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259 lines
6.9 KiB
C
259 lines
6.9 KiB
C
#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include "hashindex.h"
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typedef struct {
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char magic[8];
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int32_t num_entries;
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int32_t num_buckets;
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int8_t key_size;
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int8_t value_size;
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} __attribute__((__packed__)) HashHeader;
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#define MAGIC "DARCHASH"
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#define EMPTY ((int32_t)-1)
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#define DELETED ((int32_t)-2)
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#define BUCKET_ADDR_READ(index, idx) (index->buckets + (idx * index->bucket_size))
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#define BUCKET_ADDR_WRITE(index, idx) (index->buckets + (idx * index->bucket_size))
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#define BUCKET_IS_DELETED(index, idx) (*((int32_t *)(BUCKET_ADDR_READ(index, idx) + index->key_size)) == DELETED)
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#define BUCKET_IS_EMPTY(index, idx) (*((int32_t *)(BUCKET_ADDR_READ(index, idx) + index->key_size)) == EMPTY)
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#define BUCKET_MATCHES_KEY(index, idx, key) (memcmp(key, BUCKET_ADDR_READ(index, idx), index->key_size) == 0)
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#define BUCKET_MARK_DELETED(index, idx) (*((int32_t *)(BUCKET_ADDR_WRITE(index, idx) + index->key_size)) = DELETED)
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/* Private API */
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static int
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hashindex_index(HashIndex *index, const void *key)
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{
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return *((uint32_t *)key) % index->num_buckets;
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}
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static int
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hashindex_lookup(HashIndex *index, const void *key)
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{
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int didx = -1;
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int start = hashindex_index(index, key);
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int idx = start;
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for(;;) {
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if(BUCKET_IS_EMPTY(index, idx))
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{
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return -1;
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}
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if(BUCKET_IS_DELETED(index, idx)) {
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if(didx == -1) {
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didx = idx;
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}
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}
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else if(BUCKET_MATCHES_KEY(index, idx, key)) {
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if (didx != -1) {
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memcpy(BUCKET_ADDR_WRITE(index, didx), BUCKET_ADDR_READ(index, idx), index->bucket_size);
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BUCKET_MARK_DELETED(index, idx);
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idx = didx;
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}
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return idx;
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}
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idx = (idx + 1) % index->num_buckets;
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if(idx == start) {
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return -1;
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}
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}
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}
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static void
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hashindex_resize(HashIndex *index, int capacity)
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{
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char *new_path = malloc(strlen(index->path) + 5);
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strcpy(new_path, index->path);
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strcat(new_path, ".tmp");
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HashIndex *new = hashindex_create(new_path, capacity, index->key_size, index->value_size);
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void *key = NULL;
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while((key = hashindex_next_key(index, key))) {
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hashindex_set(new, key, hashindex_get(index, key));
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}
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munmap(index->map_addr, index->map_length);
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index->map_addr = new->map_addr;
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index->map_length = new->map_length;
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index->num_buckets = new->num_buckets;
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index->limit = new->limit;
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index->buckets = new->buckets;
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unlink(index->path);
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rename(new_path, index->path);
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free(new_path);
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free(new->path);
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free(new);
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}
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/* Public API */
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HashIndex *
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hashindex_open(const char *path)
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{
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int fd = open(path, O_RDWR);
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if(fd < 0) {
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fprintf(stderr, "Failed to open %s\n", path);
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return NULL;
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}
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off_t length = lseek(fd, 0, SEEK_END);
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void *addr = mmap(0, length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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close(fd);
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if(addr == MAP_FAILED) {
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fprintf(stderr, "Failed to mmap %s", path);
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}
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HashHeader *header = (HashHeader *)addr;
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HashIndex *index = malloc(sizeof(HashIndex));
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index->path = malloc(strlen(path) + 1);
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strcpy(index->path, path);
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index->map_addr = addr;
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index->map_length = length;
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index->num_entries = header->num_entries;
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index->num_buckets = header->num_buckets;
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index->key_size = header->key_size;
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index->value_size = header->value_size;
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index->bucket_size = index->key_size + index->value_size;
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index->buckets = (addr + sizeof(HashHeader));
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index->limit = (int)(index->num_buckets * .75);
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return index;
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}
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HashIndex *
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hashindex_create(const char *path, int capacity, int key_size, int value_size)
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{
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FILE *fd;
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int i;
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if(!(fd = fopen(path, "w"))) {
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fprintf(stderr, "Failed to create %s\n", path);
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return NULL;
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}
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HashHeader header;
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memcpy(header.magic, MAGIC, sizeof(MAGIC) - 1);
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header.num_entries = 0;
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header.num_buckets = capacity;
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header.key_size = key_size;
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header.value_size = value_size;
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int bucket_size = key_size + value_size;
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char *bucket = calloc(bucket_size, 1);
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if(fwrite(&header, 1, sizeof(header), fd) != sizeof(header))
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goto error;
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*((int32_t *)(bucket + key_size)) = EMPTY;
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for(i = 0; i < capacity; i++) {
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if(fwrite(bucket, 1, bucket_size, fd) != bucket_size)
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goto error;
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}
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free(bucket);
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fclose(fd);
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return hashindex_open(path);
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error:
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fclose(fd);
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free(bucket);
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return NULL;
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}
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void
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hashindex_clear(HashIndex *index)
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{
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int i;
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for(i = 0; i < index->num_buckets; i++) {
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BUCKET_MARK_DELETED(index, i);
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}
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index->num_entries = 0;
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hashindex_resize(index, 16);
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}
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void
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hashindex_flush(HashIndex *index)
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{
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*((int32_t *)(index->map_addr + 8)) = index->num_entries;
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*((int32_t *)(index->map_addr + 12)) = index->num_buckets;
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msync(index->map_addr, index->map_length, MS_SYNC);
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}
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void
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hashindex_close(HashIndex *index)
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{
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hashindex_flush(index);
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munmap(index->map_addr, index->map_length);
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free(index->path);
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free(index);
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}
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const void *
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hashindex_get(HashIndex *index, const void *key)
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{
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int idx = hashindex_lookup(index, key);
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if(idx < 0) {
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return NULL;
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}
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return BUCKET_ADDR_READ(index, idx) + index->key_size;
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}
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void
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hashindex_set(HashIndex *index, const void *key, const void *value)
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{
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int idx = hashindex_lookup(index, key);
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uint8_t *ptr;
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if(idx < 0)
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{
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if(index->num_entries > index->limit) {
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hashindex_resize(index, index->num_buckets * 2);
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}
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idx = hashindex_index(index, key);
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while(!BUCKET_IS_EMPTY(index, idx) && !BUCKET_IS_DELETED(index, idx)) {
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idx = (idx + 1) % index->num_buckets;
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}
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ptr = BUCKET_ADDR_WRITE(index, idx);
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memcpy(ptr, key, index->key_size);
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memcpy(ptr + index->key_size, value, index->value_size);
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index->num_entries += 1;
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}
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else
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{
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memcpy(BUCKET_ADDR_WRITE(index, idx) + index->key_size, value, index->value_size);
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}
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}
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void
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hashindex_delete(HashIndex *index, const void *key)
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{
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int idx = hashindex_lookup(index, key);
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if (idx < 0) {
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return;
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}
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BUCKET_MARK_DELETED(index, idx);
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index->num_entries -= 1;
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}
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void *
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hashindex_next_key(HashIndex *index, const void *key)
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{
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int idx = 0;
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if(key) {
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idx = 1 + (key - index->buckets) / index->bucket_size;
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}
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if (idx == index->num_buckets)
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return NULL;
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while(BUCKET_IS_EMPTY(index, idx) || BUCKET_IS_DELETED(index, idx)) {
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idx ++;
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if (idx == index->num_buckets)
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return NULL;
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}
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return BUCKET_ADDR_READ(index, idx);
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}
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int
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hashindex_get_size(HashIndex *index)
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{
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return index->num_entries;
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}
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