path: root/src/packet_storage.c

#include <pthread.h>
#include <stdint.h>
#include <stdlib.h>
// dependency: zlib
#include <zlib.h>
//
#include "common.c"

const uint64_t max_storage = 1 << 16;

#define hash_fmt                                                                                   \
    "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x"                             \
    "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x"

#define hash_ref(_hash)                                                                            \
    _hash[ 0 ], _hash[ 1 ], _hash[ 2 ], _hash[ 3 ], _hash[ 4 ], _hash[ 5 ], _hash[ 6 ],            \
        _hash[ 7 ], _hash[ 8 ], _hash[ 9 ], _hash[ 10 ], _hash[ 11 ], _hash[ 12 ], _hash[ 13 ],    \
        _hash[ 14 ], _hash[ 15 ], _hash[ 16 ], _hash[ 17 ], _hash[ 18 ], _hash[ 19 ], _hash[ 20 ], \
        _hash[ 21 ], _hash[ 22 ], _hash[ 23 ], _hash[ 24 ], _hash[ 25 ], _hash[ 26 ], _hash[ 27 ], \
        _hash[ 28 ], _hash[ 29 ], _hash[ 30 ], _hash[ 31 ]

uint64_t current_packet_ptr = 0;
uint64_t packet_count       = 0;
struct data_packet_entry {
    struct data_packet packet;
    uint64_t           next;
    uint64_t           prev;
    bool               is_full;
}* packet_storage;

// TODO: yes, i know it's weird, but this has to be zero
#define minus_one ((uint64_t) 0)

struct data_packet* load_packet(FILE* file) {
    if (!file) { return NULL; }

    fseek(file, 0, SEEK_END);
    size_t file_size = ftell(file);
    fseek(file, 0, SEEK_SET);

    if (file_size == 0) {
        fclose(file);
        return NULL;
    }

    byte comp_buf[ file_size ];

    size_t r = fread(comp_buf, 1, file_size, file);
    fclose(file);
    if (r != file_size) { return NULL; }

    byte buffer[ PACKET_SIZE ];

    uLongf dest_len = (uLongf) PACKET_SIZE;
    int    unres    = uncompress(buffer, &dest_len, comp_buf, (uLongf) file_size);

    if (unres != Z_OK || dest_len != (uLongf) PACKET_SIZE) { return NULL; }

    bool                success;
    struct data_packet* packet = malloc(sizeof(struct data_packet));
    if (!packet) { return NULL; }
    *packet = s2data_packet(PACKET_SIZE, buffer, &success);

    if (!success) {
        free(packet);
        return NULL;
    }

    return packet;
}

uint64_t set_data_packet(struct data_packet* new_packet);

struct data_packet_entry* get_data_packet(const hash _hash) {
    uint64_t hash_val;
    memcpy(&hash_val, _hash, sizeof(uint64_t));
    uint64_t cur_index = hash_val % max_storage;

    pthread_mutex_lock(&packet_storage_mutex);

    struct data_packet_entry* current_entry = &packet_storage[ cur_index ];
    while (cur_index != minus_one) {
        if (current_entry->is_full
            && memcmp(current_entry->packet.hash, _hash, sizeof(hash)) == 0) {
            pthread_mutex_unlock(&packet_storage_mutex);
            return current_entry;
        }

        cur_index = current_entry->next;
        if (cur_index != minus_one) { current_entry = &packet_storage[ cur_index ]; }
    }

    pthread_mutex_unlock(&packet_storage_mutex);
    char filename[ 128 ];
    sprintf(filename, "packets/" hash_fmt ".bin", hash_ref(_hash));
    FILE* file = fopen(filename, "rb");

    struct data_packet* packet = load_packet(file);

    if (packet) {
        uint64_t add_idx = set_data_packet(packet);
        if (add_idx != minus_one) {
            free(packet);
            return &packet_storage[ add_idx ];
        } else {
            static __thread struct data_packet_entry temp_entry;
            temp_entry.packet = *packet;
            free(packet);
            return &temp_entry;
        }
    }

    return NULL;
}

uint64_t set_data_packet(struct data_packet* new_packet) {
    pthread_mutex_lock(&packet_storage_mutex);

    uint64_t hash_val;
    memcpy(&hash_val, new_packet->hash, sizeof(uint64_t));
    uint64_t start_index = hash_val % max_storage;
    uint64_t cur_index   = start_index;

    struct data_packet_entry* current_entry = &packet_storage[ cur_index ];

    while (true) {
        if (current_entry->is_full
            && memcmp(current_entry->packet.hash, new_packet->hash, sizeof(hash)) == 0) {
            memcpy(&current_entry->packet, new_packet, sizeof(struct data_packet));
            pthread_mutex_unlock(&packet_storage_mutex);
            return cur_index;
        }

        if (current_entry->next == minus_one) break;
        cur_index     = current_entry->next;
        current_entry = &packet_storage[ cur_index ];
    }

    if (!current_entry->is_full) {
        memcpy(&current_entry->packet, new_packet, sizeof(struct data_packet));
        current_entry->is_full = true;
        current_entry->next    = minus_one;
        current_entry->prev    = minus_one;
        packet_count++;
        pthread_mutex_unlock(&packet_storage_mutex);
        return cur_index;
    }

    uint64_t probes             = 0;
    uint64_t linear_probe_index = (cur_index + 1) % max_storage;

    while (probes < max_storage) {
        struct data_packet_entry* empty_slot = &packet_storage[ linear_probe_index ];

        if (!empty_slot->is_full) {
            memcpy(&empty_slot->packet, new_packet, sizeof(struct data_packet));
            empty_slot->is_full = true;
            empty_slot->next    = minus_one;
            empty_slot->prev    = cur_index;
            current_entry->next = linear_probe_index;
            packet_count++;
            pthread_mutex_unlock(&packet_storage_mutex);
            return linear_probe_index;
        }

        linear_probe_index = (linear_probe_index + 1) % max_storage;
        probes++;
    }

    // table full
    pthread_mutex_unlock(&packet_storage_mutex);
    return minus_one;
}

#define overload __attribute__((overloadable))

bool _delete_at_index(uint64_t index);

overload void delete_data_packet(hash _hash) {
    pthread_mutex_lock(&packet_storage_mutex);

    uint64_t hash_val;
    memcpy(&hash_val, _hash, sizeof(uint64_t));
    uint64_t start_index = hash_val % max_storage;
    uint64_t cur_index   = start_index;

    while (cur_index != minus_one) {
        struct data_packet_entry* current_entry = &packet_storage[ cur_index ];
        if (current_entry->is_full
            && memcmp(current_entry->packet.hash, _hash, sizeof(hash)) == 0) {
            _delete_at_index(cur_index);
            pthread_mutex_unlock(&packet_storage_mutex);
            return;
        }

        if (current_entry->next == minus_one) {
            pthread_mutex_unlock(&packet_storage_mutex);
            return;
        }
        cur_index = current_entry->next;
    }

    pthread_mutex_unlock(&packet_storage_mutex);
}

overload void delete_data_packet(uint64_t index) {
    pthread_mutex_lock(&packet_storage_mutex);
    _delete_at_index(index);
    pthread_mutex_unlock(&packet_storage_mutex);
}

// caller must already have a lock!
bool _delete_at_index(uint64_t index) {
    if (index >= max_storage) return false;
    struct data_packet_entry* current_entry = &packet_storage[ index ];
    if (!current_entry->is_full) return false;

    if (current_entry->prev != minus_one) {
        struct data_packet_entry* prev_entry = &packet_storage[ current_entry->prev ];
        prev_entry->next                     = current_entry->next;
    }

    if (current_entry->next != minus_one) {
        struct data_packet_entry* next_entry = &packet_storage[ current_entry->next ];
        next_entry->prev                     = current_entry->prev;
    }

    current_entry->is_full = false;
    current_entry->next    = minus_one;
    current_entry->prev    = minus_one;

    return true;
}