From aa41f26a26fcff212ecc55750a4806d83a6cf5dc Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Sat, 18 Sep 2021 11:10:11 -0700
Subject: Chapter 19.4 - 19.5

---
 clox/src/table.c | 142 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 clox/src/table.c

(limited to 'clox/src/table.c')

diff --git a/clox/src/table.c b/clox/src/table.c
new file mode 100644
index 0000000..5b6f3f9
--- /dev/null
+++ b/clox/src/table.c
@@ -0,0 +1,142 @@
+#include <stdlib.h>
+#include <string.h>
+
+#include "memory.h"
+#include "object.h"
+#include "table.h"
+#include "value.h"
+
+#define TABLE_MAX_LOAD 0.75
+
+void initTable(Table *table) {
+  table->count = 0;
+  table->capacity = 0;
+  table->entries = NULL;
+}
+
+void freeTable(Table *table) {
+  FREE_ARRAY(Entry, table->entries, table->capacity);
+  initTable(table);
+}
+
+static Entry *findEntry(Entry *entries, int capacity, ObjString *key) {
+  uint32_t index = key->hash % capacity;
+  Entry *tombstone = NULL;
+
+  for (;;) {
+    Entry *entry = &entries[index];
+    if (entry->key == NULL) {
+      if (IS_NIL(entry->value)) {
+        // Empty entry.
+        return tombstone != NULL ? tombstone : entry;
+      } else {
+        // We found a tombstone.
+        if (tombstone == NULL)
+          tombstone = entry;
+      }
+    } else if (entry->key == key) {
+      // We found the entry.
+      return entry;
+    }
+
+    index = (index + 1) % capacity;
+  }
+}
+
+bool tableGet(Table *table, ObjString *key, Value *value) {
+  if (table->count == 0)
+    return false;
+
+  Entry *entry = findEntry(table->entries, table->capacity, key);
+  if (entry->key == NULL)
+    return false;
+
+  *value = entry->value;
+  return true;
+}
+
+static void adjustCapacity(Table *table, int capacity) {
+  Entry *entries = ALLOCATE(Entry, capacity);
+  for (int i = 0; i < capacity; i++) {
+    entries[i].key = NULL;
+    entries[i].value = NIL_VAL;
+  }
+
+  table->count = 0;
+  for (int i = 0; i < table->capacity; i++) {
+    Entry *entry = &table->entries[i];
+    if (entry->key == NULL)
+      continue;
+
+    Entry *dest = findEntry(entries, capacity, entry->key);
+    dest->key = entry->key;
+    dest->value = entry->value;
+    table->count++;
+  }
+
+  FREE_ARRAY(Entry, table->entries, table->capacity);
+  table->entries = entries;
+  table->capacity = capacity;
+}
+
+bool tableSet(Table *table, ObjString *key, Value value) {
+  if (table->count + 1 > table->capacity * TABLE_MAX_LOAD) {
+    int capacity = GROW_CAPACITY(table->capacity);
+    adjustCapacity(table, capacity);
+  }
+
+  Entry *entry = findEntry(table->entries, table->capacity, key);
+  bool isNewKey = entry->key == NULL;
+  if (isNewKey && IS_NIL(entry->value))
+    table->count++;
+
+  entry->key = key;
+  entry->value = value;
+  return isNewKey;
+}
+
+bool tableDelete(Table *table, ObjString *key) {
+  if (table->count == 0)
+    return false;
+
+  /* Find the entry. */
+  Entry *entry = findEntry(table->entries, table->capacity, key);
+  if (entry->key == NULL)
+    return false;
+
+  /* Place a tombstone in the entry. */
+  entry->key = NULL;
+  entry->value = BOOL_VAL(true);
+  return true;
+}
+
+void tableAddAll(Table *from, Table *to) {
+  for (int i = 0; i < from->capacity; i++) {
+    Entry *entry = &from->entries[i];
+    if (entry->key != NULL) {
+      tableSet(to, entry->key, entry->value);
+    }
+  }
+}
+
+ObjString *tableFindString(Table *table, const char *chars, int length,
+                           uint32_t hash) {
+  if (table->count == 0)
+    return NULL;
+
+  uint32_t index = hash % table->capacity;
+  for (;;) {
+    Entry *entry = &table->entries[index];
+    if (entry->key == NULL) {
+      /* Stop if we find an empty non-tombstone entry. */
+      if (IS_NIL(entry->value))
+        return NULL;
+    } else if (entry->key->length == length && entry->key->hash == hash &&
+               memcmp(entry->key->chars, chars, length) == 0) {
+      /* We found it. */
+      return entry->key;
+    }
+
+    index = (index + 1) % table->capacity;
+  }
+}
-- 
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