damus

commit c996e5f8b3b827eb1091aaa2954eea3fab968172
parent e9c1671d06f74c38bc62348f84db353b48ec2a38
Author: William Casarin <jb55@jb55.com>
Date:   Thu,  6 Mar 2025 10:42:10 -0800

perf: don't use regex in trim_{prefix,suffix}

regex is overkill for this, and performance is quite bad

Fixes: b131c74ee367 ("Add prefix and suffix string trimming functions")
Signed-off-by: William Casarin <jb55@jb55.com>

Diffstat:
M
damus.xcodeproj/project.pbxproj
 | 
4
++++
M
damus/Models/NoteContent.swift
 | 
12
++++++++++--
A
damusTests/Benchmarking.swift
 | 
72
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

3 files changed, 86 insertions(+), 2 deletions(-)
diff --git a/damus.xcodeproj/project.pbxproj b/damus.xcodeproj/project.pbxproj
@@ -47,6 +47,7 @@
 		4C0A3F93280F66F5000448DE /* ReplyMap.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C0A3F92280F66F5000448DE /* ReplyMap.swift */; };
 		4C0C03992A61E27B0098B3B8 /* primal.wasm in Resources */ = {isa = PBXBuildFile; fileRef = 4C0C03972A61E27B0098B3B8 /* primal.wasm */; };
 		4C0C039A2A61E27B0098B3B8 /* bool_setting.wasm in Resources */ = {isa = PBXBuildFile; fileRef = 4C0C03982A61E27B0098B3B8 /* bool_setting.wasm */; };
+		4C0ED07F2D7A1E260020D8A2 /* Benchmarking.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C0ED07E2D7A1E260020D8A2 /* Benchmarking.swift */; };
 		4C1253502A76C5B20004F4B8 /* UnfollowedNotify.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C12534F2A76C5B20004F4B8 /* UnfollowedNotify.swift */; };
 		4C1253522A76C6130004F4B8 /* ComposeNotify.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C1253512A76C6130004F4B8 /* ComposeNotify.swift */; };
 		4C1253542A76C7D60004F4B8 /* LogoutNotify.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C1253532A76C7D60004F4B8 /* LogoutNotify.swift */; };
@@ -1925,6 +1926,7 @@
 		4C0A3F92280F66F5000448DE /* ReplyMap.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ReplyMap.swift; sourceTree = "<group>"; };
 		4C0C03972A61E27B0098B3B8 /* primal.wasm */ = {isa = PBXFileReference; lastKnownFileType = file; name = primal.wasm; path = nostrscript/primal.wasm; sourceTree = SOURCE_ROOT; };
 		4C0C03982A61E27B0098B3B8 /* bool_setting.wasm */ = {isa = PBXFileReference; lastKnownFileType = file; name = bool_setting.wasm; path = nostrscript/bool_setting.wasm; sourceTree = SOURCE_ROOT; };
+		4C0ED07E2D7A1E260020D8A2 /* Benchmarking.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Benchmarking.swift; sourceTree = "<group>"; };
 		4C12534F2A76C5B20004F4B8 /* UnfollowedNotify.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UnfollowedNotify.swift; sourceTree = "<group>"; };
 		4C1253512A76C6130004F4B8 /* ComposeNotify.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ComposeNotify.swift; sourceTree = "<group>"; };
 		4C1253532A76C7D60004F4B8 /* LogoutNotify.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LogoutNotify.swift; sourceTree = "<group>"; };
@@ -3772,6 +3774,7 @@
 				4C2D34402BDAF1B300F9FB44 /* NIP10Tests.swift */,
 				D72E12792BEEEED000F4F781 /* NostrFilterTests.swift */,
 				3A96E3FD2D6BCE3800AE1630 /* RepostedTests.swift */,
+				4C0ED07E2D7A1E260020D8A2 /* Benchmarking.swift */,
 			);
 			path = damusTests;
 			sourceTree = "<group>";
@@ -5002,6 +5005,7 @@
 				4C9B0DEE2A65A75F00CBDA21 /* AttrStringTestExtensions.swift in Sources */,
 				4C19AE552A5D977400C90DB7 /* HashtagTests.swift in Sources */,
 				D72927AD2BAB515C00F93E90 /* RelayURLTests.swift in Sources */,
+				4C0ED07F2D7A1E260020D8A2 /* Benchmarking.swift in Sources */,
 				3A3040ED29A5CB86008A0F29 /* ReplyDescriptionTests.swift in Sources */,
 				D71DC1EC2A9129C3006E207C /* PostViewTests.swift in Sources */,
 				3AAC7A022A60FE72002B50DF /* LocalizationUtilTests.swift in Sources */,
diff --git a/damus/Models/NoteContent.swift b/damus/Models/NoteContent.swift
@@ -257,12 +257,20 @@ func mention_str(_ m: Mention<MentionRef>, profiles: Profiles) -> CompatibleText
 
 // trim suffix whitespace and newlines
 func trim_suffix(_ str: String) -> String {
-    return str.replacingOccurrences(of: "\\s+$", with: "", options: .regularExpression)
+    var result = str
+    while result.last?.isWhitespace == true {
+        result.removeLast()
+    }
+    return result
 }
 
 // trim prefix whitespace and newlines
 func trim_prefix(_ str: String) -> String {
-    return str.replacingOccurrences(of: "^\\s+", with: "", options: .regularExpression)
+    var result = str
+    while result.first?.isWhitespace == true {
+        result.removeFirst()
+    }
+    return result
 }
 
 struct LongformContent {
diff --git a/damusTests/Benchmarking.swift b/damusTests/Benchmarking.swift
@@ -0,0 +1,72 @@
+//
+//  Benchmarking.swift
+//  damusTests
+//
+//  Created by William Casarin on 3/6/25.
+//
+
+import Testing
+import XCTest
+@testable import damus
+
+class BenchmarkingTests: XCTestCase {
+    
+    // Old regex-based implementations for comparison
+    func trim_suffix_regex(_ str: String) -> String {
+        return str.replacingOccurrences(of: "\\s+$", with: "", options: .regularExpression)
+    }
+    
+    func trim_prefix_regex(_ str: String) -> String {
+        return str.replacingOccurrences(of: "^\\s+", with: "", options: .regularExpression)
+    }
+    
+    // Test strings with different characteristics
+    lazy var testStrings: [String] = [
+        "   Hello World   ",                                // Simple whitespace
+        "   \n\t  Hello World \n\t   ",                     // Mixed whitespace
+        String(repeating: " ", count: 1000) + "Hello",      // Large prefix
+        "Hello" + String(repeating: " ", count: 1000),      // Large suffix
+        String(repeating: " ", count: 500) + "Hello" + String(repeating: " ", count: 500) // Both
+    ]
+    
+    func testTrimSuffixRegexPerformance() throws {
+        measure {
+            for str in testStrings {
+                _ = trim_suffix_regex(str)
+            }
+        }
+    }
+    
+    func testTrimSuffixNewPerformance() throws {
+        measure {
+            for str in testStrings {
+                _ = trim_suffix(str)
+            }
+        }
+    }
+    
+    func testTrimPrefixRegexPerformance() throws {
+        measure {
+            for str in testStrings {
+                _ = trim_prefix_regex(str)
+            }
+        }
+    }
+    
+    func testTrimPrefixNewPerformance() throws {
+        measure {
+            for str in testStrings {
+                _ = trim_prefix(str)
+            }
+        }
+    }
+    
+    func testTrimFunctionCorrectness() throws {
+        // Verify that both implementations produce the same results
+        for str in testStrings {
+            XCTAssertEqual(trim_suffix(str), trim_suffix_regex(str), "New trim_suffix implementation produces different results")
+            XCTAssertEqual(trim_prefix(str), trim_prefix_regex(str), "New trim_prefix implementation produces different results")
+        }
+    }
+}
+