From cfb6dd2ea8907f6ff3aaf24bc579c7c2b1d86e90 Mon Sep 17 00:00:00 2001
From: Arkadiy Paronyan <arkady.paronyan@gmail.com>
Date: Fri, 13 Jan 2017 09:52:23 +0100
Subject: [PATCH] Optimized hash lookups (#4144)

* Optimize hash comparison

* Use libc
---
 Cargo.lock              |  1 +
 util/bigint/Cargo.toml  |  1 +
 util/bigint/src/hash.rs | 20 ++++++--------------
 util/bigint/src/lib.rs  |  1 +
 4 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 4f9c48dd7..632048c0d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -382,6 +382,7 @@ version = "0.1.2"
 dependencies = [
  "bigint 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "heapsize 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.19 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
diff --git a/util/bigint/Cargo.toml b/util/bigint/Cargo.toml
index 5fe02865c..5d47713fc 100644
--- a/util/bigint/Cargo.toml
+++ b/util/bigint/Cargo.toml
@@ -12,6 +12,7 @@ bigint = "1.0"
 rustc-serialize = "0.3"
 heapsize = "0.3"
 rand = "0.3.12"
+libc = "0.2"
 
 [features]
 x64asm_arithmetic=[]
diff --git a/util/bigint/src/hash.rs b/util/bigint/src/hash.rs
index fb9fbbd72..34eff3962 100644
--- a/util/bigint/src/hash.rs
+++ b/util/bigint/src/hash.rs
@@ -26,6 +26,7 @@ use rand::Rng;
 use rand::os::OsRng;
 use rustc_serialize::hex::{FromHex, FromHexError};
 use bigint::{Uint, U256};
+use libc::{c_void, memcmp};
 
 /// Trait for a fixed-size byte array to be used as the output of hash functions.
 pub trait FixedHash: Sized {
@@ -214,25 +215,16 @@ macro_rules! impl_hash {
 
 		impl PartialEq for $from {
 			fn eq(&self, other: &Self) -> bool {
-				for i in 0..$size {
-					if self.0[i] != other.0[i] {
-						return false;
-					}
-				}
-				true
+				unsafe { memcmp(self.0.as_ptr() as *const c_void, other.0.as_ptr() as *const c_void, $size) == 0 }
 			}
 		}
 
 		impl Ord for $from {
 			fn cmp(&self, other: &Self) -> Ordering {
-				for i in 0..$size {
-					if self.0[i] > other.0[i] {
-						return Ordering::Greater;
-					} else if self.0[i] < other.0[i] {
-						return Ordering::Less;
-					}
-				}
-				Ordering::Equal
+				let r = unsafe { memcmp(self.0.as_ptr() as *const c_void, other.0.as_ptr() as *const c_void, $size) };
+				if r < 0 { return Ordering::Less }
+				if r > 0 { return Ordering::Greater }
+				return Ordering::Equal;
 			}
 		}
 
diff --git a/util/bigint/src/lib.rs b/util/bigint/src/lib.rs
index e394ba7fb..28ab5b10e 100644
--- a/util/bigint/src/lib.rs
+++ b/util/bigint/src/lib.rs
@@ -21,6 +21,7 @@
 extern crate rand;
 extern crate rustc_serialize;
 extern crate bigint;
+extern crate libc;
 #[macro_use] extern crate heapsize;
 
 pub mod hash;