PowerShell 7.0如何计算按块读取的大文件的哈希和

debugcn 发表于 Dev

科斯蒂安

该脚本应复制文件并计算它们的哈希值总和。我的目标是使该函数读取文件而不是3（read_for_copy + read_for_hash + read_for_another_copy）一次，以最大程度地减少网络负载。因此，我尝试读取一块文件，然后计算md5哈希和并将文件写出到几个位置。文件大小可能从100 MB到2 TB，甚至更大。此时无需检查文件身份，只需计算初始文件的哈希值即可。

而且我对计算散列总和感到困惑：

    $ifile = "C:\Users\User\Desktop\inputfile"
    $ofile = "C:\Users\User\Desktop\outputfile_1"
    $ofile2 = "C:\Users\User\Desktop\outputfile_2"
    
    $md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
    $bufferSize = 10mb
    $stream = [System.IO.File]::OpenRead($ifile)
    $makenew = [System.IO.File]::OpenWrite($ofile)
    $makenew2 = [System.IO.File]::OpenWrite($ofile2)
    $buffer = new-object Byte[] $bufferSize
    
    while ( $stream.Position -lt $stream.Length ) {
       
     $bytesRead = $stream.Read($buffer, 0, $bufferSize)
     $makenew.Write($buffer, 0, $bytesread) 
     $makenew2.Write($buffer, 0, $bytesread) 
    
     # I am stuck here
     $hash = [System.BitConverter]::ToString($md5.ComputeHash($buffer)) -replace "-",""      
            
            }
    
    $stream.Close()
    $makenew.Close()
    $makenew2.Close()

如何收集数据块以计算整个文件的哈希？

还有一个额外的问题：是否可以在并行模式下计算哈希并写出数据？特别考虑到workflow {parallel{}}PS版本6不支持的内容？

非常感谢

科斯蒂安

最终上市

$ifile = "C:\Users\User\Desktop\inputfile"
$ofile = "C:\Users\User\Desktop\outputfile_1"
$ofile2 = "C:\Users\User\Desktop\outputfile_2"

$md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
$bufferSize = 1mb
$stream = [System.IO.File]::OpenRead($ifile)
$makenew = [System.IO.File]::OpenWrite($ofile)
$makenew2 = [System.IO.File]::OpenWrite($ofile2)
$buffer = new-object Byte[] $bufferSize

while ( $stream.Position -lt $stream.Length ) 
{
     $bytesRead = $stream.Read($buffer, 0, $bufferSize)
     $makenew.Write($buffer, 0, $bytesread) 
     $makenew2.Write($buffer, 0, $bytesread) 
    
     $hash = $md5.TransformBlock($buffer, 0 , $bytesRead, $null , 0)  
} 

$md5.TransformFinalBlock([byte[]]::new(0), 0, 0)
$hash = [BitConverter]::ToString($md5.Hash).Replace('-','')      
$hash
$stream.Flush()
$stream.Close()
$makenew.Flush()
$makenew.Close()
$makenew2.Flush()
$makenew2.Close()

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