sign: handle decode methods sign from can value

- add enumeration that represents the way of encoding:
    enum sign_t
    {
		UNSIGNED = 0,
		SIGN_BIT = 1,
		ONES_COMPLEMENT = 2,
		TWOS_COMPLEMENT = 3,
		SIGN_BIT_EXTERN = 4
    };

- the function handle_sign allows to transform value if negative and
return the sign of the value in order to be multiplied at the end ot the
parcing

Change-Id: I5766a286488170d930422474b4c4f3a8578ca726
Signed-off-by: Clément Bénier <clement.benier@iot.bzh>

diff --git a/low-can-binding/can/can-decoder.cpp b/low-can-binding/can/can-decoder.cpp
index a6b6c14..f64a843 100644 (file)
--- a/low-can-binding/can/can-decoder.cpp
+++ b/low-can-binding/can/can-decoder.cpp
@@ -23,6 +23,66 @@
 #include "../binding/low-can-hat.hpp"
 #include "../utils/converter.hpp"
 
+/// @brief Handle sign of the signal according to several decoding methods
+///
+/// @param[in] signal - The signal
+/// @param[in] data_signal - The data of the signal
+/// @param[in] new_end_bit - The last bit of in the last byte of the data (data_signal[0])
+/// @param[in] can_data - The whole can data (needed for SIGN BIT EXTERN)
+///
+/// @return Returns the sign of the data
+///
+int decoder_t::handle_sign(const signal_t& signal, std::vector<uint8_t>& data_signal, uint8_t new_end_bit, const std::vector<uint8_t>& can_data)
+{
+       uint8_t data_byte = 0;
+       uint8_t mask = 0;
+       int end_bit = 0;
+
+       if(signal.get_sign() == sign_t::UNSIGNED)
+               return 1;
+       else if(signal.get_sign() == sign_t::SIGN_BIT_EXTERN) {
+               end_bit = signal.get_bit_sign_position()%8;
+               mask = static_cast<uint8_t>((1 << (end_bit + 1)) - 1);
+               data_byte = can_data[signal.get_bit_sign_position()/8] & mask;
+       }
+       else {
+               end_bit = new_end_bit;
+               mask = static_cast<uint8_t>((1 << (end_bit + 1)) - 1);
+               data_byte = data_signal[0] & mask;
+       }
+
+       //if negative: decode with right method
+       if(data_byte  >> end_bit) {
+               switch(signal.get_sign())
+               {
+                       //remove the sign bit to get the absolute value
+                       case sign_t::SIGN_BIT:
+                               data_signal[0] = static_cast<uint8_t>(data_signal[0] & (mask >> 1));
+                               break;
+                       //same method twos complement = ones complement + 1
+                       case sign_t::ONES_COMPLEMENT:
+                       case sign_t::TWOS_COMPLEMENT:
+                               //complement only until end_bit
+                               data_signal[0] = ((data_signal[0] ^ mask) & mask);
+                               if(data_signal.size() > 1) {
+                                       for(int i=1; i < data_signal.size(); i++) {
+                                               data_signal[i] = data_signal[i] ^ 0xFF;
+                                       }
+                               }
+                               if(signal.get_sign() == sign_t::TWOS_COMPLEMENT)
+                                       data_signal[data_signal.size() - 1] = static_cast<uint8_t>(data_signal[data_signal.size() - 1] + 1);
+                               break;
+                       case sign_t::SIGN_BIT_EXTERN:
+                               break;
+                       default:
+                               AFB_ERROR("Not a valid sign entry %d, considering the value as unsigned", signal.get_sign());
+                               break;
+               }
+               return -1;
+       }
+       return 1;
+}
+
 /// @brief Parses the signal's bitfield from the given data and returns the raw
 /// value.
 ///
@@ -48,6 +108,9 @@ float decoder_t::parse_signal_bitfield(signal_t& signal, std::shared_ptr<message
 
        for(int i=new_start_byte;i<=new_end_byte;i++)
                data_signal.push_back(data[i]);
+       }
+
+       int sign = handle_sign(signal, data_signal, new_end_bit, data);
 
 //     if(bit_size > 255)
 //             AFB_ERROR("Error signal %s to long bit size", signal.get_name().c_str());
@@ -58,7 +121,7 @@ float decoder_t::parse_signal_bitfield(signal_t& signal, std::shared_ptr<message
        if(data_signal.size() > 65535)
                AFB_ERROR("Too long data signal %s", signal.get_name().c_str());
 
-       return bitfield_parse_float(data_signal.data(), (uint16_t) data_signal.size(),
+       return static_cast<float>(sign) * bitfield_parse_float(data_signal.data(), (uint16_t) data_signal.size(),
                        new_start_bit, bit_size, signal.get_factor(),
                        signal.get_offset());
 }
@@ -297,7 +360,7 @@ openxc_DynamicField decoder_t::translate_signal(signal_t& signal, std::shared_pt
        if(!signal.get_message()->frame_layout_is_little())
        {
                signal.set_bit_position(converter_t::bit_position_swap(signal.get_bit_position(),signal.get_bit_size()));
-       }       
+       }
        // Must call the decoders every time, regardless of if we are going to
        // decide to send the signal or not.
        openxc_DynamicField decoded_value = decoder_t::decode_signal(signal,

diff --git a/low-can-binding/can/can-decoder.hpp b/low-can-binding/can/can-decoder.hpp
index a5e3acb..02a2c7e 100644 (file)
--- a/low-can-binding/can/can-decoder.hpp
+++ b/low-can-binding/can/can-decoder.hpp
@@ -24,6 +24,7 @@
 class decoder_t
 {
 public:
+       static int handle_sign(const signal_t& signal, std::vector<uint8_t>& data_signal, uint8_t new_end_bit, const std::vector<uint8_t>& can_data);
        static float parse_signal_bitfield(signal_t& signal, std::shared_ptr<message_t> message);
 
        static openxc_DynamicField decode_state(signal_t& signal, std::shared_ptr<message_t> message, bool* send);

diff --git a/low-can-binding/can/signals.cpp b/low-can-binding/can/signals.cpp
index 2b87dc6..da8df98 100755 (executable)
--- a/low-can-binding/can/signals.cpp
+++ b/low-can-binding/can/signals.cpp
@@ -46,7 +46,8 @@ signal_t::signal_t(
        bool received,
        std::pair<bool, int> multiplex,
        bool is_big_endian,
-       bool is_signed,
+       sign_t sign,
+       int32_t bit_sign_position,
        std::string unit)
        : parent_{nullptr},
         generic_name_{ generic_name }
@@ -67,7 +68,8 @@ signal_t::signal_t(
        , last_value_{.0f}
        , multiplex_{multiplex}
        , is_big_endian_{is_big_endian}
-       , is_signed_{is_signed}
+       , sign_{sign}
+       , bit_sign_position_{bit_sign_position}
        , unit_{unit}
 {}
 
@@ -235,9 +237,14 @@ bool signal_t::get_is_big_endian() const
        return is_big_endian_;
 }
 
-bool signal_t::get_is_signed() const
+sign_t signal_t::get_sign() const
 {
-       return is_signed_;
+       return sign_;
+}
+
+int32_t signal_t::get_bit_sign_position() const
+{
+       return bit_sign_position_;
 }
 
 const std::string signal_t::get_unit() const

diff --git a/low-can-binding/can/signals.hpp b/low-can-binding/can/signals.hpp
index d9453c5..bf77998 100755 (executable)
--- a/low-can-binding/can/signals.hpp
+++ b/low-can-binding/can/signals.hpp
@@ -60,6 +60,14 @@ typedef openxc_DynamicField (*signal_decoder)(signal_t& signal, std::shared_ptr<
 typedef uint64_t (*signal_encoder)(signal_t& signal,
                 const openxc_DynamicField& field, bool* send);
 
+enum sign_t
+{
+               UNSIGNED = 0,
+               SIGN_BIT = 1,
+               ONES_COMPLEMENT = 2,
+               TWOS_COMPLEMENT = 3,
+               SIGN_BIT_EXTERN = 4
+};
 
 class signal_t
 {
@@ -100,7 +108,8 @@ private:
                                                                                If bool is true, that indicate that is a multiplexor
                                                                                If int is different of 0, that indicate the link with a multiplexor */
        bool is_big_endian_; /*!< is_big_endian - True if the signal's data are meant to be read as a big_endian */
-       bool is_signed_; /* !< is_signed_ - True if the data is signed */
+       sign_t sign_; /* !< sign_ - if the data is signed it indicates the encode */
+       int32_t bit_sign_position_; /*!< bit_sign_position_ - The bit that indicates the sign of the signal in its CAN message*/
        std::string unit_; /* !< unit_ - The unit of the data */
 
 public:
@@ -123,7 +132,8 @@ public:
                bool received,
                std::pair<bool, int> multiplex,
                bool is_big_endian,
-               bool is_signed,
+               sign_t sign,
+               int32_t bit_sign_position,
                std::string unit);
 
 
@@ -164,7 +174,8 @@ public:
        std::pair<float, uint64_t> get_last_value_with_timestamp() const;
        std::pair<bool, int> get_multiplex() const;
        bool get_is_big_endian() const;
-       bool get_is_signed() const;
+       sign_t get_sign() const;
+       int32_t get_bit_sign_position() const;
        const std::string get_unit() const;
 
        void set_parent(std::shared_ptr<message_definition_t> parent);