support non-local remote transports (#57)

* support non-local remote transports

* fix LogosResult

* allow getting client over specific transport

* fix ssl

* investiage ssl error

* pr comments

* allow transport set configuration on any module

* pr comments

* add docs

* pr comments

* propagate only non-qt dependencies

* restore ABI compatibility

cpp/implementations/plain/rpc_framing.cpp

@@ -0,0 +1,76 @@
+#include "rpc_framing.h"
+
+#include <cstring>
+
+namespace logos::plain {
+
+namespace {
+
+void writeBe32(std::vector<uint8_t>& out, uint32_t n)
+{
+    out.push_back(static_cast<uint8_t>((n >> 24) & 0xff));
+    out.push_back(static_cast<uint8_t>((n >> 16) & 0xff));
+    out.push_back(static_cast<uint8_t>((n >>  8) & 0xff));
+    out.push_back(static_cast<uint8_t>( n        & 0xff));
+}
+
+uint32_t readBe32(const uint8_t* p)
+{
+    return (uint32_t(p[0]) << 24) | (uint32_t(p[1]) << 16)
+         | (uint32_t(p[2]) <<  8) |  uint32_t(p[3]);
+}
+
+} // anonymous namespace
+
+std::vector<uint8_t>
+encodeFrame(MessageType tag, const std::vector<uint8_t>& payload)
+{
+    // Total frame body length = 1 byte (tag) + payload bytes. The 4-byte
+    // length prefix is not included in the length value it describes.
+    const uint64_t bodyLen = 1u + payload.size();
+    if (bodyLen > kMaxFrameLength)
+        throw FramingError("frame too large");
+
+    std::vector<uint8_t> out;
+    out.reserve(4 + bodyLen);
+    writeBe32(out, static_cast<uint32_t>(bodyLen));
+    out.push_back(static_cast<uint8_t>(tag));
+    out.insert(out.end(), payload.begin(), payload.end());
+    return out;
+}
+
+std::vector<uint8_t>
+encodeFrame(IWireCodec& codec, const AnyMessage& msg)
+{
+    return encodeFrame(messageTypeOf(msg), codec.encode(msg));
+}
+
+void FrameReader::append(const uint8_t* data, std::size_t len)
+{
+    m_buf.insert(m_buf.end(), data, data + len);
+}
+
+bool FrameReader::next(MessageType& tag, std::vector<uint8_t>& payload)
+{
+    // Need at least 4 bytes for the length prefix.
+    if (m_buf.size() < 4) return false;
+
+    const uint32_t bodyLen = readBe32(m_buf.data());
+    if (bodyLen == 0)                         throw FramingError("zero-length frame");
+    if (bodyLen > kMaxFrameLength)            throw FramingError("frame length exceeds cap");
+
+    const std::size_t total = 4u + bodyLen;
+    if (m_buf.size() < total) return false;
+
+    // Tag + payload.
+    tag = static_cast<MessageType>(m_buf[4]);
+    payload.assign(m_buf.begin() + 5, m_buf.begin() + total);
+
+    // Drop the consumed bytes. erase from front is O(n) in buffer size;
+    // acceptable while frames are small and rare. Can switch to a ring
+    // buffer if profiling ever flags this.
+    m_buf.erase(m_buf.begin(), m_buf.begin() + total);
+    return true;
+}
+
+} // namespace logos::plain