From ead16110bbece2f4bb5774084690e1cebfa1bfed Mon Sep 17 00:00:00 2001
From: arkpar <arkady.paronyan@gmail.com>
Date: Sat, 30 Jan 2016 23:02:55 +0100
Subject: [PATCH] Ethash disk cache

---
 ethash/Cargo.toml     |  2 ++
 ethash/src/compute.rs | 58 ++++++++++++++++++++++++++++++++++++++++++-
 ethash/src/lib.rs     | 39 ++++++++++++++++++++---------
 3 files changed, 86 insertions(+), 13 deletions(-)

diff --git a/ethash/Cargo.toml b/ethash/Cargo.toml
index 16af6525c..4c0b3d65e 100644
--- a/ethash/Cargo.toml
+++ b/ethash/Cargo.toml
@@ -6,4 +6,6 @@ authors = ["arkpar <arkadiy@ethcore.io"]
 [lib]
 
 [dependencies]
+log = "0.3"
+lru-cache = "0.0"
 sha3 = { path = "../util/sha3" }
diff --git a/ethash/src/compute.rs b/ethash/src/compute.rs
index 2cbb7ea64..56b120d1d 100644
--- a/ethash/src/compute.rs
+++ b/ethash/src/compute.rs
@@ -6,7 +6,11 @@
 use std::mem;
 use std::ptr;
 use sizes::{CACHE_SIZES, DAG_SIZES};
-use sha3::{self};
+use sha3;
+use std::slice;
+use std::path::PathBuf;
+use std::io::{Read, Write, self};
+use std::fs::{self, File};
 
 pub const ETHASH_EPOCH_LENGTH: u64 = 30000;
 pub const ETHASH_CACHE_ROUNDS: usize = 3;
@@ -76,6 +80,45 @@ impl Light {
 	pub fn compute(&self, header_hash: &H256, nonce: u64) -> ProofOfWork {
 		light_compute(self, header_hash, nonce)
 	}
+
+	pub fn file_path(block_number: u64) -> PathBuf {
+		let mut home = ::std::env::home_dir().unwrap();
+		home.push(".ethash");
+		home.push("light");
+		let seed_hash = get_seedhash(block_number);
+		home.push(to_hex(&seed_hash));
+		home
+	}
+
+	pub fn from_file(block_number: u64) -> io::Result<Light> {
+		let path = Light::file_path(block_number);
+		let mut file = try!(File::open(path));
+		
+		let cache_size = get_cache_size(block_number);
+		if try!(file.metadata()).len() != cache_size as u64 {
+			return Err(io::Error::new(io::ErrorKind::Other, "Cache file size mismatch"));
+		}
+		let num_nodes = cache_size / NODE_BYTES;
+		let mut nodes: Vec<Node> = Vec::new();
+		nodes.resize(num_nodes, unsafe { mem::uninitialized() });
+		let buf = unsafe { slice::from_raw_parts_mut(nodes.as_mut_ptr() as *mut u8, cache_size) };
+		try!(file.read_exact(buf));
+		Ok(Light {
+			cache: nodes,
+			block_number: block_number,
+		})
+	}
+
+	pub fn to_file(&self) -> io::Result<()> {
+		let path = Light::file_path(self.block_number);
+		try!(fs::create_dir_all(path.parent().unwrap()));
+		let mut file = try!(File::create(path));
+		
+		let cache_size = self.cache.len() * NODE_BYTES;
+		let buf = unsafe { slice::from_raw_parts(self.cache.as_ptr() as *const u8, cache_size) };
+		try!(file.write(buf)); 
+		Ok(())
+	}
 }
 
 #[inline]
@@ -249,6 +292,19 @@ fn light_new(block_number: u64) -> Light {
 	}
 }
 
+static CHARS: &'static[u8] = b"0123456789abcdef";
+fn to_hex(bytes: &[u8]) -> String {
+	let mut v = Vec::with_capacity(bytes.len() * 2);
+	for &byte in bytes.iter() {
+		v.push(CHARS[(byte >> 4) as usize]);
+		v.push(CHARS[(byte & 0xf) as usize]);
+	}
+
+	unsafe {
+		String::from_utf8_unchecked(v)
+	}
+}
+
 #[test]
 fn test_difficulty_test() {
 	let hash = [0xf5, 0x7e, 0x6f, 0x3a, 0xcf, 0xc0, 0xdd, 0x4b, 0x5b, 0xf2, 0xbe, 0xe4, 0x0a, 0xb3, 0x35, 0x8a, 0xa6, 0x87, 0x73, 0xa8, 0xd0, 0x9f, 0x5e, 0x59, 0x5e, 0xab, 0x55, 0x94, 0x05,  0x52, 0x7d, 0x72];
diff --git a/ethash/src/lib.rs b/ethash/src/lib.rs
index e87ee1a03..17853c985 100644
--- a/ethash/src/lib.rs
+++ b/ethash/src/lib.rs
@@ -1,25 +1,28 @@
 //! Ethash implementation
 //! See https://github.com/ethereum/wiki/wiki/Ethash
 extern crate sha3;
+extern crate lru_cache;
+#[macro_use]
+extern crate log;
 mod sizes;
 mod compute;
 
+use lru_cache::LruCache;
 use compute::Light;
 pub use compute::{quick_get_difficulty, H256, ProofOfWork, ETHASH_EPOCH_LENGTH};
 
-use std::collections::HashMap;
-use std::sync::RwLock;
+use std::sync::{Arc, Mutex};
 
 /// Lighy/Full cache manager
 pub struct EthashManager {
-	lights: RwLock<HashMap<u64, Light>>,
+	lights: Mutex<LruCache<u64, Arc<Light>>>
 }
 
 impl EthashManager {
 	/// Create a new new instance of ethash manager
 	pub fn new() -> EthashManager {
 		EthashManager { 
-			lights: RwLock::new(HashMap::new())
+			lights: Mutex::new(LruCache::new(2))
 		}
 	}
 
@@ -30,15 +33,27 @@ impl EthashManager {
 	/// `nonce` - The nonce to pack into the mix
 	pub fn compute_light(&self, block_number: u64, header_hash: &H256, nonce: u64) -> ProofOfWork {
 		let epoch = block_number / ETHASH_EPOCH_LENGTH;
-		while !self.lights.read().unwrap().contains_key(&epoch) {
-			if let Ok(mut lights) = self.lights.try_write()
-			{
-				if !lights.contains_key(&epoch) {
-					let light = Light::new(block_number);
-					lights.insert(epoch, light);
+		let light = {
+			let mut lights = self.lights.lock().unwrap();
+			match lights.get_mut(&epoch).map(|l| l.clone()) {
+				None => {
+					let light = match Light::from_file(block_number) {
+						Ok(light) => Arc::new(light),
+						Err(e) => { 
+							debug!("Light cache file not found for {}:{}", block_number, e);
+							let light = Light::new(block_number);
+							if let Err(e) = light.to_file() {
+								warn!("Light cache file write error: {}", e);
+							}
+							Arc::new(light)
+						}
+					};
+					lights.insert(epoch, light.clone());
+					light
 				}
+				Some(light) => light
 			}
-		}
-		self.lights.read().unwrap().get(&epoch).unwrap().compute(header_hash, nonce)
+		};
+		light.compute(header_hash, nonce)
 	}
 }