110 lines
3.1 KiB
Rust
110 lines
3.1 KiB
Rust
// Copyright 2015-2019 Parity Technologies (UK) Ltd.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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extern crate elastic_array;
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#[macro_use]
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extern crate lazy_static;
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extern crate rlp;
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mod common;
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use std::cmp;
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use std::collections::HashMap;
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use elastic_array::ElasticArray1024;
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use rlp::{Rlp, RlpStream};
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use common::{SNAPSHOT_SWAPPER, BLOCKS_SWAPPER};
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pub fn snapshot_swapper() -> &'static Swapper<'static> {
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&SNAPSHOT_SWAPPER as &Swapper
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}
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pub fn blocks_swapper() -> &'static Swapper<'static> {
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&BLOCKS_SWAPPER as &Swapper
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}
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/// A trait used to compress rlp.
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pub trait Compressor {
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/// Get compressed version of given rlp.
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fn compressed(&self, rlp: &[u8]) -> Option<&[u8]>;
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}
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/// A trait used to convert compressed rlp into it's original version.
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pub trait Decompressor {
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/// Get decompressed rlp.
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fn decompressed(&self, compressed: &[u8]) -> Option<&[u8]>;
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}
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/// Call this function to compress rlp.
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pub fn compress(c: &[u8], swapper: &Compressor) -> ElasticArray1024<u8> {
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let rlp = Rlp::new(c);
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if rlp.is_data() {
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ElasticArray1024::from_slice(swapper.compressed(rlp.as_raw()).unwrap_or_else(|| rlp.as_raw()))
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} else {
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map_rlp(&rlp, |r| compress(r.as_raw(), swapper))
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}
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}
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/// Call this function to decompress rlp.
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pub fn decompress(c: &[u8], swapper: &Decompressor) -> ElasticArray1024<u8> {
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let rlp = Rlp::new(c);
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if rlp.is_data() {
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ElasticArray1024::from_slice(swapper.decompressed(rlp.as_raw()).unwrap_or_else(|| rlp.as_raw()))
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} else {
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map_rlp(&rlp, |r| decompress(r.as_raw(), swapper))
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}
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}
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fn map_rlp<F: Fn(&Rlp) -> ElasticArray1024<u8>>(rlp: &Rlp, f: F) -> ElasticArray1024<u8> {
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let mut stream = RlpStream::new_list(rlp.item_count().unwrap_or_default());
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for subrlp in rlp.iter() {
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stream.append_raw(&f(&subrlp), 1);
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}
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stream.drain().as_slice().into()
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}
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/// Stores RLPs used for compression
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pub struct Swapper<'a> {
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compressed_to_rlp: HashMap<&'a [u8], &'a [u8]>,
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rlp_to_compressed: HashMap<&'a [u8], &'a [u8]>,
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}
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impl<'a> Swapper<'a> {
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/// Construct a swapper from a list of common RLPs
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pub fn new(rlps_to_swap: &[&'a [u8]], compressed: &[&'a [u8]]) -> Self {
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if rlps_to_swap.len() > 0x7e {
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panic!("Invalid usage, only 127 RLPs can be swappable.");
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}
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let items = cmp::min(rlps_to_swap.len(), compressed.len());
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let mut compressed_to_rlp = HashMap::with_capacity(items);
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let mut rlp_to_compressed = HashMap::with_capacity(items);
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for (&rlp, &compressed) in rlps_to_swap.iter().zip(compressed.iter()) {
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compressed_to_rlp.insert(compressed, rlp);
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rlp_to_compressed.insert(rlp, compressed);
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}
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Swapper {
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compressed_to_rlp,
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rlp_to_compressed,
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}
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}
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}
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impl<'a> Decompressor for Swapper<'a> {
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fn decompressed(&self, compressed: &[u8]) -> Option<&[u8]> {
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self.compressed_to_rlp.get(compressed).cloned()
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}
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}
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impl<'a> Compressor for Swapper<'a> {
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fn compressed(&self, rlp: &[u8]) -> Option<&[u8]> {
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self.rlp_to_compressed.get(rlp).cloned()
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}
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}
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