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Hugoberry/Unz.m

Last active Mar 20, 2017
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Replicating R unz function in Power Query. Based on http://sql10.blogspot.co.uk/2016/06/reading-zip-files-in-powerquery-m.html
(binaryZip,fileName) =>
let
//shorthand
UInt32 = BinaryFormat.ByteOrder(BinaryFormat.UnsignedInteger32,ByteOrder.LittleEndian),
UInt16 = BinaryFormat.ByteOrder(BinaryFormat.UnsignedInteger16,ByteOrder.LittleEndian),
//ZIP file header fixed size structure
Header = BinaryFormat.Record([
MiscHeader = BinaryFormat.Binary(14),
CompressedSize = UInt32,
UncompressedSize = UInt32,
FileNameLen = UInt16,
ExtraFieldLen = UInt16]),
//ZIP file header dynamic size structure
FileData = (h)=> BinaryFormat.Record([
FileName = BinaryFormat.Text(h[FileNameLen]),
ExtraField = BinaryFormat.Text(h[ExtraFieldLen]),
UncompressedData = BinaryFormat.Transform(
BinaryFormat.Binary(h[CompressedSize]),
(x) => try
Binary.Buffer(Binary.Decompress(x, Compression.Deflate))
otherwise null)]),
//Parsing the binary in search for PKZIP header signature
ZipIterator = BinaryFormat.Choice(UInt32, (signature) => if signature <> 0x04034B50
then BinaryFormat.Record([FileName=null])
else BinaryFormat.Choice(Header,(z)=>FileData(z))),
ZipFormat = BinaryFormat.List(ZipIterator),
out = List.Select(ZipFormat(binaryZip), each _[FileName]=fileName)
in
out{0}[UncompressedData]
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