[utils] Add unit tests for Vector

Also, fix the implementation of {operator==} and add {operator!=}.
{operator==} could not be instantiated on a {Vector<T>} where T is not
const, as it would access the fields of another instantiation of Vector
({T} vs {const T}).

R=jkummerow@chromium.org

Bug: v8:9810
Change-Id: I65c2d3071a781f6fe7a624b727d2770b43b7f7a9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1932363
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65155}

src/utils/vector.h

@@ -118,14 +118,11 @@ class Vector {
   }
 
   bool operator==(const Vector<const T> other) const {
-    if (length_ != other.length_) return false;
-    if (start_ == other.start_) return true;
-    for (size_t i = 0; i < length_; ++i) {
-      if (start_[i] != other.start_[i]) {
-        return false;
-      }
-    }
-    return true;
+    return std::equal(begin(), end(), other.begin(), other.end());
+  }
+
+  bool operator!=(const Vector<const T> other) const {
+    return !operator==(other);
   }
 
  private:

test/unittests/BUILD.gn

@@ -215,6 +215,7 @@ v8_source_set("unittests_sources") {
     "utils/detachable-vector-unittest.cc",
     "utils/locked-queue-unittest.cc",
     "utils/utils-unittest.cc",
+    "utils/vector-unittest.cc",
     "wasm/control-transfer-unittest.cc",
     "wasm/decoder-unittest.cc",
     "wasm/function-body-decoder-unittest.cc",

test/unittests/utils/vector-unittest.cc

@@ -0,0 +1,61 @@
+// Copyright 2019 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/utils/utils.h"
+#include "testing/gtest-support.h"
+
+namespace v8 {
+namespace internal {
+
+TEST(VectorTest, Factories) {
+  auto vec = CStrVector("foo");
+  EXPECT_EQ(3u, vec.size());
+  EXPECT_EQ(0, memcmp(vec.begin(), "foo", 3));
+
+  vec = ArrayVector("foo");
+  EXPECT_EQ(4u, vec.size());
+  EXPECT_EQ(0, memcmp(vec.begin(), "foo\0", 4));
+
+  vec = CStrVector("foo\0\0");
+  EXPECT_EQ(3u, vec.size());
+  EXPECT_EQ(0, memcmp(vec.begin(), "foo", 3));
+
+  vec = CStrVector("");
+  EXPECT_EQ(0u, vec.size());
+
+  vec = CStrVector("\0");
+  EXPECT_EQ(0u, vec.size());
+}
+
+// Test operator== and operator!= on different Vector types.
+TEST(VectorTest, Equals) {
+  auto foo1 = CStrVector("foo");
+  auto foo2 = ArrayVector("ffoo") + 1;
+  CHECK_EQ(4, foo2.size());  // Includes trailing '\0'.
+  foo2.Truncate(foo2.size() - 1);
+  // This is a requirement for the test.
+  CHECK_NE(foo1.begin(), foo2.begin());
+  CHECK_EQ(foo1, foo2);
+
+  // Compare Vector<char> against Vector<const char>.
+  char arr1[] = {'a', 'b', 'c'};
+  char arr2[] = {'a', 'b', 'c'};
+  char arr3[] = {'a', 'b', 'd'};
+  Vector<char> vec1_char = ArrayVector(arr1);
+  Vector<const char> vec1_const_char = vec1_char;
+  Vector<char> vec2_char = ArrayVector(arr2);
+  Vector<char> vec3_char = ArrayVector(arr3);
+  CHECK_NE(vec1_char.begin(), vec2_char.begin());
+  // Note: We directly call operator== and operator!= here (without CHECK_EQ or
+  // CHECK_NE) to have full control over the arguments.
+  CHECK(vec1_char == vec1_const_char);
+  CHECK(vec1_char == vec2_char);
+  CHECK(vec1_const_char == vec2_char);
+  CHECK(vec1_const_char != vec3_char);
+  CHECK(vec3_char != vec2_char);
+  CHECK(vec3_char != vec1_const_char);
+}
+
+}  // namespace internal
+}  // namespace v8