Chapter 30.2

clox/src/table.c

@@ -20,7 +20,7 @@ void freeTable(Table *table) {
 }
 
 static Entry *findEntry(Entry *entries, int capacity, ObjString *key) {
-  uint32_t index = key->hash % capacity;
+  uint32_t index = key->hash & (capacity - 1);
   Entry *tombstone = NULL;
 
   for (;;) {
@@ -39,7 +39,7 @@ static Entry *findEntry(Entry *entries, int capacity, ObjString *key) {
       return entry;
     }
 
-    index = (index + 1) % capacity;
+    index = (index + 1) & (capacity - 1);
   }
 }
 
@@ -124,7 +124,7 @@ ObjString *tableFindString(Table *table, const char *chars, int length,
   if (table->count == 0)
     return NULL;
 
-  uint32_t index = hash % table->capacity;
+  uint32_t index = hash & (table->capacity - 1);
   for (;;) {
     Entry *entry = &table->entries[index];
     if (entry->key == NULL) {
@@ -137,7 +137,7 @@ ObjString *tableFindString(Table *table, const char *chars, int length,
       return entry->key;
     }
 
-    index = (index + 1) % table->capacity;
+    index = (index + 1) & (table->capacity - 1);
   }
 }