Powershell: improving LDIF file to CSV conversion - performance

Question

I have the below code to convert an LDIF file (over 100.000 lines) to a CSV file (over 4.000 lines), but I'm not sure I'm happy with the time it takes - although I don't know how long it should take really; maybe that's a normal time on my laptop (Core i5 7th Gen, 16GB RAM, SSD drive)?
Would there be any room for improvement? (especially for the parsing if possible, which takes 30 seconds)
# Reducing & editing data to process:
# -----------------------------------
$original = Get-Content $IN_ldif_file
$reduced = (($original | select-string -pattern '^cust[A-Z]','^$' -CaseSensitive).Line) -replace ':: ', ': ' -replace '^cust',''
"Writing reduced LDIF file..." # < 1 sec
(Measure-Command { Set-Content $reducedLDIF -Value $reduced -Encoding UTF8 }).TotalSeconds
# Parsing the relevant data:
# --------------------------
$inData = New-Object -TypeName System.IO.StreamReader -ArgumentList $reducedLDIF
$a = #{} # initialize the temporary hash
$lineNum = $rcdNum = 0 # initialize the counters
"Parsing reduced LDIF file..." # 27-36 sec
(Measure-Command {
# Begin reading and processing the input file:
$results = while (-not $inData.EndOfStream)
{
$line = $inData.ReadLine()
Write-Verbose "$("{0:D4}" -f ++$lineNum)|$("{0:D4}|" -f $rcdNum)$line"
if (($line -match "^\s*$") -or $inData.EndOfStream )
{
# blank line or end of stream - dump the hash as an object and reinit the hash
[PSCustomObject]$a
$a = #{}
$rcdNum++
} else {
# build up hash table for the object
$key, $value = $line -split ": "
$a[$key] = $value
}
}
$inData.Close()
}).TotalSeconds
# Populating & writing the CSV file:
# ----------------------------------
"Populating the CSV data..." # 7-11 sec
(Measure-Command {
$out = $results |
select "Attribute01",
"Attribute02",
"Attribute03",
<# etc... #>
#{n="Attribute39"; E={$_."Attribute20"}}, # Attribute39 (not in LDIF) takes value of Attribute20
"Attribute40"
}).TotalSeconds
"Writing CSV file..." # < 1 sec
(Measure-Command { $out | Export-CSV $OUT_csv_file -NoTypeInformation }).TotalSeconds
Note: I actually don't need to export the "$reduced" data to a file (e.g. "$reducedLDIF"), but the piece of code I found for the parsing seems to require a file.
Thanks!

Answer 1

So I found a way to cut the parsing time by almost half, by re-using the data in the $reduced variable that's already in memory:
$a = #{} # initialize the temporary hash
$lineNum = $rcdNum = 0 # initialize the counters
"Parsing reduced LDIF file..."
(Measure-Command {
$results = ForEach ($line in $reduced) {
Write-Verbose "$("{0:D6}" -f ++$lineNum)|$("{0:D4}|" -f $rcdNum)$line"
if ($line -match "^\s*$")
{ # blank line or end of stream - dump the hash as an object and reinit the hash
[PSCustomObject]$a
$a = #{}
$rcdNum++
}
else {
# build up hash table for the object
$key, $value = $line -split ": "
$a[$key] = $value
}
}
}).TotalSeconds
This is already more acceptable (about 16 sec instead of 30).