THRIFT-923. cpp: Implement a fully nonblocking server and client

There are three major parts of this:
1/ New callback-style interfaces for for a few key Thrift components:
   TAsyncProcessor for servers and TAsyncChannel for clients.
2/ Concrete implementations of TAsyncChannel and a server for
   TAsyncProcessor based on evhttp.
3/ Async-style code generation for C++

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@1005127 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/src/async/TEvhttpServer.cpp b/lib/cpp/src/async/TEvhttpServer.cpp
new file mode 100644
index 0000000..2997597
--- /dev/null
+++ b/lib/cpp/src/async/TEvhttpServer.cpp
@@ -0,0 +1,154 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include "TEvhttpServer.h"
+#include "TAsyncBufferProcessor.h"
+#include "transport/TBufferTransports.h"
+#include <evhttp.h>
+
+using apache::thrift::transport::TMemoryBuffer;
+
+namespace apache { namespace thrift { namespace async {
+
+
+struct TEvhttpServer::RequestContext {
+  struct evhttp_request* req;
+  boost::shared_ptr<apache::thrift::transport::TMemoryBuffer> ibuf;
+  boost::shared_ptr<apache::thrift::transport::TMemoryBuffer> obuf;
+
+  RequestContext(struct evhttp_request* req);
+};
+
+
+TEvhttpServer::TEvhttpServer(boost::shared_ptr<TAsyncBufferProcessor> processor)
+  : processor_(processor)
+  , eb_(NULL)
+  , eh_(NULL)
+{}
+
+
+TEvhttpServer::TEvhttpServer(boost::shared_ptr<TAsyncBufferProcessor> processor, int port)
+  : processor_(processor)
+  , eb_(NULL)
+  , eh_(NULL)
+{
+  // Create event_base and evhttp.
+  eb_ = event_base_new();
+  if (eb_ == NULL) {
+    abort();  // XXX
+  }
+  eh_ = evhttp_new(eb_);
+  if (eh_ == NULL) {
+    event_base_free(eb_);
+    abort();  // XXX
+  }
+
+  // Bind to port.
+  int ret = evhttp_bind_socket(eh_, NULL, port);
+  if (ret < 0) {
+    evhttp_free(eh_);
+    event_base_free(eb_);
+  }
+
+  // Register a handler.  If you use the other constructor,
+  // you will want to do this yourself.
+  // Don't forget to unregister before destorying this TEvhttpServer.
+  evhttp_set_cb(eh_, "/", request, (void*)this);
+}
+
+
+TEvhttpServer::~TEvhttpServer() {
+  if (eh_ != NULL) {
+    evhttp_free(eh_);
+  }
+  if (eb_ != NULL) {
+    event_base_free(eb_);
+  }
+}
+
+
+int TEvhttpServer::serve() {
+  if (eb_ == NULL) {
+    abort();  // XXX
+  }
+  return event_base_dispatch(eb_);
+}
+
+
+TEvhttpServer::RequestContext::RequestContext(struct evhttp_request* req) : req(req)
+  , ibuf(new TMemoryBuffer(EVBUFFER_DATA(req->input_buffer), EVBUFFER_LENGTH(req->input_buffer)))
+  , obuf(new TMemoryBuffer())
+{}
+
+
+void TEvhttpServer::request(struct evhttp_request* req, void* self) {
+  static_cast<TEvhttpServer*>(self)->process(req);
+}
+
+
+void TEvhttpServer::process(struct evhttp_request* req) {
+  RequestContext* ctx = new RequestContext(req);
+  return processor_->process(
+      std::tr1::bind(
+        &TEvhttpServer::complete,
+        this,
+        ctx,
+        std::tr1::placeholders::_1),
+      ctx->ibuf,
+      ctx->obuf);
+}
+
+
+void TEvhttpServer::complete(RequestContext* ctx, bool success) {
+  std::auto_ptr<RequestContext> ptr(ctx);
+
+  int code = 200;
+  const char* reason = "OK";
+
+  int rv = evhttp_add_header(ctx->req->output_headers, "Content-Type", "application/x-thrift");
+  if (rv != 0) {
+    // TODO: Log an error.
+  }
+
+  struct evbuffer* buf = evbuffer_new();
+  if (buf == NULL) {
+    // TODO: Log an error.
+  } else {
+    uint8_t* obuf;
+    uint32_t sz;
+    ctx->obuf->getBuffer(&obuf, &sz);
+    int ret = evbuffer_add(buf, obuf, sz);
+    if (ret != 0) {
+      // TODO: Log an error.
+    }
+  }
+
+  evhttp_send_reply(ctx->req, code, reason, buf);
+  if (buf != NULL) {
+    evbuffer_free(buf);
+  }
+}
+
+
+struct event_base* TEvhttpServer::getEventBase() {
+  return eb_;
+}
+
+
+}}} // apache::thrift::async