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path: root/prototype/fw/src/microcobs.c
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#include <stdint.h>
#include "microcobs.h"
#include <stdio.h>

ssize_t cobs_encode_sg(const struct sg_entry input[], uint8_t *output, size_t output_len)
{
	size_t idx_pos = 0;
	size_t out_pos = 1;
	ssize_t sg_idx = 0;

	const struct sg_entry *e = input;
	/* fprintf(stderr, "\nsg_entry %016x %zd\n", e->target, e->size); */
	while (e->size >= 0) {
		if (sg_idx == e->size) {
			sg_idx = 0;
			e++;
			/* fprintf(stderr, "\nsg_entry %016x %zd\n", e->target, e->size); */
			continue;
		}

		if (out_pos >= output_len)
			return -1;

		uint8_t inbyte = e->target[sg_idx];
		/* fprintf(stderr, "%02x ", inbyte); */
		sg_idx += 1;

		if (out_pos - idx_pos >= 255) {
			output[idx_pos] = 255;
			idx_pos = out_pos;
			out_pos += 1;

			if (out_pos >= output_len)
				return -1;
		}

		if (inbyte) {
			output[out_pos] = inbyte;
			out_pos += 1;
		} else {
			output[idx_pos] = out_pos - idx_pos;
			idx_pos = out_pos;
			out_pos += 1;
		}
	}

	if (out_pos >= output_len)
		return -1;
	output[idx_pos] = out_pos - idx_pos;
	output[out_pos] = 0x00;
	/* fprintf(stderr, "\n"); */
	/* fprintf(stderr, "Finishing %d %d %d\n", idx_pos, out_pos, out_pos - idx_pos); */

	return out_pos + 1;
}

ssize_t cobs_encode(const uint8_t *input, size_t input_len, uint8_t *output, size_t output_len)
{
	size_t idx_pos = 0;
	size_t out_pos = 1;
	size_t in_pos = 0;

	while (in_pos < input_len) {
		if (out_pos >= output_len)
			return -1;

		uint8_t inbyte = input[in_pos];
		/* fprintf(stderr, "%02x ", inbyte); */
		in_pos += 1;

		if (out_pos - idx_pos >= 255) {
			output[idx_pos] = 255;
			idx_pos = out_pos;
			out_pos += 1;

			if (out_pos >= output_len)
				return -1;
		}

		if (inbyte) {
			output[out_pos] = inbyte;
			out_pos += 1;
		} else {
			output[idx_pos] = out_pos - idx_pos;
			idx_pos = out_pos;
			out_pos += 1;
		}
	}

	if (out_pos >= output_len)
		return -1;
	output[idx_pos] = out_pos - idx_pos;
	output[out_pos] = 0x00;
	/* fprintf(stderr, "\n"); */
	/* fprintf(stderr, "Finishing %d %d %d\n", idx_pos, out_pos, out_pos - idx_pos); */

	return out_pos + 1;
}

/* input and output may overlap. */
ssize_t cobs_decode(const uint8_t *input, size_t input_len, uint8_t *output, size_t output_len)
{
	size_t out_pos = 0;
	size_t in_pos = 0;

	if (input_len == 0)
		return -1;

	while (in_pos < input_len) {
		size_t len = input[in_pos];
		/* fprintf(stderr, "Length @%03d = %03d\n", in_pos, len); */
		in_pos += 1;

		for (size_t i=0; i<len-1; i++) {
			if (in_pos >= input_len)
				break;
			/* fprintf(stderr, "Copy %03d -> %03d %02x\n", in_pos, out_pos, input[in_pos]); */
			output[out_pos] = input[in_pos];
			in_pos += 1;
			out_pos += 1;
		}

		if (in_pos < input_len && len < 255) {
			/* fprintf(stderr, "Zero %03d %02x\n", out_pos); */
			output[out_pos] = 0;
			out_pos += 1;
		}
	}
	
	return out_pos;
}