cannam@89: See below some functions declarations for Visual Basic.
cannam@89: 
cannam@89: Frequently Asked Question:
cannam@89: 
cannam@89: Q: Each time I use the compress function I get the -5 error (not enough
cannam@89:    room in the output buffer).
cannam@89: 
cannam@89: A: Make sure that the length of the compressed buffer is passed by
cannam@89:    reference ("as any"), not by value ("as long"). Also check that
cannam@89:    before the call of compress this length is equal to the total size of
cannam@89:    the compressed buffer and not zero.
cannam@89: 
cannam@89: 
cannam@89: From: "Jon Caruana" <jon-net@usa.net>
cannam@89: Subject: Re: How to port zlib declares to vb?
cannam@89: Date: Mon, 28 Oct 1996 18:33:03 -0600
cannam@89: 
cannam@89: Got the answer! (I haven't had time to check this but it's what I got, and
cannam@89: looks correct):
cannam@89: 
cannam@89: He has the following routines working:
cannam@89:         compress
cannam@89:         uncompress
cannam@89:         gzopen
cannam@89:         gzwrite
cannam@89:         gzread
cannam@89:         gzclose
cannam@89: 
cannam@89: Declares follow: (Quoted from Carlos Rios <c_rios@sonda.cl>, in Vb4 form)
cannam@89: 
cannam@89: #If Win16 Then   'Use Win16 calls.
cannam@89: Declare Function compress Lib "ZLIB.DLL" (ByVal compr As
cannam@89:         String, comprLen As Any, ByVal buf As String, ByVal buflen
cannam@89:         As Long) As Integer
cannam@89: Declare Function uncompress Lib "ZLIB.DLL" (ByVal uncompr
cannam@89:         As String, uncomprLen As Any, ByVal compr As String, ByVal
cannam@89:         lcompr As Long) As Integer
cannam@89: Declare Function gzopen Lib "ZLIB.DLL" (ByVal filePath As
cannam@89:         String, ByVal mode As String) As Long
cannam@89: Declare Function gzread Lib "ZLIB.DLL" (ByVal file As
cannam@89:         Long, ByVal uncompr As String, ByVal uncomprLen As Integer)
cannam@89:         As Integer
cannam@89: Declare Function gzwrite Lib "ZLIB.DLL" (ByVal file As
cannam@89:         Long, ByVal uncompr As String, ByVal uncomprLen As Integer)
cannam@89:         As Integer
cannam@89: Declare Function gzclose Lib "ZLIB.DLL" (ByVal file As
cannam@89:         Long) As Integer
cannam@89: #Else
cannam@89: Declare Function compress Lib "ZLIB32.DLL"
cannam@89:         (ByVal compr As String, comprLen As Any, ByVal buf As
cannam@89:         String, ByVal buflen As Long) As Integer
cannam@89: Declare Function uncompress Lib "ZLIB32.DLL"
cannam@89:         (ByVal uncompr As String, uncomprLen As Any, ByVal compr As
cannam@89:         String, ByVal lcompr As Long) As Long
cannam@89: Declare Function gzopen Lib "ZLIB32.DLL"
cannam@89:         (ByVal file As String, ByVal mode As String) As Long
cannam@89: Declare Function gzread Lib "ZLIB32.DLL"
cannam@89:         (ByVal file As Long, ByVal uncompr As String, ByVal
cannam@89:         uncomprLen As Long) As Long
cannam@89: Declare Function gzwrite Lib "ZLIB32.DLL"
cannam@89:         (ByVal file As Long, ByVal uncompr As String, ByVal
cannam@89:         uncomprLen As Long) As Long
cannam@89: Declare Function gzclose Lib "ZLIB32.DLL"
cannam@89:         (ByVal file As Long) As Long
cannam@89: #End If
cannam@89: 
cannam@89: -Jon Caruana
cannam@89: jon-net@usa.net
cannam@89: Microsoft Sitebuilder Network Level 1 Member - HTML Writer's Guild Member
cannam@89: 
cannam@89: 
cannam@89: Here is another example from Michael <michael_borgsys@hotmail.com> that he
cannam@89: says conforms to the VB guidelines, and that solves the problem of not
cannam@89: knowing the uncompressed size by storing it at the end of the file:
cannam@89: 
cannam@89: 'Calling the functions:
cannam@89: 'bracket meaning: <parameter> [optional] {Range of possible values}
cannam@89: 'Call subCompressFile(<path with filename to compress> [, <path with
cannam@89: filename to write to>, [level of compression {1..9}]])
cannam@89: 'Call subUncompressFile(<path with filename to compress>)
cannam@89: 
cannam@89: Option Explicit
cannam@89: Private lngpvtPcnSml As Long 'Stores value for 'lngPercentSmaller'
cannam@89: Private Const SUCCESS As Long = 0
cannam@89: Private Const strFilExt As String = ".cpr"
cannam@89: Private Declare Function lngfncCpr Lib "zlib.dll" Alias "compress2" (ByRef
cannam@89: dest As Any, ByRef destLen As Any, ByRef src As Any, ByVal srcLen As Long,
cannam@89: ByVal level As Integer) As Long
cannam@89: Private Declare Function lngfncUcp Lib "zlib.dll" Alias "uncompress" (ByRef
cannam@89: dest As Any, ByRef destLen As Any, ByRef src As Any, ByVal srcLen As Long)
cannam@89: As Long
cannam@89: 
cannam@89: Public Sub subCompressFile(ByVal strargOriFilPth As String, Optional ByVal
cannam@89: strargCprFilPth As String, Optional ByVal intLvl As Integer = 9)
cannam@89:     Dim strCprPth As String
cannam@89:     Dim lngOriSiz As Long
cannam@89:     Dim lngCprSiz As Long
cannam@89:     Dim bytaryOri() As Byte
cannam@89:     Dim bytaryCpr() As Byte
cannam@89:     lngOriSiz = FileLen(strargOriFilPth)
cannam@89:     ReDim bytaryOri(lngOriSiz - 1)
cannam@89:     Open strargOriFilPth For Binary Access Read As #1
cannam@89:         Get #1, , bytaryOri()
cannam@89:     Close #1
cannam@89:     strCprPth = IIf(strargCprFilPth = "", strargOriFilPth, strargCprFilPth)
cannam@89: 'Select file path and name
cannam@89:     strCprPth = strCprPth & IIf(Right(strCprPth, Len(strFilExt)) =
cannam@89: strFilExt, "", strFilExt) 'Add file extension if not exists
cannam@89:     lngCprSiz = (lngOriSiz * 1.01) + 12 'Compression needs temporary a bit
cannam@89: more space then original file size
cannam@89:     ReDim bytaryCpr(lngCprSiz - 1)
cannam@89:     If lngfncCpr(bytaryCpr(0), lngCprSiz, bytaryOri(0), lngOriSiz, intLvl) =
cannam@89: SUCCESS Then
cannam@89:         lngpvtPcnSml = (1# - (lngCprSiz / lngOriSiz)) * 100
cannam@89:         ReDim Preserve bytaryCpr(lngCprSiz - 1)
cannam@89:         Open strCprPth For Binary Access Write As #1
cannam@89:             Put #1, , bytaryCpr()
cannam@89:             Put #1, , lngOriSiz 'Add the the original size value to the end
cannam@89: (last 4 bytes)
cannam@89:         Close #1
cannam@89:     Else
cannam@89:         MsgBox "Compression error"
cannam@89:     End If
cannam@89:     Erase bytaryCpr
cannam@89:     Erase bytaryOri
cannam@89: End Sub
cannam@89: 
cannam@89: Public Sub subUncompressFile(ByVal strargFilPth As String)
cannam@89:     Dim bytaryCpr() As Byte
cannam@89:     Dim bytaryOri() As Byte
cannam@89:     Dim lngOriSiz As Long
cannam@89:     Dim lngCprSiz As Long
cannam@89:     Dim strOriPth As String
cannam@89:     lngCprSiz = FileLen(strargFilPth)
cannam@89:     ReDim bytaryCpr(lngCprSiz - 1)
cannam@89:     Open strargFilPth For Binary Access Read As #1
cannam@89:         Get #1, , bytaryCpr()
cannam@89:     Close #1
cannam@89:     'Read the original file size value:
cannam@89:     lngOriSiz = bytaryCpr(lngCprSiz - 1) * (2 ^ 24) _
cannam@89:               + bytaryCpr(lngCprSiz - 2) * (2 ^ 16) _
cannam@89:               + bytaryCpr(lngCprSiz - 3) * (2 ^ 8) _
cannam@89:               + bytaryCpr(lngCprSiz - 4)
cannam@89:     ReDim Preserve bytaryCpr(lngCprSiz - 5) 'Cut of the original size value
cannam@89:     ReDim bytaryOri(lngOriSiz - 1)
cannam@89:     If lngfncUcp(bytaryOri(0), lngOriSiz, bytaryCpr(0), lngCprSiz) = SUCCESS
cannam@89: Then
cannam@89:         strOriPth = Left(strargFilPth, Len(strargFilPth) - Len(strFilExt))
cannam@89:         Open strOriPth For Binary Access Write As #1
cannam@89:             Put #1, , bytaryOri()
cannam@89:         Close #1
cannam@89:     Else
cannam@89:         MsgBox "Uncompression error"
cannam@89:     End If
cannam@89:     Erase bytaryCpr
cannam@89:     Erase bytaryOri
cannam@89: End Sub
cannam@89: Public Property Get lngPercentSmaller() As Long
cannam@89:     lngPercentSmaller = lngpvtPcnSml
cannam@89: End Property