clox/table.c

/**
  ******************************************************************************
  * @file           : table.c
  * @author         : simon
  * @brief          : None
  * @attention      : None
  * @date           : 2023/8/24
  ******************************************************************************
  */

#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);
}
/// 查找位置，hash 冲突使用 线性探测(Linear probing) 策略
/// \param entries
/// \param capacity
/// \param key
/// \return 应该设置的位置
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 key.
      return entry;
    }

    index = (index + 1) % capacity;
  }
}
/// Allocating and resizing
/// \param table
/// \param capacity
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;
  }

  // 原来的 entry 重新放置到新位置
  table->count = 0;
  for (int i = 0; i < table->capacity; i++) {
    Entry *src = &table->entries[i];
    if (src->key == NULL) continue;

    Entry *dest = findEntry(entries, capacity, src->key);
    dest->key = src->key;
    dest->value = src->value;
    table->count++;
  }

  FREE_ARRAY(Entry, table->entries, table->capacity);
  table->entries = entries;
  table->capacity = capacity;
}
bool tableGet(Table *table, ObjString *key, Value *value) {
  // the table is completely empty
  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;
}
bool tableSet(Table *table, ObjString *key, Value value) {
  // 容量少于75% 就开始扩容
  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;
  }
  return NULL;
}