cc/gapic/connection.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed 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.
 */

#ifndef GAPIC_CONNECTION_H
#define GAPIC_CONNECTION_H

#include <cstddef>
#include <memory>
#include <string>

namespace gapic {

// Abstract base class for representing a connection to a remote with simple helper methods for
// sending specific data types.
class Connection {
public:
    // Constant that can be passed to accept() to indicate that the call should
    // block with no timeouts until a connection is made, or the socket closes.
    static const int NO_TIMEOUT = -1;

    virtual ~Connection() {}

    // Try to send size bytes of data from the specified buffer using the underlying connection.
    // Will block if the connection is not ready. Returns the number of bytes successfully sent
    // (possibly less then size if an error occurred).
    virtual size_t send(const void* data, size_t size) = 0;

    // Tries to read size bytes to the buffer specified by data on the underlying connection and
    // blocks until the data is available. Returns the number of bytes successfully retrieved
    // (possibly less then size if an error occurred).
    virtual size_t recv(void* data, size_t size) = 0;

    // Returns the last error message raised by the connection.
    virtual const char* error() = 0;

    // Accept an incoming connection request on the underlying connection and returns the new
    // connection corresponding to it. The returned connection is ready to use.
    // If timeoutMS is NO_TIMEOUT, then the connection will block forever.
    virtual std::unique_ptr<Connection> accept(int timeoutMS = NO_TIMEOUT) = 0;

    // Helper methods for sending and receiving strings
    bool sendString(const std::string& s);
    bool sendString(const char* s);
    bool readString(std::string* s);

    // Helper method for sending plain-old-data values.
    // Returns true if the send was successful, otherwise false.
    template<typename T> inline bool send(const T& data);
};

template<typename T>
inline bool Connection::send(const T& data) {
    return send(&data, sizeof(T)) == sizeof(T);
}

}  // namespace gapic

#endif  // GAPIC_CONNECTION_H