From e488a0bc1b9062d95542589dccdee0d0e1e20e0a Mon Sep 17 00:00:00 2001
From: Maciej Bilas <m.bilas@adform.com>
Date: Tue, 16 Jan 2018 15:12:03 +0100
Subject: [PATCH 1/3] fromBuffer: don't append to roaringArray slices when not
 necessary

---
 roaringarray.go | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/roaringarray.go b/roaringarray.go
index fbee02d7..89da6bbb 100644
--- a/roaringarray.go
+++ b/roaringarray.go
@@ -580,13 +580,16 @@ func (ra *roaringArray) fromBuffer(buf []byte) (int64, error) {
 	}
 
 	// Allocate slices upfront as number of containers is known
-	ra.containers = make([]container, 0, size)
-	ra.keys = make([]uint16, 0, size)
-	ra.needCopyOnWrite = make([]bool, 0, size)
+	ra.containers = make([]container, size)
+	ra.keys = make([]uint16, size)
+	ra.needCopyOnWrite = make([]bool, size)
 
 	for i := uint32(0); i < size; i++ {
 		key := uint16(keycard[2*i])
 		card := int(keycard[2*i+1]) + 1
+		ra.keys[i] = key
+		ra.needCopyOnWrite[i] = true
+
 		if haveRunContainers && isRun.contains(uint16(i)) {
 			// run container
 			nr := binary.LittleEndian.Uint16(buf[pos:])
@@ -596,7 +599,7 @@ func (ra *roaringArray) fromBuffer(buf []byte) (int64, error) {
 				card: int64(card),
 			}
 			pos += int(nr) * 4
-			ra.appendContainer(key, &nb, true)
+			ra.containers[i] = &nb
 		} else if card > arrayDefaultMaxSize {
 			// bitmap container
 			nb := bitmapContainer{
@@ -604,14 +607,14 @@ func (ra *roaringArray) fromBuffer(buf []byte) (int64, error) {
 				bitmap:      byteSliceAsUint64Slice(buf[pos : pos+arrayDefaultMaxSize*2]),
 			}
 			pos += arrayDefaultMaxSize * 2
-			ra.appendContainer(key, &nb, true)
+			ra.containers[i] = &nb
 		} else {
 			// array container
 			nb := arrayContainer{
 				byteSliceAsUint16Slice(buf[pos : pos+card*2]),
 			}
 			pos += card * 2
-			ra.appendContainer(key, &nb, true)
+			ra.containers[i] = &nb
 		}
 	}
 

From d3a8c122b6c1a783e024b19a1aca8c5c6d7830b2 Mon Sep 17 00:00:00 2001
From: Maciej Bilas <m.bilas@adform.com>
Date: Tue, 16 Jan 2018 15:56:32 +0100
Subject: [PATCH 2/3] Add generic uint64SliceAsByteSlice

---
 serialization_generic.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/serialization_generic.go b/serialization_generic.go
index da852338..7fcef769 100644
--- a/serialization_generic.go
+++ b/serialization_generic.go
@@ -59,6 +59,16 @@ func (bc *bitmapContainer) asLittleEndianByteSlice() []byte {
 	return by
 }
 
+func uint64SliceAsByteSlice(slice []uint64) []byte {
+	by := make([]byte, len(slice)*8)
+
+	for i, v := range slice {
+		binary.LittleEndian.PutUint64(by[i*8:], v)
+	}
+
+	return by
+}
+
 func byteSliceAsUint16Slice(slice []byte) []uint16 {
 	if len(slice)%2 != 0 {
 		panic("Slice size should be divisible by 2")

From 61fc009801ec0a4210ab58f795902260f35b02b8 Mon Sep 17 00:00:00 2001
From: Maciej Bilas <maciej.bilas@gmail.com>
Date: Wed, 31 Jan 2018 14:41:22 +0100
Subject: [PATCH 3/3] FromBuffer: no-copy _isRunBitmap_

---
 roaringarray.go | 21 +++++----------------
 1 file changed, 5 insertions(+), 16 deletions(-)

diff --git a/roaringarray.go b/roaringarray.go
index 89da6bbb..ee2db7c0 100644
--- a/roaringarray.go
+++ b/roaringarray.go
@@ -541,7 +541,7 @@ func (ra *roaringArray) fromBuffer(buf []byte) (int64, error) {
 	pos += 4
 	var size uint32 // number of containers
 	haveRunContainers := false
-	var isRun *bitmapContainer
+	var isRunBitmap []byte
 
 	// cookie header
 	if cookie&0x0000FFFF == serialCookie {
@@ -549,20 +549,9 @@ func (ra *roaringArray) fromBuffer(buf []byte) (int64, error) {
 		size = uint32(uint16(cookie>>16) + 1) // number of containers
 
 		// create is-run-container bitmap
-		bytesToRead := (int(size) + 7) / 8
-		by := buf[pos : pos+bytesToRead]
-		pos += bytesToRead
-		isRun = newBitmapContainer()
-		i := 0
-		for ; len(by) >= 8; i++ {
-			isRun.bitmap[i] = binary.LittleEndian.Uint64(by)
-			by = by[8:]
-		}
-		if len(by) > 0 {
-			bx := make([]byte, 8)
-			copy(bx, by)
-			isRun.bitmap[i] = binary.LittleEndian.Uint64(bx)
-		}
+		isRunBitmapSize := (int(size) + 7) / 8
+		isRunBitmap = buf[pos : pos+isRunBitmapSize]
+		pos += isRunBitmapSize
 	} else if cookie == serialCookieNoRunContainer {
 		size = binary.LittleEndian.Uint32(buf[pos:])
 		pos += 4
@@ -590,7 +579,7 @@ func (ra *roaringArray) fromBuffer(buf []byte) (int64, error) {
 		ra.keys[i] = key
 		ra.needCopyOnWrite[i] = true
 
-		if haveRunContainers && isRun.contains(uint16(i)) {
+		if haveRunContainers && isRunBitmap[i/8]&(1<<(i%8)) != 0 {
 			// run container
 			nr := binary.LittleEndian.Uint16(buf[pos:])
 			pos += 2