1 files changed, 110 insertions, 0 deletions

diff --git a/src/hash_map.c b/src/hash_map.c
new file mode 100644
index 0000000..b9c3b37
--- /dev/null
+++ b/src/hash_map.c
@@ -0,0 +1,110 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include "hash_map.h"
+
+#define INITIAL_SIZE (16)
+#define LOAD_FACTOR_THRESHOLD (0.75)
+
+typedef struct Pair {
+  char *key;
+  int value;
+  struct Pair *next;
+} Pair;
+
+typedef struct HashMap {
+  Pair **table;
+  size_t size;
+  size_t count;
+} HashMap;
+
+static unsigned int hash(const char *key, size_t size) {
+  unsigned int hash_value = 0;
+  while (*key)hash_value = (hash_value * 31) + *key++;
+  return hash_value % size;
+}
+
+hashmap_t hashmap_create(void) {
+  HashMap *map = (HashMap *)malloc(sizeof(HashMap));
+  assert(map);
+  map->size = INITIAL_SIZE;
+  map->count = 0;
+  map->table = (Pair **)calloc(map->size, sizeof(Pair *));
+  assert(map->table);
+  return map;
+}
+
+static void resize(hashmap_t map) {
+  size_t new_size = ((HashMap*)map)->size * 2;
+  Pair **new_table = (Pair **)calloc(new_size, sizeof(Pair *));
+  assert(new_table);
+  for (size_t i = 0; i < ((HashMap*)map)->size; ++i) {
+    Pair *pair = ((HashMap*)map)->table[i];
+    while (pair) {
+      unsigned int index = hash(pair->key, new_size);
+      Pair *next = pair->next;
+      pair->next = new_table[index];
+      new_table[index] = pair;
+      pair = next;
+    }
+  }
+  free(((HashMap*)map)->table);
+  ((HashMap*)map)->table = new_table;
+  ((HashMap*)map)->size = new_size;
+}
+
+void hashmap_insert(hashmap_t map, const char *key, int value) {
+  if ((float)((HashMap*)map)->count / ((HashMap*)map)->size > LOAD_FACTOR_THRESHOLD) resize(((HashMap*)map));
+  unsigned int index = hash(key, ((HashMap*)map)->size);
+  Pair *new_pair = (Pair *)malloc(sizeof(Pair));
+  assert(new_pair);
+  new_pair->key = strdup(key);
+  assert(new_pair->key);
+  new_pair->value = value;
+  new_pair->next = ((HashMap*)map)->table[index];
+  ((HashMap*)map)->table[index] = new_pair;
+  ((HashMap*)map)->count++;
+}
+
+int *hashmap_get(hashmap_t map, const char *key) {
+  unsigned int index = hash(key, ((HashMap*)map)->size);
+  Pair *pair = ((HashMap*)map)->table[index];
+  while (pair) {
+    if (strcmp(pair->key, key) == 0) return &pair->value;
+    pair = pair->next;
+  }
+  return NULL;
+}
+
+void hashmap_delete(hashmap_t map, const char *key) {
+  unsigned int index = hash(key, ((HashMap*)map)->size);
+  Pair *pair = ((HashMap*)map)->table[index];
+  Pair *prev = NULL;
+  while (pair) {
+    if (strcmp(pair->key, key) == 0) {
+      if (prev) prev->next = pair->next;
+      else ((HashMap*)map)->table[index] = pair->next;
+      free(pair->key);
+      free(pair);
+      ((HashMap*)map)->count--;
+      return;
+    }
+    prev = pair;
+    pair = pair->next;
+  }
+}
+
+void hashmap_free(hashmap_t map) {
+  for (size_t i = 0; i < ((HashMap*)map)->size; ++i) {
+    Pair *pair = ((HashMap*)map)->table[i];
+    while (pair){
+      Pair *temp = pair;
+      pair = pair->next;
+      free(temp->key);
+      free(temp);
+    }
+  }
+  free(((HashMap*)map)->table);
+  free(((HashMap*)map));
+}
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