PowerShell切割或合并文件

Split-Merge-File.ps1

# Obtain a suitable buffer length by partial file length
function Get-BufferLength ([int]$partialFileLength)
{
[int]$MinBufferLength = 1MB
# No need to consume great amount memory，initialize as 50M, you can adjust it from here.
[int]$MaxBufferLength = 50MB

if($partialFileLength -ge 1GB) { return $MaxBufferLength}
elseif( $partialFileLength -le 50MB) { return $MinBufferLength }
else{ return [int]( $MaxBufferLength/1GB * $partialFileLength )}
}

# Write partial stream to file from current position
function Write-PartialStreamToFile
{
param(
[IO.FileStream]$stream,
[long]$length,
[string]$outputFile
)

#copy stream to file
function Copy-Stream( [int]$bufferLength )
{
[byte[]]$buffer = New-Object byte[]( $bufferLength )

# Read partial file data to memory buffer
$stream.Read($buffer,0,$buffer.Length) | Out-Null

# Flush buffer to file
$outStream = New-Object IO.FileStream($outputFile,'Append','Write','Read')
$outStream.Write($buffer,0,$buffer.Length)
$outStream.Flush()
$outStream.Close()
}

$maxBuffer = Get-BufferLength $length
$remBuffer = 0
$loop = [Math]::DivRem($length,$maxBuffer,[ref]$remBuffer)

if($loop -eq 0)
{
Copy-Stream $remBuffer
return
}

1..$loop | foreach {
$bufferLength = $maxBuffer

# let last loop contains remanent length
if( ($_ -eq $loop) -and ($remBuffer -gt 0) )
{
$bufferLength = $maxBuffer + $remBuffer
}
Copy-Stream $bufferLength

# show outer progress
$progress = [int]($_*100/$loop)
write-progress -activity 'Writting file' -status 'Progress' -id 2 -percentcomplete $progress -currentOperation "$progress %"
}
}

# split a large file into mutiple parts by part count or part length
function Split-File
{
param(
[Parameter(Mandatory=$True)]
[IO.FileInfo]$File,
[Switch]$ByPartCount,
[Switch]$ByPartLength,
[int]$PartCount,
[int]$PartLength,
[IO.DirectoryInfo]$OutputDir = '.'
)

# Argument validation
if(-not $File.Exists) { throw "Source file [$File] not exists" }
if(-not $OutputDir.Exists) { mkdir $OutputDir.FullName | Out-Null}
if( (-not $ByPartCount) -and (-not $ByPartLength) )
{
throw 'Must specify one of parameter, [ByPartCount] or [ByPartLength]'
}
elseif( $ByPartCount )
{
if($PartCount -le 1) {throw '[PartCount] must larger than 1'}
$PartLength = $File.Length / $PartCount
}
elseif( $ByPartLength )
{
if($PartLength -lt 1) { throw '[PartLength] must larger than 0' }
if($PartLength -ge $File.Length) { throw '[PartLength] must less than source file' }
$temp = $File.Length /$PartLength
$PartCount = [int]$temp
if( ($File.Length % $PartLength) -gt 0 -and ( $PartCount -lt $temp ) )
{
$PartCount++
}
}

$stream = New-Object IO.FileStream($File.FullName,
[IO.FileMode]::Open ,[IO.FileAccess]::Read ,[IO.FileShare]::Read )

# Make sure each part file name ended like '001' so that it's convenient to merge
[string]$numberMaskStr = [string]::Empty.PadLeft( [int]([Math]::Log10($PartCount) + 1), "0" )

1 .. $PartCount | foreach {
$outputFile = Join-Path $OutputDir ( "{0}.part_{1} " -f $File.Name , $_.ToString( $numberMaskStr ) )
# show outer progress
$progress = [int]($_*100/$PartCount)
write-progress -activity "Splitting file" -status "Progress $progress %" -Id 1 -percentcomplete $progress -currentOperation "Handle file $outputFile"
if($_ -eq $PartCount)
{
Write-PartialStreamToFile $stream ($stream.Length - $stream.Position) $outputFile
}
else
{
Write-PartialStreamToFile $stream $PartLength $outputFile
}
}
$stream.Close()
}

function Merge-File
{
param(
[Parameter(Mandatory=$True)]
[IO.DirectoryInfo]$SourceDir,
[string]$Filter,
[IO.FileInfo]$OutputFile
)

# arguments validation
if ( -not $SourceDir.Exists ) { throw "Directory $SourceDir not exists." }
$files = dir $SourceDir -Filter $Filter
if($files -eq $null){ throw "No matched file in directory $SourceDir"}

# output stream
$outputStream = New-Object IO.FileStream($OutputFile.FullName,
[IO.FileMode]::Append ,[IO.FileAccess]::Write ,[IO.FileShare]::Read )

# merge file
$files | foreach{
#input stream
$inputStream = New-Object IO.FileStream($_.FullName,
[IO.FileMode]::Open ,[IO.FileAccess]::Read ,[IO.FileShare]::Read )

$bufferLength = Get-BufferLength -partialFileLength $_.Length
while($inputStream.Position -lt $inputStream.Length)
{
if( ($inputStream.Position + $bufferLength) -gt $inputStream.Length)
{
$bufferLength = $inputStream.Length - $inputStream.Position
}

# show outer progress
$progress = [int]($inputStream.Position *100/ $inputStream.Length)
write-progress -activity 'Merging file' -status "Progress $progress %" -percentcomplete $progress

# read file to memory buffer
$buffer= New-Object byte[]( $bufferLength )
$inputStream.Read( $buffer,0,$buffer.Length) | Out-Null

#flush buffer to file
$outputStream.Write( $buffer,0,$buffer.Length) | Out-Null
$outputStream.Flush()
}
$inputStream.Close()
}
$outputStream.Close()}


导入函数 Split-Merge-File, .后面空格加脚本

. .\Split-Merge-File.ps1


分割文件

Split-File -File 'D:\source\test.dat' -ByPartLength -PartLength 50MB -OutputDir 'D:\source\'


合并文件

Merge-File -SourceDir 'D:\source\' -Filter "*part*" -OutputFile 'D:\source\test.dat'


验证文件SHA1

certutil -hashfile D:\source\test.dat SHA1


参考文章

https://www.cnblogs.com/qiushuiblog/p/11510896.html