Refactor API + Implement Chunking + Ring Backend Support

[landhb]

Large re-design of the exposed API while trying to minimize performance/protocol changes.

• The portal-lib crate will be split into a higher-level API and a lower-level API exposed via crate::protocol.

A higher level file send will look like:

let portal = Portal::init(Direction::Sender, id, password)?;

// conduct the handshake with the peer
portal.handshake(&mut stream)?;

// Optional: implement a custom callback to display how much
// has been transferred
fn progress(transferred: usize) {
    println!("sent {:?} bytes", transferred);
}

portal.send_file(&mut stream, "/etc/passwd", Some(progress));

A higher level file recv will look like:

let portal = Portal::init(Direction::Receiver, id, password)?;

// conduct the handshake with the peer
portal.handshake(&mut stream)?;

// Optional: User callback to confirm/deny a transfer. If
// none is provided, this will default accept the incoming file.
// Return true to accept, false to reject the transfer.
fn confirm_download(path: &str, size: u64) -> bool { true }

// Optional: implement a custom callback to display how much
// has been transferred
fn progress(transferred: usize) {
    println!("sent {:?} bytes", transferred);
}

portal.recv_file(&mut client, Path::new("/tmp"), Some(confirm_download), Some(progress));

[github-actions]

Benchmark for 36fa8fb

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Test	Base	PR	%
encrypt & send 100k	496.8±30.55µs	282.5±14.62µs	-43.14%
encrypt & send 1M	4.3±0.15ms	2.5±0.07ms	-41.86%
larger-files/encrypt & send 100M	440.3±4.31ms	261.8±4.09ms	-40.54%
larger-files/encrypt & send 500M	2.2±0.02s	1272.4±15.39ms	-42.16%
larger-files/receive & decrypt 100M	815.4±7.21ms	1098.1±14.42ms	+34.67%
larger-files/receive & decrypt 500M	4.8±0.29s	6.3±0.19s	+31.25%
receive & decrypt 100k	564.8±14.87µs	548.6±21.22µs	-2.87%
receive & decrypt 1M	5.8±0.23ms	6.0±0.23ms	+3.45%

[codecov-commenter]

Codecov Report

Merging #11 (329042d) into master (77333fc) will increase coverage by 1.36%.
The diff coverage is 92.63%.

@@            Coverage Diff             @@
##           master      #11      +/-   ##
==========================================
+ Coverage   91.96%   93.33%   +1.36%     
==========================================
  Files           4        4              
  Lines         448      210     -238     
==========================================
- Hits          412      196     -216     
+ Misses         36       14      -22     

Impacted Files	Coverage Δ
lib/src/protocol/exchange.rs	81.81% <81.81%> (ø)
lib/src/lib.rs	94.04% <92.18%> (+0.52%)	⬆️
lib/src/protocol/mod.rs	95.38% <95.38%> (ø)
lib/src/protocol/encrypted.rs	100.00% <100.00%> (ø)
client/src/main.rs

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[github-actions]

Benchmark for 6cec841

Click to view benchmark

Test	Base	PR	%
encrypt & send 100k	315.1±0.51µs	199.6±0.43µs	-36.66%
encrypt & send 1M	3.1±0.00ms	1838.1±18.37µs	-40.71%
larger-files/encrypt & send 100M	324.8±0.11ms	207.1±0.87ms	-36.24%
larger-files/encrypt & send 500M	1635.0±0.87ms	1036.0±1.39ms	-36.64%
larger-files/receive & decrypt 100M	568.5±1.68ms	672.0±8.50ms	+18.21%
larger-files/receive & decrypt 500M	3.6±0.15s	4.7±0.27s	+30.56%
receive & decrypt 100k	338.3±0.34µs	295.3±0.30µs	-12.71%
receive & decrypt 1M	3.6±0.08ms	3.0±0.00ms	-16.67%

[github-actions]

Benchmark for 3547e5f

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Test	Base	PR	%
encrypt & send 100k	283.2±0.33µs	182.7±0.46µs	-35.49%
encrypt & send 1M	2.7±0.01ms	1689.6±3.99µs	-37.42%
larger-files/encrypt & send 100M	292.1±0.17ms	188.6±0.22ms	-35.43%
larger-files/encrypt & send 500M	1449.0±0.89ms	N/A	N/A
larger-files/receive & decrypt 100M	505.3±12.09ms	188.1±1.46s	+37125.41%
larger-files/receive & decrypt 500M	3.2±0.25s	N/A	N/A
receive & decrypt 100k	339.0±3.67µs	314.6±0.98µs	-7.20%
receive & decrypt 1M	3.1±0.02ms	6.8±0.05ms	+119.35%

[github-actions]

Benchmark for 67d0649

Click to view benchmark

Test	Base	PR	%
encrypt & send 100k	281.0±1.74µs	206.3±1.84µs	-26.58%
encrypt & send 1M	2.7±0.01ms	1677.0±28.67µs	-37.89%
larger-files/encrypt & send 100M	290.6±0.30ms	185.7±0.51ms	-36.10%
larger-files/encrypt & send 500M	1484.8±72.24ms	1030.2±4.77ms	-30.62%
larger-files/receive & decrypt 100M	532.3±1.23ms	184.6±23.74ms	-65.32%
larger-files/receive & decrypt 500M	3.6±0.22s	1095.2±284.11ms	-69.58%
receive & decrypt 100k	297.8±1.31µs	181.3±3.56µs	-39.12%
receive & decrypt 1M	3.1±0.01ms	1580.1±51.83µs	-49.03%