rlp_compress/
lib.rs

1// Copyright 2015-2020 Parity Technologies (UK) Ltd.
2//
3// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
6// option. This file may not be copied, modified, or distributed
7// except according to those terms.
8
9extern crate elastic_array;
10#[macro_use]
11extern crate lazy_static;
12extern crate tetsy_rlp;
13
14mod common;
15
16use std::cmp;
17use std::collections::HashMap;
18use elastic_array::ElasticArray1024;
19use tetsy_rlp::{Rlp, RlpStream};
20use common::{SNAPSHOT_SWAPPER, BLOCKS_SWAPPER};
21
22pub fn snapshot_swapper() -> &'static Swapper<'static> {
23	&SNAPSHOT_SWAPPER as &Swapper
24}
25
26pub fn blocks_swapper() -> &'static Swapper<'static> {
27	&BLOCKS_SWAPPER as &Swapper
28}
29
30/// A trait used to compress rlp.
31pub trait Compressor {
32	/// Get compressed version of given rlp.
33	fn compressed(&self, rlp: &[u8]) -> Option<&[u8]>;
34}
35
36/// A trait used to convert compressed rlp into it's original version.
37pub trait Decompressor {
38	/// Get decompressed rlp.
39	fn decompressed(&self, compressed: &[u8]) -> Option<&[u8]>;
40}
41
42/// Call this function to compress rlp.
43pub fn compress(c: &[u8], swapper: &dyn Compressor) -> ElasticArray1024<u8> {
44	let rlp = Rlp::new(c);
45	if rlp.is_data() {
46		ElasticArray1024::from_slice(swapper.compressed(rlp.as_raw()).unwrap_or_else(|| rlp.as_raw()))
47	} else {
48		map_rlp(&rlp, |r| compress(r.as_raw(), swapper))
49	}
50}
51
52/// Call this function to decompress rlp.
53pub fn decompress(c: &[u8], swapper: &dyn Decompressor) -> ElasticArray1024<u8> {
54	let rlp = Rlp::new(c);
55	if rlp.is_data() {
56		ElasticArray1024::from_slice(swapper.decompressed(rlp.as_raw()).unwrap_or_else(|| rlp.as_raw()))
57	} else {
58		map_rlp(&rlp, |r| decompress(r.as_raw(), swapper))
59	}
60}
61
62fn map_rlp<F: Fn(&Rlp) -> ElasticArray1024<u8>>(rlp: &Rlp, f: F) -> ElasticArray1024<u8> {
63	let mut stream = RlpStream::new_list(rlp.item_count().unwrap_or_default());
64	for subrlp in rlp.iter() {
65		stream.append_raw(&f(&subrlp), 1);
66	}
67	stream.drain().as_slice().into()
68}
69
70/// Stores RLPs used for compression
71pub struct Swapper<'a> {
72	compressed_to_rlp: HashMap<&'a [u8], &'a [u8]>,
73	rlp_to_compressed: HashMap<&'a [u8], &'a [u8]>,
74}
75
76impl<'a> Swapper<'a> {
77	/// Construct a swapper from a list of common RLPs
78	pub fn new(rlps_to_swap: &[&'a [u8]], compressed: &[&'a [u8]]) -> Self {
79		if rlps_to_swap.len() > 0x7e {
80			panic!("Invalid usage, only 127 RLPs can be swappable.");
81		}
82
83		let items = cmp::min(rlps_to_swap.len(), compressed.len());
84		let mut compressed_to_rlp = HashMap::with_capacity(items);
85		let mut rlp_to_compressed = HashMap::with_capacity(items);
86
87		for (&rlp, &compressed) in rlps_to_swap.iter().zip(compressed.iter()) {
88			compressed_to_rlp.insert(compressed, rlp);
89			rlp_to_compressed.insert(rlp, compressed);
90		}
91
92		Swapper {
93			compressed_to_rlp,
94			rlp_to_compressed,
95		}
96	}
97}
98
99impl<'a> Decompressor for Swapper<'a> {
100	fn decompressed(&self, compressed: &[u8]) -> Option<&[u8]> {
101		self.compressed_to_rlp.get(compressed).cloned()
102	}
103}
104
105impl<'a> Compressor for Swapper<'a> {
106	fn compressed(&self, rlp: &[u8]) -> Option<&[u8]> {
107		self.rlp_to_compressed.get(rlp).cloned()
108	}
109}
rlp_compress/lib.rs

rlp_compress/
lib.rs
