From 9b919186abb7d4fc1e3917ebd65fc361d0b8ddf8 Mon Sep 17 00:00:00 2001
From: JakeQZ <jake@qzdesign.co.uk>
Date: Sat, 29 Jun 2024 08:22:55 +0100
Subject: [PATCH] [TASK] Avoid poor scaling of array_search() with very long
 arrays (#628)

When there were many many elements in `$aStack`, starting the delimiter search from the beginning for each loop iteration was very slow.  This is addressed by building a new array, rather than modifying `$aStack` in place, and iterating over it in a single pass.  A particular 1.6M style string is now parsed in 5 seconds rather than 4 minutes.

Co-authored-by: Bart Butler <bart+github@pm.me>
---
 CHANGELOG.md        |  2 ++
 src/Value/Value.php | 19 +++++++++++++------
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3f293533..e29397aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Changed
 
+- Improve performance of Value::parseValue with many delimiters by refactoring to remove array_search() (#413)
+
 ### Deprecated
 
 ### Removed
diff --git a/src/Value/Value.php b/src/Value/Value.php
index ce6d5790..6be2110c 100644
--- a/src/Value/Value.php
+++ b/src/Value/Value.php
@@ -67,23 +67,30 @@ public static function parseValue(ParserState $oParserState, array $aListDelimit
         }
         // Convert the list to list objects
         foreach ($aListDelimiters as $sDelimiter) {
-            if (count($aStack) === 1) {
+            $iStackLength = count($aStack);
+            if ($iStackLength === 1) {
                 return $aStack[0];
             }
-            $iStartPosition = null;
-            while (($iStartPosition = array_search($sDelimiter, $aStack, true)) !== false) {
+            $aNewStack = [];
+            for ($iStartPosition = 0; $iStartPosition < $iStackLength; ++$iStartPosition) {
+                if ($iStartPosition === ($iStackLength - 1) || $sDelimiter !== $aStack[$iStartPosition + 1]) {
+                    $aNewStack[] = $aStack[$iStartPosition];
+                    continue;
+                }
                 $iLength = 2; //Number of elements to be joined
-                for ($i = $iStartPosition + 2; $i < count($aStack); $i += 2, ++$iLength) {
+                for ($i = $iStartPosition + 3; $i < $iStackLength; $i += 2, ++$iLength) {
                     if ($sDelimiter !== $aStack[$i]) {
                         break;
                     }
                 }
                 $oList = new RuleValueList($sDelimiter, $oParserState->currentLine());
-                for ($i = $iStartPosition - 1; $i - $iStartPosition + 1 < $iLength * 2; $i += 2) {
+                for ($i = $iStartPosition; $i - $iStartPosition < $iLength * 2; $i += 2) {
                     $oList->addListComponent($aStack[$i]);
                 }
-                array_splice($aStack, $iStartPosition - 1, $iLength * 2 - 1, [$oList]);
+                $aNewStack[] = $oList;
+                $iStartPosition += $iLength * 2 - 2;
             }
+            $aStack = $aNewStack;
         }
         if (!isset($aStack[0])) {
             throw new UnexpectedTokenException(