See below some functions declarations for Visual Basic. Frequently Asked Question: Q: Each time I use the compress function I get the -5 error (not enough room in the output buffer). A: Make sure that the length of the compressed buffer is passed by reference ("as any"), not by value ("as long"). Also check that before the call of compress this length is equal to the total size of the compressed buffer and not zero. From: "Jon Caruana" Subject: Re: How to port zlib declares to vb? Date: Mon, 28 Oct 1996 18:33:03 -0600 Got the answer! (I haven't had time to check this but it's what I got, and looks correct): He has the following routines working: compress uncompress gzopen gzwrite gzread gzclose Declares follow: (Quoted from Carlos Rios , in Vb4 form) #If Win16 Then 'Use Win16 calls. Declare Function compress Lib "ZLIB.DLL" (ByVal compr As String, comprLen As Any, ByVal buf As String, ByVal buflen As Long) As Integer Declare Function uncompress Lib "ZLIB.DLL" (ByVal uncompr As String, uncomprLen As Any, ByVal compr As String, ByVal lcompr As Long) As Integer Declare Function gzopen Lib "ZLIB.DLL" (ByVal filePath As String, ByVal mode As String) As Long Declare Function gzread Lib "ZLIB.DLL" (ByVal file As Long, ByVal uncompr As String, ByVal uncomprLen As Integer) As Integer Declare Function gzwrite Lib "ZLIB.DLL" (ByVal file As Long, ByVal uncompr As String, ByVal uncomprLen As Integer) As Integer Declare Function gzclose Lib "ZLIB.DLL" (ByVal file As Long) As Integer #Else Declare Function compress Lib "ZLIB32.DLL" (ByVal compr As String, comprLen As Any, ByVal buf As String, ByVal buflen As Long) As Integer Declare Function uncompress Lib "ZLIB32.DLL" (ByVal uncompr As String, uncomprLen As Any, ByVal compr As String, ByVal lcompr As Long) As Long Declare Function gzopen Lib "ZLIB32.DLL" (ByVal file As String, ByVal mode As String) As Long Declare Function gzread Lib "ZLIB32.DLL" (ByVal file As Long, ByVal uncompr As String, ByVal uncomprLen As Long) As Long Declare Function gzwrite Lib "ZLIB32.DLL" (ByVal file As Long, ByVal uncompr As String, ByVal uncomprLen As Long) As Long Declare Function gzclose Lib "ZLIB32.DLL" (ByVal file As Long) As Long #End If -Jon Caruana jon-net@usa.net Microsoft Sitebuilder Network Level 1 Member - HTML Writer's Guild Member Here is another example from Michael that he says conforms to the VB guidelines, and that solves the problem of not knowing the uncompressed size by storing it at the end of the file: 'Calling the functions: 'bracket meaning: [optional] {Range of possible values} 'Call subCompressFile( [, , [level of compression {1..9}]]) 'Call subUncompressFile() Option Explicit Private lngpvtPcnSml As Long 'Stores value for 'lngPercentSmaller' Private Const SUCCESS As Long = 0 Private Const strFilExt As String = ".cpr" Private Declare Function lngfncCpr Lib "zlib.dll" Alias "compress2" (ByRef dest As Any, ByRef destLen As Any, ByRef src As Any, ByVal srcLen As Long, ByVal level As Integer) As Long Private Declare Function lngfncUcp Lib "zlib.dll" Alias "uncompress" (ByRef dest As Any, ByRef destLen As Any, ByRef src As Any, ByVal srcLen As Long) As Long Public Sub subCompressFile(ByVal strargOriFilPth As String, Optional ByVal strargCprFilPth As String, Optional ByVal intLvl As Integer = 9) Dim strCprPth As String Dim lngOriSiz As Long Dim lngCprSiz As Long Dim bytaryOri() As Byte Dim bytaryCpr() As Byte lngOriSiz = FileLen(strargOriFilPth) ReDim bytaryOri(lngOriSiz - 1) Open strargOriFilPth For Binary Access Read As #1 Get #1, , bytaryOri() Close #1 strCprPth = IIf(strargCprFilPth = "", strargOriFilPth, strargCprFilPth) 'Select file path and name strCprPth = strCprPth & IIf(Right(strCprPth, Len(strFilExt)) = strFilExt, "", strFilExt) 'Add file extension if not exists lngCprSiz = (lngOriSiz * 1.01) + 12 'Compression needs temporary a bit more space then original file size ReDim bytaryCpr(lngCprSiz - 1) If lngfncCpr(bytaryCpr(0), lngCprSiz, bytaryOri(0), lngOriSiz, intLvl) = SUCCESS Then lngpvtPcnSml = (1# - (lngCprSiz / lngOriSiz)) * 100 ReDim Preserve bytaryCpr(lngCprSiz - 1) Open strCprPth For Binary Access Write As #1 Put #1, , bytaryCpr() Put #1, , lngOriSiz 'Add the the original size value to the end (last 4 bytes) Close #1 Else MsgBox "Compression error" End If Erase bytaryCpr Erase bytaryOri End Sub Public Sub subUncompressFile(ByVal strargFilPth As String) Dim bytaryCpr() As Byte Dim bytaryOri() As Byte Dim lngOriSiz As Long Dim lngCprSiz As Long Dim strOriPth As String lngCprSiz = FileLen(strargFilPth) ReDim bytaryCpr(lngCprSiz - 1) Open strargFilPth For Binary Access Read As #1 Get #1, , bytaryCpr() Close #1 'Read the original file size value: lngOriSiz = bytaryCpr(lngCprSiz - 1) * (2 ^ 24) _ + bytaryCpr(lngCprSiz - 2) * (2 ^ 16) _ + bytaryCpr(lngCprSiz - 3) * (2 ^ 8) _ + bytaryCpr(lngCprSiz - 4) ReDim Preserve bytaryCpr(lngCprSiz - 5) 'Cut of the original size value ReDim bytaryOri(lngOriSiz - 1) If lngfncUcp(bytaryOri(0), lngOriSiz, bytaryCpr(0), lngCprSiz) = SUCCESS Then strOriPth = Left(strargFilPth, Len(strargFilPth) - Len(strFilExt)) Open strOriPth For Binary Access Write As #1 Put #1, , bytaryOri() Close #1 Else MsgBox "Uncompression error" End If Erase bytaryCpr Erase bytaryOri End Sub Public Property Get lngPercentSmaller() As Long lngPercentSmaller = lngpvtPcnSml End Property