Merge pull request #39 from chris-morgan/optional-time-dependency

Shift the time dependency to a "stats" feature

.travis.yml

@@ -1,3 +1,4 @@
 language: rust
 script:
   - (cd phf && cargo test)
+  - (cd phf_mac && cargo test --features stats)

README.md

@@ -8,7 +8,11 @@ Rust-PHF is a library to generate efficient lookup tables at compile time using
 
 It currently uses the
 [CHD algorithm](http://cmph.sourceforge.net/papers/esa09.pdf) and can generate
-a 100,000 entry map in roughly .4 seconds.
+a 100,000 entry map in roughly .4 seconds. By default statistics are not
+produced, but if you use the `phf_mac` crate with the `stats` feature enabled
+(writing `phf_mac/stats` in the `[dependencies]` section of your `Cargo.toml`
+instead of `phf_mac`) and set the environment variable `PHF_STATS` it will
+issue a compiler note about how long it took.
 
 Documentation is available at https://sfackler.github.io/doc/phf
 

phf_mac/Cargo.toml

@@ -12,9 +12,13 @@ path = "src/lib.rs"
 plugin = true
 test = false
 
+[features]
+stats = ["time"]
+
 [dependencies.phf_shared]
 path = "../phf_shared"
 version = "=0.4.8"
 
-[dependencies]
-time = "0.1"
+[dependencies.time]
+version = "0.1"
+optional = true

phf_mac/src/lib.rs

@@ -7,6 +7,7 @@
 
 extern crate rand;
 extern crate syntax;
+#[cfg(feature = "stats")]
 extern crate time;
 extern crate rustc;
 extern crate phf_shared;

phf_mac/src/util.rs

@@ -13,8 +13,6 @@ use rand::{Rng, SeedableRng, XorShiftRng};
 
 use phf_shared::{self, PhfHash};
 
-use time;
-
 const DEFAULT_LAMBDA: uint = 5;
 
 const FIXED_SEED: [u32; 4] = [3141592653, 589793238, 462643383, 2795028841];
@@ -86,8 +84,13 @@ pub struct HashState {
 }
 
 pub fn generate_hash(cx: &mut ExtCtxt, sp: Span, entries: &[Entry]) -> HashState {
+    #[cfg(feature = "stats")]
+    use time::precise_time_s;
+    #[cfg(not(feature = "stats"))]
+    fn precise_time_s() -> f64 { 0.0 }
+
     let mut rng: XorShiftRng = SeedableRng::from_seed(FIXED_SEED);
-    let start = time::precise_time_s();
+    let start = precise_time_s();
     let state;
     loop {
         match try_generate_hash(entries, &mut rng) {
@@ -98,8 +101,8 @@ pub fn generate_hash(cx: &mut ExtCtxt, sp: Span, entries: &[Entry]) -> HashState
             None => {}
         }
     }
-    let time = time::precise_time_s() - start;
-    if os::getenv("PHF_STATS").is_some() {
+    let time = precise_time_s() - start;
+    if cfg!(feature = "stats") && os::getenv("PHF_STATS").is_some() {
         cx.span_note(sp, &*format!("PHF generation took {} seconds", time));
     }