Allow counters to be disabled

Summary:
Some codecs may not want counters enabled. Right now that will
`std::terminate`. Allow disabled counters, and add a test.

Reviewed By: felixhandte

Differential Revision: D14327170

fbshipit-source-id: 37858518c80e192e351e8578e088b59732d2a0cb

folly/compression/Counters.h

@@ -69,13 +69,14 @@ namespace detail {
 /// Wrapper around the makeCompressionCounterHandler() extension point.
 class CompressionCounter {
  public:
-  CompressionCounter() {}
+  CompressionCounter() : initialized_(true) {}
   CompressionCounter(
       folly::io::CodecType codecType,
       folly::StringPiece codecName,
       folly::Optional<int> level,
       CompressionCounterKey key,
-      CompressionCounterType counterType) {
+      CompressionCounterType counterType)
+      : initialized_(false) {
     initialize_ = [=]() {
       return makeCompressionCounterHandler(
           codecType, codecName, level, key, counterType);
@@ -112,7 +113,7 @@ class CompressionCounter {
     }
   }
 
-  bool initialized_{false};
+  bool initialized_;
   folly::Function<folly::Function<void(double)>()> initialize_;
   folly::Function<void(double)> increment_;
 };

folly/compression/test/CompressionTest.cpp

@@ -464,6 +464,35 @@ static bool codecHasFlush(CodecType type) {
   return type != CodecType::BZIP2;
 }
 
+namespace {
+class NoCountersCodec : public Codec {
+ public:
+  NoCountersCodec()
+      : Codec(CodecType::NO_COMPRESSION, {}, {}, /* counters */ false) {}
+
+ private:
+  uint64_t doMaxCompressedLength(uint64_t uncompressedLength) const override {
+    return uncompressedLength;
+  }
+
+  std::unique_ptr<IOBuf> doCompress(const IOBuf* buf) override {
+    return buf->clone();
+  }
+
+  std::unique_ptr<IOBuf> doUncompress(const IOBuf* buf, Optional<uint64_t>)
+      override {
+    return buf->clone();
+  }
+};
+} // namespace
+
+TEST(CodecTest, NoCounters) {
+  NoCountersCodec codec;
+  for (size_t i = 0; i < 1000; ++i) {
+    EXPECT_EQ("hello", codec.uncompress(codec.compress("hello")));
+  }
+}
+
 class StreamingUnitTest : public testing::TestWithParam<CodecType> {
  protected:
   void SetUp() override {

folly/compression/test/CountersTest.cpp

@@ -49,3 +49,8 @@ TEST(FollyCountersTest, AvgWorks) {
     counter += 5;
   }
 }
+
+TEST(FollyCountersTest, DefaultConstruction) {
+  CompressionCounter counter;
+  ++counter;
+}