Sensor Objects

This includes all the sensor objects including a few
implementations, including dbus and sysfs sensors.

Change-Id: I9897c79f9fd463f00f0e02aeb6c32ffa89635dbe
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/sensors/host.cpp b/sensors/host.cpp
new file mode 100644
index 0000000..44e83d8
--- /dev/null
+++ b/sensors/host.cpp
@@ -0,0 +1,73 @@
+/**
+ * Copyright 2017 Google Inc.
+ *
+ * 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.
+ */
+
+#include <cmath>
+#include <iostream>
+#include <memory>
+#include <mutex>
+
+#include "host.hpp"
+
+std::unique_ptr<Sensor> HostSensor::CreateTemp(
+    const std::string& name,
+    int64_t timeout,
+    sdbusplus::bus::bus& bus,
+    const char* objPath,
+    bool defer)
+{
+    auto sensor = std::make_unique<HostSensor>(name, timeout, bus, objPath, defer);
+    sensor->value(0);
+
+    // TODO(venture): Need to not hard-code that this is DegreesC and scale
+    // 10x-3 unless it is! :D
+    sensor->unit(ValueInterface::Unit::DegreesC);
+    sensor->scale(-3);
+    sensor->emit_object_added();
+
+    /* TODO(venture): Need to set that _updated is set to epoch or something
+     * else.  what is the default value?
+     */
+    return sensor;
+}
+
+int64_t HostSensor::value(int64_t value)
+{
+    std::lock_guard<std::mutex> guard(_lock);
+
+    _updated = std::chrono::high_resolution_clock::now();
+    _value = value * pow(10, scale()); /* scale value */
+
+    return ValueObject::value(value);
+}
+
+ReadReturn HostSensor::read(void)
+{
+    std::lock_guard<std::mutex> guard(_lock);
+
+    /* This doesn't sanity check anything, that's the caller's job. */
+    struct ReadReturn r = {
+        _value,
+        _updated
+    };
+
+    return r;
+}
+
+void HostSensor::write(double value)
+{
+    throw std::runtime_error("Not Implemented.");
+}
+