Reference read

Perf:

$ time target/release/fast-fantoir FANTOIR0721

real	0m0,608s
user	0m0,526s
sys	0m0,081s

$ time target/debug/fast-fantoir FANTOIR0721

real	0m11,664s
user	0m11,549s
sys	0m0,113s

I highly suspect the release build to optimize out the useless file
read, partially explaining the *MASSIVE* perf difference between the
release build and the debug one.

This gives up a baseline speed order though. We should probably be
able to stay below 1 minute to generate the DB.

.gitignore

@@ -0,0 +1 @@
+/target

Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "fast-fantoir"
+version = "0.1.0"

Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "fast-fantoir"
+version = "0.1.0"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

shell.nix

@@ -0,0 +1,5 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  nativeBuildInputs = [ pkgs.rustc pkgs.cargo ];
+}

src/main.rs

@@ -0,0 +1,19 @@
+use std::fs::File;
+use std::io::{BufReader, BufRead};
+
+fn main() -> std::io::Result<()> {
+    let fantoir_path = std::env::args().nth(1).unwrap();
+    let file = match File::open(&fantoir_path) {
+        Err(err) => panic!("Cannot read file {}: {}", fantoir_path, err),
+        Ok(file) => file,
+    };
+    let reader = BufReader::new(file);
+
+    for line in reader.lines() {
+        match line {
+            Ok(_l) => (),
+            Err(err) => panic!("Cannot read line: {}", err),
+        }
+    };
+    Ok(())
+}

src/main.rs~

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}