From 6bec8e2285e6e504baea019628fbf99f40a4900b Mon Sep 17 00:00:00 2001
From: Simon Warta <simon@warta.it>
Date: Sun, 13 Dec 2020 23:53:16 +0100
Subject: [PATCH] Use memmap2 in deserialize_from_file

---
 Cargo.lock               | 10 ++++++++++
 lib/engine/Cargo.toml    |  1 +
 lib/engine/src/engine.rs |  6 ++++--
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index b8d5542992c..a0bd26d1942 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1186,6 +1186,15 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "memmap2"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b70ca2a6103ac8b665dc150b142ef0e4e89df640c9e6cf295d189c3caebe5a"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "memoffset"
 version = "0.6.1"
@@ -2612,6 +2621,7 @@ dependencies = [
  "backtrace",
  "bincode",
  "lazy_static",
+ "memmap2",
  "more-asserts",
  "rustc-demangle",
  "serde",
diff --git a/lib/engine/Cargo.toml b/lib/engine/Cargo.toml
index efa4c8f900d..72aa3350f3d 100644
--- a/lib/engine/Cargo.toml
+++ b/lib/engine/Cargo.toml
@@ -18,6 +18,7 @@ target-lexicon = { version = "0.11", default-features = false }
 # flexbuffers = { path = "../../../flatbuffers/rust/flexbuffers", version = "0.1.0" }
 backtrace = "0.3"
 rustc-demangle = "0.1"
+memmap2 = "0.1.0"
 more-asserts = "0.2"
 thiserror = "1.0"
 serde = { version = "1.0", features = ["derive", "rc"] }
diff --git a/lib/engine/src/engine.rs b/lib/engine/src/engine.rs
index 2828bfc52a3..8cfceb3a83f 100644
--- a/lib/engine/src/engine.rs
+++ b/lib/engine/src/engine.rs
@@ -2,6 +2,7 @@
 
 use crate::tunables::Tunables;
 use crate::{Artifact, DeserializeError};
+use memmap2::Mmap;
 use std::path::Path;
 use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
 use std::sync::Arc;
@@ -51,8 +52,9 @@ pub trait Engine {
         &self,
         file_ref: &Path,
     ) -> Result<Arc<dyn Artifact>, DeserializeError> {
-        let bytes = std::fs::read(file_ref)?;
-        self.deserialize(&bytes)
+        let file = std::fs::File::open(file_ref)?;
+        let mmap = Mmap::map(&file)?;
+        self.deserialize(&mmap)
     }
 
     /// A unique identifier for this object.