Question

我有一个包含数据的“容器”。大小为+ - 100MB。在容器中有几个标记事物开头的“数据集”。

现在我需要获取给定dataid的索引。（例如：dataid''4CFE7197-0029-006B-1AD4-000000000012'）

我尝试了几种方法。但此时“ReadAllBytes”是最高效的。

ReadAll - ＆gt;平均0.6秒

Using oReader As New BinaryReader(File.Open(sContainerPath, FileMode.Open, FileAccess.Read))
    Dim iLength As Integer = CInt(oReader.BaseStream.Length)
    Dim oValue As Byte() = Nothing
    oValue = oReader.ReadBytes(iLength)
    Dim enc As New System.Text.ASCIIEncoding
    Dim sFileContent As String = enc.GetString(oValue)

    Dim r As Regex = New Regex(sDataId)
    Dim lPosArcID As Integer = r.Match(sFileContent).Index
    If lPosArcID > 0 Then
        Return lPosArcID
    End If
End Using

ReadByteByByte - ＆gt;平均1.4秒

Using oReader As BinaryReader = New BinaryReader(File.Open(sContainerPath, FileMode.Open, FileAccess.Read))
    Dim valueSearch As StringSearch = New StringSearch(sDataId)

    Dim readByte As Byte
    While (InlineAssignHelper(readByte, oReader.ReadByte()) >= 0)
        index += 1
        If valueSearch.Found(readByte) Then
            Return index - iDataIdLength
        End If
    End While
End Using



Public Class StringSearch
    Private ReadOnly oValue() As Byte
    Private iValueIndex As Integer = -1

    Public Sub New(value As String)
        Dim oEncoding As New System.Text.ASCIIEncoding
        Me.oValue = oEncoding.GetBytes(value)
    End Sub

    Public Function Found(oNextByte As Byte) As Boolean

        If oValue(iValueIndex + 1) = oNextByte Then
            iValueIndex += 1

            If iValueIndex + 1 = oValue.Count Then Return True
        Else
            iValueIndex = -1
        End If

        Return False
    End Function
End Class

Public Function InlineAssignHelper(Of T)(ByRef target As T, ByVal value As T) As T
    target = value
    Return value
End Function

我发现很难相信没有更快的方法。 100MB文件的0.6秒不是可接受的时间。

我尝试过的另一种方法是分割成X字节（100,1000，..）的块。但是很慢。

我可以尝试一种方法的帮助吗？

查找大文件性能中的字符串索引

0 个答案: