zlib.net具有相同長度的2個文件導致壓縮後有2個不同的最終長度

Question

在vb.net上使用zlib.net壓縮字節後，具有相同長度的兩個文件具有不同長度是正常的嗎？

這是我使用使用zlib.net參考壓縮模塊，2檔是almose相同，有中庸之道小於100個字節使差在它們之間

Imports System.IO 
Imports zlib 

Module zlib_compression 

    Public Sub CopyStream(ByRef input As System.IO.Stream, ByRef output As   System.IO.Stream) 

     Dim num1 As Integer 
     Dim buffer1 As Byte() = New Byte(2000 - 1) {} 
     num1 = input.Read(buffer1, 0, 2000) 
     Do While (num1 > 0) 
      output.Write(buffer1, 0, num1) 
      num1 = input.Read(buffer1, 0, 2000) 
     Loop 
     output.Flush() 

    End Sub 


    Public Function Compress(ByVal InputBytes As Byte()) As Byte() 

     Using output As New MemoryStream 
      Dim outZStream As Stream = New ZOutputStream(output,   zlib.zlibConst.Z_BEST_SPEED) 
      Using input As Stream = New MemoryStream(InputBytes) 
       CopyStream(input, outZStream) 
       outZStream.Close()    'do not remove 
       Return output.ToArray() 
      End Using 
     End Using 

    End Function 

    Public Function Decompress(ByVal InputBytes As Byte()) As Byte() 

     Using output As New MemoryStream 
      Using outZStream As Stream = New ZOutputStream(output) 
       Using input As Stream = New MemoryStream(InputBytes) 
        CopyStream(input, outZStream) 
        Return output.ToArray() 
       End Using 
      End Using 
     End Using 

    End Function 


End Module 

Answer 1

當然，是的。事實上，這是必然的。無法將所有相同長度的文件無損地壓縮爲較小的尺寸，因爲較小尺寸中沒有足夠的位來標識所有原始文件。如果一些被壓縮，那麼一些必須被擴展。