From eb6abb020e895c917fb34a7f052b67b57910c2d6 Mon Sep 17 00:00:00 2001
From: Dima Korolev <dmitry.korolev@gmail.com>
Date: Sun, 1 Sep 2019 10:41:56 -0700
Subject: [PATCH] Made it possible to "unit test" code from within
 implementations.

---
 benchmark_base64.cc              | 45 +++++++++++++++++++++++++-------
 ensure_implementations_compile.h |  7 ++++-
 implementations.h                |  9 +++++++
 3 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/benchmark_base64.cc b/benchmark_base64.cc
index f4f43be..d96b34f 100644
--- a/benchmark_base64.cc
+++ b/benchmark_base64.cc
@@ -31,6 +31,33 @@ DEFINE_uint64(n, 0, "The number of blocks to benchmark on, keep at zero to deriv
 DEFINE_double(gb, ndebug ? 0.1 : 0.01, "If `--n` is not set, the number of (unencoded) gigabytes to run the test on.");
 DEFINE_bool(log, false, "Output extra details, to stderr. By default, MB/s will be printed, to stdout.");
 
+template <bool, typename LHS, typename RHS>
+struct EXPECT_EQ_IMPL final {
+  static void DoIt(LHS&& lhs, RHS&& rhs) {
+    if (lhs != rhs) {
+      std::cerr << "\b\b\bFail.\nDetails: '" << lhs << "' != '" << rhs << "'.\n";
+      std::exit(-1);
+    }
+  }
+};
+
+template <typename LHS, typename RHS>
+struct EXPECT_EQ_IMPL<true, LHS, RHS> final {
+  static void DoIt(std::string const& lhs, std::string const& rhs) {
+    if (lhs != rhs) {
+      std::cerr << "\b\b\bFail.\nDetails: '" << lhs << "' != '" << rhs << "'.\n";
+      std::exit(-1);
+    }
+  }
+};
+
+template <typename LHS, typename RHS>
+inline void EXPECT_EQ(LHS&& lhs, RHS&& rhs) {
+  EXPECT_EQ_IMPL<current::strings::is_string_type<LHS>::value || current::strings::is_string_type<RHS>::value,
+                 current::decay<LHS>,
+                 current::decay<RHS>>::DoIt(std::forward<LHS>(lhs), std::forward<RHS>(rhs));
+}
+
 namespace implementations {
 
 #define BASE64_PERFTEST_EXPAND_MACRO_IMPL(x) x
@@ -45,14 +72,19 @@ struct Code;
 // The canonical implementation keeps a member `std::string tmp` as the stateful storage.
 // This is to enable performance tests against other implementations, that are not using `std::string`-s.
 
+struct HasInit {
+  virtual ~HasInit() = default;
+  virtual void Init() const {}
+};
+
 #define IMPLEMENTATION(name)                                                                     \
   static constexpr int index_##name = BASE64_PERFTEST_EXPAND_MACRO(__COUNTER__) - counter_begin; \
   template <>                                                                                    \
-  struct Name<index_##name> {                                                                    \
+  struct Name<index_##name> final {                                                              \
     static char const* HumanReadableName() { return #name; }                                     \
   };                                                                                             \
   template <>                                                                                    \
-  struct Code<index_##name>
+  struct Code<index_##name> final : HasInit
 
 #include "implementations.h"
 
@@ -63,17 +95,12 @@ static constexpr int total = BASE64_PERFTEST_EXPAND_MACRO(__COUNTER__) - counter
 template <class IMPL>
 void Run(size_t n, std::vector<std::string> const& input, std::vector<std::string> const& golden, size_t total_bytes) {
   IMPL impl;
+  impl.Init();
 
   if (FLAGS_log) {
     std::cerr << "Testing correctness: ...";
   }
 
-  auto const EXPECT_EQ = [](std::string const& lhs, std::string const& rhs) {
-    if (lhs != rhs) {
-      std::cerr << "\b\b\bFail.\nDetails: '" << lhs << "' != '" << rhs << "'.\n";
-      std::exit(-1);
-    }
-  };
   auto const Base64Encode = [&impl](std::string const& original) { return impl.DoEncode(original); };
   auto const Base64Decode = [&impl](std::string const& encoded) { return impl.DoDecode(encoded); };
 
@@ -157,7 +184,7 @@ void Run(size_t n, std::vector<std::string> const& input, std::vector<std::strin
   }
 }
 
-struct Registry {
+struct Registry final {
   std::vector<std::string> names;
   std::map<
       std::string,
diff --git a/ensure_implementations_compile.h b/ensure_implementations_compile.h
index d341bb4..70abf41 100644
--- a/ensure_implementations_compile.h
+++ b/ensure_implementations_compile.h
@@ -11,5 +11,10 @@
 #include "current/bricks/util/singleton.h"
 
 #ifndef IMPLEMENTATION
-#define IMPLEMENTATION(x) struct unused_implementation_##x
+struct HasInitStub {
+  virtual ~HasInitStub() = default;
+  virtual void Init() const {}
+};
+#define EXPECT_EQ(...)
+#define IMPLEMENTATION(x) struct unused_implementation_##x final : HasInitStub
 #endif
diff --git a/implementations.h b/implementations.h
index 735f24f..808be1d 100644
--- a/implementations.h
+++ b/implementations.h
@@ -3,6 +3,15 @@
 #include "ensure_implementations_compile.h"
 
 IMPLEMENTATION(vanilla) {
+  void Init() const override {
+    EXPECT_EQ(4, 2 + 2);
+    std::string const foo = "foo";
+    std::string const bar = "bar";
+    EXPECT_EQ("foobar", foo + bar);
+    // EXPECT_EQ(5, 2 * 2);  // This would fail.
+    // EXPECT_EQ("foo", "bar");  // This would fail.
+  }
+
   std::string placeholder;
   current::strings::Chunk DoEncode(current::strings::Chunk chunk) {
     placeholder = current::Base64Encode(chunk.c_str(), chunk.length());