[OpenWrt-Devel] [RFC] libubox/binary.h design proposal

[Etienne Champetier]

Hi,

2015-10-04 22:47 GMT+02:00 Javier Domingo Cansino <javierdo1 at gmail.com>:

> Hello,
>
> I asked Friday on IRC how to write blobs, I was suggested using
> blob_raw_put from libubox/blob.h, but as I have to implement a binary
> protocol that uses different endianess, non aligned data etc., I think the
> best solution is creating a set of helper functions to write/read blobs.
>

I don't know what you really want to do, but have you looked at protobuf?
https://en.wikipedia.org/wiki/Protocol_Buffers



>
> As this is quite generic library, there might already exist some work done
> that I am missing (please link!). I would love to have feedback from this
> design before typing code.
>
> I have started my work on github[1], which is basically a header file with
> the following comment and some prototype ideas. The syntax I have thought
> is described there, but it basically follows a printf syntax, allowing raw
> chars to be written.
>
> Cheers!
>
> /*
>  * Syntax for the function is as follows.
>  *   %[n][a][lb][01r]{i,y,w,d,q,s}
>  *
>  *   All the characters that don't follow this will be treated as raw chars
>  *   to be written as they are.
>  *
>  * Data type
>  *   * i - bit
>  *   * y - byte
>  *   * w - 2 byte word
>  *   * d - 4 byte word
>  *   * q - 8 byte word
>  *   * s - string without termination (use strlen()+1 in quantity to null)
>  *
>  * Data value
>  *   * 0 - fill the specified space with zeros
>  *   * 1 - fill the specified space with ones
>  *   * r - fill the specified space with random data
>  *
>  *   String data type is not valid in this case
>  *
>  * Endianess. No conversion by default
>  *   * l - little endian
>  *   * b - big endian
>  *
>  * Alignment. No alignment by default
>  *   * a - align this to it's datatype
>  *         bits are aligned to byte
>  *
>  * Quantity. One by default
>  *   * n - number of same datatype (placed together)
>  *         this denotes length of string, padded with 0
>  *
>  * Some examples:
>  *   * %4lw - 4 little endian 2 byte word
>  *   * %2i  - 2 bits 'ab' from value b'000000ab'
>  *   * %2bi - 2 bits 'ab' from value b'000000ba'
>  *   * %2li - 2 bits 'ab' from value b'ab000000'
>  *
>  */
>
>
> [1] Github branch: https://github.com/txomon/libubox
>
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>
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