From 486e8834d61c6ba0668413da655dfa02d820f182 Mon Sep 17 00:00:00 2001
From: DBotThePony <dbotthepony@yandex.ru>
Date: Sat, 17 Feb 2024 23:43:39 +0700
Subject: [PATCH] Faster free bitmap search

---
 .../ru/dbotthepony/kommons/io/BTreeDB6.kt     | 37 ++++++-------------
 1 file changed, 12 insertions(+), 25 deletions(-)

diff --git a/src/main/kotlin/ru/dbotthepony/kommons/io/BTreeDB6.kt b/src/main/kotlin/ru/dbotthepony/kommons/io/BTreeDB6.kt
index d4783d0..5a403db 100644
--- a/src/main/kotlin/ru/dbotthepony/kommons/io/BTreeDB6.kt
+++ b/src/main/kotlin/ru/dbotthepony/kommons/io/BTreeDB6.kt
@@ -5,7 +5,6 @@ import it.unimi.dsi.fastutil.ints.IntArraySet
 import it.unimi.dsi.fastutil.ints.IntOpenHashSet
 import it.unimi.dsi.fastutil.objects.Object2IntAVLTreeMap
 import it.unimi.dsi.fastutil.objects.ObjectArrayList
-import it.unimi.dsi.fastutil.objects.ObjectArraySet
 import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet
 import ru.dbotthepony.kommons.util.CarriedExecutor
 import ru.dbotthepony.kommons.util.KOptional
@@ -451,23 +450,16 @@ class BTreeDB6 private constructor(override val file: File, private var reader:
 			return result
 		}
 
-		if (after != INVALID_BLOCK_INDEX) {
+		if (after != INVALID_BLOCK_INDEX && !occupiedBlocksBitmap[after + 1]) {
 			// if we can allocate enough blocks after specified index, allocate there (reduce fragmentation)
-			var correct = true
+			val findOccupied = occupiedBlocksBitmap.nextSetBit(after + 1)
 			val find = after + 1
 
-			for (i2 in 0 until size) {
-				if (occupiedBlocksBitmap[i2 + find]) {
-					correct = false
-					break
-				}
-			}
-
-			if (correct) {
+			if (findOccupied == -1 || findOccupied - find >= size) {
 				val blocks = ArrayList<Block>(size)
+				occupiedBlocksBitmap.set(find, find + size)
 
 				for (i2 in 0 until size) {
-					occupiedBlocksBitmap[i2 + find] = true
 					val block = Block(i2 + find)
 					block.nextBlock = INVALID_BLOCK_INDEX
 					block.type = type
@@ -482,29 +474,24 @@ class BTreeDB6 private constructor(override val file: File, private var reader:
 		var i = 0
 
 		while (true) {
-			val find = occupiedBlocksBitmap.nextClearBit(i)
-			var correct = true
+			val findFree = occupiedBlocksBitmap.nextClearBit(i)
+			val findOccupied = occupiedBlocksBitmap.nextSetBit(findFree)
 
-			for (i2 in 0 until size) {
-				if (occupiedBlocksBitmap[i2 + find]) {
-					correct = false
-					i = find + i2 + 1
-					break
-				}
-			}
-
-			if (correct) {
+			if (findOccupied == -1 || findOccupied - findFree >= size) {
 				val blocks = ArrayList<Block>(size)
 
+				occupiedBlocksBitmap.set(findFree, findFree + size)
+
 				for (i2 in 0 until size) {
-					occupiedBlocksBitmap[i2 + find] = true
-					val block = Block(i2 + find)
+					val block = Block(i2 + findFree)
 					block.nextBlock = INVALID_BLOCK_INDEX
 					block.type = type
 					blocks.add(block)
 				}
 
 				return blocks
+			} else {
+				i = findOccupied + 1
 			}
 		}
 	}