parseSignals should fail if frame data length is too small

[TheWhiteBug]

Hello. Doing some test I got what I consider unexpected results as I was sending incomplete frames; i.e. frames where the data buffer was not large enough to actually contain signal data..

Here is a draft of a patch I would like you to consider. Not certain if the check is correct but it does appear to "patch" the issue, preventing unexpected parsing success. I certainly would like to have your point of view on this.

dbc_parser_cpp$ git diff | sed 's/^M//g'
diff --git a/include/libdbc/message.hpp b/include/libdbc/message.hpp
index e903fed..b31b960 100644
--- a/include/libdbc/message.hpp
+++ b/include/libdbc/message.hpp
@@ -19,6 +19,7 @@ struct Message {
                ErrorBigEndian,
                ErrorUnknownID,
                ErrorInvalidConversion,
+               ErrorMessageTooShort, // or something...
        };

        /*!
diff --git a/src/message.cpp b/src/message.cpp
index 443526a..97233c0 100644
--- a/src/message.cpp
+++ b/src/message.cpp
@@ -31,6 +31,8 @@ Message::ParseSignalsStatus Message::parseSignals(const std::vector<uint8_t>& da
        const auto len = size * 8;
        uint64_t v = 0;
        for (const auto& signal : m_signals) {
+               if (signal.size > len)
+                       return ParseSignalsStatus::ErrorMessageTooShort;
                if (signal.is_bigendian) {
                        uint32_t start_bit = 8 * (signal.start_bit / 8) + (7 - (signal.start_bit % 8)); // Calculation taken from python CAN
                        v = data_big_endian << start_bit;