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STL之hashtable源代码剖析
// Filename: stl_hashtable.h
////////////////////////////////////////////////////////////////////////////////
// 本实作的hashtable採用的是开链法, 其内存布局例如以下
////////////////////////////////////////////////////////////////////////////////
// 对于产生哈希冲突的结点, 我们採取在其位置维护一个链表才处理之
//
// ------------------------------------------------------------------------
// | | | | | | ..... | | | | |
// ------------------------------------------------------------------------
// | | |
// ↓ ↓ ↓
// -------- -------- -------- -------- --------
// | next |->0 | next |->| next |->| next |->0 | next |->0
// -------- -------- -------- -------- --------
// | data | | data | | data | | data | | data |
// -------- -------- -------- -------- --------
////////////////////////////////////////////////////////////////////////////////
/*
* Copyright (c) 1996,1997
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*
*
* Copyright (c) 1994
* Hewlett-Packard Company
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Hewlett-Packard Company makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*
*/
/* NOTE: This is an internal header file, included by other STL headers.
* You should not attempt to use it directly.
*/
#ifndef __SGI_STL_INTERNAL_HASHTABLE_H
#define __SGI_STL_INTERNAL_HASHTABLE_H
// hashtable类用于实现哈希关联容器hash_set, hash_map, hash_multiset和hash_multimap
#include <stl_algobase.h>
#include <stl_alloc.h>
#include <stl_construct.h>
#include <stl_tempbuf.h>
#include <stl_algo.h>
#include <stl_uninitialized.h>
#include <stl_function.h>
#include <stl_vector.h>
#include <stl_hash_fun.h>
__STL_BEGIN_NAMESPACE
// 这个是哈希表中维护的链表结点
template <class Value>
struct __hashtable_node
{
__hashtable_node* next;
Value val;
};
// 这里使用前置声明, 否则后面的交叉引用会导致编译错误
template <class Value, class Key, class HashFcn,
class ExtractKey, class EqualKey, class Alloc = alloc>
class hashtable;
template <class Value, class Key, class HashFcn,
class ExtractKey, class EqualKey, class Alloc>
struct __hashtable_iterator;
template <class Value, class Key, class HashFcn,
class ExtractKey, class EqualKey, class Alloc>
struct __hashtable_const_iterator;
template <class Value, class Key, class HashFcn,
class ExtractKey, class EqualKey, class Alloc>
struct __hashtable_iterator
{
// 注意: hashtable不提供reverse iterator, 也不提供operator --
typedef hashtable<Value, Key, HashFcn, ExtractKey, EqualKey, Alloc>
hashtable;
typedef __hashtable_iterator<Value, Key, HashFcn,
ExtractKey, EqualKey, Alloc>
iterator;
typedef __hashtable_const_iterator<Value, Key, HashFcn,
ExtractKey, EqualKey, Alloc>
const_iterator;
typedef __hashtable_node<Value> node;
typedef forward_iterator_tag iterator_category;
typedef Value value_type;
typedef ptrdiff_t difference_type;
typedef size_t size_type;
typedef Value& reference;
typedef Value* pointer;
// 本实作中hasntable是由一个线性表作为hash表, 而表内的每个被映射的
// 哈希结点内部维护这一个链表, 用于处理哈希冲突, 此即开链法
node* cur; // 当前的位置, 是线性表中的链表结点
hashtable* ht; // 线性表中的位置
__hashtable_iterator(node* n, hashtable* tab) : cur(n), ht(tab) {}
__hashtable_iterator() {}
reference operator*() const { return cur->val; }
#ifndef __SGI_STL_NO_ARROW_OPERATOR
// 假设编译器支持'->'则重载, 具体见我在<stl_list.h>中的剖析
pointer operator->() const { return &(operator*()); }
#endif /* __SGI_STL_NO_ARROW_OPERATOR */
// 具体解析见实现部分
iterator& operator++();
iterator operator++(int);
bool operator==(const iterator& it) const { return cur == it.cur; }
bool operator!=(const iterator& it) const { return cur != it.cur; }
};
// const情况基本和上面一致
template <class Value, class Key, class HashFcn,
class ExtractKey, class EqualKey, class Alloc>
struct __hashtable_const_iterator
{
typedef hashtable<Value, Key, HashFcn, ExtractKey, EqualKey, Alloc>
hashtable;
typedef __hashtable_iterator<Value, Key, HashFcn,
ExtractKey, EqualKey, Alloc>
iterator;
typedef __hashtable_const_iterator<Value, Key, HashFcn,
ExtractKey, EqualKey, Alloc>
const_iterator;
typedef __hashtable_node<Value> node;
typedef forward_iterator_tag iterator_category;
typedef Value value_type;
typedef ptrdiff_t difference_type;
typedef size_t size_type;
typedef const Value& reference;
typedef const Value* pointer;
const node* cur;
const hashtable* ht;
__hashtable_const_iterator(const node* n, const hashtable* tab)
: cur(n), ht(tab) {}
__hashtable_const_iterator() {}
__hashtable_const_iterator(const iterator& it) : cur(it.cur), ht(it.ht) {}
reference operator*() const { return cur->val; }
#ifndef __SGI_STL_NO_ARROW_OPERATOR
pointer operator->() const { return &(operator*()); }
#endif /* __SGI_STL_NO_ARROW_OPERATOR */
const_iterator& operator++();
const_iterator operator++(int);
bool operator==(const const_iterator& it) const { return cur == it.cur; }
bool operator!=(const const_iterator& it) const { return cur != it.cur; }
};
// 假设long至少为32-bits, 否则依据情况自己改动
static const int __stl_num_primes = 28;
static const unsigned long __stl_prime_list[__stl_num_primes] =
{
53, 97, 193, 389, 769,
1543, 3079, 6151, 12289, 24593,
49157, 98317, 196613, 393241, 786433,
1572869, 3145739, 6291469, 12582917, 25165843,
50331653, 100663319, 201326611, 402653189, 805306457,
1610612741, 3221225473ul, 4294967291ul
};
// 返回大于n的最小素数
inline unsigned long __stl_next_prime(unsigned long n)
{
const unsigned long* first = __stl_prime_list;
const unsigned long* last = __stl_prime_list + __stl_num_primes;
const unsigned long* pos = lower_bound(first, last, n);
return pos == last ? *(last - 1) : *pos;
}
// Value: 结点的valule类型
// Key: 结点的key类型
// HashFcn: hash function
// ExtractKey: 从结点中取出键值的方法
// EqualKey: 推断键值是否同样的方法
// Alloc: allocator, 默认alloc
template <class Value, class Key, class HashFcn,
class ExtractKey, class EqualKey,
class Alloc>
class hashtable
{
public:
typedef Key key_type;
typedef Value value_type;
typedef HashFcn hasher;
typedef EqualKey key_equal;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef value_type* pointer;
typedef const value_type* const_pointer;
typedef value_type& reference;
typedef const value_type& const_reference;
// 获取hash相关的函数
hasher hash_funct() const { return hash; }
key_equal key_eq() const { return equals; }
private:
// 具体剖析參考<stl_fun_fun.h>
hasher hash;
key_equal equals;
ExtractKey get_key;
typedef __hashtable_node<Value> node;
typedef simple_alloc<node, Alloc> node_allocator;
vector<node*,Alloc> buckets; // 线性表以vector实作
size_type num_elements;
public:
typedef __hashtable_iterator<Value, Key, HashFcn, ExtractKey, EqualKey,
Alloc>
iterator;
typedef __hashtable_const_iterator<Value, Key, HashFcn, ExtractKey, EqualKey,
Alloc>
const_iterator;
friend struct
__hashtable_iterator<Value, Key, HashFcn, ExtractKey, EqualKey, Alloc>;
friend struct
__hashtable_const_iterator<Value, Key, HashFcn, ExtractKey, EqualKey, Alloc>;
public:
// 以下这些函数STL容器的表现基本一致,
// 不做说明, 能够參看<stl_vector.h>, <stl_list.h>中的解析
hashtable(size_type n,
const HashFcn& hf,
const EqualKey& eql,
const ExtractKey& ext)
: hash(hf), equals(eql), get_key(ext), num_elements(0)
{
initialize_buckets(n);
}
hashtable(size_type n,
const HashFcn& hf,
const EqualKey& eql)
: hash(hf), equals(eql), get_key(ExtractKey()), num_elements(0)
{
initialize_buckets(n);
}
hashtable(const hashtable& ht)
: hash(ht.hash), equals(ht.equals), get_key(ht.get_key), num_elements(0)
{
copy_from(ht);
}
hashtable& operator= (const hashtable& ht)
{
if (&ht != this) {
clear();
hash = ht.hash;
equals = ht.equals;
get_key = ht.get_key;
copy_from(ht);
}
return *this;
}
~hashtable() { clear(); }
size_type size() const { return num_elements; }
size_type max_size() const { return size_type(-1); }
bool empty() const { return size() == 0; }
void swap(hashtable& ht)
{
__STD::swap(hash, ht.hash);
__STD::swap(equals, ht.equals);
__STD::swap(get_key, ht.get_key);
buckets.swap(ht.buckets);
__STD::swap(num_elements, ht.num_elements);
}
iterator begin()
{
for (size_type n = 0; n < buckets.size(); ++n)
if (buckets[n])
return iterator(buckets[n], this);
return end();
}
iterator end() { return iterator(0, this); }
const_iterator begin() const
{
for (size_type n = 0; n < buckets.size(); ++n)
if (buckets[n])
return const_iterator(buckets[n], this);
return end();
}
const_iterator end() const { return const_iterator(0, this); }
friend bool
operator== __STL_NULL_TMPL_ARGS (const hashtable&, const hashtable&);
public:
// 线性表中的结点数
size_type bucket_count() const { return buckets.size(); }
// 线性表最多能分配的结点数
size_type max_bucket_count() const
{ return __stl_prime_list[__stl_num_primes - 1]; }
// 返回指定key映射了多少value
size_type elems_in_bucket(size_type bucket) const
{
size_type result = 0;
for (node* cur = buckets[bucket]; cur; cur = cur->next)
result += 1;
return result;
}
// 插入操作, 不同意反复
pair<iterator, bool> insert_unique(const value_type& obj)
{
// 首先推断容量是否够用, 否则就又一次配置
resize(num_elements + 1);
return insert_unique_noresize(obj);
}
// 插入操作, 同意反复
iterator insert_equal(const value_type& obj)
{
resize(num_elements + 1);
return insert_equal_noresize(obj);
}
pair<iterator, bool> insert_unique_noresize(const value_type& obj);
iterator insert_equal_noresize(const value_type& obj);
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
void insert_unique(InputIterator f, InputIterator l)
{
insert_unique(f, l, iterator_category(f));
}
template <class InputIterator>
void insert_equal(InputIterator f, InputIterator l)
{
insert_equal(f, l, iterator_category(f));
}
template <class InputIterator>
void insert_unique(InputIterator f, InputIterator l,
input_iterator_tag)
{
for ( ; f != l; ++f)
insert_unique(*f);
}
template <class InputIterator>
void insert_equal(InputIterator f, InputIterator l,
input_iterator_tag)
{
for ( ; f != l; ++f)
insert_equal(*f);
}
template <class ForwardIterator>
void insert_unique(ForwardIterator f, ForwardIterator l,
forward_iterator_tag)
{
size_type n = 0;
distance(f, l, n);
resize(num_elements + n);
for ( ; n > 0; --n, ++f)
insert_unique_noresize(*f);
}
template <class ForwardIterator>
void insert_equal(ForwardIterator f, ForwardIterator l,
forward_iterator_tag)
{
size_type n = 0;
distance(f, l, n);
resize(num_elements + n);
for ( ; n > 0; --n, ++f)
insert_equal_noresize(*f);
}
#else /* __STL_MEMBER_TEMPLATES */
void insert_unique(const value_type* f, const value_type* l)
{
size_type n = l - f;
resize(num_elements + n);
for ( ; n > 0; --n, ++f)
insert_unique_noresize(*f);
}
void insert_equal(const value_type* f, const value_type* l)
{
size_type n = l - f;
resize(num_elements + n);
for ( ; n > 0; --n, ++f)
insert_equal_noresize(*f);
}
void insert_unique(const_iterator f, const_iterator l)
{
size_type n = 0;
distance(f, l, n);
resize(num_elements + n);
for ( ; n > 0; --n, ++f)
insert_unique_noresize(*f);
}
void insert_equal(const_iterator f, const_iterator l)
{
size_type n = 0;
distance(f, l, n);
resize(num_elements + n);
for ( ; n > 0; --n, ++f)
insert_equal_noresize(*f);
}
#endif /*__STL_MEMBER_TEMPLATES */
reference find_or_insert(const value_type& obj);
// 查找指定key
iterator find(const key_type& key)
{
size_type n = bkt_num_key(key);
node* first;
for ( first = buckets[n];
first && !equals(get_key(first->val), key);
first = first->next)
{}
return iterator(first, this);
}
const_iterator find(const key_type& key) const
{
size_type n = bkt_num_key(key);
const node* first;
for ( first = buckets[n];
first && !equals(get_key(first->val), key);
first = first->next)
{}
return const_iterator(first, this);
}
// 返回key元素的个数
size_type count(const key_type& key) const
{
const size_type n = bkt_num_key(key);
size_type result = 0;
for (const node* cur = buckets[n]; cur; cur = cur->next)
if (equals(get_key(cur->val), key))
++result;
return result;
}
pair<iterator, iterator> equal_range(const key_type& key);
pair<const_iterator, const_iterator> equal_range(const key_type& key) const;
// 擦除元素
size_type erase(const key_type& key);
void erase(const iterator& it);
void erase(iterator first, iterator last);
void erase(const const_iterator& it);
void erase(const_iterator first, const_iterator last);
void resize(size_type num_elements_hint);
void clear();
private:
size_type next_size(size_type n) const { return __stl_next_prime(n); }
// 预留空间, 并进行初始化
void initialize_buckets(size_type n)
{
const size_type n_buckets = next_size(n);
buckets.reserve(n_buckets);
buckets.insert(buckets.end(), n_buckets, (node*) 0);
num_elements = 0;
}
size_type bkt_num_key(const key_type& key) const
{
return bkt_num_key(key, buckets.size());
}
// 获取obj映射位置, 要经过一个mod过程
size_type bkt_num(const value_type& obj) const
{
return bkt_num_key(get_key(obj));
}
size_type bkt_num_key(const key_type& key, size_t n) const
{
return hash(key) % n;
}
size_type bkt_num(const value_type& obj, size_t n) const
{
return bkt_num_key(get_key(obj), n);
}
// 分配空间并进行构造
node* new_node(const value_type& obj)
{
node* n = node_allocator::allocate();
n->next = 0;
__STL_TRY {
construct(&n->val, obj);
return n;
}
__STL_UNWIND(node_allocator::deallocate(n));
}
// 析构并释放空间
void delete_node(node* n)
{
destroy(&n->val);
node_allocator::deallocate(n);
}
// 解析见实现部分
void erase_bucket(const size_type n, node* first, node* last);
void erase_bucket(const size_type n, node* last);
void copy_from(const hashtable& ht);
};
template <class V, class K, class HF, class ExK, class EqK, class A>
__hashtable_iterator<V, K, HF, ExK, EqK, A>&
__hashtable_iterator<V, K, HF, ExK, EqK, A>::operator++()
{
const node* old = cur;
cur = cur->next; // 当前链表结点的下一个结点, 假设不为0
// 那么它就是我们要的
// 链表结点恰好是最后一个结点, 我们要在线性表的下一个表格的链表中查找
if (!cur)
{
size_type bucket = ht->bkt_num(old->val);
while (!cur && ++bucket < ht->buckets.size())
cur = ht->buckets[bucket];
}
return *this;
}
template <class V, class K, class HF, class ExK, class EqK, class A>
inline __hashtable_iterator<V, K, HF, ExK, EqK, A>
__hashtable_iterator<V, K, HF, ExK, EqK, A>::operator++(int)
{
iterator tmp = *this;
++*this; // 触发operator ++()
return tmp;
}
// const情况同上
template <class V, class K, class HF, class ExK, class EqK, class A>
__hashtable_const_iterator<V, K, HF, ExK, EqK, A>&
__hashtable_const_iterator<V, K, HF, ExK, EqK, A>::operator++()
{
const node* old = cur;
cur = cur->next;
if (!cur) {
size_type bucket = ht->bkt_num(old->val);
while (!cur && ++bucket < ht->buckets.size())
cur = ht->buckets[bucket];
}
return *this;
}
template <class V, class K, class HF, class ExK, class EqK, class A>
inline __hashtable_const_iterator<V, K, HF, ExK, EqK, A>
__hashtable_const_iterator<V, K, HF, ExK, EqK, A>::operator++(int)
{
const_iterator tmp = *this;
++*this;
return tmp;
}
// 对于不支持偏特化的编译器提供traits支持
#ifndef __STL_CLASS_PARTIAL_SPECIALIZATION
template <class V, class K, class HF, class ExK, class EqK, class All>
inline forward_iterator_tag
iterator_category(const __hashtable_iterator<V, K, HF, ExK, EqK, All>&)
{
return forward_iterator_tag();
}
template <class V, class K, class HF, class ExK, class EqK, class All>
inline V* value_type(const __hashtable_iterator<V, K, HF, ExK, EqK, All>&)
{
return (V*) 0;
}
template <class V, class K, class HF, class ExK, class EqK, class All>
inline hashtable<V, K, HF, ExK, EqK, All>::difference_type*
distance_type(const __hashtable_iterator<V, K, HF, ExK, EqK, All>&)
{
return (hashtable<V, K, HF, ExK, EqK, All>::difference_type*) 0;
}
template <class V, class K, class HF, class ExK, class EqK, class All>
inline forward_iterator_tag
iterator_category(const __hashtable_const_iterator<V, K, HF, ExK, EqK, All>&)
{
return forward_iterator_tag();
}
template <class V, class K, class HF, class ExK, class EqK, class All>
inline V*
value_type(const __hashtable_const_iterator<V, K, HF, ExK, EqK, All>&)
{
return (V*) 0;
}
template <class V, class K, class HF, class ExK, class EqK, class All>
inline hashtable<V, K, HF, ExK, EqK, All>::difference_type*
distance_type(const __hashtable_const_iterator<V, K, HF, ExK, EqK, All>&)
{
return (hashtable<V, K, HF, ExK, EqK, All>::difference_type*) 0;
}
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
template <class V, class K, class HF, class Ex, class Eq, class A>
bool operator==(const hashtable<V, K, HF, Ex, Eq, A>& ht1,
const hashtable<V, K, HF, Ex, Eq, A>& ht2)
{
typedef typename hashtable<V, K, HF, Ex, Eq, A>::node node;
if (ht1.buckets.size() != ht2.buckets.size())
return false;
for (int n = 0; n < ht1.buckets.size(); ++n) {
node* cur1 = ht1.buckets[n];
node* cur2 = ht2.buckets[n];
for ( ; cur1 && cur2 && cur1->val == cur2->val;
cur1 = cur1->next, cur2 = cur2->next)
{}
if (cur1 || cur2)
return false;
}
return true;
}
// 假设编译器支持模板函数特化优先级
// 那么将全局的swap实现为使用hashtable私有的swap以提高效率
#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER
template <class Val, class Key, class HF, class Extract, class EqKey, class A>
inline void swap(hashtable<Val, Key, HF, Extract, EqKey, A>& ht1,
hashtable<Val, Key, HF, Extract, EqKey, A>& ht2) {
ht1.swap(ht2);
}
#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */
// 在不须要又一次调整容量的情况下插入元素, key不能够反复
template <class V, class K, class HF, class Ex, class Eq, class A>
pair<typename hashtable<V, K, HF, Ex, Eq, A>::iterator, bool>
hashtable<V, K, HF, Ex, Eq, A>::insert_unique_noresize(const value_type& obj)
{
// 获取待插入元素在hashtable中的索引
const size_type n = bkt_num(obj);
node* first = buckets[n];
for (node* cur = first; cur; cur = cur->next)
// 假设keu反复, 在不进行插入, 并告知用户插入失败
if (equals(get_key(cur->val), get_key(obj)))
return pair<iterator, bool>(iterator(cur, this), false);
// 插入结点
node* tmp = new_node(obj);
tmp->next = first;
buckets[n] = tmp;
++num_elements;
return pair<iterator, bool>(iterator(tmp, this), true);
}
// 在不须要又一次调整容量的情况下插入元素, key能够反复
template <class V, class K, class HF, class Ex, class Eq, class A>
typename hashtable<V, K, HF, Ex, Eq, A>::iterator
hashtable<V, K, HF, Ex, Eq, A>::insert_equal_noresize(const value_type& obj)
{
const size_type n = bkt_num(obj);
node* first = buckets[n];
for (node* cur = first; cur; cur = cur->next)
if (equals(get_key(cur->val), get_key(obj))) {
node* tmp = new_node(obj);
tmp->next = cur->next;
cur->next = tmp;
++num_elements;
return iterator(tmp, this);
}
node* tmp = new_node(obj);
tmp->next = first;
buckets[n] = tmp;
++num_elements;
return iterator(tmp, this);
}
// 这个用于支持hash_map操作
template <class V, class K, class HF, class Ex, class Eq, class A>
typename hashtable<V, K, HF, Ex, Eq, A>::reference
hashtable<V, K, HF, Ex, Eq, A>::find_or_insert(const value_type& obj)
{
resize(num_elements + 1);
size_type n = bkt_num(obj);
node* first = buckets[n];
for (node* cur = first; cur; cur = cur->next)
if (equals(get_key(cur->val), get_key(obj)))
return cur->val;
node* tmp = new_node(obj);
tmp->next = first;
buckets[n] = tmp;
++num_elements;
return tmp->val;
}
// 查找满足key的区间
template <class V, class K, class HF, class Ex, class Eq, class A>
pair<typename hashtable<V, K, HF, Ex, Eq, A>::iterator,
typename hashtabfind_or_insertle<V, K, HF, Ex, Eq, A>::iterator>
hashtable<V, K, HF, Ex, Eq, A>::equal_range(const key_type& key)
{
typedef pair<iterator, iterator> pii;
const size_type n = bkt_num_key(key);
for (node* first = buckets[n]; first; first = first->next) {
if (equals(get_key(first->val), key)) {
for (node* cur = first->next; cur; cur = cur->next)
if (!equals(get_key(cur->val), key))
return pii(iterator(first, this), iterator(cur, this));
for (size_type m = n + 1; m < buckets.size(); ++m)
if (buckets[m])
return pii(iterator(first, this),
iterator(buckets[m], this));
return pii(iterator(first, this), end());
}
}
return pii(end(), end());
}
template <class V, class K, class HF, class Ex, class Eq, class A>
pair<typename hashtable<V, K, HF, Ex, Eq, A>::const_iterator,
typename hashtable<V, K, HF, Ex, Eq, A>::const_iterator>
hashtable<V, K, HF, Ex, Eq, A>::equal_range(const key_type& key) const
{
typedef pair<const_iterator, const_iterator> pii;
const size_type n = bkt_num_key(key);
for (const node* first = buckets[n] ; first; first = first->next) {
if (equals(get_key(first->val), key)) {
for (const node* cur = first->next; cur; cur = cur->next)
if (!equals(get_key(cur->val), key))
return pii(const_iterator(first, this),
const_iterator(cur, this));
for (size_type m = n + 1; m < buckets.size(); ++m)
if (buckets[m])
return pii(const_iterator(first, this),
const_iterator(buckets[m], this));
return pii(const_iterator(first, this), end());
}
}
return pii(end(), end());
}
// 擦除指定元素
template <class V, class K, class HF, class Ex, class Eq, class A>
typename hashtable<V, K, HF, Ex, Eq, A>::size_type
hashtable<V, K, HF, Ex, Eq, A>::erase(const key_type& key)
{
// 计算映射位置
const size_type n = bkt_num_key(key);
node* first = buckets[n];
size_type erased = 0;
// 開始查找并删除
if (first) {
node* cur = first;
node* next = cur->next;
while (next) {
if (equals(get_key(next->val), key)) {
cur->next = next->next;
delete_node(next);
next = cur->next;
++erased;
--num_elements;
}
else {
cur = next;
next = cur->next;
}
}
if (equals(get_key(first->val), key)) {
buckets[n] = first->next;
delete_node(first);
++erased;
--num_elements;
}
}
return erased;
}
template <class V, class K, class HF, class Ex, class Eq, class A>
void hashtable<V, K, HF, Ex, Eq, A>::erase(const iterator& it)
{
if (node* const p = it.cur) {
const size_type n = bkt_num(p->val);
node* cur = buckets[n];
if (cur == p) {
buckets[n] = cur->next;
delete_node(cur);
--num_elements;
}
else {
node* next = cur->next;
while (next) {
if (next == p) {
cur->next = next->next;
delete_node(next);
--num_elements;
break;
}
else {
cur = next;
next = cur->next;
}
}
}
}
}
// 擦除指定区间的元素
template <class V, class K, class HF, class Ex, class Eq, class A>
void hashtable<V, K, HF, Ex, Eq, A>::erase(iterator first, iterator last)
{
size_type f_bucket = first.cur ?
bkt_num(first.cur->val) : buckets.size();
size_type l_bucket = last.cur ? bkt_num(last.cur->val) : buckets.size();
if (first.cur == last.cur)
return;
else if (f_bucket == l_bucket)
erase_bucket(f_bucket, first.cur, last.cur);
else {
erase_bucket(f_bucket, first.cur, 0);
for (size_type n = f_bucket + 1; n < l_bucket; ++n)
erase_bucket(n, 0);
if (l_bucket != buckets.size())
erase_bucket(l_bucket, last.cur);
}
}
template <class V, class K, class HF, class Ex, class Eq, class A>
inline void
hashtable<V, K, HF, Ex, Eq, A>::erase(const_iterator first,
const_iterator last)
{
erase(iterator(const_cast<node*>(first.cur),
const_cast<hashtable*>(first.ht)),
iterator(const_cast<node*>(last.cur),
const_cast<hashtable*>(last.ht)));
}
template <class V, class K, class HF, class Ex, class Eq, class A>
inline void
hashtable<V, K, HF, Ex, Eq, A>::erase(const const_iterator& it)
{
erase(iterator(const_cast<node*>(it.cur),
const_cast<hashtable*>(it.ht)));
}
// 调整hashtable的容量
template <class V, class K, class HF, class Ex, class Eq, class A>
void hashtable<V, K, HF, Ex, Eq, A>::resize(size_type num_elements_hint)
{
const size_type old_n = buckets.size();
// 假设新调整的大小小于当前大小, 不进行更改
if (num_elements_hint > old_n) {
const size_type n = next_size(num_elements_hint);
// 假设已经到达hashtable的容量的极限, 那么也不进行更改
if (n > old_n) {
// 建立新的线性表来扩充容量
vector<node*, A> tmp(n, (node*) 0);
__STL_TRY {
// 先面開始copy
for (size_type bucket = 0; bucket < old_n; ++bucket) {
node* first = buckets[bucket];
while (first) {
size_type new_bucket = bkt_num(first->val, n);
buckets[bucket] = first->next;
first->next = tmp[new_bucket];
tmp[new_bucket] = first;
first = buckets[bucket];
}
}
buckets.swap(tmp);
}
# ifdef __STL_USE_EXCEPTIONS
catch(...) {
for (size_type bucket = 0; bucket < tmp.size(); ++bucket) {
while (tmp[bucket]) {
node* next = tmp[bucket]->next;
delete_node(tmp[bucket]);
tmp[bucket] = next;
}
}
throw;
}
# endif /* __STL_USE_EXCEPTIONS */
}
}
}
// 擦除指定映射位置的全部元素
template <class V, class K, class HF, class Ex, class Eq, class A>
void hashtable<V, K, HF, Ex, Eq, A>::erase_bucket(const size_type n,
node* first, node* last)
{
node* cur = buckets[n];
if (cur == first)
erase_bucket(n, last);
else {
node* next;
for (next = cur->next; next != first; cur = next, next = cur->next)
;
while (next) {
cur->next = next->next;
delete_node(next);
next = cur->next;
--num_elements;
}
}
}
template <class V, class K, class HF, class Ex, class Eq, class A>
void
hashtable<V, K, HF, Ex, Eq, A>::erase_bucket(const size_type n, node* last)
{
node* cur = buckets[n];
while (cur != last) {
node* next = cur->next;
delete_node(cur);
cur = next;
buckets[n] = cur;
--num_elements;
}
}
// 清空hashtable, 可是不释放vector的内存
template <class V, class K, class HF, class Ex, class Eq, class A>
void hashtable<V, K, HF, Ex, Eq, A>::clear()
{
for (size_type i = 0; i < buckets.size(); ++i) {
node* cur = buckets[i];
while (cur != 0) {
node* next = cur->next;
delete_node(cur);
cur = next;
}
buckets[i] = 0;
}
num_elements = 0;
}
// 复制还有一个hashtable给当前hashtable
template <class V, class K, class HF, class Ex, class Eq, class A>
void hashtable<V, K, HF, Ex, Eq, A>::copy_from(const hashtable& ht)
{
// 首先清空当前hashtable
buckets.clear();
// 预留足够容量
buckets.reserve(ht.buckets.size());
// 完毕初始化操作, 这是hashtable的先验条件
buckets.insert(buckets.end(), ht.buckets.size(), (node*) 0);
__STL_TRY {
// 開始copy操作
for (size_type i = 0; i < ht.buckets.size(); ++i) {
if (const node* cur = ht.buckets[i]) {
node* copy = new_node(cur->val);
buckets[i] = copy;
for (node* next = cur->next; next; cur = next, next = cur->next) {
copy->next = new_node(next->val);
copy = copy->next;
}
}
}
num_elements = ht.num_elements;
}
__STL_UNWIND(clear());
}
__STL_END_NAMESPACE
#endif /* __SGI_STL_INTERNAL_HASHTABLE_H */
// Local Variables:
// mode:C++
// End:
STL之hashtable源代码剖析