Linux链表(哈希,双向)使用总结

本文详细介绍了Linux内核中链表和哈希表的具体实现方式,包括双向链表的基本操作如添加、删除等,并提供了哈希表的具体实现细节,如哈希函数的设计和哈希表的操作函数。

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代码实现:

stddef.h

#ifndef __STDDEF_H__
#define __STDDEF_H__

#ifdef __cplusplus
extern "C" {
#endif
#include <stdint.h>

#if defined(__cplusplus)
#define NULL			(0)
#else
#define NULL			((void *)0)
#endif

#if (defined(__GNUC__) && (__GNUC__ >= 4))
#define offsetof(type, member)				__builtin_offsetof(type, member)
#else
#define offsetof(type, field)				((size_t)(&((type *)0)->field))
#endif
#define container_of(ptr, type, member)		({const typeof(((type *)0)->member) *__mptr = (ptr); (type *)((char *)__mptr - offsetof(type,member));})

#if (defined(__GNUC__) && (__GNUC__ >= 3))
#define likely(expr)	(__builtin_expect(!!(expr), 1))
#define unlikely(expr)	(__builtin_expect(!!(expr), 0))
#else
#define likely(expr)	(!!(expr))
#define unlikely(expr)	(!!(expr))
#endif

#define min(a, b)		({typeof(a) _amin = (a); typeof(b) _bmin = (b); (void)(&_amin == &_bmin); _amin < _bmin ? _amin : _bmin;})
#define max(a, b)		({typeof(a) _amax = (a); typeof(b) _bmax = (b); (void)(&_amax == &_bmax); _amax > _bmax ? _amax : _bmax;})
#define clamp(v, a, b)	min(max(a, v), b)

#define ifloor(x)		((x) > 0 ? (int)(x) : (int)((x) - 0.9999999999))
#define iround(x)		((x) > 0 ? (int)((x) + 0.5) : (int)((x) - 0.5))
#define iceil(x)		((x) > 0 ? (int)((x) + 0.9999999999) : (int)(x))
#define idiv255(x)		((((int)(x) + 1) * 257) >> 16)

#define X(...)			("" #__VA_ARGS__ "")

#define roundup_pow_of_two(n)       \
(                                   \
    __builtin_constant_p(n) ? (     \
    (n == 1) ? 1 :                  \
    (1UL << (ilog2((n) - 1) + 1))   \
               ) :                  \
    __roundup_pow_of_two(n)         \
)
 
#define rounddown_pow_of_two(n)     \
(                                   \
    __builtin_constant_p(n) ? (     \
    (1UL << ilog2(n))) :            \
    __rounddown_pow_of_two(n)       \
)

static uint32_t shash(const char * s)
{     
    uint32_t v = 5381;
    if(s)
    {                   
        while(*s)       
            v = (v << 5) + v + (*s++);
    } 
    return v;           
} 

#ifdef __cplusplus
}
#endif

#endif /* __STDDEF_H__ */

log2.h

#ifndef __LOG2_H__
#define __LOG2_H__

#ifdef __cplusplus
extern "C" {
#endif

#include <string.h>
#include <stdint.h>

static inline __attribute__((always_inline)) int fls(int x)
{
    return x ? sizeof(x) * 8 - __builtin_clz(x) : 0;
}

static inline __attribute__((always_inline)) int fls64(uint64_t x)
{
	uint32_t h = x >> 32;
	if (h)
		return fls(h) + 32;
	return fls(x);
}

static inline __attribute__((always_inline)) unsigned fls_long(unsigned long l)
{
	if(sizeof(l) == 4)
		return fls(l);
	return fls64(l);
}

static inline __attribute__((const)) int __ilog2_u32(uint32_t n)
{
	return fls(n) - 1;
}

static inline __attribute__((const)) int __ilog2_u64(uint64_t n)
{
	return fls64(n) - 1;
}

static inline __attribute__((const)) int is_power_of_2(unsigned long n)
{
	return (n != 0 && ((n & (n - 1)) == 0));
}

static inline __attribute__((const)) unsigned long __roundup_pow_of_two(unsigned long n)
{
	return 1UL << fls_long(n - 1);
}

static inline __attribute__((const)) unsigned long __rounddown_pow_of_two(unsigned long n)
{
	return 1UL << (fls_long(n) - 1);
}

#define ilog2(n)					\
(									\
	__builtin_constant_p(n) ? (		\
		(n) < 2 ? 0 :				\
		(n) & (1ULL << 63) ? 63 :	\
		(n) & (1ULL << 62) ? 62 :	\
		(n) & (1ULL << 61) ? 61 :	\
		(n) & (1ULL << 60) ? 60 :	\
		(n) & (1ULL << 59) ? 59 :	\
		(n) & (1ULL << 58) ? 58 :	\
		(n) & (1ULL << 57) ? 57 :	\
		(n) & (1ULL << 56) ? 56 :	\
		(n) & (1ULL << 55) ? 55 :	\
		(n) & (1ULL << 54) ? 54 :	\
		(n) & (1ULL << 53) ? 53 :	\
		(n) & (1ULL << 52) ? 52 :	\
		(n) & (1ULL << 51) ? 51 :	\
		(n) & (1ULL << 50) ? 50 :	\
		(n) & (1ULL << 49) ? 49 :	\
		(n) & (1ULL << 48) ? 48 :	\
		(n) & (1ULL << 47) ? 47 :	\
		(n) & (1ULL << 46) ? 46 :	\
		(n) & (1ULL << 45) ? 45 :	\
		(n) & (1ULL << 44) ? 44 :	\
		(n) & (1ULL << 43) ? 43 :	\
		(n) & (1ULL << 42) ? 42 :	\
		(n) & (1ULL << 41) ? 41 :	\
		(n) & (1ULL << 40) ? 40 :	\
		(n) & (1ULL << 39) ? 39 :	\
		(n) & (1ULL << 38) ? 38 :	\
		(n) & (1ULL << 37) ? 37 :	\
		(n) & (1ULL << 36) ? 36 :	\
		(n) & (1ULL << 35) ? 35 :	\
		(n) & (1ULL << 34) ? 34 :	\
		(n) & (1ULL << 33) ? 33 :	\
		(n) & (1ULL << 32) ? 32 :	\
		(n) & (1ULL << 31) ? 31 :	\
		(n) & (1ULL << 30) ? 30 :	\
		(n) & (1ULL << 29) ? 29 :	\
		(n) & (1ULL << 28) ? 28 :	\
		(n) & (1ULL << 27) ? 27 :	\
		(n) & (1ULL << 26) ? 26 :	\
		(n) & (1ULL << 25) ? 25 :	\
		(n) & (1ULL << 24) ? 24 :	\
		(n) & (1ULL << 23) ? 23 :	\
		(n) & (1ULL << 22) ? 22 :	\
		(n) & (1ULL << 21) ? 21 :	\
		(n) & (1ULL << 20) ? 20 :	\
		(n) & (1ULL << 19) ? 19 :	\
		(n) & (1ULL << 18) ? 18 :	\
		(n) & (1ULL << 17) ? 17 :	\
		(n) & (1ULL << 16) ? 16 :	\
		(n) & (1ULL << 15) ? 15 :	\
		(n) & (1ULL << 14) ? 14 :	\
		(n) & (1ULL << 13) ? 13 :	\
		(n) & (1ULL << 12) ? 12 :	\
		(n) & (1ULL << 11) ? 11 :	\
		(n) & (1ULL << 10) ? 10 :	\
		(n) & (1ULL <<  9) ?  9 :	\
		(n) & (1ULL <<  8) ?  8 :	\
		(n) & (1ULL <<  7) ?  7 :	\
		(n) & (1ULL <<  6) ?  6 :	\
		(n) & (1ULL <<  5) ?  5 :	\
		(n) & (1ULL <<  4) ?  4 :	\
		(n) & (1ULL <<  3) ?  3 :	\
		(n) & (1ULL <<  2) ?  2 :	\
		1 ) :						\
	(sizeof(n) <= 4) ?				\
	__ilog2_u32(n) :				\
	__ilog2_u64(n)					\
 )

#define roundup_pow_of_two(n)		\
(									\
	__builtin_constant_p(n) ? (		\
	(n == 1) ? 1 :					\
	(1UL << (ilog2((n) - 1) + 1))	\
			   ) :					\
	__roundup_pow_of_two(n)			\
 )

#define rounddown_pow_of_two(n)		\
(									\
	__builtin_constant_p(n) ? (		\
	(1UL << ilog2(n))) :			\
	__rounddown_pow_of_two(n)		\
 )

#ifdef __cplusplus
}
#endif

#endif /* __LOG2_H__ */

list.h

#ifndef __LIST_H__
#define __LIST_H__

#ifdef __cplusplus
extern "C" {
#endif

#include "stddef.h"

/*
 * Simple doubly linked list implementation.
 *
 * Some of the internal functions ("__xxx") are useful when
 * manipulating whole lists rather than single entries, as
 * sometimes we already know the next/prev entries and we can
 * generate better code by using them directly rather than
 * using the generic single-entry routines.
 */

struct list_head {
	struct list_head * next, * prev;
};

#define LIST_HEAD(name) \
	struct list_head name = { &(name), &(name) }

static inline void init_list_head(struct list_head * list)
{
	list->next = list;
	list->prev = list;
}

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add(struct list_head * new,
			      struct list_head * prev,
			      struct list_head * next)
{
	next->prev = new;
	new->next = next;
	new->prev = prev;
	prev->next = new;
}

/**
 * list_add - add a new entry
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void list_add(struct list_head * new, struct list_head * head)
{
	__list_add(new, head, head->next);
}

/**
 * list_add_tail - add a new entry
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static inline void list_add_tail(struct list_head * new, struct list_head * head)
{
	__list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
	next->prev = prev;
	prev->next = next;
}

/**
 * list_del - deletes entry from list.
 * @entry: the element to delete from the list.
 * Note: list_empty() on entry does not return true after this, the entry is
 * in an undefined state.
 */
static inline void __list_del_entry(struct list_head * entry)
{
	__list_del(entry->prev, entry->next);
}

static inline void list_del(struct list_head *entry)
{
	__list_del_entry(entry);
	entry->next = 0;
	entry->prev = 0;
}

/**
 * list_replace - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * If @old was empty, it will be overwritten.
 */
static inline void list_replace(struct list_head * old,
				struct list_head * new)
{
	new->next = old->next;
	new->next->prev = new;
	new->prev = old->prev;
	new->prev->next = new;
}

static inline void list_replace_init(struct list_head * old,
					struct list_head * new)
{
	list_replace(old, new);
	init_list_head(old);
}

/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
static inline void list_del_init(struct list_head * entry)
{
	__list_del_entry(entry);
	init_list_head(entry);
}

/**
 * list_move - delete from one list and add as another's head
 * @list: the entry to move
 * @head: the head that will precede our entry
 */
static inline void list_move(struct list_head * list, struct list_head * head)
{
	__list_del_entry(list);
	list_add(list, head);
}

/**
 * list_move_tail - delete from one list and add as another's tail
 * @list: the entry to move
 * @head: the head that will follow our entry
 */
static inline void list_move_tail(struct list_head * list,
				  struct list_head * head)
{
	__list_del_entry(list);
	list_add_tail(list, head);
}

/**
 * list_bulk_move_tail - move a subsection of a list to its tail
 * @head: the head that will follow our entry
 * @first: first entry to move
 * @last: last entry to move, can be the same as first
 *
 * Move all entries between @first and including @last before @head.
 * All three entries must belong to the same linked list.
 */
static inline void list_bulk_move_tail(struct list_head * head,
				       struct list_head * first,
				       struct list_head * last)
{
	first->prev->next = last->next;
	last->next->prev = first->prev;

	head->prev->next = first;
	first->prev = head->prev;

	last->next = head;
	head->prev = last;
}

/**
 * list_is_first - tests whether @list is the first entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_first(const struct list_head * list,
				const struct list_head * head)
{
	return list->prev == head;
}

/**
 * list_is_last - tests whether @list is the last entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_last(const struct list_head * list,
				const struct list_head * head)
{
	return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
static inline int list_empty(const struct list_head * head)
{
	return head->next == head;
}

/**
 * list_empty_careful - tests whether a list is empty and not being modified
 * @head: the list to test
 *
 * Description:
 * tests whether a list is empty _and_ checks that no other CPU might be
 * in the process of modifying either member (next or prev)
 *
 * NOTE: using list_empty_careful() without synchronization
 * can only be safe if the only activity that can happen
 * to the list entry is list_del_init(). Eg. it cannot be used
 * if another CPU could re-list_add() it.
 */
static inline int list_empty_careful(const struct list_head * head)
{
	struct list_head * next = head->next;
	return (next == head) && (next == head->prev);
}

/**
 * list_rotate_left - rotate the list to the left
 * @head: the head of the list
 */
static inline void list_rotate_left(struct list_head * head)
{
	struct list_head * first;

	if (!list_empty(head))
	{
		first = head->next;
		list_move_tail(first, head);
	}
}

/**
 * list_is_singular - tests whether a list has just one entry.
 * @head: the list to test.
 */
static inline int list_is_singular(const struct list_head * head)
{
	return !list_empty(head) && (head->next == head->prev);
}

static inline void __list_cut_position(struct list_head * list,
		struct list_head * head, struct list_head * entry)
{
	struct list_head * new_first = entry->next;
	list->next = head->next;
	list->next->prev = list;
	list->prev = entry;
	entry->next = list;
	head->next = new_first;
	new_first->prev = head;
}

/**
 * list_cut_position - cut a list into two
 * @list: a new list to add all removed entries
 * @head: a list with entries
 * @entry: an entry within head, could be the head itself
 *	and if so we won't cut the list
 *
 * This helper moves the initial part of @head, up to and
 * including @entry, from @head to @list. You should
 * pass on @entry an element you know is on @head. @list
 * should be an empty list or a list you do not care about
 * losing its data.
 *
 */
static inline void list_cut_position(struct list_head * list,
		struct list_head * head, struct list_head * entry)
{
	if(list_empty(head))
		return;
	if(list_is_singular(head) &&
		(head->next != entry && head != entry))
		return;
	if(entry == head)
		init_list_head(list);
	else
		__list_cut_position(list, head, entry);
}

/**
 * list_cut_before - cut a list into two, before given entry
 * @list: a new list to add all removed entries
 * @head: a list with entries
 * @entry: an entry within head, could be the head itself
 *
 * This helper moves the initial part of @head, up to but
 * excluding @entry, from @head to @list.  You should pass
 * in @entry an element you know is on @head.  @list should
 * be an empty list or a list you do not care about losing
 * its data.
 * If @entry == @head, all entries on @head are moved to
 * @list.
 */
static inline void list_cut_before(struct list_head * list,
				   struct list_head * head,
				   struct list_head * entry)
{
	if (head->next == entry)
	{
		init_list_head(list);
		return;
	}
	list->next = head->next;
	list->next->prev = list;
	list->prev = entry->prev;
	list->prev->next = list;
	head->next = entry;
	entry->prev = head;
}

static inline void __list_splice(const struct list_head * list,
				 struct list_head * prev,
				 struct list_head * next)
{
	struct list_head * first = list->next;
	struct list_head * last = list->prev;

	first->prev = prev;
	prev->next = first;

	last->next = next;
	next->prev = last;
}

/**
 * list_splice - join two lists, this is designed for stacks
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice(const struct list_head * list,
				struct list_head * head)
{
	if(!list_empty(list))
		__list_splice(list, head, head->next);
}

/**
 * list_splice_tail - join two lists, each list being a queue
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice_tail(struct list_head * list,
				struct list_head * head)
{
	if(!list_empty(list))
		__list_splice(list, head->prev, head);
}

/**
 * list_splice_init - join two lists and reinitialise the emptied list.
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * The list at @list is reinitialised
 */
static inline void list_splice_init(struct list_head * list,
				    struct list_head * head)
{
	if(!list_empty(list))
	{
		__list_splice(list, head, head->next);
		init_list_head(list);
	}
}

/**
 * list_splice_tail_init - join two lists and reinitialise the emptied list
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * Each of the lists is a queue.
 * The list at @list is reinitialised
 */
static inline void list_splice_tail_init(struct list_head * list,
					 struct list_head * head)
{
	if(!list_empty(list))
	{
		__list_splice(list, head->prev, head);
		init_list_head(list);
	}
}

/**
 * list_entry - get the struct for this entry
 * @ptr:	the &struct list_head pointer.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 */
#define list_entry(ptr, type, member) \
	container_of(ptr, type, member)

/**
 * list_first_entry - get the first element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_first_entry(ptr, type, member) \
	list_entry((ptr)->next, type, member)

/**
 * list_last_entry - get the last element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_last_entry(ptr, type, member) \
	list_entry((ptr)->prev, type, member)

/**
 * list_first_entry_or_null - get the first element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 *
 * Note that if the list is empty, it returns NULL.
 */
#define list_first_entry_or_null(ptr, type, member) ({ \
	struct list_head * head__ = (ptr); \
	struct list_head * pos__ = head__->next; \
	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
})

/**
 * list_next_entry - get the next element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_next_entry(pos, member) \
	list_entry((pos)->member.next, typeof(*(pos)), member)

/**
 * list_prev_entry - get the prev element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_prev_entry(pos, member) \
	list_entry((pos)->member.prev, typeof(*(pos)), member)

/**
 * list_for_each	-	iterate over a list
 * @pos:	the &struct list_head to use as a loop cursor.
 * @head:	the head for your list.
 */
#define list_for_each(pos, head) \
	for (pos = (head)->next; pos != (head); pos = pos->next)

/**
 * list_for_each_prev	-	iterate over a list backwards
 * @pos:	the &struct list_head to use as a loop cursor.
 * @head:	the head for your list.
 */
#define list_for_each_prev(pos, head) \
	for (pos = (head)->prev; pos != (head); pos = pos->prev)

/**
 * list_for_each_safe - iterate over a list safe against removal of list entry
 * @pos:	the &struct list_head to use as a loop cursor.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
#define list_for_each_safe(pos, n, head) \
	for (pos = (head)->next, n = pos->next; pos != (head); \
		pos = n, n = pos->next)

/**
 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
 * @pos:	the &struct list_head to use as a loop cursor.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
#define list_for_each_prev_safe(pos, n, head) \
	for (pos = (head)->prev, n = pos->prev; \
	     pos != (head); \
	     pos = n, n = pos->prev)

/**
 * list_for_each_entry	-	iterate over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry(pos, head, member) \
	for (pos = list_first_entry(head, typeof(*pos), member); \
	     &pos->member != (head); \
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_reverse - iterate backwards over list of given type.
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member) \
	for (pos = list_last_entry(head, typeof(*pos), member); \
	     &pos->member != (head); \
	     pos = list_prev_entry(pos, member))

/**
 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
 * @pos:	the type * to use as a start point
 * @head:	the head of the list
 * @member:	the name of the list_head within the struct.
 *
 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
 */
#define list_prepare_entry(pos, head, member) \
	((pos) ? : list_entry(head, typeof(*pos), member))

/**
 * list_for_each_entry_continue - continue iteration over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define list_for_each_entry_continue(pos, head, member) \
	for (pos = list_next_entry(pos, member); \
	     &pos->member != (head); \
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_continue_reverse - iterate backwards from the given point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define list_for_each_entry_continue_reverse(pos, head, member) \
	for (pos = list_prev_entry(pos, member); \
	     &pos->member != (head); \
	     pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_from - iterate over list of given type from the current point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member) \
	for (; &pos->member != (head); \
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_from_reverse - iterate backwards over list of given type
 *                                    from the current point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, continuing from current position.
 */
#define list_for_each_entry_from_reverse(pos, head, member) \
	for (; &pos->member != (head); \
	     pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member) \
	for (pos = list_first_entry(head, typeof(*pos), member), \
		n = list_next_entry(pos, member); \
	     &pos->member != (head); \
	     pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_continue - continue list iteration safe against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member) \
	for (pos = list_next_entry(pos, member), \
		n = list_next_entry(pos, member); \
	     &pos->member != (head); \
	     pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate over list of given type from current point, safe against
 * removal of list entry.
 */
#define list_for_each_entry_safe_from(pos, n, head, member) \
	for (n = list_next_entry(pos, member); \
	     &pos->member != (head); \
	     pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, safe against removal
 * of list entry.
 */
#define list_for_each_entry_safe_reverse(pos, n, head, member) \
	for (pos = list_last_entry(head, typeof(*pos), member), \
		n = list_prev_entry(pos, member); \
	     &pos->member != (head); \
	     pos = n, n = list_prev_entry(n, member))

/**
 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
 * @pos:	the loop cursor used in the list_for_each_entry_safe loop
 * @n:		temporary storage used in list_for_each_entry_safe
 * @member:	the name of the list_head within the struct.
 *
 * list_safe_reset_next is not safe to use in general if the list may be
 * modified concurrently (eg. the lock is dropped in the loop body). An
 * exception to this is if the cursor element (pos) is pinned in the list,
 * and list_safe_reset_next is called after re-taking the lock and before
 * completing the current iteration of the loop body.
 */
#define list_safe_reset_next(pos, n, member) \
	n = list_next_entry(pos, member)

/*
 * Double linked lists with a single pointer list head.
 * Mostly useful for hash tables where the two pointer list head is
 * too wasteful.
 * You lose the ability to access the tail in O(1).
 */
struct hlist_head {
	struct hlist_node * first;
};

struct hlist_node {
	struct hlist_node * next, ** pprev;
};

#define HLIST_HEAD(name) \
	struct hlist_head name = { .first = NULL }

static inline void init_hlist_head(struct hlist_head * hlist)
{
	hlist->first = NULL;
}

static inline void init_hlist_node(struct hlist_node * h)
{
	h->next = NULL;
	h->pprev = NULL;
}

static inline int hlist_unhashed(const struct hlist_node * h)
{
	return !h->pprev;
}

static inline int hlist_empty(const struct hlist_head * h)
{
	return !h->first;
}

static inline void __hlist_del(struct hlist_node * n)
{
	struct hlist_node * next = n->next;
	struct hlist_node ** pprev = n->pprev;

	*pprev = next;
	if(next)
		next->pprev = pprev;
}

static inline void hlist_del(struct hlist_node * n)
{
	__hlist_del(n);
	n->next = 0;
	n->pprev = 0;
}

static inline void hlist_del_init(struct hlist_node * n)
{
	if(!hlist_unhashed(n))
	{
		__hlist_del(n);
		init_hlist_node(n);
	}
}

static inline void hlist_add_head(struct hlist_node * n, struct hlist_head * h)
{
	struct hlist_node * first = h->first;
	n->next = first;
	if(first)
		first->pprev = &n->next;
	h->first = n;
	n->pprev = &h->first;
}

/* next must be != NULL */
static inline void hlist_add_before(struct hlist_node * n,
					struct hlist_node * next)
{
	n->pprev = next->pprev;
	n->next = next;
	next->pprev = &n->next;
	*(n->pprev) = n;
}

static inline void hlist_add_behind(struct hlist_node * n,
				    struct hlist_node * prev)
{
	n->next = prev->next;
	prev->next = n;
	n->pprev = &prev->next;

	if(n->next)
		n->next->pprev = &n->next;
}

/* after that we'll appear to be on some hlist and hlist_del will work */
static inline void hlist_add_fake(struct hlist_node * n)
{
	n->pprev = &n->next;
}

static inline int hlist_fake(struct hlist_node * h)
{
	return h->pprev == &h->next;
}

/*
 * Check whether the node is the only node of the head without
 * accessing head:
 */
static inline int hlist_is_singular_node(struct hlist_node * n, struct hlist_head * h)
{
	return !n->next && n->pprev == &h->first;
}

/*
 * Move a list from one list head to another. Fixup the pprev
 * reference of the first entry if it exists.
 */
static inline void hlist_move_list(struct hlist_head * old,
				   struct hlist_head * new)
{
	new->first = old->first;
	if(new->first)
		new->first->pprev = &new->first;
	old->first = NULL;
}

#define hlist_entry(ptr, type, member) \
	container_of(ptr, type, member)

#define hlist_for_each(pos, head) \
	for (pos = (head)->first; pos; pos = pos->next)

#define hlist_for_each_safe(pos, n, head) \
	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
	     pos = n)

#define hlist_entry_safe(ptr, type, member) \
	({ typeof(ptr) ____ptr = (ptr); \
	   ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
	})

/**
 * hlist_for_each_entry	- iterate over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry(pos, head, member) \
	for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member); \
	     pos; \
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
 * @pos:	the type * to use as a loop cursor.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_continue(pos, member) \
	for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member); \
	     pos; \
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
 * @pos:	the type * to use as a loop cursor.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_from(pos, member) \
	for (; pos; \
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:	the type * to use as a loop cursor.
 * @n:		another &struct hlist_node to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_safe(pos, n, head, member) \
	for (pos = hlist_entry_safe((head)->first, typeof(*pos), member); \
	     pos && ({ n = pos->member.next; 1; }); \
	     pos = hlist_entry_safe(n, typeof(*pos), member))

#ifdef __cplusplus
}
#endif

#endif /* __LIST_H__ */

hmap.h

#ifndef __HMAP_H__
#define __HMAP_H__

#ifdef __cplusplus
extern "C" {
#endif

#include "list.h"

struct hmap_entry_t {
	struct hlist_node node;
	struct list_head head;
	char * key;
	void * value;
};

struct hmap_t {
	struct hlist_head * hash;
	struct list_head list;
	unsigned int size;
	unsigned int n;
	void (*callback)(struct hmap_t * m, struct hmap_entry_t * e);
};

#define hmap_for_each_entry(entry, m) \
	list_for_each_entry(entry, &(m)->list, head)

#define hmap_for_each_entry_reverse(entry, m) \
	list_for_each_entry_reverse(entry, &(m)->list, head)

struct hmap_t * hmap_alloc(int size, void (*cb)(struct hmap_t *, struct hmap_entry_t *));
void hmap_free(struct hmap_t * m);
void hmap_clear(struct hmap_t * m);
void hmap_add(struct hmap_t * m, const char * key, void * value);
void hmap_remove(struct hmap_t * m, const char * key);
void hmap_sort(struct hmap_t * m);
void * hmap_search(struct hmap_t * m, const char * key);

#ifdef __cplusplus
}
#endif

#endif /* __HMAP_H__ */

hmap.c

#include "stddef.h"
#include <string.h>
#include "list.h"
#include "hmap.h"
#include <stdlib.h>
#include "log2.h"

struct hmap_t * hmap_alloc(int size, void (*cb)(struct hmap_t *, struct hmap_entry_t *))
{
	struct hmap_t * m;
	int i;

	if(size < 16)
		size = 16;
	if(size & (size - 1))
		size = roundup_pow_of_two(size);

	m = malloc(sizeof(struct hmap_t));
	if(!m)
		return NULL;

	m->hash = malloc(sizeof(struct hlist_head) * size);
	if(!m->hash)
	{
		free(m);
		return NULL;
	}
	for(i = 0; i < size; i++)
		init_hlist_head(&m->hash[i]);
	init_list_head(&m->list);
	m->size = size;
	m->n = 0;
	m->callback = cb;

	return m;
}

void hmap_free(struct hmap_t * m)
{
	if(m)
	{
		hmap_clear(m);
		free(m->hash);
		free(m);
	}
}

void hmap_clear(struct hmap_t * m)
{
	struct hmap_entry_t * pos, * n;

	if(m)
	{
		list_for_each_entry_safe(pos, n, &m->list, head)
		{
			hlist_del(&pos->node);
			list_del(&pos->head);
			m->n--;
			if(m->callback)
				m->callback(m, pos);
			free(pos->key);
			free(pos);
		}
	}
}

static void hmap_resize(struct hmap_t * m, unsigned int size)
{
	struct hmap_entry_t * pos, * n;
	struct hlist_head * hash;
	int i;

	if(!m)
		return;

	if(size < 16)
		size = 16;
	if(size & (size - 1))
		size = roundup_pow_of_two(size);

	hash = malloc(sizeof(struct hlist_head) * size);
	if(!hash)
		return;
	for(i = 0; i < size; i++)
		init_hlist_head(&hash[i]);

	list_for_each_entry_safe(pos, n, &m->list, head)
	{
		hlist_del(&pos->node);
	}
	free(m->hash);

	m->hash = hash;
	m->size = size;
	list_for_each_entry_safe(pos, n, &m->list, head)
	{
		hlist_add_head(&pos->node, &m->hash[shash(pos->key) & (m->size - 1)]);
	}
}

void hmap_add(struct hmap_t * m, const char * key, void * value)
{
	struct hmap_entry_t * pos;
	struct hlist_node * n;

	if(!m || !key)
		return;

	hlist_for_each_entry_safe(pos, n, &m->hash[shash(key) & (m->size - 1)], node)
	{
		if(strcmp(pos->key, key) == 0)
		{
			if(pos->value != value)
				pos->value = value;
			return;
		}
	}

	if(m->n > (m->size >> 1))
		hmap_resize(m, m->size << 1);

	pos = malloc(sizeof(struct hmap_entry_t));
	if(!pos)
		return;

	pos->key = strdup(key);
	pos->value = value;
	init_hlist_node(&pos->node);
	hlist_add_head(&pos->node, &m->hash[shash(pos->key) & (m->size - 1)]);
	init_list_head(&pos->head);
	list_add_tail(&pos->head, &m->list);
	m->n++;
}

void hmap_remove(struct hmap_t * m, const char * key)
{
	struct hmap_entry_t * pos;
	struct hlist_node * n;

	if(!m || !key)
		return;

	if((m->size > 16) && (m->n < (m->size >> 1)))
		hmap_resize(m, m->size >> 1);

	hlist_for_each_entry_safe(pos, n, &m->hash[shash(key) & (m->size - 1)], node)
	{
		if(strcmp(pos->key, key) == 0)
		{
			hlist_del(&pos->node);
			list_del(&pos->head);
			m->n--;
			free(pos->key);
			free(pos);
			return;
		}
	}
}

void * hmap_search(struct hmap_t * m, const char * key)
{
	struct hmap_entry_t * pos;
	struct hlist_node * n;

	if(!m || !key)
		return NULL;

	hlist_for_each_entry_safe(pos, n, &m->hash[shash(key) & (m->size - 1)], node)
	{
		if(strcmp(pos->key, key) == 0)
			return pos->value;
	}
	return NULL;
}

main.c

#include <stdio.h>
#include <stdlib.h>
#include "hmap.h"

static void hmap_entry_callback(struct hmap_t * m, struct hmap_entry_t * e)
{                                                             
    if(e)               
    {
		//free(e->value);           
    }
} 

int main(void)
{
	struct hmap_t *map = hmap_alloc(128, hmap_entry_callback);
	if(map == NULL)
	{
		perror("fatal error.\n");
		return -1;
	}

	hmap_add(map, "wife", "weixin");
	hmap_add(map, "husband", "caozilong");
	hmap_add(map, "son", "caoyikang");

	printf("wife %s.\n", (char*)hmap_search(map, "wife"));
	printf("son %s.\n", (char*)hmap_search(map, "son"));
	printf("husband %s.\n", (char*)hmap_search(map, "husband"));
	hmap_remove(map, "husband");
	printf("husband %s.\n", (char*)hmap_search(map, "husband"));

	hmap_free(map);
	return 0;
}

添加释放

#include <stdio.h>
#include <stdlib.h>
#include "hmap.h"

static void hmap_entry_callback(struct hmap_t * m, struct hmap_entry_t * e)
{                                                             
    if(e)               
    {
		printf("%s line %d, key %s value %s.\n", __func__, __LINE__, (char*)e->key, (char*)e->value);
		//free(e->key);           
    }
} 

int main(void)
{
	struct hmap_t *map = hmap_alloc(128, hmap_entry_callback);
	if(map == NULL)
	{
		perror("fatal error.\n");
		return -1;
	}

	hmap_add(map, "wife", "weixin");
	hmap_add(map, "husband", "caozilong");
	hmap_add(map, "son", "caoyikang");

	printf("wife %s.\n", (char*)hmap_search(map, "wife"));
	printf("son %s.\n", (char*)hmap_search(map, "son"));
	printf("husband %s.\n", (char*)hmap_search(map, "husband"));
	hmap_remove(map, "husband");
	printf("husband %s.\n", (char*)hmap_search(map, "husband"));

	hmap_free(map);
	return 0;
}

LIST_HEAD

  1 #include <stdio.h>
  2
  3 int main(void)
  4 {
  5     int i = 0;
  6
  7     for(i = 0, printf("%s line %d, loop left.\n", __func__, __LINE__) ; \
  8             printf("%s line %d, loop mid.\n", __func__, __LINE__), i < 3; \
  9             i ++, printf("%s line %d, loop right.\n", __func__, __LINE__))
 10     {
 11         printf("%s line %d, loop body, i %d.\n", __func__, __LINE__, i);
 12     }
 13
 14     return 0;
 15 }
~/Workspace/for$ ./a.out
main line 7, loop left.
main line 8, loop mid.
main line 11, loop body, i 0.
main line 9, loop right.
main line 8, loop mid.
main line 11, loop body, i 1.
main line 9, loop right.
main line 8, loop mid.
main line 11, loop body, i 2.
main line 9, loop right.
main line 8, loop mid.
~/Workspace/for$

list_for_each_entry/list_for_each

1.list_for_each和list_for_each_entry都是遍历链表的两个宏,本质上都是for循环。
2.他们做的事情本质上都一样,判断链表项是不是链表头,指向链表的下一项。
3.他们的区别:list_for_each遍历的链表,其链表项不属于某个结构体。或者说不关心它是不是包含在某个结构体中,head为起始位置和判断位置,但是HEAD本身并不会作为循环体中的引用成员。
list_for_each_entry遍历的链表,其每一项都是某个结构体中的成员,单纯遍历链表还不行,还要找到包含这个链表项的结构体的地址,从而为下一步应用该结构体做好准备。和list_for_each类似,head可以属于某个结构体,也可以不属于,作为起始索引位置和结束判断条件,循环体中不会出现此对象。

如果一个已经挂入链表的ENTRY再次加入,会不会有BUG?

当然会,这样做会破坏链表结构,导致不可预知的错误,而且这种错误都非常难查。如果把链表堪称连接件,连接件被挪动位置了,但是原来的位置指向连接件的指针仍然没有变,变化的只是连接件自己发出的指针换了位置,这样的破碎链表是完不成任务的。

Linux内核既有HASH框架实现

Linux hashtable既有实现在头文件include/linux/hashtable.h中。

定义:

DEFINE_HASHTABLE

DEFINE_READ_MOSTLY_HASHTABLE

DECLARE_HASHTABLE

操作

hash_init

hash_add

hash_add_rcu

hash_empty

hash_del

hash_del_rcu

为何HASH表的长度最好是质数?

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int hash_func(int idx, int tblsize)
{
	return idx % tblsize;
}

#define DATA_NUM (1000000UL)
int main(int argc, char **argv)
{
	int i;
	int *hash_table;
	int interval, table_size, data_size;
	float ratio, sum = 0.0f;
	if (argc != 3) {
		fprintf(stderr, "%s line %d, please use like this ./program interval hashsize.\n",
		        __func__, __LINE__);

		return -1;
	}

	interval = atoi(argv[1]);
	table_size = atoi(argv[2]);

	printf("%s line %d, interval %d, table size %d.\n", __func__, __LINE__, interval, table_size);

	data_size = sizeof(int) * table_size;
	hash_table = malloc(data_size);
	if (hash_table == NULL) {
		fprintf(stderr, "%s line %d, alloc buffer failure.\n",
		        __func__, __LINE__);

		return -1;
	}

	memset(hash_table, 0x00, data_size);

	for (i = 0; i < DATA_NUM; i++) {
		int entry = hash_func(i * interval, table_size);
		hash_table[entry]++;
	}

	for (i = 0; i < table_size; i++) {
		float r = hash_table[i] / (double)DATA_NUM;
		printf("hash_table[%d]: %f.\n", i, r);
		sum += r;
	}

	printf("sum %f.\n", sum);
	free(hash_table);

	return 0;
}

./program 程序key间隔 HASH表长度:

如果key间隔是1,则HASH表长度是不是素数无所谓。

但是当key间隔不是1的时候,素数长度的HASH表将会减少冲突可能:

参考文档

算法分析:哈希表的大小为何是素数_哈希函数为什么要质数-优快云博客


结束

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