Add working server example.

capnproto-example/calculator-server.c++

@@ -0,0 +1,215 @@
+// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
+// Licensed under the MIT License:
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#include "calculator.capnp.h"
+#include <kj/debug.h>
+#include <capnp/ez-rpc.h>
+#include <capnp/message.h>
+#include <iostream>
+
+typedef unsigned int uint;
+
+kj::Promise<double> readValue(Calculator::Value::Client value) {
+  // Helper function to asynchronously call read() on a Calculator::Value and
+  // return a promise for the result.  (In the future, the generated code might
+  // include something like this automatically.)
+
+  return value.readRequest().send()
+      .then([](capnp::Response<Calculator::Value::ReadResults> result) {
+    return result.getValue();
+  });
+}
+
+kj::Promise<double> evaluateImpl(
+    Calculator::Expression::Reader expression,
+    capnp::List<double>::Reader params = capnp::List<double>::Reader()) {
+  // Implementation of CalculatorImpl::evaluate(), also shared by
+  // FunctionImpl::call().  In the latter case, `params` are the parameter
+  // values passed to the function; in the former case, `params` is just an
+  // empty list.
+
+  switch (expression.which()) {
+    case Calculator::Expression::LITERAL:
+      return expression.getLiteral();
+
+    case Calculator::Expression::PREVIOUS_RESULT:
+      return readValue(expression.getPreviousResult());
+
+    case Calculator::Expression::PARAMETER: {
+      KJ_REQUIRE(expression.getParameter() < params.size(),
+                 "Parameter index out-of-range.");
+      return params[expression.getParameter()];
+    }
+
+    case Calculator::Expression::CALL: {
+      auto call = expression.getCall();
+      auto func = call.getFunction();
+
+      // Evaluate each parameter.
+      kj::Array<kj::Promise<double>> paramPromises =
+          KJ_MAP(param, call.getParams()) {
+            return evaluateImpl(param, params);
+          };
+
+      // Join the array of promises into a promise for an array.
+      kj::Promise<kj::Array<double>> joinedParams =
+          kj::joinPromises(kj::mv(paramPromises));
+
+      // When the parameters are complete, call the function.
+      return joinedParams.then([KJ_CPCAP(func)](kj::Array<double>&& paramValues) mutable {
+        auto request = func.callRequest();
+        request.setParams(paramValues);
+        return request.send().then(
+            [](capnp::Response<Calculator::Function::CallResults>&& result) {
+          return result.getValue();
+        });
+      });
+    }
+
+    default:
+      // Throw an exception.
+      KJ_FAIL_REQUIRE("Unknown expression type.");
+  }
+}
+
+class ValueImpl final: public Calculator::Value::Server {
+  // Simple implementation of the Calculator.Value Cap'n Proto interface.
+
+public:
+  ValueImpl(double value): value(value) {}
+
+  kj::Promise<void> read(ReadContext context) {
+    context.getResults().setValue(value);
+    return kj::READY_NOW;
+  }
+
+private:
+  double value;
+};
+
+class FunctionImpl final: public Calculator::Function::Server {
+  // Implementation of the Calculator.Function Cap'n Proto interface, where the
+  // function is defined by a Calculator.Expression.
+
+public:
+  FunctionImpl(uint paramCount, Calculator::Expression::Reader body)
+      : paramCount(paramCount) {
+    this->body.setRoot(body);
+  }
+
+  kj::Promise<void> call(CallContext context) {
+    auto params = context.getParams().getParams();
+    KJ_REQUIRE(params.size() == paramCount, "Wrong number of parameters.");
+
+    return evaluateImpl(body.getRoot<Calculator::Expression>(), params)
+        .then([KJ_CPCAP(context)](double value) mutable {
+      context.getResults().setValue(value);
+    });
+  }
+
+private:
+  uint paramCount;
+  // The function's arity.
+
+  capnp::MallocMessageBuilder body;
+  // Stores a permanent copy of the function body.
+};
+
+class OperatorImpl final: public Calculator::Function::Server {
+  // Implementation of the Calculator.Function Cap'n Proto interface, wrapping
+  // basic binary arithmetic operators.
+
+public:
+  OperatorImpl(Calculator::Operator op): op(op) {}
+
+  kj::Promise<void> call(CallContext context) {
+    auto params = context.getParams().getParams();
+    KJ_REQUIRE(params.size() == 2, "Wrong number of parameters.");
+
+    double result;
+    switch (op) {
+      case Calculator::Operator::ADD:     result = params[0] + params[1]; break;
+      case Calculator::Operator::SUBTRACT:result = params[0] - params[1]; break;
+      case Calculator::Operator::MULTIPLY:result = params[0] * params[1]; break;
+      case Calculator::Operator::DIVIDE:  result = params[0] / params[1]; break;
+      default:
+        KJ_FAIL_REQUIRE("Unknown operator.");
+    }
+
+    context.getResults().setValue(result);
+    return kj::READY_NOW;
+  }
+
+private:
+  Calculator::Operator op;
+};
+
+class CalculatorImpl final: public Calculator::Server {
+  // Implementation of the Calculator Cap'n Proto interface.
+
+public:
+  kj::Promise<void> evaluate(EvaluateContext context) override {
+    return evaluateImpl(context.getParams().getExpression())
+        .then([KJ_CPCAP(context)](double value) mutable {
+      context.getResults().setValue(kj::heap<ValueImpl>(value));
+    });
+  }
+
+  kj::Promise<void> defFunction(DefFunctionContext context) override {
+    auto params = context.getParams();
+    context.getResults().setFunc(kj::heap<FunctionImpl>(
+        params.getParamCount(), params.getBody()));
+    return kj::READY_NOW;
+  }
+
+  kj::Promise<void> getOperator(GetOperatorContext context) override {
+    context.getResults().setFunc(kj::heap<OperatorImpl>(
+        context.getParams().getOp()));
+    return kj::READY_NOW;
+  }
+};
+
+int main(int argc, const char* argv[]) {
+  if (argc != 2) {
+    std::cerr << "usage: " << argv[0] << " ADDRESS[:PORT]\n"
+        "Runs the server bound to the given address/port.\n"
+        "ADDRESS may be '*' to bind to all local addresses.\n"
+        ":PORT may be omitted to choose a port automatically." << std::endl;
+    return 1;
+  }
+
+  // Set up a server.
+  capnp::EzRpcServer server(kj::heap<CalculatorImpl>(), argv[1]);
+
+  // Write the port number to stdout, in case it was chosen automatically.
+  auto& waitScope = server.getWaitScope();
+  uint port = server.getPort().wait(waitScope);
+  if (port == 0) {
+    // The address format "unix:/path/to/socket" opens a unix domain socket,
+    // in which case the port will be zero.
+    std::cout << "Listening on Unix socket..." << std::endl;
+  } else {
+    std::cout << "Listening on port " << port << "..." << std::endl;
+  }
+
+  // Run forever, accepting connections and handling requests.
+  kj::NEVER_DONE.wait(waitScope);
+}