[libc][CPP] Add all_of and find_if_not to algorithm.h (#94058)

This is needed for the allocator implementation for malloc.

libc/src/__support/CPP/algorithm.h

@@ -25,6 +25,21 @@ template <class T> LIBC_INLINE constexpr const T &min(const T &a, const T &b) {
   return (a < b) ? a : b;
 }
 
+template <class InputIt, class UnaryPred>
+LIBC_INLINE constexpr InputIt find_if_not(InputIt first, InputIt last,
+                                          UnaryPred q) {
+  for (; first != last; ++first)
+    if (!q(*first))
+      return first;
+
+  return last;
+}
+
+template <class InputIt, class UnaryPred>
+LIBC_INLINE constexpr bool all_of(InputIt first, InputIt last, UnaryPred p) {
+  return find_if_not(first, last, p) == last;
+}
+
 } // namespace cpp
 } // namespace LIBC_NAMESPACE
 

libc/test/src/__support/CPP/CMakeLists.txt

@@ -1,5 +1,15 @@
 add_custom_target(libc-cpp-utils-tests)
 
+add_libc_test(
+  algorithm_test
+  SUITE
+    libc-cpp-utils-tests
+  SRCS
+    algorithm_test.cpp
+  DEPENDS
+    libc.src.__support.CPP.algorithm
+  )
+
 add_libc_test(
   array_test
   SUITE

libc/test/src/__support/CPP/algorithm_test.cpp

@@ -0,0 +1,47 @@
+//===-- Unittests for Algorithm -------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/algorithm.h"
+#include "src/__support/CPP/array.h"
+#include "test/UnitTest/Test.h"
+
+// TODO(https://github.com/llvm/llvm-project/issues/94066): Add unittests for
+// the remaining algorithm functions.
+namespace LIBC_NAMESPACE::cpp {
+
+TEST(LlvmLibcAlgorithmTest, FindIfNot) {
+  array<int, 4> nums{1, 2, 3, 4};
+  EXPECT_EQ(find_if_not(nums.begin(), nums.end(), [](int i) { return i == 0; }),
+            nums.begin());
+  EXPECT_EQ(find_if_not(nums.begin(), nums.end(), [](int i) { return i == 1; }),
+            nums.begin() + 1);
+  EXPECT_EQ(find_if_not(nums.begin(), nums.end(), [](int i) { return i < 4; }),
+            nums.begin() + 3);
+  EXPECT_EQ(find_if_not(nums.begin(), nums.end(), [](int i) { return i < 5; }),
+            nums.end());
+
+  EXPECT_EQ(
+      find_if_not(nums.begin() + 1, nums.end(), [](int i) { return i == 0; }),
+      nums.begin() + 1);
+  EXPECT_EQ(
+      find_if_not(nums.begin(), nums.begin(), [](int i) { return i == 0; }),
+      nums.begin());
+}
+
+TEST(LlvmLibcAlgorithmTest, AllOf) {
+  array<int, 4> nums{1, 2, 3, 4};
+  EXPECT_TRUE(all_of(nums.begin(), nums.end(), [](int i) { return i < 5; }));
+  EXPECT_FALSE(all_of(nums.begin(), nums.end(), [](int i) { return i < 4; }));
+  EXPECT_TRUE(
+      all_of(nums.begin(), nums.begin() + 3, [](int i) { return i < 4; }));
+  EXPECT_TRUE(
+      all_of(nums.begin() + 1, nums.end(), [](int i) { return i > 1; }));
+  EXPECT_TRUE(all_of(nums.begin(), nums.begin(), [](int i) { return i < 0; }));
+}
+
+} // namespace LIBC_NAMESPACE::cpp