RE: #445: Transfer-codings

On Thursday,10 April 2014 08:17, Matthew Kerwin wrote:
> I wanted to keep the rank because I'd like the ability for someone to change their mind about an encoding.
> I would be happy with a single bit, if I could come up with a way to pack it into the settings frame that doesn't make me feel yucky. ...

I'm neutral on whether you use a single value for this setting or keep a table like Amos wants. ( I always slightly lean towards KISS though.)  I just didn't realize there was a desire to dynamically switch between so many options.

Another idea for the setting...

7-bit encoding with 1-bit on/off (128 possible encodings) - you could still pack four encodings into a single setting value
```
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |F| Encoding(7) |F| Encoding(7) |F| Encoding(7) |F| Encoding(7) |
  +-------------------------------+-------------------------------+
```

The msb in the encoding field ("T") of the DATA frame could be used to signal the presence of an optional (encoding-specific) trailer that signals the offset and length of the uncompressed data captured within the compressed frame.
This might allow intermediaries to quickly index the underlying uncompressed data.
I don't care strongly about this idea, only if the intermediaries think it would be useful. I'd rather keep it simple.

e.g.

```
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Pad High? (8) |  Pad Low? (8) |T| Encoding?(8)|
 +-------------------------------+-------------------------------+
 |                            Data (*)                         ...
 +---------------------------------------------------------------+
 |                  Uncompressed Offset High? (32)               |
 +---------------------------------------------------------------+
 |                  Uncompressed Offset Low? (32)                |
 +---------------------------------------------------------------+
 |                    Uncompressed Length? (32)                  |
 +---------------------------------------------------------------+
 |                           Padding (*)                       ...
 +---------------------------------------------------------------+
 |                           Padding (*)                       ...
 +---------------------------------------------------------------+
```


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