cache.h

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/*
 * SPDX-FileCopyrightText: 2020 HAW Hamburg
 * SPDX-License-Identifier: LGPL-2.1-only
 */
 
#pragma once

 
#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include "clist.h"
#include "net/nanocoap.h"
#include "hashes/sha256.h"
#include "ztimer.h"
 
#ifdef __cplusplus
extern "C" {
#endif

#ifndef CONFIG_NANOCOAP_CACHE_ENTRIES
#define CONFIG_NANOCOAP_CACHE_ENTRIES          (8)
#endif

#ifndef CONFIG_NANOCOAP_CACHE_KEY_LENGTH
#define CONFIG_NANOCOAP_CACHE_KEY_LENGTH       (8)
#endif

#ifndef CONFIG_NANOCOAP_CACHE_RESPONSE_SIZE
#define CONFIG_NANOCOAP_CACHE_RESPONSE_SIZE    (128)
#endif

typedef struct {
    clist_node_t node;

    uint8_t cache_key[CONFIG_NANOCOAP_CACHE_KEY_LENGTH];

    coap_pkt_t response_pkt;

    uint8_t response_buf[CONFIG_NANOCOAP_CACHE_RESPONSE_SIZE];
 
    size_t response_len; 
 
    uint8_t request_method; 
#if IS_USED(MODULE_GCOAP) || defined(DOXYGEN)
    bool truncated;         
#endif  /* IS_USED(MODULE_GCOAP) || defined(DOXYGEN) */

    uint32_t max_age;
} nanocoap_cache_entry_t;

typedef int (*nanocoap_cache_replacement_strategy_t)(void);

typedef int (*nanocoap_cache_update_strategy_t)(clist_node_t *node);

#if IS_USED(MODULE_NANOCOAP_CACHE)
void nanocoap_cache_init(void);
#else
static inline void nanocoap_cache_init(void)
{
    return;
}
#endif

size_t nanocoap_cache_used_count(void);

size_t nanocoap_cache_free_count(void);

nanocoap_cache_entry_t *nanocoap_cache_process(const uint8_t *cache_key, unsigned request_method,
                                               const coap_pkt_t *resp, size_t resp_len);
nanocoap_cache_entry_t *nanocoap_cache_add_by_req(const coap_pkt_t *req,
                                                  const coap_pkt_t *resp,
                                                  size_t resp_len);

nanocoap_cache_entry_t *nanocoap_cache_add_by_key(const uint8_t *cache_key,
                                                  unsigned request_method,
                                                  const coap_pkt_t *resp,
                                                  size_t resp_len);

nanocoap_cache_entry_t *nanocoap_cache_request_lookup(const coap_pkt_t *req);

nanocoap_cache_entry_t *nanocoap_cache_key_lookup(const uint8_t *cache_key);

int nanocoap_cache_del(const nanocoap_cache_entry_t *ce);

void nanocoap_cache_key_generate(const coap_pkt_t *req, uint8_t *cache_key);

void nanocoap_cache_key_options_generate(const coap_pkt_t *req, void *cache_key);

void nanocoap_cache_key_blockreq_options_generate(const coap_pkt_t *req, void *cache_key);

ssize_t nanocoap_cache_key_compare(uint8_t *cache_key1, uint8_t *cache_key2);

static inline bool nanocoap_cache_entry_is_stale(const nanocoap_cache_entry_t *ce, uint32_t now)
{
    /* see https://en.wikipedia.org/w/index.php?title=Serial_number_arithmetic&oldid=1085516466#General_solution */
    return ((int)(now - ce->max_age) > 0);
}
 
#ifdef __cplusplus
}
#endif