mirror of https://github.com/borgbackup/borg.git
456 lines
14 KiB
C
456 lines
14 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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#if defined (__SVR4) && defined (__sun)
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#include <sys/isa_defs.h>
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#endif
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#if (defined(BYTE_ORDER) && (BYTE_ORDER == BIG_ENDIAN)) || \
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(defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)) || \
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(defined(_BIG_ENDIAN) && defined(__SVR4)&&defined(__sun))
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#define BORG_BIG_ENDIAN 1
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#elif (defined(BYTE_ORDER) && (BYTE_ORDER == LITTLE_ENDIAN)) || \
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(defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)) || \
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(defined(_LITTLE_ENDIAN) && defined(__SVR4)&&defined(__sun))
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#define BORG_BIG_ENDIAN 0
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#else
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#error Unknown byte order
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#endif
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#if BORG_BIG_ENDIAN
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#define _le32toh(x) __builtin_bswap32(x)
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#define _htole32(x) __builtin_bswap32(x)
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#else
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#define _le32toh(x) (x)
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#define _htole32(x) (x)
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#endif
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#define MAGIC "BORG_IDX"
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#define MAGIC_LEN 8
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typedef struct {
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char magic[MAGIC_LEN];
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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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typedef struct {
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void *buckets;
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int num_entries;
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int num_buckets;
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int key_size;
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int value_size;
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off_t bucket_size;
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int lower_limit;
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int upper_limit;
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} HashIndex;
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/* prime (or w/ big prime factors) hash table sizes
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* not sure we need primes for borg's usage (as we have a hash function based
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* on sha256, we can assume an even, seemingly random distribution of values),
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* but OTOH primes don't harm.
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* also, growth of the sizes starts with fast-growing 2x steps, but slows down
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* more and more down to 1.1x. this is to avoid huge jumps in memory allocation,
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* like e.g. 4G -> 8G.
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* these values are generated by hash_sizes.py.
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*/
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static int hash_sizes[] = {
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1031, 2053, 4099, 8209, 16411, 32771, 65537, 131101, 262147, 445649,
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757607, 1287917, 2189459, 3065243, 4291319, 6007867, 8410991,
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11775359, 16485527, 23079703, 27695653, 33234787, 39881729, 47858071,
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57429683, 68915617, 82698751, 99238507, 119086189, 144378011, 157223263,
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173476439, 190253911, 209915011, 230493629, 253169431, 278728861,
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306647623, 337318939, 370742809, 408229973, 449387209, 493428073,
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543105119, 596976533, 657794869, 722676499, 795815791, 874066969,
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962279771, 1057701643, 1164002657, 1280003147, 1407800297, 1548442699,
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1703765389, 1873768367, 2062383853, /* 32bit int ends about here */
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};
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#define HASH_MIN_LOAD .25
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#define HASH_MAX_LOAD .75 /* don't go higher than 0.75, otherwise performance severely suffers! */
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#define MAX(x, y) ((x) > (y) ? (x): (y))
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#define NELEMS(x) (sizeof(x) / sizeof((x)[0]))
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#define EMPTY _htole32(0xffffffff)
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#define DELETED _htole32(0xfffffffe)
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#define BUCKET_ADDR(index, idx) (index->buckets + (idx * index->bucket_size))
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#define BUCKET_MATCHES_KEY(index, idx, key) (memcmp(key, BUCKET_ADDR(index, idx), index->key_size) == 0)
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#define BUCKET_IS_DELETED(index, idx) (*((uint32_t *)(BUCKET_ADDR(index, idx) + index->key_size)) == DELETED)
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#define BUCKET_IS_EMPTY(index, idx) (*((uint32_t *)(BUCKET_ADDR(index, idx) + index->key_size)) == EMPTY)
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#define BUCKET_MARK_DELETED(index, idx) (*((uint32_t *)(BUCKET_ADDR(index, idx) + index->key_size)) = DELETED)
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#define BUCKET_MARK_EMPTY(index, idx) (*((uint32_t *)(BUCKET_ADDR(index, idx) + index->key_size)) = EMPTY)
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#define EPRINTF_MSG(msg, ...) fprintf(stderr, "hashindex: " msg "\n", ##__VA_ARGS__)
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#define EPRINTF_MSG_PATH(path, msg, ...) fprintf(stderr, "hashindex: %s: " msg "\n", path, ##__VA_ARGS__)
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#define EPRINTF(msg, ...) fprintf(stderr, "hashindex: " msg "(%s)\n", ##__VA_ARGS__, strerror(errno))
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#define EPRINTF_PATH(path, msg, ...) fprintf(stderr, "hashindex: %s: " msg " (%s)\n", path, ##__VA_ARGS__, strerror(errno))
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static HashIndex *hashindex_read(const char *path);
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static int hashindex_write(HashIndex *index, const char *path);
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static HashIndex *hashindex_init(int capacity, int key_size, int value_size);
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static const void *hashindex_get(HashIndex *index, const void *key);
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static int hashindex_set(HashIndex *index, const void *key, const void *value);
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static int hashindex_delete(HashIndex *index, const void *key);
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static void *hashindex_next_key(HashIndex *index, const void *key);
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/* Private API */
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static void hashindex_free(HashIndex *index);
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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 _le32toh(*((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(index, didx), BUCKET_ADDR(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 int
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hashindex_resize(HashIndex *index, int capacity)
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{
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HashIndex *new;
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void *key = NULL;
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int32_t key_size = index->key_size;
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if(!(new = hashindex_init(capacity, key_size, index->value_size))) {
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return 0;
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}
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while((key = hashindex_next_key(index, key))) {
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if(!hashindex_set(new, key, key + key_size)) {
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/* This can only happen if there's a bug in the code calculating capacity */
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hashindex_free(new);
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return 0;
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}
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}
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free(index->buckets);
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index->buckets = new->buckets;
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index->num_buckets = new->num_buckets;
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index->lower_limit = new->lower_limit;
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index->upper_limit = new->upper_limit;
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free(new);
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return 1;
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}
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int get_lower_limit(int num_buckets){
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int min_buckets = hash_sizes[0];
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if (num_buckets <= min_buckets)
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return 0;
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return (int)(num_buckets * HASH_MIN_LOAD);
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}
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int get_upper_limit(int num_buckets){
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int max_buckets = hash_sizes[NELEMS(hash_sizes) - 1];
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if (num_buckets >= max_buckets)
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return num_buckets;
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return (int)(num_buckets * HASH_MAX_LOAD);
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}
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int size_idx(int size){
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/* find the hash_sizes index with entry >= size */
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int elems = NELEMS(hash_sizes);
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int entry, i=0;
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do{
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entry = hash_sizes[i++];
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}while((entry < size) && (i < elems));
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if (i >= elems)
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return elems - 1;
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i--;
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return i;
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}
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int fit_size(int current){
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int i = size_idx(current);
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return hash_sizes[i];
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}
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int grow_size(int current){
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int i = size_idx(current) + 1;
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int elems = NELEMS(hash_sizes);
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if (i >= elems)
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return hash_sizes[elems - 1];
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return hash_sizes[i];
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}
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int shrink_size(int current){
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int i = size_idx(current) - 1;
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if (i < 0)
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return hash_sizes[0];
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return hash_sizes[i];
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}
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/* Public API */
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static HashIndex *
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hashindex_read(const char *path)
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{
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FILE *fd;
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off_t length, buckets_length, bytes_read;
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HashHeader header;
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HashIndex *index = NULL;
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if((fd = fopen(path, "rb")) == NULL) {
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EPRINTF_PATH(path, "fopen for reading failed");
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return NULL;
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}
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bytes_read = fread(&header, 1, sizeof(HashHeader), fd);
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if(bytes_read != sizeof(HashHeader)) {
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if(ferror(fd)) {
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EPRINTF_PATH(path, "fread header failed (expected %ju, got %ju)",
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(uintmax_t) sizeof(HashHeader), (uintmax_t) bytes_read);
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}
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else {
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EPRINTF_MSG_PATH(path, "fread header failed (expected %ju, got %ju)",
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(uintmax_t) sizeof(HashHeader), (uintmax_t) bytes_read);
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}
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goto fail;
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}
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if(fseek(fd, 0, SEEK_END) < 0) {
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EPRINTF_PATH(path, "fseek failed");
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goto fail;
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}
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if((length = ftell(fd)) < 0) {
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EPRINTF_PATH(path, "ftell failed");
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goto fail;
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}
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if(fseek(fd, sizeof(HashHeader), SEEK_SET) < 0) {
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EPRINTF_PATH(path, "fseek failed");
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goto fail;
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}
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if(memcmp(header.magic, MAGIC, MAGIC_LEN)) {
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EPRINTF_MSG_PATH(path, "Unknown MAGIC in header");
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goto fail;
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}
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buckets_length = (off_t)_le32toh(header.num_buckets) * (header.key_size + header.value_size);
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if((size_t) length != sizeof(HashHeader) + buckets_length) {
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EPRINTF_MSG_PATH(path, "Incorrect file length (expected %ju, got %ju)",
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(uintmax_t) sizeof(HashHeader) + buckets_length, (uintmax_t) length);
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goto fail;
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}
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if(!(index = malloc(sizeof(HashIndex)))) {
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EPRINTF_PATH(path, "malloc header failed");
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goto fail;
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}
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if(!(index->buckets = malloc(buckets_length))) {
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EPRINTF_PATH(path, "malloc buckets failed");
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free(index);
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index = NULL;
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goto fail;
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}
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bytes_read = fread(index->buckets, 1, buckets_length, fd);
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if(bytes_read != buckets_length) {
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if(ferror(fd)) {
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EPRINTF_PATH(path, "fread buckets failed (expected %ju, got %ju)",
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(uintmax_t) buckets_length, (uintmax_t) bytes_read);
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}
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else {
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EPRINTF_MSG_PATH(path, "fread buckets failed (expected %ju, got %ju)",
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(uintmax_t) buckets_length, (uintmax_t) bytes_read);
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}
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free(index->buckets);
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free(index);
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index = NULL;
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goto fail;
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}
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index->num_entries = _le32toh(header.num_entries);
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index->num_buckets = _le32toh(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->lower_limit = get_lower_limit(index->num_buckets);
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index->upper_limit = get_upper_limit(index->num_buckets);
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fail:
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if(fclose(fd) < 0) {
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EPRINTF_PATH(path, "fclose failed");
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}
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return index;
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}
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static HashIndex *
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hashindex_init(int capacity, int key_size, int value_size)
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{
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HashIndex *index;
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int i;
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capacity = fit_size(capacity);
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if(!(index = malloc(sizeof(HashIndex)))) {
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EPRINTF("malloc header failed");
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return NULL;
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}
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if(!(index->buckets = calloc(capacity, key_size + value_size))) {
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EPRINTF("malloc buckets failed");
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free(index);
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return NULL;
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}
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index->num_entries = 0;
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index->key_size = key_size;
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index->value_size = value_size;
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index->num_buckets = capacity;
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index->bucket_size = index->key_size + index->value_size;
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index->lower_limit = get_lower_limit(index->num_buckets);
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index->upper_limit = get_upper_limit(index->num_buckets);
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for(i = 0; i < capacity; i++) {
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BUCKET_MARK_EMPTY(index, i);
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}
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return index;
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}
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static void
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hashindex_free(HashIndex *index)
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{
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free(index->buckets);
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free(index);
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}
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static int
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hashindex_write(HashIndex *index, const char *path)
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{
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off_t buckets_length = (off_t)index->num_buckets * index->bucket_size;
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FILE *fd;
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HashHeader header = {
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.magic = MAGIC,
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.num_entries = _htole32(index->num_entries),
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.num_buckets = _htole32(index->num_buckets),
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.key_size = index->key_size,
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.value_size = index->value_size
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};
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int ret = 1;
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if((fd = fopen(path, "wb")) == NULL) {
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EPRINTF_PATH(path, "fopen for writing failed");
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return 0;
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}
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if(fwrite(&header, 1, sizeof(header), fd) != sizeof(header)) {
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EPRINTF_PATH(path, "fwrite header failed");
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ret = 0;
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}
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if(fwrite(index->buckets, 1, buckets_length, fd) != (size_t) buckets_length) {
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EPRINTF_PATH(path, "fwrite buckets failed");
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ret = 0;
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}
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if(fclose(fd) < 0) {
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EPRINTF_PATH(path, "fclose failed");
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}
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return ret;
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}
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static 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(index, idx) + index->key_size;
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}
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static int
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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->upper_limit) {
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if(!hashindex_resize(index, grow_size(index->num_buckets))) {
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return 0;
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}
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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(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(index, idx) + index->key_size, value, index->value_size);
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}
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return 1;
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}
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static int
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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 1;
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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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if(index->num_entries < index->lower_limit) {
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if(!hashindex_resize(index, shrink_size(index->num_buckets))) {
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return 0;
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}
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}
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return 1;
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}
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static 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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}
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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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}
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return BUCKET_ADDR(index, idx);
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}
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static 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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