File specification

Normally, I'd post this in General VB, but threads that I start there don't go that far and don't help much. But you hackers tend to know how to break things. :)

I am working on a file specification for PassProg 2. Ignoring encryption for now (I'll work on that after I know what to encrypt :)), I need a way to store data in the following format:

Code:

---

File
|
+-- Entries
    |
    +-- Username
    +-- Password
    +-- Comments
    +-- etc.

---

So there are multiple entries in a file, and each entry contains a username, password, date, etc. What I did in PassProg 1 was use an INI file, but that was crude, IMHO. Any ideas for a proprietary PP2 format?

Make a linked list :)

What you do is, have a header Type containing info about the file, for example:

VB Code:

Type PP2Header
    sOwnerName As String*64 ' Or whatever
    lOtherRandomThing As Long
    lFirstEntry As Long ' Location in the file of the first entry
End Type

You have one of those first in the file (perhaps some signature bytes as well?) and then follow it up with the entry types. This is where it gets clever...

VB Code:

Type PP2Entry
    sName As String*64 ' Entry name
    lType As Long ' Entry type (possibly use an Enum for this?
    lLocation As Long ' Location in the file of the data for this entry
    lLength As Long ' Length of the associated data
End Type

Then you can have different Types for different things you need to store.

It's a bit abstract, but you might get the gist of it :)

Do you have an example of what it would look like? BTW, I forgot, a master password for the file would be stored there too (not as part of an entry, but by itself).

Example of what looking like what?

What a sample file would look like.

OK you'd have to give me a moment alone with a hex editor though ;) It wouldn't really look like much, but I'll see what I can do (I think in terms of 8-byte aligned and packed structs rather than Types).

BTW, ALL of the fields must be able to support 65,535 characters (the capacity of a textbox). I was thinking of something newline-delimited.

Oh. I was thinking of something groovy and complicated but pretty simple to read into the program. Do you mind if the fields are padded at all? This is so much easier in C where strings have a nice fat NULL on the end :rolleyes:

Newline-delimited text files are ok, but a ***** to process.

What do mean, "padded?" Surrounded by null chars or spaces, or am I not thinking along the correct lines?

OK, for example you needed to hold 65536 chars per type field. Is it ok just to have that allocated in the type, or to store them separately using a length? Be a bit of a bastard to write but your choice...

Sorry, I still don't understand. Do you mean declare them in VB as String * 65535?

Yep.

Oooh....65535 is the maximum length for a fixed length string. HAHAHA :p

Sorry ;)

Oh. If you do that you'll have 65K wasted for every entry :eek:

And one big file, considering that PassProg 2 will support up to however many items a listview or Long can store, whichever is smaller. :eek:

OK prepare yourself for a way cool method.

1. Header
2. Index of data items and their sizes
3. Entries begin here, and they refer to data items by ID
4. Data items follow in a big mess

Just coding it up now (this looks cool :D)

Code:

---

Type PP2File
    sOwnerName As String
    lOtherRandomThing As Long
    PP2Entries() as PP2Entry
End Type

Type PP2Entry
    sName As String
    lType As Long
    lLocation As Long
    Data as String
End Type
...
dim x as PP2File
...
Put#f,,x'in a file opened in binary

---

Strings are dynamic length though :confused:

Won't that totally bugger it up?

Nope, typenested strings and arrays will include a 2 or 6 byte descriptor making things so much easier

It all depends on whether you want sequential or random access. Fixed length records are pretty much a necessity for random access but not for sequential access.

Instead of making a proprietary format, why don't you just use XML and let the encryption obfuscate the data?

But then you've got a huge waste of space using XML.

VB Code:

Private Sub btnRead_Click()
    Dim x As PP2File
    Open "temp.pp2" For Binary As #1
        Get #1, , x
    Close #1
    Dim i As Long
    Dim nd As Node
    Set nd = tvDisplay.Nodes.Add(, , , x.sOwnerName)
    For i = LBound(x.PP2Entries) To UBound(x.PP2Entries)
        Dim ndb As Node
        Set ndb = tvDisplay.Nodes.Add(nd, tvwChild, , x.PP2Entries(i).sName)
        tvDisplay.Nodes.Add ndb, tvwChild, , x.PP2Entries(i).Data
    Next i
End Sub
Private Sub btnWrite_Click()
    Dim x As PP2File
    x.sOwnerName = "Mike Parks"
    ReDim x.PP2Entries(0 To 1)
    x.PP2Entries(0).sName = "Hi there"
    x.PP2Entries(0).Data = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    x.PP2Entries(1).sName = "Different"
    x.PP2Entries(1).Data = "BLAH BLAH BLAH"
    Open "temp.pp2" For Binary As #1
        Put #1, , x
    Close #1
End Sub

:)

I thought you were lazy parksie ? :p

That's why I did it in VB :p