borg/darc/_hashindex.c

260 lines
6.9 KiB
C

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