BStringList: add Sort() with custom functions

fix #9268 and a TODO

Change-Id: I3148b32221f34f5fb270d8892a6fc80f69ba2e29
Reviewed-on: https://review.haiku-os.org/c/haiku/+/11104
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/os/support/StringList.h

@@ -36,7 +36,10 @@ public:
 
 	// Reorder items
 			void				Sort(bool ignoreCase = false);
-									// TODO: Sort() with custom sort function.
+			void				Sort(int (*compareFunc)(const char*,
+									const char*, void* context), void* context);
+			void				Sort(int (*compareFunc)(const BString&,
+									const BString&, void* context), void* context);
 			bool				Swap(int32 indexA, int32 indexB);
 			bool				Move(int32 fromIndex, int32 toIndex);
 

src/kits/support/StringList.cpp

@@ -212,6 +212,48 @@ BStringList::Sort(bool ignoreCase)
 }
 
 
+void
+BStringList::Sort(int (*compareFunc)(const BString&, const BString&, void* context),
+	void* context)
+{
+	struct _sortContext {
+		static int localSort(const void* pa, const void* pb, void* customSort) {
+			struct _sortContext* context = (struct _sortContext*)customSort;
+			return context->compareFunc(BString::Private::StringFromData(*(char **)pa),
+				BString::Private::StringFromData(*(char **)pb), context->context);
+		}
+		int (*compareFunc)(const BString&, const BString&, void* context);
+		void* context;
+	} sortContext;
+	sortContext.compareFunc = compareFunc;
+	sortContext.context = context;
+
+	const char** list = (const char**)fStrings.Items();
+	qsort_r(list, fStrings.CountItems(), sizeof(*list), _sortContext::localSort, &sortContext);
+}
+
+
+void
+BStringList::Sort(int (*compareFunc)(const char*, const char*, void* context),
+	void* context)
+{
+	struct _sortContext {
+		static int localSort(const void* pa, const void* pb, void* customSort) {
+			struct _sortContext* context = (struct _sortContext*)customSort;
+			return context->compareFunc(*(const char **)pa,
+				*(const char **)pb, context->context);
+		}
+		int (*compareFunc)(const char*, const char*, void* context);
+		void* context;
+	} sortContext;
+	sortContext.compareFunc = compareFunc;
+	sortContext.context = context;
+
+	const char** list = (const char**)fStrings.Items();
+	qsort_r(list, fStrings.CountItems(), sizeof(*list), _sortContext::localSort, &sortContext);
+}
+
+
 bool
 BStringList::Swap(int32 indexA, int32 indexB)
 {

src/tests/kits/support/Jamfile

@@ -41,6 +41,8 @@ UnitTestLib libsupporttest.so
 		StringSubCopyTest.cpp
 		StringUTF8Test.cpp
 
+		StringListTest.cpp
+
 	: be [ TargetLibstdc++ ] libsupporttest_RemoteTestObject.so
 ;
 

src/tests/kits/support/StringListTest.cpp

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2026, Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <String.h>
+#include <StringList.h>
+
+#include <TestSuiteAddon.h>
+#include <cppunit/TestFixture.h>
+#include <cppunit/extensions/HelperMacros.h>
+
+
+static int
+CompareWithData(const char* a, const char* b, void* context)
+{
+	return strcmp(a, b);
+}
+
+
+static int
+CompareWithDataBString(const BString& a, const BString& b, void* context)
+{
+	return a.Compare(b);
+}
+
+
+
+
+class StringListTest : public CppUnit::TestFixture {
+public:
+	CPPUNIT_TEST_SUITE(StringListTest);
+	CPPUNIT_TEST(SortItems_IsSorted);
+	CPPUNIT_TEST_SUITE_END();
+
+	void SortItems_IsSorted();
+
+private:
+	void Initialize(BStringList& list, int size);
+	bool Equals(const BStringList& list1, const BStringList& list2);
+	bool IsSorted(const BStringList& list);
+};
+
+
+void
+StringListTest::Initialize(BStringList& list, int size)
+{
+	const char* fruits[] = {"Apple", "Orange", "Banana", "Grapes", "Cherry"};
+	for (int32 i = 0; i < size; i++)
+		list.Add(BString(fruits[i % 5]));
+}
+
+
+bool
+StringListTest::Equals(const BStringList& list1, const BStringList& list2)
+{
+	const int32 n = list1.CountStrings();
+	if (n != list2.CountStrings())
+		return false;
+
+	for (int32 i = 0; i < n; i++) {
+		BString item1 = list1.StringAt(i);
+		BString item2 = list2.StringAt(i);
+		if (item1 != item2)
+			return false;
+	}
+
+	return true;
+}
+
+
+bool
+StringListTest::IsSorted(const BStringList& list)
+{
+	BString previtem = list.StringAt(0);
+	for (int32 i = 1; i < list.CountStrings(); i++) {
+		BString item = list.StringAt(i);
+		if (item.Compare(previtem) < 0)
+			return false;
+		previtem = item;
+	}
+	return true;
+}
+
+
+void
+StringListTest::SortItems_IsSorted()
+{
+	for (int i = 10; i <= 20; i++) {
+		BStringList list;
+		Initialize(list, i);
+
+		BStringList clone(list);
+		CPPUNIT_ASSERT(Equals(list, clone));
+
+		list.Sort(CompareWithData, NULL);
+		CPPUNIT_ASSERT(IsSorted(list));
+
+		clone.Sort(CompareWithDataBString, NULL);
+		CPPUNIT_ASSERT(IsSorted(clone));
+		CPPUNIT_ASSERT(Equals(list, clone));
+	}
+}
+
+
+CPPUNIT_TEST_SUITE_NAMED_REGISTRATION(StringListTest, getTestSuiteName());