TinyFrame/TinyFrame.c

//---------------------------------------------------------------------------
#include "TinyFrame.h"
#include <string.h>
//---------------------------------------------------------------------------

/* Note: payload length determines the Rx buffer size. Max 256 */
#define TF_MAX_PAYLOAD 256
#define TF_SOF_BYTE 0x01


enum TFState {
	TFState_SOF = 0,  //!< Wait for SOF
	TFState_ID,       //!< Wait for ID
	TFState_NOB,      //!< Wait for Number Of Bytes
	TFState_PAYLOAD,  //!< Receive payload
	TFState_CKSUM     //!< Wait for Checksum
};

typedef struct _IdListener_struct {
	unsigned int id;
	TinyFrameListener fn;
} IdListener;

typedef struct _TypeListener_struct_ {
	unsigned char type;
	TinyFrameListener fn;
} TypeListener;

typedef struct _GenericListener_struct_ {
	TinyFrameListener fn;
} GenericListener;

/**
 * Frame parser internal state
 */
static struct TinyFrameStruct {
	/* Own state */
	bool peer_bit;          //!< Own peer bit (unqiue to avoid msg ID clash)
	unsigned int next_id;   //!< Next frame / frame chain ID

	/* Parser state */
	enum TFState state;
	unsigned int id;        //!< Incoming packet ID
	unsigned int nob;       //!< Payload length
	unsigned char pldbuf[TF_MAX_PAYLOAD+1]; //!< Payload byte buffer
	unsigned int rxi;       //!< Receive counter (for payload or other fields)
	unsigned int cksum;     //!< Continually updated checksum

	/* --- Callbacks --- */

	/* Transaction callbacks */
	IdListener id_listeners[TF_MAX_ID_LST];
	TypeListener type_listeners[TF_MAX_TYPE_LST];
	GenericListener generic_listeners[TF_MAX_GEN_LST];

	char sendbuf[TF_MAX_PAYLOAD+1];
} tf;


/**
 * Initialize the TinyFrame engine.
 * This can also be used to completely reset it (removing all listeners etc)
 *
 * @param peer_bit - peer bit to use for self
 */
void TF_Init(bool peer_bit)
{
	memset(&tf, 0, sizeof(struct TinyFrameStruct));

	tf.peer_bit = peer_bit;
}


/**
 * Reset the frame parser state machine.
 */
void TF_ResetParser(void)
{
	tf.state = TFState_SOF;
	tf.cksum = 0;
}


/**
 * Register a frame type listener.
 *
 * @param frame_type - frame ID to listen for
 * @param cb - callback
 * @return slot index (for removing), or TF_ERROR (-1)
 */
int TF_AddIdListener(unsigned int frame_id, TinyFrameListener cb)
{
	int i;

	for (i = 0; i < TF_MAX_ID_LST; i++) {
		if (tf.id_listeners[i].fn == NULL) {
			tf.id_listeners[i].fn = cb;
			tf.id_listeners[i].id = frame_id;
			return i;
		}
	}

	return TF_ERROR;
}


/**
 * Register a frame type listener.
 *
 * @param frame_type - frame type to listen for
 * @param cb - callback
 * @return slot index (for removing), or TF_ERROR (-1)
 */
int TF_AddTypeListener(unsigned char frame_type, TinyFrameListener cb)
{
	int i;

	for (i = 0; i < TF_MAX_TYPE_LST; i++) {
		if (tf.type_listeners[i].fn == NULL) {
			tf.type_listeners[i].fn = cb;
			tf.type_listeners[i].type = frame_type;
			return TF_MAX_ID_LST + i;
		}
	}

	return TF_ERROR;
}


/**
 * Register a generic listener.
 *
 * @param cb - callback
 * @return slot index (for removing), or TF_ERROR (-1)
 */
int TF_AddGenericListener(TinyFrameListener cb)
{
	int i;

	for (i = 0; i < TF_MAX_GEN_LST; i++) {
		if (tf.generic_listeners[i].fn == NULL) {
			tf.generic_listeners[i].fn = cb;
			return TF_MAX_ID_LST + TF_MAX_TYPE_LST + i;
		}
	}

	return TF_ERROR;
}


/**
 * Remove a rx callback function by the index received when registering it
 *
 * @param index - index in the callbacks table
 */
void TF_RemoveListener(unsigned int index)
{
	// all listener arrays share common "address space"
	if (index < TF_MAX_ID_LST) {
		tf.id_listeners[index].fn = NULL;
	}
	else if (index < TF_MAX_ID_LST + TF_MAX_TYPE_LST) {
		tf.type_listeners[index - TF_MAX_ID_LST].fn = NULL;
	}
	else if (index < TF_MAX_ID_LST + TF_MAX_TYPE_LST + TF_MAX_GEN_LST) {
		tf.generic_listeners[index - TF_MAX_ID_LST - TF_MAX_TYPE_LST].fn = NULL;
	}
}

void TF_RemoveIdListener(unsigned int frame_id)
{
	int i;
	for (i = 0; i < TF_MAX_ID_LST; i++) {
		if (tf.id_listeners[i].fn != NULL && tf.id_listeners[i].id == frame_id) {
			tf.id_listeners[i].fn = NULL;
		}
	}
}

void TF_RemoveTypeListener(unsigned char type)
{
	int i;
	for (i = 0; i < TF_MAX_TYPE_LST; i++) {
		if (tf.type_listeners[i].fn != NULL && tf.type_listeners[i].type == type) {
			tf.type_listeners[i].fn = NULL;
		}
	}
}


/**
 * Remove a callback by the function pointer
 *
 * @param cb - callback function to remove
 */
void TF_RemoveListenerFn(TinyFrameListener cb)
{
	int i;

	for (i = 0; i < TF_MAX_ID_LST; i++) {
		if (tf.id_listeners[i].fn == cb) {
			tf.id_listeners[i].fn = NULL;
		}
	}

	for (i = 0; i < TF_MAX_TYPE_LST; i++) {
		if (tf.type_listeners[i].fn == cb) {
			tf.type_listeners[i].fn = NULL;
		}
	}

	for (i = 0; i < TF_MAX_GEN_LST; i++) {
		if (tf.generic_listeners[i].fn == cb) {
			tf.generic_listeners[i].fn = NULL;
		}
	}
}


/**
 * Accept incoming bytes & parse frames
 *
 * @param buffer - byte buffer to process
 * @param count - nr of bytes in the buffer
 */
void TF_Accept(const unsigned char *buffer, unsigned int count)
{
	unsigned int i;

	for (i = 0; i < count; i++) {
		TF_AcceptChar(buffer[i]);
	}
}


/**
 * Process a single received character
 *
 * @param c - rx character
 */
void TF_AcceptChar(unsigned char c)
{
	int i;
	bool rv, brk;

	switch (tf.state)
	{
	case TFState_SOF:
		if (c == TF_SOF_BYTE) {
			tf.cksum = 0;
			tf.state = TFState_ID;
		}
		break;

	case TFState_ID:
		tf.id = c;
		tf.state = TFState_NOB;
		break;

	case TFState_NOB:
		tf.nob = c + 1; // using 0..255 as 1..256
		tf.state = TFState_PAYLOAD;
		tf.rxi = 0;
		break;

	case TFState_PAYLOAD:
		tf.pldbuf[tf.rxi++] = c;
		if (tf.rxi == tf.nob) {
			tf.state = TFState_CKSUM;
		}
		break;

	case TFState_CKSUM:
		tf.state = TFState_SOF;

		if (tf.cksum == (unsigned int)c) {
			// Add 0 at the end of the data in the buffer (useful if it was a string)
			tf.pldbuf[tf.rxi] = '\0';
			brk = false;

			// Fire listeners
			for (i = 0; i < TF_MAX_ID_LST; i++) {
				if (tf.id_listeners[i].fn && tf.id_listeners[i].id == tf.id) {
					rv = tf.id_listeners[i].fn(tf.id, tf.pldbuf, tf.nob);
					if (rv) {
						brk = true;
						break;
					}
				}
			}

			if (!brk) {
				for (i = 0; i < TF_MAX_TYPE_LST; i++) {
					if (tf.type_listeners[i].fn &&
						tf.type_listeners[i].type == tf.pldbuf[0]) {
						rv = tf.type_listeners[i].fn(tf.id, tf.pldbuf, tf.nob);
						if (rv) {
							brk = true;
							break;
						}
					}
				}
			}

			if (!brk) {
				for (i = 0; i < TF_MAX_GEN_LST; i++) {
					if (tf.generic_listeners[i].fn) {
						rv = tf.generic_listeners[i].fn(tf.id, tf.pldbuf, tf.nob);
						if (rv) {
							break;
						}
					}
				}
			}
		} else {
			// Fail, return to base state
			tf.state = TFState_SOF;
        }
		break;
	}

	// Update the checksum
	tf.cksum ^= c;
}


/**
 * Compose a frame
 *
 * @param outbuff - buffer to store the result in
 * @param msgid - message ID is stored here, if not NULL
 * @param payload - data buffer
 * @param len - payload size in bytes, 0 to use strlen
 * @param explicit_id - ID to use, -1 to chose next free
 * @return nr of bytes in outbuff used by the frame, -1 on failure
 */
int TF_Compose(unsigned char *outbuff, unsigned int *msgid,
			   const unsigned char *payload, unsigned int payload_len,
			   int explicit_id
) {
	unsigned int i;
	unsigned int id;
	int xor;

	// sanitize len
	if (payload_len > TF_MAX_PAYLOAD) return TF_ERROR;
	if (payload_len == 0) payload_len = strlen(payload);

    // Gen ID
	if (explicit_id == TF_NEXT_ID) {
		id = tf.next_id++;
		if (tf.peer_bit) {
			id |= 0x80;
		}

		if (tf.next_id > 0x7F) {
			tf.next_id = 0;
		}
	} else {
		id = explicit_id;
	}

	outbuff[0] = TF_SOF_BYTE;
	outbuff[1] = id & 0xFF;
	outbuff[2] = (payload_len - 1) & 0xFF; // use 0..255 as 1..256
	memcpy(outbuff+3, payload, payload_len);

	xor = 0;
	for (i = 0; i < payload_len + 3; i++) {
		xor ^= outbuff[i];
	}

	outbuff[payload_len + 3] = xor;

	if (msgid != NULL) *msgid = id;

	return payload_len + 4;
}


/**
 * Send a frame, and optionally attach an ID listener for response.
 *
 * @param payload - data to send
 * @param payload_len - nr of bytes to send
 * @return listener ID if listener was attached, else -1 (FT_ERROR)
 */
int TF_Send(const unsigned char *payload,
			 unsigned int payload_len,
			 TinyFrameListener listener)
{
	unsigned int msgid;
	int len;
	int lstid = TF_ERROR;
	len = TF_Compose(tf.sendbuf, &msgid, payload, payload_len, TF_NEXT_ID);
	if (listener) lstid = TF_AddIdListener(msgid, listener);
	TF_WriteImpl(tf.sendbuf, len);
	return lstid;
}


/**
 * Send a response to a received message.
 *
 * @param payload - data to send
 * @param payload_len - nr of bytes to send
 * @param frame_id - ID of the original frame
 */
void TF_Respond(const unsigned char *payload,
			   unsigned int payload_len,
			   int frame_id)
{
	int len;
	len = TF_Compose(tf.sendbuf, NULL, payload, payload_len, frame_id);
	TF_WriteImpl(tf.sendbuf, len);
}


int TF_Send1(const unsigned char b0,
			 TinyFrameListener listener)
{
	unsigned char b[] = {b0};
	return TF_Send(b, 1, listener);
}


int TF_Send2(const unsigned char b0,
			 const unsigned char b1,
			 TinyFrameListener listener)
{
	unsigned char b[] = {b0, b1};
	return TF_Send(b, 2, listener);
}