Diff: packet.h

Revision:

0:aca5a32d2759

diff -r 000000000000 -r aca5a32d2759 packet.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/packet.h	Fri Mar 18 22:33:32 2016 +0000
@@ -0,0 +1,102 @@
+#ifndef _PACKET_H_
+#define _PACKET_H_
+
+namespace telemetry {
+class TransmitPacket;
+class ReceivePacketBuffer;
+
+namespace internal {
+  template<typename T> void pkt_write(TransmitPacket& interface, T data);
+  template<typename T> T buf_read(ReceivePacketBuffer& buffer);
+}
+
+// Abstract base class for building a packet to be transmitted.
+// Implementation is unconstrained - writes may either be buffered or passed
+// directly to the hardware transmit buffers.
+class TransmitPacket {
+public:
+  virtual ~TransmitPacket() {}
+
+  // Writes a 8-bit unsigned integer to the packet stream.
+  virtual void write_uint8(uint8_t data) = 0;
+  // Writes a 16-bit unsigned integer to the packet stream.
+  virtual void write_uint16(uint16_t data) = 0;
+  // Writes a 32-bit unsigned integer to the packet stream.
+  virtual void write_uint32(uint32_t data) = 0;
+  // Writes a float to the packet stream.
+  virtual void write_float(float data) = 0;
+
+  // Generic templated write operations.
+  template<typename T> void write(T data) {
+    internal::pkt_write<T>(*this, data);
+  }
+
+  // Finish the packet and writes data to the transmit stream (if not already
+  // done). No more data may be written afterwards.
+  virtual void finish() = 0;
+};
+
+class ReceivePacketBuffer {
+public:
+  ReceivePacketBuffer(HalInterface& hal);
+
+  // Starts a new packet, resetting the packet length and read pointer.
+  void new_packet();
+
+  // Appends a new byte onto this packet, advancing the packet length
+  void add_byte(uint8_t byte);
+
+  // Reads a 8-bit unsigned integer from the packet stream, advancing buffer.
+  uint8_t read_uint8();
+  // Reads a 16-bit unsigned integer from the packet stream, advancing buffer.
+  uint16_t read_uint16();
+  // Reads a 32-bit unsigned integer from the packet stream, advancing buffer.
+  uint32_t read_uint32();
+  // Reads a float from the packet stream, advancing buffer.
+  float read_float();
+
+  // Generic templated write operations.
+  template<typename T> T read() {
+	return internal::buf_read<T>(*this);
+  }
+
+protected:
+  HalInterface& hal;
+
+  size_t packet_length;
+  size_t read_loc;
+  uint8_t data[MAX_RECEIVE_PACKET_LENGTH];
+};
+
+// A telemetry packet with a length known before data is written to it.
+// Data is written directly to the hardware transmit buffers without packet
+// buffering. Assumes transmit buffers won't fill up.
+class FixedLengthTransmitPacket : public TransmitPacket {
+public:
+  FixedLengthTransmitPacket(HalInterface& hal, size_t length);
+
+  void write_byte(uint8_t data);
+
+  void write_uint8(uint8_t data);
+  void write_uint16(uint16_t data);
+  void write_uint32(uint32_t data);
+  void write_float(float data);
+
+  virtual void finish();
+
+protected:
+  HalInterface& hal;
+
+  // Predetermined length, in bytes, of this packet's payload, for sanity check.
+  size_t length;
+
+  // Current length, in bytes, of this packet's payload.
+  size_t count;
+
+  // Is the packet valid?
+  bool valid;
+};
+
+}
+
+#endif