Snappy serialization.

c++/Makefile.ekam

@@ -4,13 +4,13 @@ all:
 	echo "You probably accidentally told Eclipse to build.  Stopping."
 
 once:
-	CXX=g++-4.7 CXXFLAGS='-std=gnu++0x -O2 -Wall' LIBS='-lz -pthread' ekam -j6
+	CXX=g++-4.7 CXXFLAGS='-std=gnu++0x -O2 -DNDEBUG -Wall' LIBS='-lz -pthread' ekam -j6
 
 continuous:
 	CXX=g++-4.7 CXXFLAGS='-std=gnu++0x -g -Wall' LIBS='-lz -pthread' ekam -j6 -c -n :51315
 
 continuous-opt:
-	CXX=g++-4.7 CXXFLAGS='-std=gnu++0x -O2 -Wall' LIBS='-lz -pthread' ekam -j6 -c -n :51315
+	CXX=g++-4.7 CXXFLAGS='-std=gnu++0x -O2 -DNDEBUG -Wall' LIBS='-lz -pthread' ekam -j6 -c -n :51315
 
 clean:
 	rm -rf bin lib tmp

c++/src/capnproto/benchmark/benchmark-capnproto.c++

@@ -23,6 +23,7 @@
 
 #include "benchmark.capnp.h"
 #include <capnproto/serialize.h>
+#include <capnproto/serialize-snappy.h>
 #include <unistd.h>
 #include <stdlib.h>
 #include <inttypes.h>
@@ -185,13 +186,53 @@ public:
 
 // =======================================================================================
 
+class CountingOutputStream: public FdOutputStream {
+public:
+  CountingOutputStream(int fd): FdOutputStream(fd), throughput(0) {}
+
+  uint64_t throughput;
+
+  void write(const void* buffer, size_t size) override {
+    FdOutputStream::write(buffer, size);
+    throughput += size;
+  }
+
+  void write(ArrayPtr<const ArrayPtr<const byte>> pieces) override {
+    FdOutputStream::write(pieces);
+    for (auto& piece: pieces) {
+      throughput += piece.size();
+    }
+  }
+};
+
+// =======================================================================================
+
+struct Uncompressed {
+  typedef StreamFdMessageReader MessageReader;
+
+  static inline void write(OutputStream& output, MessageBuilder& builder) {
+    writeMessage(output, builder);
+  }
+};
+
+struct SnappyCompressed {
+  typedef SnappyFdMessageReader MessageReader;
+
+  static inline void write(OutputStream& output, MessageBuilder& builder) {
+    writeSnappyMessage(output, builder);
+  }
+};
+
+// =======================================================================================
+
+template <typename Compression>
 struct NoScratch {
   struct ScratchSpace {};
 
-  class MessageReader: public StreamFdMessageReader {
+  class MessageReader: public Compression::MessageReader {
   public:
     inline MessageReader(int fd, ScratchSpace& scratch)
-        : StreamFdMessageReader(fd) {}
+        : Compression::MessageReader(fd) {}
   };
 
   class MessageBuilder: public MallocMessageBuilder {
@@ -200,16 +241,16 @@ struct NoScratch {
   };
 };
 
-template <size_t size>
+template <typename Compression, size_t size>
 struct UseScratch {
   struct ScratchSpace {
     word words[size];
   };
 
-  class MessageReader: public StreamFdMessageReader {
+  class MessageReader: public Compression::MessageReader {
   public:
     inline MessageReader(int fd, ScratchSpace& scratch)
-        : StreamFdMessageReader(fd, ReaderOptions(), arrayPtr(scratch.words, size)) {}
+        : Compression::MessageReader(fd, ReaderOptions(), arrayPtr(scratch.words, size)) {}
   };
 
   class MessageBuilder: public MallocMessageBuilder {
@@ -221,8 +262,9 @@ struct UseScratch {
 
 // =======================================================================================
 
-template <typename TestCase, typename ReuseStrategy>
-void syncClient(int inputFd, int outputFd, uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t syncClient(int inputFd, int outputFd, uint64_t iters) {
+  CountingOutputStream output(outputFd);
   typename ReuseStrategy::ScratchSpace scratch;
 
   for (; iters > 0; --iters) {
@@ -231,7 +273,7 @@ void syncClient(int inputFd, int outputFd, uint64_t iters) {
       typename ReuseStrategy::MessageBuilder builder(scratch);
       expected = TestCase::setupRequest(
           builder.template initRoot<typename TestCase::Request>());
-      writeMessageToFd(outputFd, builder);
+      Compression::write(output, builder);
     }
 
     {
@@ -242,23 +284,28 @@ void syncClient(int inputFd, int outputFd, uint64_t iters) {
       }
     }
   }
+
+  return output.throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void asyncClientSender(int outputFd,
-                       ProducerConsumerQueue<typename TestCase::Expectation>* expectations,
-                       uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t asyncClientSender(int outputFd,
+                           ProducerConsumerQueue<typename TestCase::Expectation>* expectations,
+                           uint64_t iters) {
+  CountingOutputStream output(outputFd);
   typename ReuseStrategy::ScratchSpace scratch;
 
   for (; iters > 0; --iters) {
     typename ReuseStrategy::MessageBuilder builder(scratch);
     expectations->post(TestCase::setupRequest(
         builder.template initRoot<typename TestCase::Request>()));
-    writeMessageToFd(outputFd, builder);
+    Compression::write(output, builder);
   }
+
+  return output.throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
+template <typename TestCase, typename ReuseStrategy, typename Compression>
 void asyncClientReceiver(int inputFd,
                          ProducerConsumerQueue<typename TestCase::Expectation>* expectations,
                          uint64_t iters) {
@@ -274,17 +321,20 @@ void asyncClientReceiver(int inputFd,
   }
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void asyncClient(int inputFd, int outputFd, uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t asyncClient(int inputFd, int outputFd, uint64_t iters) {
   ProducerConsumerQueue<typename TestCase::Expectation> expectations;
   std::thread receiverThread(
-      asyncClientReceiver<TestCase, ReuseStrategy>, inputFd, &expectations, iters);
-  asyncClientSender<TestCase, ReuseStrategy>(outputFd, &expectations, iters);
+      asyncClientReceiver<TestCase, ReuseStrategy, Compression>, inputFd, &expectations, iters);
+  uint64_t throughput =
+      asyncClientSender<TestCase, ReuseStrategy, Compression>(outputFd, &expectations, iters);
   receiverThread.join();
+  return throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void server(int inputFd, int outputFd, uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t server(int inputFd, int outputFd, uint64_t iters) {
+  CountingOutputStream output(outputFd);
   typename ReuseStrategy::ScratchSpace builderScratch;
   typename ReuseStrategy::ScratchSpace readerScratch;
 
@@ -293,12 +343,14 @@ void server(int inputFd, int outputFd, uint64_t iters) {
     typename ReuseStrategy::MessageReader reader(inputFd, readerScratch);
     TestCase::handleRequest(reader.template getRoot<typename TestCase::Request>(),
                             builder.template initRoot<typename TestCase::Response>());
-    writeMessageToFd(outputFd, builder);
+    Compression::write(output, builder);
   }
+
+  return output.throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void passByObject(uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t passByObject(uint64_t iters) {
   typename ReuseStrategy::ScratchSpace requestScratch;
   typename ReuseStrategy::ScratchSpace responseScratch;
 
@@ -315,10 +367,13 @@ void passByObject(uint64_t iters) {
       throw std::logic_error("Incorrect response.");
     }
   }
+
+  return 0;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void passByBytes(uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t passByBytes(uint64_t iters) {
+  uint64_t throughput = 0;
   typename ReuseStrategy::ScratchSpace requestScratch;
   typename ReuseStrategy::ScratchSpace responseScratch;
 
@@ -328,22 +383,26 @@ void passByBytes(uint64_t iters) {
         requestBuilder.template initRoot<typename TestCase::Request>());
 
     Array<word> requestBytes = messageToFlatArray(requestBuilder);
+    throughput += requestBytes.size() * sizeof(word);
     FlatArrayMessageReader requestReader(requestBytes.asPtr());
     typename ReuseStrategy::MessageBuilder responseBuilder(responseScratch);
     TestCase::handleRequest(requestReader.template getRoot<typename TestCase::Request>(),
                             responseBuilder.template initRoot<typename TestCase::Response>());
 
     Array<word> responseBytes = messageToFlatArray(responseBuilder);
+    throughput += responseBytes.size() * sizeof(word);
     FlatArrayMessageReader responseReader(responseBytes.asPtr());
     if (!TestCase::checkResponse(
         responseReader.template getRoot<typename TestCase::Response>(), expected)) {
       throw std::logic_error("Incorrect response.");
     }
   }
+
+  return throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy, typename Func>
-void passByPipe(Func&& clientFunc, uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression, typename Func>
+uint64_t passByPipe(Func&& clientFunc, uint64_t iters) {
   int clientToServer[2];
   int serverToClient[2];
   if (pipe(clientToServer) < 0) throw OsException(errno);
@@ -355,14 +414,22 @@ void passByPipe(Func&& clientFunc, uint64_t iters) {
     close(clientToServer[0]);
     close(serverToClient[1]);
 
-    clientFunc(serverToClient[0], clientToServer[1], iters);
+    uint64_t throughput = clientFunc(serverToClient[0], clientToServer[1], iters);
+
+    FdOutputStream(clientToServer[1]).write(&throughput, sizeof(throughput));
+
     exit(0);
   } else {
     // Server.
     close(clientToServer[1]);
     close(serverToClient[0]);
 
-    server<TestCase, ReuseStrategy>(clientToServer[0], serverToClient[1], iters);
+    uint64_t throughput =
+        server<TestCase, ReuseStrategy, Compression>(clientToServer[0], serverToClient[1], iters);
+
+    uint64_t clientThroughput = 0;
+    FdInputStream(clientToServer[0]).InputStream::read(&clientThroughput, sizeof(clientThroughput));
+    throughput += clientThroughput;
 
     int status;
     if (waitpid(child, &status, 0) != child) {
@@ -371,52 +438,72 @@ void passByPipe(Func&& clientFunc, uint64_t iters) {
     if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
       throw std::logic_error("Child exited abnormally.");
     }
+
+    return throughput;
   }
 }
 
-template <typename ReuseStrategy>
-void doBenchmark(const std::string& mode, uint64_t iters) {
+template <typename ReuseStrategy, typename Compression>
+uint64_t doBenchmark(const std::string& mode, uint64_t iters) {
   if (mode == "client") {
-    syncClient<ExpressionTestCase, ReuseStrategy>(STDIN_FILENO, STDOUT_FILENO, iters);
+    return syncClient<ExpressionTestCase, ReuseStrategy, Compression>(
+        STDIN_FILENO, STDOUT_FILENO, iters);
   } else if (mode == "server") {
-    server<ExpressionTestCase, ReuseStrategy>(STDIN_FILENO, STDOUT_FILENO, iters);
+    return server<ExpressionTestCase, ReuseStrategy, Compression>(
+        STDIN_FILENO, STDOUT_FILENO, iters);
   } else if (mode == "object") {
-    passByObject<ExpressionTestCase, ReuseStrategy>(iters);
+    return passByObject<ExpressionTestCase, ReuseStrategy, Compression>(iters);
   } else if (mode == "bytes") {
-    passByBytes<ExpressionTestCase, ReuseStrategy>(iters);
+    return passByBytes<ExpressionTestCase, ReuseStrategy, Compression>(iters);
   } else if (mode == "pipe") {
-    passByPipe<ExpressionTestCase, ReuseStrategy>(
-        syncClient<ExpressionTestCase, ReuseStrategy>, iters);
+    return passByPipe<ExpressionTestCase, ReuseStrategy, Compression>(
+        syncClient<ExpressionTestCase, ReuseStrategy, Compression>, iters);
   } else if (mode == "pipe-async") {
-    passByPipe<ExpressionTestCase, ReuseStrategy>(
-        asyncClient<ExpressionTestCase, ReuseStrategy>, iters);
+    return passByPipe<ExpressionTestCase, ReuseStrategy, Compression>(
+        asyncClient<ExpressionTestCase, ReuseStrategy, Compression>, iters);
   } else {
     std::cerr << "Unknown mode: " << mode << std::endl;
     exit(1);
   }
 }
 
+template <typename Compression>
+uint64_t doBenchmark2(const std::string& mode, const std::string& reuse, uint64_t iters) {
+  if (reuse == "reuse") {
+    return doBenchmark<UseScratch<Compression, 1024>, Compression>(mode, iters);
+  } else if (reuse == "no-reuse") {
+    return doBenchmark<NoScratch<Compression>, Compression>(mode, iters);
+  } else {
+    std::cerr << "Unknown reuse mode: " << reuse << std::endl;
+    exit(1);
+  }
+}
+
 int main(int argc, char* argv[]) {
-  if (argc != 4) {
-    std::cerr << "USAGE:  " << argv[0] << " MODE REUSE ITERATION_COUNT" << std::endl;
+  if (argc != 5) {
+    std::cerr << "USAGE:  " << argv[0] << " MODE REUSE COMPRESSION ITERATION_COUNT" << std::endl;
     return 1;
   }
 
-  uint64_t iters = strtoull(argv[3], nullptr, 0);
+  uint64_t iters = strtoull(argv[4], nullptr, 0);
   srand(123);
 
   std::cerr << "Doing " << iters << " iterations..." << std::endl;
 
-  std::string reuse = argv[2];
-  if (reuse == "reuse") {
-    doBenchmark<UseScratch<1024>>(argv[1], iters);
-  } else if (reuse == "no-reuse") {
-    doBenchmark<NoScratch>(argv[1], iters);
+  uint64_t throughput;
+
+  std::string compression = argv[3];
+  if (compression == "none") {
+    throughput = doBenchmark2<Uncompressed>(argv[1], argv[2], iters);
+  } else if (compression == "snappy") {
+    throughput = doBenchmark2<SnappyCompressed>(argv[1], argv[2], iters);
   } else {
-    std::cerr << "Unknown reuse mode: " << reuse << std::endl;
+    std::cerr << "Unknown compression mode: " << compression << std::endl;
     return 1;
   }
 
+  std::cerr << "Average messages size = " << (throughput / iters) << std::endl;
+
   return 0;
 }
 

c++/src/capnproto/benchmark/benchmark-protobuf.c++

@@ -35,6 +35,8 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <semaphore.h>
+#include <snappy/snappy.h>
+#include <snappy/snappy-sinksource.h>
 
 namespace capnproto {
 namespace benchmark {
@@ -225,40 +227,109 @@ struct ReusableMessages {
 // to do naively, but tricky to implement without accidentally losing various optimizations.  These
 // two functions should be optimal.
 
-void writeDelimited(const google::protobuf::MessageLite& message,
-                    google::protobuf::io::FileOutputStream* rawOutput) {
-  google::protobuf::io::CodedOutputStream output(rawOutput);
-  const int size = message.ByteSize();
-  output.WriteVarint32(size);
-  uint8_t* buffer = output.GetDirectBufferForNBytesAndAdvance(size);
-  if (buffer != NULL) {
-    message.SerializeWithCachedSizesToArray(buffer);
-  } else {
-    message.SerializeWithCachedSizes(&output);
-    if (output.HadError()) {
-      throw OsException(rawOutput->GetErrno());
+struct Uncompressed {
+  typedef google::protobuf::io::FileInputStream InputStream;
+  typedef google::protobuf::io::FileOutputStream OutputStream;
+
+  static uint64_t write(const google::protobuf::MessageLite& message,
+                        google::protobuf::io::FileOutputStream* rawOutput) {
+    google::protobuf::io::CodedOutputStream output(rawOutput);
+    const int size = message.ByteSize();
+    output.WriteVarint32(size);
+    uint8_t* buffer = output.GetDirectBufferForNBytesAndAdvance(size);
+    if (buffer != NULL) {
+      message.SerializeWithCachedSizesToArray(buffer);
+    } else {
+      message.SerializeWithCachedSizes(&output);
+      if (output.HadError()) {
+        throw OsException(rawOutput->GetErrno());
+      }
     }
+
+    return size;
   }
-}
 
-void readDelimited(google::protobuf::io::ZeroCopyInputStream* rawInput,
+  static void read(google::protobuf::io::ZeroCopyInputStream* rawInput,
                    google::protobuf::MessageLite* message) {
-  google::protobuf::io::CodedInputStream input(rawInput);
-  uint32_t size;
-  if (!input.ReadVarint32(&size)) {
-    throw std::logic_error("Read failed.");
+    google::protobuf::io::CodedInputStream input(rawInput);
+    uint32_t size;
+    GOOGLE_CHECK(input.ReadVarint32(&size));
+
+    auto limit = input.PushLimit(size);
+
+    GOOGLE_CHECK(message->MergePartialFromCodedStream(&input) &&
+                 input.ConsumedEntireMessage());
+
+    input.PopLimit(limit);
   }
 
-  auto limit = input.PushLimit(size);
+  static void flush(google::protobuf::io::FileOutputStream* output) {
+    if (!output->Flush()) throw OsException(output->GetErrno());
+  }
+};
 
-  if (!message->MergePartialFromCodedStream(&input) ||
-      !input.ConsumedEntireMessage()) {
-    throw std::logic_error("Read failed.");
+// =======================================================================================
+// The Snappy interface is really obnoxious.  I gave up here and am just reading/writing flat
+// arrays in some static scratch space.  This probably gives protobufs an edge that it doesn't
+// deserve.
+
+void writeAll(int fd, const void* buffer, size_t size) {
+  const char* pos = reinterpret_cast<const char*>(buffer);
+  while (size > 0) {
+    ssize_t n = write(fd, pos, size);
+    GOOGLE_CHECK_GT(n, 0);
+    pos += n;
+    size -= n;
   }
+}
 
-  input.PopLimit(limit);
+void readAll(int fd, void* buffer, size_t size) {
+  char* pos = reinterpret_cast<char*>(buffer);
+  while (size > 0) {
+    ssize_t n = read(fd, pos, size);
+    GOOGLE_CHECK_GT(n, 0);
+    pos += n;
+    size -= n;
+  }
 }
 
+static char scratch[128 << 10];
+static char scratch2[128 << 10];
+
+struct SnappyCompressed {
+  typedef int InputStream;
+  typedef int OutputStream;
+
+  static uint64_t write(const google::protobuf::MessageLite& message, int* output) {
+    size_t size = message.ByteSize();
+    GOOGLE_CHECK_LE(size, sizeof(scratch));
+
+    message.SerializeWithCachedSizesToArray(reinterpret_cast<uint8_t*>(scratch));
+
+    size_t compressedSize = 0;
+    snappy::RawCompress(scratch, size, scratch2 + sizeof(uint32_t), &compressedSize);
+    uint32_t tag = compressedSize;
+    memcpy(scratch2, &tag, sizeof(tag));
+
+    writeAll(*output, scratch2, compressedSize + sizeof(tag));
+    return compressedSize + sizeof(tag);
+  }
+
+  static void read(int* input, google::protobuf::MessageLite* message) {
+    uint32_t size;
+    readAll(*input, &size, sizeof(size));
+    readAll(*input, scratch, size);
+
+    size_t uncompressedSize;
+    GOOGLE_CHECK(snappy::GetUncompressedLength(scratch, size, &uncompressedSize));
+    GOOGLE_CHECK(snappy::RawUncompress(scratch, size, scratch2));
+
+    GOOGLE_CHECK(message->ParsePartialFromArray(scratch2, uncompressedSize));
+  }
+
+  static void flush(OutputStream*) {}
+};
+
 // =======================================================================================
 
 #define REUSABLE(type) \
@@ -266,10 +337,12 @@ void readDelimited(google::protobuf::io::ZeroCopyInputStream* rawInput,
 #define SINGLE_USE(type) \
   typename ReuseStrategy::template Message<typename TestCase::type>::SingleUse
 
-template <typename TestCase, typename ReuseStrategy>
-void syncClient(int inputFd, int outputFd, uint64_t iters) {
-  google::protobuf::io::FileOutputStream output(outputFd);
-  google::protobuf::io::FileInputStream input(inputFd);
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t syncClient(int inputFd, int outputFd, uint64_t iters) {
+  uint64_t throughput = 0;
+
+  typename Compression::OutputStream output(outputFd);
+  typename Compression::InputStream input(inputFd);
 
   REUSABLE(Request) reusableRequest;
   REUSABLE(Response) reusableResponse;
@@ -277,47 +350,52 @@ void syncClient(int inputFd, int outputFd, uint64_t iters) {
   for (; iters > 0; --iters) {
     SINGLE_USE(Request) request(reusableRequest);
     typename TestCase::Expectation expected = TestCase::setupRequest(&request);
-    writeDelimited(request, &output);
-    if (!output.Flush()) throw OsException(output.GetErrno());
+    throughput += Compression::write(request, &output);
+    Compression::flush(&output);
     ReuseStrategy::doneWith(request);
 
     SINGLE_USE(Response) response(reusableResponse);
-    readDelimited(&input, &response);
+    Compression::read(&input, &response);
     if (!TestCase::checkResponse(response, expected)) {
       throw std::logic_error("Incorrect response.");
     }
     ReuseStrategy::doneWith(response);
   }
+
+  return throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void asyncClientSender(int outputFd,
-                       ProducerConsumerQueue<typename TestCase::Expectation>* expectations,
-                       uint64_t iters) {
-  google::protobuf::io::FileOutputStream output(outputFd);
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t asyncClientSender(int outputFd,
+                           ProducerConsumerQueue<typename TestCase::Expectation>* expectations,
+                           uint64_t iters) {
+  uint64_t throughput = 0;
+
+  typename Compression::OutputStream output(outputFd);
   REUSABLE(Request) reusableRequest;
 
   for (; iters > 0; --iters) {
     SINGLE_USE(Request) request(reusableRequest);
     expectations->post(TestCase::setupRequest(&request));
-    writeDelimited(request, &output);
+    throughput += Compression::write(request, &output);
+    Compression::flush(&output);
     ReuseStrategy::doneWith(request);
   }
 
-  if (!output.Flush()) throw OsException(output.GetErrno());
+  return throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
+template <typename TestCase, typename ReuseStrategy, typename Compression>
 void asyncClientReceiver(int inputFd,
                          ProducerConsumerQueue<typename TestCase::Expectation>* expectations,
                          uint64_t iters) {
-  google::protobuf::io::FileInputStream input(inputFd);
+  typename Compression::InputStream input(inputFd);
   REUSABLE(Response) reusableResponse;
 
   for (; iters > 0; --iters) {
     typename TestCase::Expectation expected = expectations->next();
     SINGLE_USE(Response) response(reusableResponse);
-    readDelimited(&input, &response);
+    Compression::read(&input, &response);
     if (!TestCase::checkResponse(response, expected)) {
       throw std::logic_error("Incorrect response.");
     }
@@ -325,39 +403,46 @@ void asyncClientReceiver(int inputFd,
   }
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void asyncClient(int inputFd, int outputFd, uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t asyncClient(int inputFd, int outputFd, uint64_t iters) {
   ProducerConsumerQueue<typename TestCase::Expectation> expectations;
   std::thread receiverThread(
-      asyncClientReceiver<TestCase, ReuseStrategy>, inputFd, &expectations, iters);
-  asyncClientSender<TestCase, ReuseStrategy>(outputFd, &expectations, iters);
+      asyncClientReceiver<TestCase, ReuseStrategy, Compression>, inputFd, &expectations, iters);
+  uint64_t throughput =
+      asyncClientSender<TestCase, ReuseStrategy, Compression>(outputFd, &expectations, iters);
   receiverThread.join();
+
+  return throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void server(int inputFd, int outputFd, uint64_t iters) {
-  google::protobuf::io::FileOutputStream output(outputFd);
-  google::protobuf::io::FileInputStream input(inputFd);
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t server(int inputFd, int outputFd, uint64_t iters) {
+  uint64_t throughput = 0;
+
+  typename Compression::OutputStream output(outputFd);
+  typename Compression::InputStream input(inputFd);
 
   REUSABLE(Request) reusableRequest;
   REUSABLE(Response) reusableResponse;
 
   for (; iters > 0; --iters) {
     SINGLE_USE(Request) request(reusableRequest);
-    readDelimited(&input, &request);
+    Compression::read(&input, &request);
 
     SINGLE_USE(Response) response(reusableResponse);
     TestCase::handleRequest(request, &response);
     ReuseStrategy::doneWith(request);
 
-    writeDelimited(response, &output);
-    if (!output.Flush()) throw std::logic_error("Write failed.");
+    throughput += Compression::write(response, &output);
+    Compression::flush(&output);
     ReuseStrategy::doneWith(response);
   }
+
+  return throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void passByObject(uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t passByObject(uint64_t iters) {
   REUSABLE(Request) reusableRequest;
   REUSABLE(Response) reusableResponse;
 
@@ -373,10 +458,14 @@ void passByObject(uint64_t iters) {
     }
     ReuseStrategy::doneWith(response);
   }
+
+  return 0;
 }
 
-template <typename TestCase, typename ReuseStrategy>
-void passByBytes(uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression>
+uint64_t passByBytes(uint64_t iters) {
+  uint64_t throughput = 0;
+
   REUSABLE(Request) reusableClientRequest;
   REUSABLE(Request) reusableServerRequest;
   REUSABLE(Response) reusableServerResponse;
@@ -389,6 +478,7 @@ void passByBytes(uint64_t iters) {
 
     typename ReuseStrategy::SingleUseString requestString(reusableRequestString);
     clientRequest.SerializePartialToString(&requestString);
+    throughput += requestString.size();
     ReuseStrategy::doneWith(clientRequest);
 
     SINGLE_USE(Request) serverRequest(reusableServerRequest);
@@ -400,6 +490,7 @@ void passByBytes(uint64_t iters) {
 
     typename ReuseStrategy::SingleUseString responseString(reusableResponseString);
     serverResponse.SerializePartialToString(&responseString);
+    throughput += responseString.size();
     ReuseStrategy::doneWith(serverResponse);
 
     SINGLE_USE(Response) clientResponse(reusableClientResponse);
@@ -410,10 +501,12 @@ void passByBytes(uint64_t iters) {
     }
     ReuseStrategy::doneWith(clientResponse);
   }
+
+  return throughput;
 }
 
-template <typename TestCase, typename ReuseStrategy, typename Func>
-void passByPipe(Func&& clientFunc, uint64_t iters) {
+template <typename TestCase, typename ReuseStrategy, typename Compression, typename Func>
+uint64_t passByPipe(Func&& clientFunc, uint64_t iters) {
   int clientToServer[2];
   int serverToClient[2];
   if (pipe(clientToServer) < 0) throw OsException(errno);
@@ -425,14 +518,21 @@ void passByPipe(Func&& clientFunc, uint64_t iters) {
     close(clientToServer[0]);
     close(serverToClient[1]);
 
-    clientFunc(serverToClient[0], clientToServer[1], iters);
+    uint64_t throughput = clientFunc(serverToClient[0], clientToServer[1], iters);
+    writeAll(clientToServer[1], &throughput, sizeof(throughput));
+
     exit(0);
   } else {
     // Server.
     close(clientToServer[1]);
     close(serverToClient[0]);
 
-    server<TestCase, ReuseStrategy>(clientToServer[0], serverToClient[1], iters);
+    uint64_t throughput =
+        server<TestCase, ReuseStrategy, Compression>(clientToServer[0], serverToClient[1], iters);
+
+    uint64_t clientThroughput = 0;
+    readAll(clientToServer[0], &clientThroughput, sizeof(clientThroughput));
+    throughput += clientThroughput;
 
     int status;
     if (waitpid(child, &status, 0) != child) {
@@ -441,52 +541,72 @@ void passByPipe(Func&& clientFunc, uint64_t iters) {
     if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
       throw std::logic_error("Child exited abnormally.");
     }
+
+    return throughput;
   }
 }
 
-template <typename ReuseStrategy>
-void doBenchmark(const std::string& mode, uint64_t iters) {
+template <typename ReuseStrategy, typename Compression>
+uint64_t doBenchmark(const std::string& mode, uint64_t iters) {
   if (mode == "client") {
-    syncClient<ExpressionTestCase, ReuseStrategy>(STDIN_FILENO, STDOUT_FILENO, iters);
+    return syncClient<ExpressionTestCase, ReuseStrategy, Compression>(
+        STDIN_FILENO, STDOUT_FILENO, iters);
   } else if (mode == "server") {
-    server<ExpressionTestCase, ReuseStrategy>(STDIN_FILENO, STDOUT_FILENO, iters);
+    return server<ExpressionTestCase, ReuseStrategy, Compression>(
+        STDIN_FILENO, STDOUT_FILENO, iters);
   } else if (mode == "object") {
-    passByObject<ExpressionTestCase, ReuseStrategy>(iters);
+    return passByObject<ExpressionTestCase, ReuseStrategy, Compression>(iters);
   } else if (mode == "bytes") {
-    passByBytes<ExpressionTestCase, ReuseStrategy>(iters);
+    return passByBytes<ExpressionTestCase, ReuseStrategy, Compression>(iters);
   } else if (mode == "pipe") {
-    passByPipe<ExpressionTestCase, ReuseStrategy>(
-        syncClient<ExpressionTestCase, ReuseStrategy>, iters);
+    return passByPipe<ExpressionTestCase, ReuseStrategy, Compression>(
+        syncClient<ExpressionTestCase, ReuseStrategy, Compression>, iters);
   } else if (mode == "pipe-async") {
-    passByPipe<ExpressionTestCase, ReuseStrategy>(
-        asyncClient<ExpressionTestCase, ReuseStrategy>, iters);
+    return passByPipe<ExpressionTestCase, ReuseStrategy, Compression>(
+        asyncClient<ExpressionTestCase, ReuseStrategy, Compression>, iters);
   } else {
     std::cerr << "Unknown mode: " << mode << std::endl;
     exit(1);
   }
 }
 
+template <typename Compression>
+uint64_t doBenchmark2(const std::string& mode, const std::string& reuse, uint64_t iters) {
+  if (reuse == "reuse") {
+    return doBenchmark<ReusableMessages, Compression>(mode, iters);
+  } else if (reuse == "no-reuse") {
+    return doBenchmark<SingleUseMessages, Compression>(mode, iters);
+  } else {
+    std::cerr << "Unknown reuse mode: " << reuse << std::endl;
+    exit(1);
+  }
+}
+
 int main(int argc, char* argv[]) {
-  if (argc != 4) {
-    std::cerr << "USAGE:  " << argv[0] << " MODE REUSE ITERATION_COUNT" << std::endl;
+  if (argc != 5) {
+    std::cerr << "USAGE:  " << argv[0] << " MODE REUSE COMPRESSION ITERATION_COUNT" << std::endl;
     return 1;
   }
 
-  uint64_t iters = strtoull(argv[3], nullptr, 0);
+  uint64_t iters = strtoull(argv[4], nullptr, 0);
   srand(123);
 
   std::cerr << "Doing " << iters << " iterations..." << std::endl;
 
-  std::string reuse = argv[2];
-  if (reuse == "reuse") {
-    doBenchmark<ReusableMessages>(argv[1], iters);
-  } else if (reuse == "no-reuse") {
-    doBenchmark<SingleUseMessages>(argv[1], iters);
+  uint64_t throughput;
+
+  std::string compression = argv[3];
+  if (compression == "none") {
+    throughput = doBenchmark2<Uncompressed>(argv[1], argv[2], iters);
+  } else if (compression == "snappy") {
+    throughput = doBenchmark2<SnappyCompressed>(argv[1], argv[2], iters);
   } else {
-    std::cerr << "Unknown reuse mode: " << reuse << std::endl;
+    std::cerr << "Unknown compression mode: " << compression << std::endl;
     return 1;
   }
 
+  std::cerr << "Average messages size = " << (throughput / iters) << std::endl;
+
   return 0;
 }
 

c++/src/capnproto/message-test.c++

+// Copyright (c) 2013, Kenton Varda <temporal@gmail.com>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "message.h"
+#include <gtest/gtest.h>
+
+namespace capnproto {
+namespace internal {
+namespace {
+
+TEST(Message, MallocBuilderWithFirstSegment) {
+  word scratch[16];
+  MallocMessageBuilder builder(arrayPtr(scratch, 16), AllocationStrategy::FIXED_SIZE);
+
+  ArrayPtr<word> segment = builder.allocateSegment(1);
+  EXPECT_EQ(scratch, segment.begin());
+  EXPECT_EQ(16u, segment.size());
+
+  segment = builder.allocateSegment(1);
+  EXPECT_NE(scratch, segment.begin());
+  EXPECT_EQ(16u, segment.size());
+
+  segment = builder.allocateSegment(1);
+  EXPECT_NE(scratch, segment.begin());
+  EXPECT_EQ(16u, segment.size());
+}
+
+// TODO:  More tests.
+
+}  // namespace
+}  // namespace internal
+}  // namespace capnproto

c++/src/capnproto/serialize-snappy-test.c++

+// Copyright (c) 2013, Kenton Varda <temporal@gmail.com>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "test.capnp.h"
+#include "serialize-snappy.h"
+#include <gtest/gtest.h>
+#include <string>
+#include <stdlib.h>
+#include "test-util.h"
+
+namespace capnproto {
+namespace internal {
+namespace {
+
+class TestMessageBuilder: public MallocMessageBuilder {
+  // A MessageBuilder that tries to allocate an exact number of total segments, by allocating
+  // minimum-size segments until it reaches the number, then allocating one large segment to
+  // finish.
+
+public:
+  explicit TestMessageBuilder(uint desiredSegmentCount)
+      : MallocMessageBuilder(0, AllocationStrategy::FIXED_SIZE),
+        desiredSegmentCount(desiredSegmentCount) {}
+  ~TestMessageBuilder() {
+    EXPECT_EQ(0u, desiredSegmentCount);
+  }
+
+  ArrayPtr<word> allocateSegment(uint minimumSize) override {
+    if (desiredSegmentCount <= 1) {
+      if (desiredSegmentCount < 1) {
+        ADD_FAILURE() << "Allocated more segments than desired.";
+      } else {
+        --desiredSegmentCount;
+      }
+      return MallocMessageBuilder::allocateSegment(SUGGESTED_FIRST_SEGMENT_WORDS);
+    } else {
+      --desiredSegmentCount;
+      return MallocMessageBuilder::allocateSegment(minimumSize);
+    }
+  }
+
+private:
+  uint desiredSegmentCount;
+};
+
+class TestPipe: public InputStream, public OutputStream {
+public:
+  TestPipe(bool lazy)
+      : lazy(lazy), readPos(0) {}
+  ~TestPipe() {}
+
+  void write(const void* buffer, size_t size) override {
+    data.append(reinterpret_cast<const char*>(buffer), size);
+  }
+
+  size_t read(void* buffer, size_t minBytes, size_t maxBytes) override {
+    CAPNPROTO_ASSERT(maxBytes <= data.size() - readPos, "Overran end of stream.");
+    size_t amount = lazy ? minBytes : maxBytes;
+    memcpy(buffer, data.data() + readPos, amount);
+    readPos += amount;
+    return amount;
+  }
+
+private:
+  bool lazy;
+  std::string data;
+  std::string::size_type readPos;
+};
+
+TEST(Snappy, RoundTrip) {
+  TestMessageBuilder builder(1);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestPipe pipe(false);
+  writeSnappyMessage(pipe, builder);
+
+  SnappyMessageReader reader(pipe);
+  checkTestMessage(reader.getRoot<TestAllTypes>());
+}
+
+TEST(Snappy, RoundTripScratchSpace) {
+  TestMessageBuilder builder(1);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestPipe pipe(false);
+  writeSnappyMessage(pipe, builder);
+
+  word scratch[1024];
+  SnappyMessageReader reader(pipe, ReaderOptions(), ArrayPtr<word>(scratch, 1024));
+  checkTestMessage(reader.getRoot<TestAllTypes>());
+}
+
+TEST(Snappy, RoundTripLazy) {
+  TestMessageBuilder builder(1);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestPipe pipe(true);
+  writeSnappyMessage(pipe, builder);
+
+  SnappyMessageReader reader(pipe);
+  checkTestMessage(reader.getRoot<TestAllTypes>());
+}
+
+TEST(Snappy, RoundTripOddSegmentCount) {
+  TestMessageBuilder builder(7);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestPipe pipe(false);
+  writeSnappyMessage(pipe, builder);
+
+  SnappyMessageReader reader(pipe);
+  checkTestMessage(reader.getRoot<TestAllTypes>());
+}
+
+TEST(Snappy, RoundTripOddSegmentCountLazy) {
+  TestMessageBuilder builder(7);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestPipe pipe(true);
+  writeSnappyMessage(pipe, builder);
+
+  SnappyMessageReader reader(pipe);
+  checkTestMessage(reader.getRoot<TestAllTypes>());
+}
+
+TEST(Snappy, RoundTripEvenSegmentCount) {
+  TestMessageBuilder builder(10);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestPipe pipe(false);
+  writeSnappyMessage(pipe, builder);
+
+  SnappyMessageReader reader(pipe);
+  checkTestMessage(reader.getRoot<TestAllTypes>());
+}
+
+TEST(Snappy, RoundTripEvenSegmentCountLazy) {
+  TestMessageBuilder builder(10);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestPipe pipe(true);
+  writeSnappyMessage(pipe, builder);
+
+  SnappyMessageReader reader(pipe);
+  checkTestMessage(reader.getRoot<TestAllTypes>());
+}
+
+TEST(Snappy, RoundTripTwoMessages) {
+  TestMessageBuilder builder(1);
+  initTestMessage(builder.initRoot<TestAllTypes>());
+
+  TestMessageBuilder builder2(1);
+  builder2.initRoot<TestAllTypes>().setTextField("Second message.");
+
+  TestPipe pipe(false);
+  writeSnappyMessage(pipe, builder);
+  writeSnappyMessage(pipe, builder2);
+
+  {
+    SnappyMessageReader reader(pipe);
+    checkTestMessage(reader.getRoot<TestAllTypes>());
+  }
+
+  {
+    SnappyMessageReader reader(pipe);
+    EXPECT_EQ("Second message.", reader.getRoot<TestAllTypes>().getTextField());
+  }
+}
+
+// TODO:  Test error cases.
+
+}  // namespace
+}  // namespace internal
+}  // namespace capnproto

c++/src/capnproto/serialize-snappy.c++

+// Copyright (c) 2013, Kenton Varda <temporal@gmail.com>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "serialize-snappy.h"
+#include "wire-format.h"
+#include <snappy/snappy.h>
+#include <snappy/snappy-sinksource.h>
+#include <vector>
+
+namespace capnproto {
+
+namespace {
+
+class InputStreamSource: public snappy::Source {
+public:
+  inline InputStreamSource(InputStream& inputStream, size_t available)
+      : inputStream(inputStream), available(available), pos(nullptr), end(nullptr) {
+    // Read at least 10 bytes (or all available bytes if less than 10), and at most the whole buffer
+    // (unless less is available).
+    size_t firstSize = inputStream.read(buffer,
+        std::min<size_t>(available, 10),
+        std::min<size_t>(available, sizeof(buffer)));
+
+    CAPNPROTO_ASSERT(snappy::GetUncompressedLength(buffer, firstSize, &uncompressedSize),
+                     "Invalid snappy-compressed data.");
+
+    pos = buffer;
+    end = pos + firstSize;
+  }
+  inline ~InputStreamSource() {};
+
+  inline size_t getUncompressedSize() { return uncompressedSize; }
+
+  // implements snappy::Source ---------------------------------------
+
+  size_t Available() const override {
+    return available;
+  }
+
+  const char* Peek(size_t* len) override {
+    *len = end - pos;
+    return pos;
+  }
+
+  void Skip(size_t n) override {
+    pos += n;
+    available -= n;
+
+    if (pos == end && available > 0) {
+      // Read more from the input.
+      pos = buffer;
+      end = pos + inputStream.read(buffer, 1, std::min<size_t>(available, sizeof(buffer)));
+    }
+  }
+
+private:
+  InputStream& inputStream;
+  size_t available;
+  size_t uncompressedSize;
+  char* pos;
+  char* end;
+  char buffer[8192];
+};
+
+}  // namespcae
+
+SnappyMessageReader::SnappyMessageReader(
+    InputStream& inputStream, ReaderOptions options, ArrayPtr<word> scratchSpace)
+    : MessageReader(options), inputStream(inputStream) {
+  internal::WireValue<uint32_t> wireCompressedSize;
+  inputStream.read(&wireCompressedSize, sizeof(wireCompressedSize));
+
+  size_t compressedSize = wireCompressedSize.get();
+  InputStreamSource source(inputStream, compressedSize);
+
+  CAPNPROTO_ASSERT(source.getUncompressedSize() % sizeof(word) == 0,
+                   "Uncompressed size was not a whole number of words.");
+  size_t uncompressedWords = source.getUncompressedSize() / sizeof(word);
+
+  if (scratchSpace.size() < uncompressedWords) {
+    space = newArray<word>(uncompressedWords);
+    scratchSpace = space;
+  }
+
+  CAPNPROTO_ASSERT(
+      snappy::RawUncompress(&source, reinterpret_cast<char*>(scratchSpace.begin())),
+      "Snappy decompression failed.");
+
+  new(&underlyingReader) FlatArrayMessageReader(scratchSpace, options);
+}
+
+SnappyMessageReader::~SnappyMessageReader() {
+  underlyingReader.~FlatArrayMessageReader();
+}
+
+ArrayPtr<const word> SnappyMessageReader::getSegment(uint id) {
+  return underlyingReader.getSegment(id);
+}
+
+SnappyFdMessageReader::~SnappyFdMessageReader() {}
+
+// =======================================================================================
+
+namespace {
+
+class SegmentArraySource: public snappy::Source {
+public:
+  SegmentArraySource(ArrayPtr<const ArrayPtr<const byte>> pieces)
+      : pieces(pieces), offset(0), available(0) {
+    for (auto& piece: pieces) {
+      available += piece.size();
+    }
+    Skip(0);  // Skip leading zero-sized pieces, if any.
+  }
+  ~SegmentArraySource() {}
+
+  // implements snappy::Source ---------------------------------------
+
+  size_t Available() const override {
+    return available;
+  }
+
+  const char* Peek(size_t* len) override {
+    if (pieces.size() == 0) {
+      *len = 0;
+      return nullptr;
+    } else {
+      *len = pieces[0].size() - offset;
+      return reinterpret_cast<const char*>(pieces[0].begin()) + offset;
+    }
+  }
+
+  void Skip(size_t n) override {
+    available -= n;
+    while (pieces.size() > 0 && n >= pieces[0].size() - offset) {
+      n -= pieces[0].size() - offset;
+      offset = 0;
+      pieces = pieces.slice(1, pieces.size());
+    }
+    offset += n;
+  }
+
+private:
+  ArrayPtr<const ArrayPtr<const byte>> pieces;
+  size_t offset;
+  size_t available;
+};
+
+class AccumulatingSink: public snappy::Sink {
+public:
+  AccumulatingSink()
+      : pos(firstPiece + sizeof(compressedSize)),
+        end(firstPiece + sizeof(firstPiece)), firstEnd(firstPiece) {}
+  ~AccumulatingSink() {}
+
+  void writeTo(size_t size, OutputStream& output) {
+    finalizePiece();
+
+    compressedSize.set(size);
+
+    ArrayPtr<const byte> pieces[morePieces.size() + 1];
+
+    pieces[0] = arrayPtr(reinterpret_cast<byte*>(firstPiece),
+                         reinterpret_cast<byte*>(firstEnd));
+    for (uint i = 0; i < morePieces.size(); i++) {
+      auto& piece = morePieces[i];
+      pieces[i + 1] = arrayPtr(reinterpret_cast<byte*>(piece.start.get()),
+                               reinterpret_cast<byte*>(piece.end));
+    }
+
+    output.write(arrayPtr(pieces, morePieces.size() + 1));
+  }
+
+  // implements snappy::Sink -----------------------------------------
+
+  void Append(const char* bytes, size_t n) override {
+    if (bytes == pos) {
+      pos += n;
+    } else {
+      size_t a = available();
+      if (n > a) {
+        memcpy(pos, bytes, a);
+        bytes += a;
+        addPiece(n);
+      }
+
+      memcpy(pos, bytes, n);
+      pos += n;
+    }
+  }
+
+  char* GetAppendBuffer(size_t length, char* scratch) override {
+    if (length > available()) {
+      addPiece(length);
+    }
+    return pos;
+  }
+
+private:
+  char* pos;
+  char* end;
+  // Stand and end point of the current available space.
+
+  char* firstEnd;
+  // End point of the used portion of the first piece.
+
+  struct Piece {
+    std::unique_ptr<char[]> start;
+    // Start point of the piece.
+
+    char* end;
+    // End point of the used portion of the piece.
+
+    Piece() = default;
+    Piece(std::unique_ptr<char[]> start, char* end): start(std::move(start)), end(end) {}
+  };
+
+  std::vector<Piece> morePieces;
+
+  union {
+    internal::WireValue<uint32_t> compressedSize;
+    char firstPiece[8192];
+  };
+
+  inline size_t available() {
+    return end - pos;
+  }
+
+  inline void finalizePiece() {
+    if (morePieces.empty()) {
+      firstEnd = pos;
+    } else {
+      morePieces.back().end = pos;
+    }
+  }
+
+  void addPiece(size_t minSize) {
+    finalizePiece();
+
+    std::unique_ptr<char[]> newPiece(new char[minSize]);
+    pos = newPiece.get();
+    end = pos + minSize;
+    morePieces.emplace_back(std::move(newPiece), pos);
+  }
+};
+
+class SnappyOutputStream: public OutputStream {
+public:
+  SnappyOutputStream(OutputStream& output): output(output), sawWrite(false) {}
+
+  // implements OutputStream -----------------------------------------
+
+  void write(const void* buffer, size_t size) override {
+    CAPNPROTO_ASSERT(false, "writeMessage() was not expected to call this.");
+  }
+
+  void write(ArrayPtr<const ArrayPtr<const byte>> pieces) {
+    CAPNPROTO_ASSERT(!sawWrite, "writeMessage() was expected to issue exactly one write.");
+    sawWrite = true;
+
+    SegmentArraySource source(pieces);
+    AccumulatingSink sink;
+    size_t size = snappy::Compress(&source, &sink);
+
+    sink.writeTo(size, output);
+  }
+
+private:
+  OutputStream& output;
+  bool sawWrite;
+};
+
+}  // namespace
+
+void writeSnappyMessage(OutputStream& output, ArrayPtr<const ArrayPtr<const word>> segments) {
+  SnappyOutputStream snappyOutput(output);
+  writeMessage(snappyOutput, segments);
+}
+
+void writeSnappyMessageToFd(int fd, ArrayPtr<const ArrayPtr<const word>> segments) {
+  FdOutputStream output(fd);
+  writeSnappyMessage(output, segments);
+}
+
+}  // namespace capnproto

c++/src/capnproto/serialize-snappy.h

+// Copyright (c) 2013, Kenton Varda <temporal@gmail.com>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef CAPNPROTO_SERIALIZE_SNAPPY_H_
+#define CAPNPROTO_SERIALIZE_SNAPPY_H_
+
+#include "serialize.h"
+
+namespace capnproto {
+
+class SnappyMessageReader: public MessageReader {
+public:
+  SnappyMessageReader(InputStream& inputStream, ReaderOptions options = ReaderOptions(),
+                      ArrayPtr<word> scratchSpace = nullptr);
+  ~SnappyMessageReader();
+
+  ArrayPtr<const word> getSegment(uint id) override;
+
+private:
+  InputStream& inputStream;
+  Array<word> space;
+
+  union {
+    FlatArrayMessageReader underlyingReader;
+  };
+};
+
+class SnappyFdMessageReader: private FdInputStream, public SnappyMessageReader {
+public:
+  SnappyFdMessageReader(int fd, ReaderOptions options = ReaderOptions(),
+                        ArrayPtr<word> scratchSpace = nullptr)
+      : FdInputStream(fd), SnappyMessageReader(*this, options, scratchSpace) {}
+  // Read message from a file descriptor, without taking ownership of the descriptor.
+
+  SnappyFdMessageReader(AutoCloseFd fd, ReaderOptions options = ReaderOptions(),
+                        ArrayPtr<word> scratchSpace = nullptr)
+      : FdInputStream(move(fd)), SnappyMessageReader(*this, options, scratchSpace) {}
+  // Read a message from a file descriptor, taking ownership of the descriptor.
+
+  ~SnappyFdMessageReader();
+};
+
+void writeSnappyMessage(OutputStream& output, MessageBuilder& builder);
+void writeSnappyMessage(OutputStream& output, ArrayPtr<const ArrayPtr<const word>> segments);
+
+void writeSnappyMessageToFd(int fd, MessageBuilder& builder);
+void writeSnappyMessageToFd(int fd, ArrayPtr<const ArrayPtr<const word>> segments);
+
+// =======================================================================================
+// inline stuff
+
+inline void writeSnappyMessage(OutputStream& output, MessageBuilder& builder) {
+  writeSnappyMessage(output, builder.getSegmentsForOutput());
+}
+
+inline void writeSnappyMessageToFd(int fd, MessageBuilder& builder) {
+  writeSnappyMessageToFd(fd, builder.getSegmentsForOutput());
+}
+
+}  // namespace capnproto
+
+#endif  // CAPNPROTO_SERIALIZE_SNAPPY_H_

c++/src/capnproto/serialize.c++

@@ -152,7 +152,7 @@ InputStreamMessageReader::InputStreamMessageReader(
     : MessageReader(options), inputStream(inputStream), readPos(nullptr) {
   internal::WireValue<uint32_t> firstWord[2];
 
-  inputStream.read(firstWord, sizeof(firstWord), sizeof(firstWord));
+  inputStream.read(firstWord, sizeof(firstWord));
 
   uint segmentCount = firstWord[0].get();
   uint segment0Size = segmentCount == 0 ? 0 : firstWord[1].get();
@@ -162,7 +162,7 @@ InputStreamMessageReader::InputStreamMessageReader(
   // Read sizes for all segments except the first.  Include padding if necessary.
   internal::WireValue<uint32_t> moreSizes[segmentCount & ~1];
   if (segmentCount > 1) {
-    inputStream.read(moreSizes, sizeof(moreSizes), sizeof(moreSizes));
+    inputStream.read(moreSizes, sizeof(moreSizes));
     for (uint i = 0; i < segmentCount - 1; i++) {
       totalWords += moreSizes[i].get();
     }
@@ -188,7 +188,7 @@ InputStreamMessageReader::InputStreamMessageReader(
   }
 
   if (segmentCount == 1) {
-    inputStream.read(scratchSpace.begin(), totalWords * sizeof(word), totalWords * sizeof(word));
+    inputStream.read(scratchSpace.begin(), totalWords * sizeof(word));
   } else if (segmentCount > 1) {
     readPos = reinterpret_cast<byte*>(scratchSpace.begin());
     readPos += inputStream.read(readPos, segment0Size * sizeof(word), totalWords * sizeof(word));
@@ -200,7 +200,16 @@ InputStreamMessageReader::~InputStreamMessageReader() {
     // Note that lazy reads only happen when we have multiple segments, so moreSegments.back() is
     // valid.
     const byte* allEnd = reinterpret_cast<const byte*>(moreSegments.back().end());
-    inputStream.skip(allEnd - readPos);
+
+    if (std::uncaught_exception()) {
+      try {
+        inputStream.skip(allEnd - readPos);
+      } catch (...) {
+        // TODO:  Devise some way to report secondary errors during unwind.
+      }
+    } else {
+      inputStream.skip(allEnd - readPos);
+    }
   }
 }
 
@@ -328,7 +337,12 @@ void FdOutputStream::write(const void* buffer, size_t size) {
     ssize_t n = ::write(fd, pos, size);
     if (n <= 0) {
       CAPNPROTO_ASSERT(n < 0, "write() returned zero.");
-      throw OsException("write", errno);
+      int error = errno;
+      if (error == EINTR) {
+        continue;
+      } else {
+        throw OsException("write", error);
+      }
     }
     pos += n;
     size -= n;

c++/src/capnproto/serialize.h

@@ -91,6 +91,9 @@ public:
   // message.  If it can't even reach minBytes, it MUST throw an exception, as the caller is not
   // expected to understand how to deal with partial reads.
 
+  inline void read(void* buffer, size_t bytes) { read(buffer, bytes, bytes); }
+  // Convenience method for reading an exact number of bytes.
+
   virtual void skip(size_t bytes);
   // Skips past the given number of bytes, discarding them.  The default implementation read()s
   // into a scratch buffer.
@@ -210,18 +213,11 @@ public:
                         ArrayPtr<word> scratchSpace = nullptr)
       : FdInputStream(fd), InputStreamMessageReader(*this, options, scratchSpace) {}
   // Read message from a file descriptor, without taking ownership of the descriptor.
-  //
-  // Since this version implies that the caller intends to read more data from the fd later on, the
-  // default is to read the entire message eagerly in the constructor, so that the fd will be
-  // deterministically positioned just past the end of the message.
 
   StreamFdMessageReader(AutoCloseFd fd, ReaderOptions options = ReaderOptions(),
                         ArrayPtr<word> scratchSpace = nullptr)
       : FdInputStream(move(fd)), InputStreamMessageReader(*this, options, scratchSpace) {}
   // Read a message from a file descriptor, taking ownership of the descriptor.
-  //
-  // Since this version implies that the caller does not intend to read any more data from the fd,
-  // the default is to read the message lazily as needed.
 
   ~StreamFdMessageReader();
 };

c++/src/capnproto/type-safety.h

@@ -116,7 +116,7 @@ class Array {
 public:
   inline Array(): ptr(nullptr), size_(0) {}
   inline Array(std::nullptr_t): ptr(nullptr), size_(0) {}
-  inline Array(Array&& other): ptr(other.ptr), size_(other.size_) {
+  inline Array(Array&& other) noexcept: ptr(other.ptr), size_(other.size_) {
     other.ptr = nullptr;
     other.size_ = 0;
   }