亚梦cos:请解释一下代码含义和隐藏的知识

Public Function GetExtName(strFileName As String) As String
Dim strTmp As String
Dim strByte As String
Dim i As Long
For i = Len(strFileName) To 1 Step -1
strByte = Mid(strFileName, i, 1)
If strByte <> "." Then
strTmp = strByte + strTmp
Else
Exit For
End If
Next i
GetExtName = strTmp
End Function

Public Function search(ByVal strPath As String, Optional strSearch As String = "") As Boolean
Dim strFileDir() As String
Dim strFile As String
Dim i As Long

Dim lDirCount As Long
On Error GoTo MyErr
If Right(strPath, 1) <> "\" Then strPath = strPath + "\"
strFile = Dir(strPath, vbDirectory Or vbHidden Or vbNormal Or vbReadOnly)
While strFile <> "" '搜索当前目录
DoEvents
If (GetAttr(strPath + strFile) And vbDirectory) = vbDirectory Then '如果找到的是目录
If strFile <> "." And strFile <> ".." Then '排除掉父目录(..)和当前目录(.)
lDirCount = lDirCount + 1 '将目录数增1
ReDim Preserve strFileDir(lDirCount) As String
strFileDir(lDirCount - 1) = strFile '用动态数组保存当前目录名
End If
Else
If strSearch = "" Then
Form1.List1.AddItem strPath + strFile
ElseIf LCase(GetExtName(strPath + strFile)) = LCase(GetExtName(strSearch)) Then
'满足搜索条件，则处理该文件
Form1.List1.AddItem strPath + strFile '将文件全名保存至列表框List1中
End If
End If
strFile = Dir
Wend
For i = 0 To lDirCount - 1
Form1.Label3.Caption = strPath + strFileDir(i)
Call search(strPath + strFileDir(i), strSearch) '递归搜索子目录
Next
ReDim strFileDir(0) '将动态数组清空
search = True '搜索成功
Exit Function
MyErr:
search = False '搜索失败
End Function