[Gambas-user] File Format Help

[John Dovey]

As a followup to my own message, this is what I've gotten to so far. I KNOW
my struct is incorrect, but I'm not sure what it should be. For those
interested, I've included a test.msg file that is maybe a better example.

Public Struct myFidoMsg 'Datatype
    fromUserName As Byte[] '36
    toUserName As Byte[] '36
    subject As Byte[] '72
    DateTime As Byte[] ' 20
    timesRead As Integer
    destNode As Integer
    origNode As Integer
    cost As Integer
    origNet As Integer
    destNet As Integer
    destZone As Integer
    origZone As Integer
    destPoint As Integer
    origPoint As Integer
    replyTo As Integer
    Attribute As Integer
    nextReply As Integer
    text As String 'null terminated
End Struct

Sub Main()

    Dim hfile As File
    Dim FidoMsg As MyFidoMsg

    hfile = Open "test.msg" For Read 'Write Create
    FidoMsg = Read #hfile As MyFidoMsg
    'Read
    'Write #hfile, FidoMsg As MyFidoMsg
    Close #hfile
end sub

On Thu, 17 Jun 2021 at 09:46, John Dovey <dovey.john at gmail.com> wrote:

> I hope no-one minds if I ask this here. I'm just really unsure how to do
> this best in Gambas.
> I want to read and write files that have a (very old) specification
> <http://ftsc.org/docs/fts-0001.016>
> Essentially, it looks like this:
>
>  1. Application Layer Data Definition : a Stored Message
>
>                                Stored Message
>
>        Offset
>       dec hex
>               .-----------------------------------------------.
>         0   0 |                                               |
>               ~                 fromUserName                  ~
>               |                   36 bytes                    |
>               +-----------------------+-----------------------+
>        36  24 |                                               |
>               ~                  toUserName                   ~
>               |                   36 bytes                    |
>               +-----------------------+-----------------------+
>        72  48 |                                               |
>               ~                    subject                    ~
>               |                   72  bytes                   |
>               +-----------------------+-----------------------+
>       144  90 |                                               |
>               ~                    DateTime                   ~
>               |                    20 bytes                   |
>               +-----------------------+-----------------------+
>       164  A4 | timesRead (low order) | timesRead (high order)|
>               +-----------------------+-----------------------+
>       166  A6 | destNode (low order)  | destNode (high order) |
>               +-----------------------+-----------------------+
>       168  A8 | origNode (low order)  | origNode (high order) |
>               +-----------------------+-----------------------+
>       170  AA |   cost (low order)    |   cost (high order)   |
>               +-----------------------+-----------------------+
>       172  AC | origNet (low order)   | origNet (high order)  |
>               +-----------------------+-----------------------+
>       174  AE | destNet (low order)   | destNet (high order)  |
>               +-----------------------+-----------------------+
>       176  B0 | destZone (optional)   | destZone (optional)   |
>               +-----------------------+-----------------------+
>       178  B2 | origZone (optional)   | origZone (optional)   |
>               +-----------------------+-----------------------+
>       180  B4 | destPoint(optional)   | destPoint(optional)   |
>               +-----------------------+-----------------------+
>       182  B6 | origPoint(optional)   | origPoint(optional)   |
>               +-----------------------+-----------------------+
>       184  B8 |  replyTo (low order)  |  replyTo (high order) |
>               +-----------------------+-----------------------+
>       186  BA | Attribute (low order) | Attribute (high order)|
>               +-----------------------+-----------------------+
>       188  BC | nextReply (low order) | nextReply (high order)|
>               +-----------------------+-----------------------+
>       190  BE |                      text                     |
>               ~                    unbounded                  ~
>               |                 null terminated               |
>               `-----------------------------------------------'
>
>       Message    = fromUserName(36)  (* Null terminated *)
>                    toUserName(36)    (* Null terminated *)
>                    subject(72)       (* see FileList below *)
>                    DateTime          (* message body was last edited *)
>                    timesRead         (* number of times msg has been read *)
>                    destNode          (* of message *)
>                    origNode          (* of message *)
>                    cost              (* in lowest unit of originator's
>                                         currency *)
>                    origNet           (* of message *)
>                    destNet           (* of message *)
>                    destZone          (* of message *)
>                    origZone          (* of message *)
>                    destPoint         (* of message *)
>                    origPoint         (* of message *)
>                    replyTo           (* msg to which this replies *)
>                    AttributeWord
>                    nextReply         (* msg which replies to this *)
>                    text(unbounded)   (* Null terminated *)
>
> There is a sample packet <https://www.dan.info/sampledata/BAD_BNDL.007> you can look at if you really want to see what it looks like, but this should give you an idea:
>
> [image: image.png]
>
>
> I'm guessing a "Struct" of some sort?
>
> Any advice would be appreciated.
>
>
> John
>
>
>
>
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