Be able to write raw frame & encode value to sent

Check whether the argument is a raw frame or a Signal + Value
to encode then send.
1 new class to handle encoding part of a value as well as
a new method for can_signal_t which return index of a map from
its value.

Change-Id: I288d2aeec28ce74c9ca35750db18557c9251e1df
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>

1 files changed, 159 insertions, 0 deletions

diff --git a/low-can-binding/can/can-encoder.cpp b/low-can-binding/can/can-encoder.cpp
new file mode 100644
index 0000000..b87407f
--- /dev/null
+++ b/low-can-binding/can/can-encoder.cpp
@@ -0,0 +1,159 @@
+/*
+ * Copyright (C) 2015, 2016 "IoT.bzh"
+ * Author "Romain Forlot" <romain.forlot@iot.bzh>
+ *
+ * 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 "can-encoder.hpp"
+
+#include "canutil/write.h"
+#include "../utils/openxc-utils.hpp"
+#include "can-message-definition.hpp"
+#include "../binding/low-can-hat.hpp"
+
+/// @brief Write a value into a CAN signal in the destination buffer.
+///
+/// @param[in] signal - The CAN signal to write, including the bit position and bit size.
+/// @param[in] value - The encoded integer value to write into the CAN signal.
+/// @param[out] data - The destination buffer.
+/// @param[in] length - The length of the destination buffer.
+///
+/// @return Returns a can_frame struct initialized and ready to be send.
+const can_frame build_frame(const can_signal_t& signal, uint64_t value)
+{
+	struct can_frame cf;
+	::memset(&cf, 0, sizeof(cf));
+
+	cf.can_id = signal.get_message()->get_id();
+	cf.can_dlc = CAN_MAX_DLEN;
+	bitfield_encode_float((float)value,
+						signal.get_bit_position(),
+						signal.get_bit_size(),
+						signal.get_factor(),
+						signal.get_offset(),
+						cf.data,
+						CAN_MAX_DLEN);
+
+	return cf;
+}
+
+/// @brief Encode a boolean into an integer, fit for a CAN signal bitfield.
+///
+/// This is a shortcut for encodeDynamicField(CanSignal*, openxc_DynamicField*,
+/// bool*) that takes care of creating the DynamicField object for you with the
+/// boolean value.
+///
+/// @param[in] signal  - The CAN signal to encode this value for..
+/// @param[in] value - The boolean value to encode
+/// @param[out] send - An output argument that will be set to false if the value should
+///     not be sent for any reason.
+///
+/// @return Returns the encoded integer. If 'send' is changed to false, the field could
+/// not be encoded and the return value is undefined.
+///
+uint64_t encoder_t::encode_boolean(const can_signal_t& signal, bool value, bool* send)
+{
+	return encode_number(signal, float(value), send);
+}
+/// @brief Encode a float into an integer, fit for a CAN signal's bitfield.
+///
+/// This is a shortcut for encodeDynamicField(CanSignal*, openxc_DynamicField*,
+/// bool*) that takes care of creating the DynamicField object for you with the
+/// float value.
+///
+/// @param[in] signal  - The CAN signal to encode this value for.
+/// @param[in] value - The float value to encode.
+/// @param[out] send - This output argument will always be set to false, so the caller will
+///      know not to publish this value to the pipeline.
+///
+/// @return Returns the encoded integer. If 'send' is changed to false, the field could
+/// not be encoded and the return value is undefined.
+///
+uint64_t encoder_t::encode_number(const can_signal_t& signal, float value, bool* send)
+{
+	return float_to_fixed_point(value, signal.get_factor(), signal.get_offset());
+}
+
+/// @brief Encode a string into an integer, fit for a CAN signal's bitfield.
+///
+/// Be aware that the behavior is undefined if there are multiple values assigned
+/// to a single state. See https://github.com/openxc/vi-firmware/issues/185.
+///
+/// This is a shortcut for encodeDynamicField(CanSignal*, openxc_DynamicField*,
+/// bool*) that takes care of creating the DynamicField object for you with the
+/// string state value.
+///
+/// @param[in] signal  - The details of the signal that contains the state mapping.
+/// @param[in] value - The string state value to encode.
+/// @param[out] send - An output argument that will be set to false if the value should
+///     not be sent for any reason.
+///
+/// @return Returns the encoded integer. If 'send' is changed to false, the field could
+/// not be encoded and the return value is undefined.
+///
+uint64_t encoder_t::encode_state(const can_signal_t& signal, const std::string& state, bool* send)
+{
+	uint64_t value = 0;
+	if(state == "")
+	{
+		AFB_DEBUG("Can't write state of "" -- not sending");
+		*send = false;
+	}
+	else
+	{
+		uint64_t signal_state = signal.get_states(state);
+		if(signal_state != -1) {
+			value = signal_state;
+		} else {
+			AFB_DEBUG("Couldn't find a valid signal state for %s", state.c_str());
+			*send = false;
+		}
+	}
+	return value;
+}
+
+/// @brief Parse a signal from a CAN message and apply any required
+/// transforations to get a human readable value.
+///
+/// If the can_signal_t has a non-NULL 'decoder' field, the raw CAN signal value
+/// will be passed to the decoder before returning.
+///
+/// @param[in] signal - The details of the signal to decode and forward.
+/// @param[in] value - The numerical value that will be converted to a boolean.
+/// @param[out] send - An output parameter that will be flipped to false if the value could
+///      not be decoded.
+///
+/// @return The decoder returns an openxc_DynamicField, which may contain a number,
+/// string or boolean. If 'send' is false, the return value is undefined.
+///
+uint64_t encoder_t::encode_DynamicField( can_signal_t& signal, const openxc_DynamicField& field, bool* send)
+{
+	uint64_t value = 0;
+	switch(field.type) {
+		case openxc_DynamicField_Type_STRING:
+			value = encode_state(signal, field.string_value, send);
+			break;
+		case openxc_DynamicField_Type_NUM:
+			value = encode_number(signal, (float)field.numeric_value, send);
+			break;
+		case openxc_DynamicField_Type_BOOL:
+			value = encode_boolean(signal, field.boolean_value, send);
+			break;
+		default:
+			AFB_DEBUG("Dynamic field didn't have a value, can't encode");
+			*send = false;
+			break;
+	}
+	return value;
+}