+/******************************************************************************
+ * @file hashtab.c
+ *****************************************************************************/
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "hashtab.h"
+
+static struct hashtab_entry *find_entry (struct hashtab_entry *entries, unsigned long capacity, struct hashtab_name *key);
+
+static int adjust_capacity (struct hashtab *table, unsigned long new_capacity) {
+
+ struct hashtab_entry *new_entries, *old_entries;
+ unsigned long i, new_count, old_capacity;
+
+ if ((new_entries = malloc (sizeof (*new_entries) * new_capacity)) == NULL) {
+ return -2;
+ }
+
+ for (i = 0; i < new_capacity; i++) {
+
+ struct hashtab_entry *entry = &new_entries[i];
+
+ entry->key = NULL;
+ entry->value = NULL;
+
+ }
+
+ old_entries = table->entries;
+ old_capacity = table->capacity;
+
+ new_count = 0;
+
+ for (i = 0; i < old_capacity; i++) {
+
+ struct hashtab_entry *entry = &old_entries[i], *dest;
+
+ if (entry->key == NULL) {
+ continue;
+ }
+
+ dest = find_entry (new_entries, new_capacity, entry->key);
+
+ dest->key = entry->key;
+ dest->value = entry->value;
+
+ new_count++;
+
+ }
+
+ free (old_entries);
+
+ table->capacity = new_capacity;
+ table->count = new_count;
+ table->entries = new_entries;
+ table->used = new_count;
+
+ return 0;
+
+}
+
+static struct hashtab_entry *find_entry (struct hashtab_entry *entries, unsigned long capacity, struct hashtab_name *key) {
+
+ struct hashtab_entry *tombstone = NULL;
+ unsigned long index;
+
+ for (index = key->hash % capacity; ; index = (index + 1) % capacity) {
+
+ struct hashtab_entry *entry = &entries[index];
+
+ if (entry->key == NULL) {
+
+ if (entry->value == NULL) {
+
+ if (tombstone == NULL) {
+ return entry;
+ }
+
+ return tombstone;
+
+ } else if (tombstone == NULL) {
+ tombstone = entry;
+ }
+
+ } else if (entry->key->bytes == key->bytes) {
+
+ if (memcmp (entry->key->chars, key->chars, key->bytes) == 0 && entry->key->hash == key->hash) {
+ return entry;
+ }
+
+ }
+
+ }
+
+}
+
+static unsigned long hash_string (const void *p, unsigned long length) {
+
+ unsigned char *str = (unsigned char *) p;
+ unsigned long i;
+
+ unsigned long result = 0;
+
+ for (i = 0; i < length; i++) {
+ result = (((unsigned short) str[i]) << 4) + (result >> 9) + result + (result >> 3) + (((unsigned short) str[i]) << 2) - (result << 12);
+ }
+
+ return result;
+
+}
+
+struct hashtab_name *hashtab_alloc_name (const char *str) {
+
+ unsigned long bytes = strlen (str), hash = hash_string (str, bytes);
+ struct hashtab_name *name;
+
+ if (!(name = malloc (sizeof (*name)))) {
+ return 0;
+ }
+
+ name->bytes = bytes;
+ name->chars = str;
+ name->hash = hash;
+
+ return name;
+
+}
+
+struct hashtab_name *hashtab_get_key (struct hashtab *table, const char *name) {
+
+ struct hashtab_name *key;
+ struct hashtab_entry *entry;
+
+ if (!table || table->count == 0 || !(key = hashtab_alloc_name (name))) {
+ return 0;
+ }
+
+ entry = find_entry (table->entries, table->capacity, key);
+ free (key);
+
+ return entry->key;
+
+}
+
+void *hashtab_get (struct hashtab *table, struct hashtab_name *key) {
+
+ struct hashtab_entry *entry;
+
+ if (!table || table->count == 0) {
+ return 0;
+ }
+
+ entry = find_entry (table->entries, table->capacity, key);
+
+ if (!entry->key) {
+ return 0;
+ }
+
+ return entry->value;
+
+}
+
+int hashtab_put (struct hashtab *table, struct hashtab_name *key, void *value) {
+
+ const int MIN_CAPACITY = 15;
+
+ struct hashtab_entry *entry;
+ int ret = 0;
+
+ if (table->used >= table->capacity / 2) {
+
+ long capacity = table->capacity * 2 - 1;
+
+ if (capacity < MIN_CAPACITY) {
+ capacity = MIN_CAPACITY;
+ }
+
+ if ((ret = adjust_capacity (table, capacity))) {
+ return ret;
+ }
+
+ }
+
+ entry = find_entry (table->entries, table->capacity, key);
+
+ if (!entry->key) {
+
+ table->count++;
+
+ if (!entry->value) {
+ table->used++;
+ }
+
+ }
+
+ entry->key = key;
+ entry->value = value;
+
+ return 0;
+
+}
+
+void hashtab_remove (struct hashtab *table, struct hashtab_name *key) {
+
+ struct hashtab_entry *entry;
+
+ if (!table || table->count == 0) {
+ return;
+ }
+
+ entry = find_entry (table->entries, table->capacity, key);
+
+ if (!entry->key) {
+ return;
+ }
+
+ entry->value = HASHTAB_TOMBSTONE;
+ entry->key = 0;
+
+ --table->count;
+}
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