From c4cf58af6f29611d788e8f82ba78cfea490cf470 Mon Sep 17 00:00:00 2001
From: Corey Richardson <corey@octayn.net>
Date: Sat, 17 Aug 2013 00:14:24 -0400
Subject: [PATCH] Initial metrics support

---
 src/libextra/extra.rs   |   2 +-
 src/libextra/metrics.rs | 164 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 165 insertions(+), 1 deletion(-)
 create mode 100644 src/libextra/metrics.rs

diff --git a/src/libextra/extra.rs b/src/libextra/extra.rs
index da6525f781558..fe4b394ed13ed 100644
--- a/src/libextra/extra.rs
+++ b/src/libextra/extra.rs
@@ -106,7 +106,7 @@ pub mod fileinput;
 pub mod flate;
 pub mod hex;
 pub mod uuid;
-
+pub mod metrics;
 
 #[cfg(unicode)]
 mod unicode;
diff --git a/src/libextra/metrics.rs b/src/libextra/metrics.rs
new file mode 100644
index 0000000000000..832950f61fe72
--- /dev/null
+++ b/src/libextra/metrics.rs
@@ -0,0 +1,164 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/*!
+ * Simple metrics gathering and reporting
+ *
+ * This is inspired from https://github.com/rcrowley/go-metrics and
+ * https://github.com/codahale/metrics.
+ */
+
+use std::local_data;
+use std::hashmap::HashMap;
+use std::container::MutableMap;
+
+pub static reg_key: local_data::Key<HashMap<~str, MetricGroup>> = &local_data::Key;
+
+/// A group of metrics with a common namespace
+pub struct MetricGroup {
+    priv name: ~str,
+    priv metrics: HashMap<~str, Metric>,
+}
+
+impl MetricGroup {
+    /// Create a new MetricGroup with the given namespace
+    pub fn new(name: ~str) -> MetricGroup {
+        MetricGroup { name: name, metrics: HashMap::new() }
+    }
+
+    /// Add a metric as a child with the given name.
+    pub fn insert(&mut self, name: ~str, m: Metric) {
+        self.metrics.insert(name, m);
+    }
+}
+
+// TLS interface
+
+/// Adds a metric to TLS
+///
+/// The name consists of any string, a period, and any string that doesn't
+/// contain a period. Example: `rustc.trans.insns.pop`. `rustc.trans.insns` is
+/// the namespace, `pop` is the name of the metric.
+pub fn add(name: ~str, m: Metric) {
+    let last = name.rfind('.').expect("all metrics require a namespace");
+    let prefix = name.slice_to(last);
+    let key = name.slice_from(last);
+
+    do local_data::modify(reg_key) |reg| {
+        let mut reg = reg.unwrap_or_default(HashMap::new());
+        if reg.contains_key_equiv(&prefix) {
+            // ugly allocation
+            let mg = reg.get_mut(&prefix.to_str());
+            mg.metrics.insert(key.to_str(), m);
+        } else {
+            let mut mg = MetricGroup::new(prefix.to_str());
+            mg.metrics.insert(key.to_str(), m);
+            reg.insert(prefix.to_str(), mg);
+        }
+        Some(reg)
+    }
+}
+
+/// Modify a metric in TLS
+///
+/// The name is the name of a metric that may or may not have been added
+/// already. The passed closure receives a mutable reference to the metric, or
+/// None.
+pub fn modify(name: ~str, f: &fn(m: Option<&mut Metric>)) {
+    let last = name.rfind('.').expect("all metrics require a namespace");
+    let prefix = name.slice_to(last);
+    let key = name.slice_from(last);
+    
+    do local_data::get_mut(reg_key) |reg| {
+        match reg {
+            Some(reg) => {
+                if reg.contains_key_equiv(&prefix) {
+                    let mg = reg.get_mut(&prefix.to_str());
+                    f(mg.metrics.find_mut(&key.to_str()));
+                } else {
+                    f(None);
+                }
+            },
+            None => f(None)
+        }
+    }
+}
+
+/// Get a metric from TLS
+///
+/// The name is the name of a metric that may or may not have been added
+/// already. The passed closure receives a reference to the metric, or None.
+pub fn get(name: ~str, f: &fn(m: Option<&Metric>)) {
+    let last = name.rfind('.').expect("all metrics require a namespace");
+    let prefix = name.slice_to(last);
+    let key = name.slice_from(last);
+    
+    do local_data::get(reg_key) |reg| {
+        match reg {
+            Some(reg) => {
+                if reg.contains_key_equiv(&prefix) {
+                    let mg = reg.get(&prefix.to_str());
+                    f(mg.metrics.find(&key.to_str()));
+                } else {
+                    f(None);
+                }
+            },
+            None => f(None)
+        }
+    }
+}
+/// The set of metrics which this library knows about
+pub enum Metric {
+    Counter(Counter),
+}
+
+/// A counter which increments and decrements over time
+pub struct Counter {
+    priv val: i64
+}
+
+// xxx: wrapping
+impl Counter {
+    /// Create a new counter
+    pub fn new   ()      -> Counter      { Counter { val: 0 } }
+    /// Get the value of the counter
+    pub fn get   (&self) -> i64          { self.val }
+    /// Set the counter to 0
+    pub fn reset (&mut self)             { self.val = 0; }
+    /// Increment the counter by `value`
+    pub fn inc   (&mut self, value: i64) { self.val += value; }
+    /// Decrement the counter by `value`
+    pub fn dec   (&mut self, value: i64) { self.val -= value; }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_counter() {
+        let mut c = Counter::new();
+        assert_eq!(c.get(), 0);
+        c.inc(5);
+        assert_eq!(c.get(), 5);
+        c.dec(2);
+        assert_eq!(c.get(), 3);
+        c.reset();
+        assert_eq!(c.get(), 0);
+    }
+
+    #[test]
+    fn test_tls() {
+        let m = Counter(Counter::new());
+        add(~"test.counter", m);
+        modify(~"test.counter", |m| m.unwrap().inc(1));
+        get(~"test.counter", |m| assert_eq!(match m.unwrap() { &Counter(ref c) => c.get() }, 1));
+    }
+}