Implemented URStream

include/ur_modern_driver/ur/stream.h

@@ -0,0 +1,30 @@
+#pragma once
+#include <string>
+#include <atomic>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+
+/// Encapsulates a TCP socket 
+class URStream {
+private:
+    int _socket_fd = -1;
+    std::string _host;
+    int _port;
+
+    std::atomic<bool> _initialized;
+    std::atomic<bool> _stopping;
+
+public:
+    URStream(std::string &host, int port) 
+        : _host(host), 
+        _port(port),
+        _initialized(false),
+        _stopping(false) {}
+
+    bool connect();
+    void disconnect();
+
+    ssize_t send(uint8_t *buf, size_t buf_len);
+    ssize_t receive(uint8_t *buf, size_t buf_len);
+};

src/ur/stream.cpp

@@ -0,0 +1,93 @@
+#include <cstring>
+#include <unistd.h>
+#include <netinet/tcp.h>
+
+#include "ur_modern_driver/ur/stream.h"
+#include "ur_modern_driver/log.h"
+
+bool URStream::connect() {
+    if(_initialized)
+        return false;
+
+    LOG_INFO("Connecting to UR @ %s:%d\n", _host.c_str(), _port);
+
+    //gethostbyname() is deprecated so use getadderinfo() as described in:
+    //http://www.beej.us/guide/bgnet/output/html/multipage/syscalls.html#getaddrinfo
+
+    std::string service = std::to_string(_port);
+    struct addrinfo hints, *result;
+    std::memset(&hints, 0, sizeof(hints));
+
+    hints.ai_family = AF_UNSPEC;
+    hints.ai_socktype = SOCK_STREAM;
+    hints.ai_flags = AI_PASSIVE;
+
+    if(getaddrinfo(_host.c_str(), service.c_str(), &hints, &result) != 0) {
+        LOG_ERROR("Failed to get host name\n");   
+        return false;
+    }
+    
+    //loop through the list of addresses untill we find one that's connectable
+    for(struct addrinfo *p = result; p != nullptr; p = p->ai_next) {
+        _socket_fd = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
+
+        if(_socket_fd == -1) //socket error?
+            continue;
+
+        if(::connect(_socket_fd, p->ai_addr, p->ai_addrlen) != 0) {
+            if(_stopping)
+                break;
+            else
+                continue; //try next addrinfo if connect fails
+        }
+
+        //disable Nagle's algorithm to ensure we sent packets as fast as possible
+        int flag = 1;
+        setsockopt(_socket_fd, IPPROTO_TCP, TCP_NODELAY, &flag, sizeof(flag));
+        _initialized = true;
+        LOG_INFO("Connection successfully established\n");
+        break;
+    }
+
+    freeaddrinfo(result);
+    if(!_initialized) 
+        LOG_ERROR("Connection failed\n");
+
+    return _initialized;
+}
+
+void URStream::disconnect() {
+    if(!_initialized || _stopping)
+        return;
+
+    _stopping = true;
+    close(_socket_fd);
+    _initialized = false;
+}
+
+ssize_t URStream::send(uint8_t *buf, size_t buf_len) {
+    if(!_initialized)
+        return -1;
+    if(_stopping)
+        return 0;
+
+    size_t total = 0;
+    size_t remaining = buf_len;
+
+    //TODO: handle reconnect?
+    //handle partial sends
+    while(total < buf_len) {
+        ssize_t sent = ::send(_socket_fd, buf+total, remaining, 0);
+        if(sent == -1) 
+            return _stopping ? 0 : -1;
+        total += sent;
+        remaining -= sent;
+    }
+
+    return total;
+}
+
+ssize_t URStream::receive(uint8_t *buf, size_t buf_len) {
+    //TODO: handle reconnect?
+    return recv(_socket_fd, buf, buf_len, 0);
+}