From 7fcab1c46e4b5165a6bddea90fe67693b359e887 Mon Sep 17 00:00:00 2001
From: Jerome Gravel-Niquet <jeromegn@gmail.com>
Date: Tue, 17 Dec 2019 20:08:37 +0000
Subject: [PATCH] Adds increment and decrement methods to Gauge (#64)

* Adds increment and decrement methods to Gauge.
---
 metrics-runtime/src/common.rs     | 18 +++++++++++++++++-
 metrics-runtime/src/data/gauge.rs | 10 ++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/metrics-runtime/src/common.rs b/metrics-runtime/src/common.rs
index f55214c..70828a9 100644
--- a/metrics-runtime/src/common.rs
+++ b/metrics-runtime/src/common.rs
@@ -164,6 +164,20 @@ impl ValueHandle {
         }
     }
 
+    pub fn increment_gauge(&self, value: i64) {
+        match self.state.deref() {
+            ValueState::Gauge(inner) => inner.fetch_add(value, Ordering::Release),
+            _ => unreachable!("tried to access as gauge, not a gauge"),
+        };
+    }
+
+    pub fn decrement_gauge(&self, value: i64) {
+        match self.state.deref() {
+            ValueState::Gauge(inner) => inner.fetch_sub(value, Ordering::Release),
+            _ => unreachable!("tried to access as gauge, not a gauge"),
+        };
+    }
+
     pub fn update_histogram(&self, value: u64) {
         match self.state.deref() {
             ValueState::Histogram(inner) => inner.record(value),
@@ -313,8 +327,10 @@ mod tests {
 
         let gauge = ValueHandle::gauge();
         gauge.update_gauge(23);
+        gauge.increment_gauge(20);
+        gauge.decrement_gauge(1);
         match gauge.snapshot() {
-            ValueSnapshot::Single(Measurement::Gauge(value)) => assert_eq!(value, 23),
+            ValueSnapshot::Single(Measurement::Gauge(value)) => assert_eq!(value, 42),
             _ => panic!("incorrect value snapshot type for gauge"),
         }
 
diff --git a/metrics-runtime/src/data/gauge.rs b/metrics-runtime/src/data/gauge.rs
index e947581..2c35f64 100644
--- a/metrics-runtime/src/data/gauge.rs
+++ b/metrics-runtime/src/data/gauge.rs
@@ -13,6 +13,16 @@ impl Gauge {
     pub fn record(&self, value: i64) {
         self.handle.update_gauge(value);
     }
+
+    /// Increments the gauge's value
+    pub fn increment(&self, value: i64) {
+        self.handle.increment_gauge(value);
+    }
+
+    /// Decrements the gauge's value
+    pub fn decrement(&self, value: i64) {
+        self.handle.decrement_gauge(value);
+    }
 }
 
 impl From<ValueHandle> for Gauge {