Pointer error with union'ed ASCIIZ pointers?

[colin glenn Member Find all posts View Profile Close colin glenn]

This is most curious. Bear in mind that I've solved my initial problem with using ASCIIZ pointers into a union'ed structure, but the results are most curious as to WHY this behavior exists.

The function (Winsock is initialized):

SUB GenerateIpPort(hDialog AS DWORD, hostToIP AS STRING)
LOCAL Work          AS STRING
LOCAL sockin        AS sockaddr_in
LOCAL dwHost        AS hostentStru PTR
LOCAL connectHost   AS ASCIIZ * 256
LOCAL zStr          AS ASCIIZ PTR * 5
LOCAL zWord         AS DWORD PTR

    sockin.sin_port = htons(80)
    connectHost = hostToIp
    dwHost = GetHostByName(connectHost)

    IF dwHost = %NULL THEN
        DisplayMessage hostToIp &" = Unresolved / Bad Host Name"
    ELSE
        Work = @[email protected]_name
        zWord = @dwHost.h_list
        zStr = @zWord
        Work = Work &" = "& USING$("#_.#_.#_.#", _
            ASC(MID$(@zStr[0],1,1)),  ASC(MID$(@zStr[0],2,1)), _
                ASC(MID$(@zStr[0],3,1)), ASC(MID$(@zStr[0],4,1)))

        Work = Work &" / "& HEX$(@dwHost.h_addr, 4)
        DisplayMessage Work

        ' this is what i was using first to get at the packed IP
        ' sockin.sin_addr.s = @zStr[0]

        sockin.sin_addr.s_addr = @@zWord
        zStr = inet_ntoa(sockin.sin_addr.s_addr)

        Work = @zStr
        Work = Work &" = "& USING$("#_.#_.#_.#", _
            sockin.sin_addr.S_un_b.s_b1, sockin.sin_addr.S_un_b.s_b2, _
                sockin.sin_addr.S_un_b.s_b3, sockin.sin_addr.S_un_b.s_b4) _
                    &" / "& HEX$(sockin.sin_addr.s_addr, 8)

        DisplayMessage Work
    END IF
END SUB

No, it's not a function yet, this is just a test to figure things out.

When called with various host names as the hostToIP string, I get the following results:

' should return the proper IP address.
GenerateIpPort CB.HNDL, "yahoo.com"
' yahoo.com = 69.147.114.224 / 0002
' 69.147.114.224 = 69.147.114.224 / E0729345
' why yes it does.

' should generate a failure to resolve.
GenerateIpPort CB.HNDL, "bad.yahoo.com"
' bad.yahoo.com = Unresolved / Bad Host Name
' yep.

' this is blocked via my HOSTS file.
GenerateIpPort CB.HNDL, "www.incredimail.com"
' www.incredimail.com = 127.-1.-1.-1 / 0002
' 127.0.0.1 = 127.0.0.1 / 0100007F
' ok, the ASC is not returning character codes below 32?

And it all works, but the results from the third "lookup" is most curious when you access the 4 bytes of the return via a ASCIIZ string pointer, it's returning the 0's and the 1 as -1.

So, is ASC failing here? And if so, how?

P.S. Title of the post was hard to come up with, ...

[Jeff Blakeney Member Find all posts View Profile Close Jeff Blakeney]

There was quite a discussion on ASC, MID$ and other statements recently. It looks like you are trying to use the string commands on a DWORD (zWord is pointer to a DWORD, zStr is a pointer to a 5 character string and you are setting its address to the address of zWord). If a character in a string is ASCII value 0, it is considered null so the MID$ of the second and third bytes of 127.0.0.1 will return a null string and ASC of a null string returns -1. I'm not sure why the fourth byte is giving you a -1.

Have you considered using PEEK instead? Instead of all the ASC(MID$(...)) in the USING$ statement, use PEEK(BYTE, @zWord), PEEK(BYTE, @zWord + 1), PEEK(BYTE, @zWord + 2), PEEK(BYTE, @zWord + 3). At least, I think that is the way it should look.