From 1373637da18b3bc58eaddae2ad5614cac94137c1 Mon Sep 17 00:00:00 2001
From: Marin Postma <postma.marin@protonmail.com>
Date: Tue, 27 Apr 2021 14:22:33 +0200
Subject: [PATCH 1/2] optimize roaring codec

---
 .../roaring_bitmap/bo_roaring_bitmap_codec.rs         | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs b/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs
index 7ceb69f9a..25c8afe2f 100644
--- a/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs
+++ b/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs
@@ -1,4 +1,6 @@
 use std::borrow::Cow;
+use std::mem::size_of;
+
 use byteorder::{NativeEndian, ReadBytesExt, WriteBytesExt};
 use roaring::RoaringBitmap;
 
@@ -7,9 +9,14 @@ pub struct BoRoaringBitmapCodec;
 impl heed::BytesDecode<'_> for BoRoaringBitmapCodec {
     type DItem = RoaringBitmap;
 
-    fn bytes_decode(mut bytes: &[u8]) -> Option<Self::DItem> {
+    fn bytes_decode(bytes: &[u8]) -> Option<Self::DItem> {
         let mut bitmap = RoaringBitmap::new();
-        while let Ok(integer) = bytes.read_u32::<NativeEndian>() {
+        let num_u32 = bytes.len() / size_of::<u32>();
+        for i in 0..num_u32 {
+            let start = i * size_of::<u32>();
+            let end = (i + 1) * size_of::<u32>();
+            let mut bytes = bytes.get(start..end)?;
+            let integer = bytes.read_u32::<NativeEndian>().ok()?;
             bitmap.insert(integer);
         }
         Some(bitmap)

From 984dc7c1ed157a3691b77a0982d06390c13ea2ce Mon Sep 17 00:00:00 2001
From: Marin Postma <postma.marin@protonmail.com>
Date: Tue, 27 Apr 2021 18:42:08 +0200
Subject: [PATCH 2/2] rewrite roaring codec without byteorder.

---
 .../roaring_bitmap/bo_roaring_bitmap_codec.rs | 26 +++++++++----------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs b/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs
index 25c8afe2f..8d1eb79dd 100644
--- a/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs
+++ b/milli/src/heed_codec/roaring_bitmap/bo_roaring_bitmap_codec.rs
@@ -1,7 +1,7 @@
 use std::borrow::Cow;
+use std::convert::TryInto;
 use std::mem::size_of;
 
-use byteorder::{NativeEndian, ReadBytesExt, WriteBytesExt};
 use roaring::RoaringBitmap;
 
 pub struct BoRoaringBitmapCodec;
@@ -11,14 +11,12 @@ impl heed::BytesDecode<'_> for BoRoaringBitmapCodec {
 
     fn bytes_decode(bytes: &[u8]) -> Option<Self::DItem> {
         let mut bitmap = RoaringBitmap::new();
-        let num_u32 = bytes.len() / size_of::<u32>();
-        for i in 0..num_u32 {
-            let start = i * size_of::<u32>();
-            let end = (i + 1) * size_of::<u32>();
-            let mut bytes = bytes.get(start..end)?;
-            let integer = bytes.read_u32::<NativeEndian>().ok()?;
-            bitmap.insert(integer);
+
+        for chunk in bytes.chunks(size_of::<u32>()) {
+            let bytes = chunk.try_into().ok()?;
+            bitmap.push(u32::from_ne_bytes(bytes));
         }
+
         Some(bitmap)
     }
 }
@@ -27,10 +25,12 @@ impl heed::BytesEncode<'_> for BoRoaringBitmapCodec {
     type EItem = RoaringBitmap;
 
     fn bytes_encode(item: &Self::EItem) -> Option<Cow<[u8]>> {
-        let mut bytes = Vec::with_capacity(item.len() as usize * 4);
-        for integer in item.iter() {
-            bytes.write_u32::<NativeEndian>(integer).ok()?;
-        }
-        Some(Cow::Owned(bytes))
+        let mut out = Vec::with_capacity(item.len() as usize * size_of::<u32>());
+
+        item.iter()
+            .map(|i| i.to_ne_bytes())
+            .for_each(|bytes| out.extend_from_slice(&bytes));
+
+        Some(Cow::Owned(out))
     }
 }