Introduce helper classes

src/gdb-stub/stream_processor.cpp

@@ -0,0 +1,93 @@
+#include "stream_processor.hpp"
+#include "checksum.hpp"
+
+#include <cassert>
+
+namespace gdb_stub
+{
+    namespace
+    {
+        void trim_data_stream_start(std::string& stream)
+        {
+            while (!stream.empty() && stream.front() != '$')
+            {
+                stream.erase(stream.begin());
+            }
+        }
+    }
+
+    bool stream_processor::has_packet() const
+    {
+        return !this->packets_.empty();
+    }
+
+    std::string stream_processor::get_next_packet()
+    {
+        if (this->packets_.empty())
+        {
+            throw std::runtime_error("No packet available");
+        }
+
+        auto packet = std::move(this->packets_.front());
+        this->packets_.pop();
+
+        return packet;
+    }
+
+    void stream_processor::push_stream_data(const std::string& data)
+    {
+        this->stream_.append(data);
+        this->process_data_stream();
+    }
+
+    void stream_processor::process_data_stream()
+    {
+        while (true)
+        {
+            trim_data_stream_start(this->stream_);
+
+            const auto end = this->stream_.find_first_of('#');
+            if (end == std::string::npos)
+            {
+                break;
+            }
+
+            const auto packet_size = end + CHECKSUM_SIZE + 1;
+
+            if (packet_size > this->stream_.size())
+            {
+                break;
+            }
+
+            auto packet = this->stream_.substr(0, packet_size);
+            this->stream_.erase(0, packet_size);
+
+            this->enqueue_packet(std::move(packet));
+        }
+    }
+
+    void stream_processor::enqueue_packet(std::string packet)
+    {
+        constexpr auto END_BYTES = CHECKSUM_SIZE + 1;
+
+        if (packet.size() < (END_BYTES + 1) //
+            || packet.front() != '$'        //
+            || packet[packet.size() - END_BYTES] != '#')
+        {
+            return;
+        }
+
+        const auto checksum = strtoul(packet.c_str() + packet.size() - CHECKSUM_SIZE, nullptr, 16);
+        assert((checksum & 0xFF) == checksum);
+
+        packet.erase(packet.begin());
+        packet.erase(packet.size() - END_BYTES, END_BYTES);
+
+        const auto computed_checksum = compute_checksum(packet);
+
+        if (computed_checksum == checksum)
+        {
+            this->packets_.push(std::move(packet));
+        }
+    }
+}