It is used a lot in clients (including our benchmark).
`Uint160` is already optimized.
```
name old time/op new time/op delta
Uint256DecodeStringLE-8 150ns ±15% 112ns ± 3% -25.23% (p=0.000 n=10+10)
name old alloc/op new alloc/op delta
Uint256DecodeStringLE-8 96.0B ± 0% 64.0B ± 0% -33.33% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
Uint256DecodeStringLE-8 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.000 n=10+10)
```
Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
We have a lot of native contract types that are converted to stack items
before serialization, then deserialized as stack items and converted back to
regular structures. stackitem.Convertible allows to remove a lot of repetitive
io.Serializable code.
This also introduces to/from converter in testserdes which unfortunately
required to change util tests to avoid circular references.
Strange as it is but I wasn't able to find any good bit field
implementation. Most of them are limited to 64 bits, some allow for wider
values (like https://github.com/emef/bitfield) but even they're not that
efficient (using bytes instead of wider types). This this minimalistic thing.
Frequently one needs to check if struct serializes/deserializes
properly. This commit implements helpers for such cases including:
1. JSON
2. io.Serializable interface
This seriously improves the serialization/deserialization performance for
several reasons:
* no time spent in `binary` reflection
* no memory allocations being made on every read/write
* uses fast ReadBytes everywhere it's appropriate
It also makes Fixed8 Serializable just for convenience.
Before this patch on block import we could easily be spending more than 6
seconds out of 30 in Uint256 encoding for UnspentBalance, now it's completely
off the radar.
It's mostly used for Serializable and in other cases where one needs to
estimate binary-encoded size of the stucture. This also simplifies future
removal of the Size() from Serializable.
The logic here is that we'll have all binary encoding/decoding done via our io
package, which simplifies error handling. This functionality doesn't belong to
util, so it's moved.
This also expands BufBinWriter with Reset() method to fit the needs of core
package.
