Add a convenient kBufferSize member to QuicInlinedStringView

This CL also makes minor corrections to the class's contract and clarifies the property tests.

PiperOrigin-RevId: 770313484

quiche/quic/core/quic_inlined_string_view.h

diff --git a/quiche/quic/core/quic_inlined_string_view.h b/quiche/quic/core/quic_inlined_string_view.h
index 23d01fc..d3e2a92 100644
--- a/quiche/quic/core/quic_inlined_string_view.h
+++ b/quiche/quic/core/quic_inlined_string_view.h
@@ -18,25 +18,28 @@
 namespace quic {
 
 // QuicInlinedStringView<kSize> is a class that is similar to absl::string_view,
-// with a notable distinction that it can inline up to `kSize` characters
-// (between 15 and 127).
+// with a notable distinction that it can inline up to `kSize - 1` characters
+// (between 15 and 253 characters).
 //
 // Important use notes:
 // - QuicInlinedStringView makes no assumptions about ownership of non-inlined
 //   data; its primary purpose is to be a building block for other data
 //   structures.
 // - Unlike a regular string_view, the data pointer for QuicInlinedStringView
-//   will start pointing to a different location if inlined.
-// - The string will be inlined iff its size is strictly below kSize; this is
-//   a guaranteeed API behavior.
+//   will start pointing to a different location if the string is inlined and
+//   non-empty. For empty strings, the data pointer is always nullptr.
+// - The string will be inlined iff its size is strictly below kSize; this is a
+//   guaranteed API behavior.
 template <size_t kSize>
 class QUICHE_NO_EXPORT QuicInlinedStringView {
  public:
-  // The largest size of a string that can be inlined.
+  // The largest size of a string that can be inlined by
+  // `QuicInlinedStringView<kSize>`.
   static constexpr size_t kMaxInlinedSize = kSize - 1;
+  static constexpr size_t kBufferSize = kSize;
 
   static_assert(kSize >= 16);
-  static_assert(kSize < 255);
+  static_assert(kSize <= 254);
 
   QuicInlinedStringView() { clear(); }
   explicit QuicInlinedStringView(absl::string_view source) {

quiche/quic/core/quic_inlined_string_view_fuzz_test.cc

diff --git a/quiche/quic/core/quic_inlined_string_view_fuzz_test.cc b/quiche/quic/core/quic_inlined_string_view_fuzz_test.cc
index d330853..61260d0 100644
--- a/quiche/quic/core/quic_inlined_string_view_fuzz_test.cc
+++ b/quiche/quic/core/quic_inlined_string_view_fuzz_test.cc
@@ -29,28 +29,29 @@
     EXPECT_EQ(quic_view.size(), view.size());
     EXPECT_EQ(quic_view.view(), view);
     EXPECT_EQ(quic_view.IsInlined(), view.size() < kSize);
+    EXPECT_EQ(quic_view.data() == nullptr, view.empty());
 
     QuicInlinedStringView<kSize> quic_view_copy(quic_view);
     EXPECT_EQ(quic_view_copy.empty(), view.empty());
     EXPECT_EQ(quic_view_copy.size(), view.size());
     EXPECT_EQ(quic_view_copy.view(), view);
     EXPECT_EQ(quic_view_copy.IsInlined(), view.size() < kSize);
+    EXPECT_EQ(quic_view_copy.data() == nullptr, view.empty());
   }
 
   static void IsEmptyAfterClear(absl::string_view view) {
     QuicInlinedStringView<kSize> quic_view(view);
     quic_view.clear();
     EXPECT_TRUE(quic_view.empty());
+    EXPECT_EQ(quic_view.size(), 0);
+    EXPECT_TRUE(quic_view.IsInlined());
   }
 
-  static void DifferentDataPointersWhenInlined(absl::string_view view) {
+  static void NonEmptyStringHasDifferentDataPointerWhenInlined(
+      absl::string_view view) {
     QuicInlinedStringView<kSize> quic_view(view);
-    if (!quic_view.empty()) {
-      const bool pointers_equal = view.data() == quic_view.data();
-      EXPECT_EQ(!pointers_equal, quic_view.IsInlined());
-    } else {
-      EXPECT_EQ(quic_view.data(), nullptr);
-    }
+    const bool pointers_equal = view.data() == quic_view.data();
+    EXPECT_EQ(!pointers_equal, quic_view.IsInlined());
   }
 };
 
@@ -61,21 +62,21 @@
 // - The value of 254 was chosen because it's the largest value supported by
 //   `QuicInlinedStringView`.
 constexpr size_t kRealisticSize =
-    decltype(BufferedSliceInlining::slice)::kMaxInlinedSize + 1;
+    decltype(BufferedSliceInlining::slice)::kBufferSize;
 static_assert(kRealisticSize == 16);
 
-void NeverCrashes16(absl::string_view view) {
+void AccessorsAreCorrect16(absl::string_view view) {
   Properties<16>::AccessorsAreCorrect(view);
 }
-void NeverCrashes24(absl::string_view view) {
+void AccessorsAreCorrect24(absl::string_view view) {
   Properties<24>::AccessorsAreCorrect(view);
 }
-void NeverCrashes254(absl::string_view view) {
+void AccessorsAreCorrect254(absl::string_view view) {
   Properties<254>::AccessorsAreCorrect(view);
 }
-FUZZ_TEST(QuicInlinedStringViewTest, NeverCrashes16);
-FUZZ_TEST(QuicInlinedStringViewTest, NeverCrashes24);
-FUZZ_TEST(QuicInlinedStringViewTest, NeverCrashes254);
+FUZZ_TEST(QuicInlinedStringViewFuzzTest, AccessorsAreCorrect16);
+FUZZ_TEST(QuicInlinedStringViewFuzzTest, AccessorsAreCorrect24);
+FUZZ_TEST(QuicInlinedStringViewFuzzTest, AccessorsAreCorrect254);
 
 void IsEmptyAfterClear16(absl::string_view view) {
   Properties<16>::IsEmptyAfterClear(view);
@@ -86,22 +87,31 @@
 void IsEmptyAfterClear254(absl::string_view view) {
   Properties<254>::IsEmptyAfterClear(view);
 }
-FUZZ_TEST(QuicInlinedStringViewTest, IsEmptyAfterClear16);
-FUZZ_TEST(QuicInlinedStringViewTest, IsEmptyAfterClear24);
-FUZZ_TEST(QuicInlinedStringViewTest, IsEmptyAfterClear254);
+FUZZ_TEST(QuicInlinedStringViewFuzzTest, IsEmptyAfterClear16);
+FUZZ_TEST(QuicInlinedStringViewFuzzTest, IsEmptyAfterClear24);
+FUZZ_TEST(QuicInlinedStringViewFuzzTest, IsEmptyAfterClear254);
 
-void DifferentDataPointersWhenInlined16(absl::string_view view) {
-  Properties<16>::DifferentDataPointersWhenInlined(view);
+void NonEmptyStringHasDifferentDataPointerWhenInlined16(
+    absl::string_view view) {
+  Properties<16>::NonEmptyStringHasDifferentDataPointerWhenInlined(view);
 }
-void DifferentDataPointersWhenInlined24(absl::string_view view) {
-  Properties<24>::DifferentDataPointersWhenInlined(view);
+void NonEmptyStringHasDifferentDataPointerWhenInlined24(
+    absl::string_view view) {
+  Properties<24>::NonEmptyStringHasDifferentDataPointerWhenInlined(view);
 }
-void DifferentDataPointersWhenInlined254(absl::string_view view) {
-  Properties<254>::DifferentDataPointersWhenInlined(view);
+void NonEmptyStringHasDifferentDataPointerWhenInlined254(
+    absl::string_view view) {
+  Properties<254>::NonEmptyStringHasDifferentDataPointerWhenInlined(view);
 }
-FUZZ_TEST(QuicInlinedStringViewTest, DifferentDataPointersWhenInlined16);
-FUZZ_TEST(QuicInlinedStringViewTest, DifferentDataPointersWhenInlined24);
-FUZZ_TEST(QuicInlinedStringViewTest, DifferentDataPointersWhenInlined254);
+FUZZ_TEST(QuicInlinedStringViewFuzzTest,
+          NonEmptyStringHasDifferentDataPointerWhenInlined16)
+    .WithDomains(fuzztest::Arbitrary<std::string>().WithMinSize(1));
+FUZZ_TEST(QuicInlinedStringViewFuzzTest,
+          NonEmptyStringHasDifferentDataPointerWhenInlined24)
+    .WithDomains(fuzztest::Arbitrary<std::string>().WithMinSize(1));
+FUZZ_TEST(QuicInlinedStringViewFuzzTest,
+          NonEmptyStringHasDifferentDataPointerWhenInlined254)
+    .WithDomains(fuzztest::Arbitrary<std::string>().WithMinSize(1));
 
 }  // namespace
 }  // namespace quic

quiche/quic/core/quic_inlined_string_view_test.cc

diff --git a/quiche/quic/core/quic_inlined_string_view_test.cc b/quiche/quic/core/quic_inlined_string_view_test.cc
index 66b062a..f717087 100644
--- a/quiche/quic/core/quic_inlined_string_view_test.cc
+++ b/quiche/quic/core/quic_inlined_string_view_test.cc
@@ -70,5 +70,29 @@
             reinterpret_cast<uintptr_t>(view_external_copy.data()));
 }
 
+TEST(QuicInlinedStringViewTest, IsEmptyAfterClear) {
+  QuicInlinedStringView<24> view("foo");
+  view.clear();
+  ASSERT_TRUE(view.empty());
+  ASSERT_EQ(view.size(), 0);
+  ASSERT_TRUE(view.IsInlined());
+}
+
+TEST(QuicInlinedStringViewTest,
+     NonEmptyStringHasDifferentDataPointerWhenInlined) {
+  absl::string_view view = "foo";
+  QuicInlinedStringView<24> quic_view(view);
+  EXPECT_TRUE(quic_view.IsInlined());
+  EXPECT_NE(view.data(), quic_view.data());
+}
+
+TEST(QuicInlinedStringViewTest,
+     NonEmptyStringHasSameDataPointerWhenNotInlined) {
+  std::string big_string(300, 'a');
+  QuicInlinedStringView<24> quic_view(big_string);
+  EXPECT_FALSE(quic_view.IsInlined());
+  EXPECT_EQ(quic_view.data(), big_string.data());
+}
+
 }  // namespace
 }  // namespace quic