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Implement layer 2 header packing and unpacking

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This commit is contained in:
Thomas Kolb 2024-06-30 17:39:56 +02:00
parent 27e2859090
commit 546d86ffb0
2 changed files with 65 additions and 0 deletions
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50
impl/src/layer2/layer2_structs.c Normal file
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@ -0,0 +1,50 @@
#include <assert.h>
#include <string.h>
#include "layer2_structs.h"
size_t layer2_encode_packet_header(const layer2_packet_header_t *header, uint8_t *encoded)
{
assert(header->src_addr_len < 4);
assert(header->dst_addr_len < 4);
assert(header->tx_seq_nr < 16);
assert(header->rx_seq_nr < 16);
size_t encoded_size = 2;
encoded[0] =
((uint8_t)header->msg_type & 0x7) << 5
| ((uint8_t)header->tx_request & 0x1) << 4
| (header->src_addr_len & 0x3) << 2
| (header->dst_addr_len & 0x3) << 0;
encoded[1] =
(header->tx_seq_nr & 0xF) << 4
| (header->rx_seq_nr & 0xF) << 0;
memcpy(encoded + encoded_size, header->src_addr, 2 * header->src_addr_len);
encoded_size += 2 * header->src_addr_len;
memcpy(encoded + encoded_size, header->dst_addr, 2 * header->dst_addr_len);
encoded_size += 2 * header->dst_addr_len;
return encoded_size;
}
bool layer2_decode_packet_header(const uint8_t *encoded, layer2_packet_header_t *header)
{
header->msg_type = (encoded[0] >> 5) & 0x7;
header->tx_request = (encoded[0] & 0x10) != 0;
header->src_addr_len = (encoded[0] >> 2) & 0x3;
header->dst_addr_len = (encoded[0] >> 0) & 0x3;
header->tx_seq_nr = (encoded[1] >> 4) & 0xF;
header->tx_seq_nr = (encoded[1] >> 0) & 0xF;
memcpy(header->src_addr, encoded + 2, 2 * header->src_addr_len);
memcpy(header->dst_addr, encoded + 2 + 2 * header->src_addr_len, 2 * header->dst_addr_len);
return true;
}

15
impl/src/layer2/layer2_structs.h
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@ -2,6 +2,7 @@
#define LAYER2_STRUCTS_H
#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
/* Common Link-layer Header */
@ -25,6 +26,20 @@ typedef struct layer2_packet_header_s {
uint8_t dst_addr[8]; //!< destination HAM-64 address
} layer2_packet_header_t;
/*!\brief Encode a layer2 packet header to the transmitted form.
* \param header The header structure to encode.
* \param encoded A byte array where the encoded header will be stored. Must have space for 18 bytes.
* \returns The number of encoded bytes. Zero if an error occurred.
*/
size_t layer2_encode_packet_header(const layer2_packet_header_t *header, uint8_t *encoded);
/*!\brief Decode a layer2 packet header from the received form.
* \param encoded A byte array containing the received header.
* \param header The header structure where the decoded information is stored.
* \returns Whether the header was decoded successfully.
*/
bool layer2_decode_packet_header(const uint8_t *encoded, layer2_packet_header_t *header);
/* Data Packet Structs */
typedef enum {