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Add a cache to data link layer for control frames with hash

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This commit is contained in:
Johnathon Slightham
2026-03-02 01:46:24 -05:00
parent 1083d3e2c0
commit bb08a2f0ba
5 changed files with 271 additions and 24 deletions
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22
components/dataLink/include/DataLinkManager.h
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@@ -46,6 +46,7 @@ static const uint16_t crc16_table[256] = {
#define ASYNC_QUEUE_WAIT_TICKS 100
#define SEQUENCE_NUM_MAP_MUTEX_MAX_WAIT_MS 50
#define MAX_RX_QUEUE_SIZE 100
#define CONTROL_FRAME_LUT_SIZE 5 // Maximum number of control frames cached in the receiver-side LFU LUT
/**
* @brief Class to represent the Data Link Layer
@@ -203,6 +204,27 @@ class DataLinkManager{
SemaphoreHandle_t send_ack_queue_mutex[MAX_CHANNELS];
std::queue<SendAckMetaData> send_ack_queue[MAX_CHANNELS];
// ==== Control Frame Hash / LFU LUT (receiver side) ====
/**
* @brief Compute a 32-bit FNV-1a hash over a byte buffer
*/
static uint32_t compute_fnv1a_hash(const uint8_t* data, size_t len);
/**
* @brief Look up a hash in the control-frame LUT.
* Returns true and populates @p out_message / @p out_header on a hit.
*/
bool lut_lookup(uint32_t hash, std::vector<uint8_t>& out_message, FrameHeader& out_header);
/**
* @brief Insert (or update) an entry in the control-frame LUT using LFU eviction.
*/
void lut_insert(uint32_t hash, const uint8_t* message, size_t message_len, const FrameHeader& header);
ControlFrameLutEntry control_frame_lut[CONTROL_FRAME_LUT_SIZE];
SemaphoreHandle_t control_frame_lut_mutex;
};
struct frame_scheduler_args {

16
components/dataLink/include/Frames.h
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@@ -30,8 +30,11 @@
#define CONTROL_FRAME_OVERHEAD 9
#define GENERIC_FRAME_OVERHEAD 14
#define CONTROL_FRAME_HASH_SIZE 4 // 4-byte FNV-1a hash prepended to control frame payload on the wire
#define MAX_GENERIC_DATA_LEN (MAX_FRAME_SIZE - GENERIC_FRAME_OVERHEAD)
#define MAX_CONTROL_DATA_LEN (MAX_FRAME_SIZE - CONTROL_FRAME_OVERHEAD)
// Control data max accounts for the 4-byte hash prefix that is prepended on transmit and stripped on receive
#define MAX_CONTROL_DATA_LEN (MAX_FRAME_SIZE - CONTROL_FRAME_OVERHEAD - CONTROL_FRAME_HASH_SIZE)
//Generic Frame Fragment ACK
#define GENERIC_FRAG_ACK_DATA_SIZE 7
@@ -107,6 +110,17 @@ typedef struct _fragment_metadata {
uint16_t num_fragments_rx;
} FragmentMetadata;
/**
* @brief Entry in the receiver-side control-frame LFU lookup table
*/
typedef struct _control_frame_lut_entry {
uint32_t hash; // FNV-1a hash of the original payload (key)
std::vector<uint8_t> message; // Cached decoded payload (sans hash prefix)
FrameHeader header; // Cached frame header
uint32_t frequency; // Hit count – used for LFU eviction
bool valid; // Is this slot populated?
} ControlFrameLutEntry;
typedef struct _receive_metadata{
std::unique_ptr<std::vector<uint8_t>> data;
uint16_t data_len;