From cfe596bd3e56ad4f86c513c7669a5e6f5bf4e39f Mon Sep 17 00:00:00 2001
From: Andres Vahter <andres.vahter@gmail.com>
Date: Sat, 9 May 2020 19:46:06 +0300
Subject: [PATCH 1/3] readme: add instructions for tests

---
 README.md | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index a0f8592e..0fb6fef6 100644
--- a/README.md
+++ b/README.md
@@ -5,11 +5,20 @@
 
 > `static` friendly data structures that don't require dynamic memory allocation
 
-# [Documentation](https://japaric.github.io/heapless/heapless/index.html)
+## [Documentation](https://japaric.github.io/heapless/heapless/index.html)
 
-# [Change log](CHANGELOG.md)
+## [Change log](CHANGELOG.md)
 
-# License
+## Tests
+
+```bash
+# run all
+cargo test --features 'serde','x86-sync-pool'
+# run only for example histbuf tests
+cargo test histbuf --features 'serde','x86-sync-pool'
+```
+
+## License
 
 Licensed under either of
 

From f5a26c04c4bdfe932928ef7a284b052cee66ff1d Mon Sep 17 00:00:00 2001
From: Andres Vahter <andres.vahter@gmail.com>
Date: Sat, 9 May 2020 20:05:19 +0300
Subject: [PATCH 2/3] histbuf: replace slow modulo operatins

on cortex m0  `%` is extremely costly
---
 src/histbuf.rs | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/histbuf.rs b/src/histbuf.rs
index 31d36cd9..85f0650c 100644
--- a/src/histbuf.rs
+++ b/src/histbuf.rs
@@ -122,7 +122,10 @@ where
     /// Writes an element to the buffer, overwriting the oldest value.
     pub fn write(&mut self, t: T) {
         self.data[self.write_at] = t;
-        self.write_at = (self.write_at + 1) % self.len();
+        self.write_at = self.write_at + 1;
+        if self.write_at == self.len() {
+            self.write_at = 0;
+        }
     }
 
     /// Clones and writes all elements in a slice to the buffer.
@@ -152,7 +155,11 @@ where
     /// assert_eq!(x.recent(), &10);
     /// ```
     pub fn recent(&self) -> &T {
-        &self.data[(self.write_at + self.len() - 1) % self.len()]
+        if self.write_at == 0 {
+            &self.data[(self.len() - 1)]
+        } else {
+            &self.data[(self.write_at - 1)]
+        }
     }
 
     /// Returns the array slice backing the buffer, without keeping track

From c6e4f5964029f0f83a372ffafaecfa4a67cd539b Mon Sep 17 00:00:00 2001
From: Andres Vahter <andres.vahter@gmail.com>
Date: Sat, 9 May 2020 21:32:55 +0300
Subject: [PATCH 3/3] histbuf: fix style

---
 src/histbuf.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/histbuf.rs b/src/histbuf.rs
index 85f0650c..3239f836 100644
--- a/src/histbuf.rs
+++ b/src/histbuf.rs
@@ -122,7 +122,7 @@ where
     /// Writes an element to the buffer, overwriting the oldest value.
     pub fn write(&mut self, t: T) {
         self.data[self.write_at] = t;
-        self.write_at = self.write_at + 1;
+        self.write_at += 1;
         if self.write_at == self.len() {
             self.write_at = 0;
         }
@@ -156,9 +156,9 @@ where
     /// ```
     pub fn recent(&self) -> &T {
         if self.write_at == 0 {
-            &self.data[(self.len() - 1)]
+            &self.data[self.len() - 1]
         } else {
-            &self.data[(self.write_at - 1)]
+            &self.data[self.write_at - 1]
         }
     }