xref: /btstack/src/btstack_slip.c (revision 2fca4dad957cd7b88f4657ed51e89c12615dda72)

/*
 * Copyright (C) 2014 BlueKitchen GmbH
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 * 4. Any redistribution, use, or modification is done solely for
 *    personal benefit and not for any commercial purpose or for
 *    monetary gain.
 *
 * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BLUEKITCHEN
 * GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Please inquire about commercial licensing options at
 * [email protected]
 *
 */

#define BTSTACK_FILE__ "btstack_slip.c"

/*
 *  btstack_slip.c
 *  SLIP encoder/decoder
 */

#include "btstack_slip.h"
#include "btstack_debug.h"

typedef enum {
	SLIP_ENCODER_DEFAULT,
	SLIP_ENCODER_SEND_C0,
	SLIP_ENCODER_SEND_DC,
	SLIP_ENCODER_SEND_DD
} btstack_slip_encoder_state_t;

// h5 slip state machine
typedef enum {
    SLIP_DECODER_UNKNOWN = 1,
    SLIP_DECODER_ACTIVE,
    SLIP_DECODER_X_C0,
    SLIP_DECODER_X_DB,
    SLIP_DECODER_COMPLETE
} btstack_slip_decoder_state_t;


// encoder
static btstack_slip_encoder_state_t encoder_state;
static const uint8_t * encoder_data;
static uint16_t  encoder_len;

// decoder
static btstack_slip_decoder_state_t decoder_state;
static uint8_t * decoder_buffer;
static uint16_t  decoder_max_size;
static uint16_t  decoder_pos;


// ENCODER

/**
 * @brief Initialise SLIP encoder with data
 * @param data
 * @param len
 */
void btstack_slip_encoder_start(const uint8_t * data, uint16_t len){
	// start with C0 SOF
	encoder_state = SLIP_ENCODER_SEND_C0;
	encoder_data  = data;
	encoder_len   = len;
}

/**
 * @brief Check if encoder has data ready
 * @return True if data ready
 */
int  btstack_slip_encoder_has_data(void){
	if (encoder_state != SLIP_ENCODER_DEFAULT) return 1;
	return encoder_len > 0u;
}

/**
 * @brief Get next byte from encoder
 * @return Next bytes from encoder
 */
uint8_t btstack_slip_encoder_get_byte(void){
	uint8_t next_byte;
	switch (encoder_state){
		case SLIP_ENCODER_DEFAULT:
			next_byte = *encoder_data++;
			encoder_len--;
			switch (next_byte){
				case BTSTACK_SLIP_SOF:
					encoder_state = SLIP_ENCODER_SEND_DC;
					next_byte = 0xdb;
					break;
				case 0xdb:
					encoder_state = SLIP_ENCODER_SEND_DD;
					next_byte = 0xdb;
				default:
                    break;
			}
			break;
		case SLIP_ENCODER_SEND_C0:
			encoder_state = SLIP_ENCODER_DEFAULT;
			return 0xc0;
		case SLIP_ENCODER_SEND_DC:
			encoder_state = SLIP_ENCODER_DEFAULT;
			next_byte = 0xdc;
			break;
		case SLIP_ENCODER_SEND_DD:
			encoder_state = SLIP_ENCODER_DEFAULT;
			next_byte = 0x0dd;
			break;
        default:
            log_error("btstack_slip_encoder_get_byte invalid state %x", encoder_state);
            return 0x00;
	}

	// After last byte, send CO SOF again
	if ((encoder_state == SLIP_ENCODER_DEFAULT) && (encoder_len == 0)){
		encoder_state = SLIP_ENCODER_SEND_C0;
	}
	return next_byte;
}

// Decoder

static void btstack_slip_decoder_reset(void){
	decoder_state = SLIP_DECODER_UNKNOWN;
	decoder_pos = 0;
}

static void btstack_slip_decoder_store_byte(uint8_t input){
	if (decoder_pos >= decoder_max_size){
	    log_error("btstack_slip_decoder_store_byte: packet to long");
	    btstack_slip_decoder_reset();
	}
	decoder_buffer[decoder_pos++] = input;
}

/**
 * @brief Initialise SLIP decoder with buffer
 * @param buffer to store received data
 * @param max_size of buffer
 */
void btstack_slip_decoder_init(uint8_t * buffer, uint16_t max_size){
	decoder_buffer = buffer;
	decoder_max_size = max_size;
	btstack_slip_decoder_reset();
}

/**
 * @brief Process received byte
 * @param data
 */

void btstack_slip_decoder_process(uint8_t input){
	switch(decoder_state){
        case SLIP_DECODER_UNKNOWN:
            if (input != BTSTACK_SLIP_SOF) break;
            btstack_slip_decoder_reset();
            decoder_state = SLIP_DECODER_X_C0;
            break;
        case SLIP_DECODER_COMPLETE:
        	log_error("btstack_slip_decoder_process called in state COMPLETE");
            btstack_slip_decoder_reset();
        	break;
        case SLIP_DECODER_X_C0:
            switch(input){
                case BTSTACK_SLIP_SOF:
                    break;
                case 0xdb:
                    decoder_state = SLIP_DECODER_X_DB;
                    break;
                default:
                    btstack_slip_decoder_store_byte(input);
                    decoder_state = SLIP_DECODER_ACTIVE;
                    break;
            }
            break;
        case SLIP_DECODER_X_DB:
            switch(input){
                case 0xdc:
                    btstack_slip_decoder_store_byte(BTSTACK_SLIP_SOF);
                    decoder_state = SLIP_DECODER_ACTIVE;
                    break;
                case 0xdd:
                    btstack_slip_decoder_store_byte(0xdb);
                    decoder_state = SLIP_DECODER_ACTIVE;
                    break;
                default:
                    btstack_slip_decoder_reset();
                    break;
            }
            break;
        case SLIP_DECODER_ACTIVE:
            switch(input){
                case BTSTACK_SLIP_SOF:
                    if (decoder_pos != 0){
                    	decoder_state = SLIP_DECODER_COMPLETE;
                    } else {
	                    btstack_slip_decoder_reset();
                    }
                    break;
                case 0xdb:
                    decoder_state = SLIP_DECODER_X_DB;
                    break;
                default:
                    btstack_slip_decoder_store_byte(input);
                    break;
            }
            break;
		default:
			btstack_assert(false);
			break;
    }
}

/**
 * @brief Get size of decoded frame
 * @return size of frame. Size = 0 => frame not complete
 */

uint16_t btstack_slip_decoder_frame_size(void){
	switch (decoder_state){
		case SLIP_DECODER_COMPLETE:
			return decoder_pos;
		default:
			return 0;
	}
}