FLAG_NUMBER, ByVal strsize,
Len
(strsize),
0
size
=
CLng
(
Trim
(strsize))
For
j
=
1
To
size
\
100
bDoLoop
=
InternetReadFileByte(hOpenUrl, b(
0
),
100
, lNumberOfBytesRead) Put F1, , b
If
Not
CBool
(lNumberOfBytesRead)
Then
Exit
For
Next
If
size
Mod
100
<>
0
Then
tmp
=
(size
Mod
100
)
-
1
ReDim
EndByte(tmp) bDoLoop
=
InternetReadFileByte(hOpenUrl, EndByte(
0
), tmp
+
1
, lNumberOfBytesRead) Put F1, , EndByte
End
If
If
hOpenUrl
<>
0
Then
InternetCloseHandle (hOpenUrl)
If
hOpen
<>
0
Then
InternetCloseHandle (hOpen) Close #
1
FileDownload
=
True
End Function
本文转自无心之柳.NET博客园博客，原文链接：http://www.cnblogs.com/9527/archive/2005/05/19/159108.html
，如需转载请自行联系原作者
