I'm sorry, that should have been :ubyte. Being able to insert arbitrary
data into a codec is a feature, though.
On Mon, Jan 12, 2015 at 6:27 AM, Tzach <tzach.livya...@gmail.com> wrote:
> Hi Zach
> Thanks for the detailed response
>
> On Wednesday, January 7, 2015 at 7:28:06 AM UTC+2, Zach Tellman wrote:
>>
>> Hey Tzach,
>>
>> If I understand what you're trying to do, you want something like this:
>>
>> [ :uint32
>> :ubyte ;; or bit-seq, depending
>> (delimited-block (prefix uint24 #(- % 5) #(+ % 5))) ]
>>
>> And then you'll need to parse the final block separately. I've left
>> defining the uint24 as an exercise for the reader (sorry, long day), but
>> using (compile-frame [:uint16 :uint8] ...) should be pretty straightforward.
>>
> This is what work for me, in case anyone is interested or want to comment
>
> (defn valid-length [l]
> (and (< l 16777216)
> (>= l 0)))
>
> (def uint24 (compile-frame [:ubyte :uint16]
> (fn [u]
> {:pre [(valid-length u)]}
> (let [u8 (bit-shift-right u 16)
> u16 (- u (bit-shift-left u8 16))]
> [u8 u16]))
> (fn [[u8 u16]]
> {:post [(valid-length %)]}
> (+ (bit-shift-left u8 16) u16))))
>
> (def avp
> (compile-frame
> [:uint32
> :ubyte
> (repeated :int32 :prefix (prefix uint24 #(- % 5) #(+ % 5))) ]
> ))
>
> My next step is to parse the bits from the header :ubyte and base on it,
> read an extra uint32 before the repeated part.
> The header is probably the answer.
>
>
>>
>> Hope that helps, happy to answer any followup questions.
>>
>
> It did help! Thanks
>
> BTW, I spent too much time trying to use (compile-frame [:uint16 :uint8])
> before realizing :uint8 is not defined.
> The result is simply encoding of the :uint8 symbol.
> I wonder if its a bug or a feature.
>
>
>
>>
>> Zach
>>
>> On Saturday, January 3, 2015 11:51:14 PM UTC-8, Tzach wrote:
>>>
>>> I'm trying to work with Gloss binary encoder/decoder, and need some help
>>> to kick start.
>>>
>>> My first task is simple(not for me ;)
>>> I have the following binary buffer to read/write:
>>>
>>> - 4 byte (32 bit) - code (uint)
>>> - 8 bit - misc flags
>>> - 3 byte (24 bit) - the entire buffer length
>>> - 4 byte (32 bit) uint value - optional, depending on on of the
>>> flags.
>>> - List of 4 byte (uints) data elements - size dependent on the
>>> overall size
>>>
>>> How should I represent this structure?
>>> Clearly I need to use *prefix* and *repeated* for the last element, but
>>> I failed to understand how.
>>> I also struggle with the optional element and how to represent a 3 byte
>>> element.
>>>
>>> Thanks!
>>>
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