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" <jon-net@usa.net>
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 <c_rios@sonda.cl>, 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 <michael_borgsys@hotmail.com> 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: <parameter> [optional] {Range of possible values}
'Call subCompressFile(<path with filename to compress> [, <path with
filename to write to>, [level of compression {1..9}]])
'Call subUncompressFile(<path with filename to compress>)
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
