我需要创建一个共享内存段，使用我创建的结构来保存节点
struct a_list
{
//The head of the list that acts as a node, this list has a next* and a prev*
struct list_head list;
unsigned long* val;
char* str;
char state;
};
我尝试在堆栈上查找答案，但他们实现了一个Node而不是我的struct，这是一个包含节点的列表
我也有这个缓冲区和追加方法，我曾经附加到这个列表中（使用malloc）但是我知道对于共享内存我不能这样做
struct buffer
{
struct a_list* buffer[BUFFER_SIZE];
int in;
int out;
};
//Method to append a file to the end of the queue (Most recently used files are at the tail)
static void append(struct a_list* ptr,const char* str, unsigned long val)
{
struct a_list* tmp;
tmp = (struct a_list*)malloc(sizeof(struct a_list));
// tmp->str = str;
tmp->str = (char *)malloc(strlen(str)+1);
strcpy(tmp->str, str);
tmp->val = (unsigned long*)malloc(sizeof(unsigned long));
memcpy(tmp->val, &val, sizeof(unsigned long));
tmp->index = (int *)malloc(sizeof(int));
memcpy(tmp->index, &buffer_p->in, sizeof(int));
tmp->address = (struct a_list*)malloc(sizeof(struct a_list*));
memcpy(tmp->address, &fileQueue, sizeof(struct a_list*));
if(list_empty(&fileQueue.list)){ //If this is the first element to be inserted into the fileQueue, initialize the head
list_add_tail( &(tmp->list), &(ptr->list) );
head = list_entry(fileQueue.list.next,struct a_list, list);
}
else{ //Else just add it to the tail of the list
list_add_tail( &(tmp->list), &(ptr->list) );
}
// while(((buffer_p->in+1)%BUFFER_SIZE) == buffer_p->out)
// ;
buffer_p->buffer[buffer_p->in] = tmp->address;
//printf("Placed: %d\n", counter);
buffer_p->in = (buffer_p->in+1) % BUFFER_SIZE;
}
在我的主要内容中，我尝试使用
初始化所有内容if ((shmid = shmget(key, (BUFFER_SIZE+2)*sizeof(int), IPC_CREAT | 0666)) < 0) {
perror("shmget");
exit(1);
}
if ((shm = shmat(shmid, NULL, 0)) < 0) {
perror("shmat");
exit(1);
}
buffer_p = (struct buffer*) shm;
buffer_p->in = 0;
buffer_p->out = 0;
我不喜欢这是如何工作的，因为我指的是一个指向某些东西的东西（它不能使用共享内存）所以我想要改变这样它实际上可以使用共享内存。我已经在共享内存上使用了Beej的指南作为指南以及几个堆栈溢出问题但似乎没有给我这个特定的情况（或者至少我不理解答案）。任何帮助都会受到赞赏，即使它只是一个可能缺失的概念。 a_list结构（fileQueue）中的list_head结构是引用内核链表实现的头文件中的结构。
编辑：这是在这个程序中使用的list_head结构，它基本上是使用列表的内核实现
/**
*
* I grub it from linux kernel source code and fix it for user space
* program. Of course, this is a GPL licensed header file.
*
* Here is a recipe to cook list.h for user space program
*
* 1. copy list.h from linux/include/list.h
* 2. remove
* - #ifdef __KERNE__ and its #endif
* - all #include line
* - prefetch() and rcu related functions
* 3. add macro offsetof() and container_of
*
* - kazutomo@mcs.anl.gov
*/
#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H
/**
* @name from other kernel headers
*/
/*@{*/
/**
* Get offset of a member
*/
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
/**
* Casts a member of a structure out to the containing structure
* @param ptr the pointer to the member.
* @param type the type of the container struct this is embedded in.
* @param member the name of the member within the struct.
*
*/
#define container_of(ptr, type, member) ({ \
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
/*@}*/
/*
* These are non-NULL pointers that will result in page faults
* under normal circumstances, used to verify that nobody uses
* non-initialized list entries.
*/
#define LIST_POISON1 ((void *) 0x00100100)
#define LIST_POISON2 ((void *) 0x00200200)
/**
* 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_INIT(name) { &(name), &(name) }
#define LIST_HEAD(name) \
struct list_head name = LIST_HEAD_INIT(name)
#define INIT_LIST_HEAD(ptr) do { \
(ptr)->next = (ptr); (ptr)->prev = (ptr); \
} while (0)
/*
* 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(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}
/**
* 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->prev, entry->next);
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(list->prev, list->next);
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(list->prev, list->next);
list_add_tail(list, 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;
}
static inline void __list_splice(struct list_head *list,
struct list_head *head)
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
struct list_head *at = head->next;
first->prev = head;
head->next = first;
last->next = at;
at->prev = last;
}
/**
* list_splice - join two lists
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static inline void list_splice(struct list_head *list, struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, 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);
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_struct within the struct.
*/
#define list_entry(ptr, type, member) \
container_of(ptr, type, member)
/**
* list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop counter.
* @head: the head for your list.
*/
#define list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); \
pos = pos->next)
/**
* __list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop counter.
* @head: the head for your list.
*
* This variant differs from list_for_each() in that it's the
* simplest possible list iteration code, no prefetching is done.
* Use this for code that knows the list to be very short (empty
* or 1 entry) most of the time.
*/
#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 counter.
* @head: the head for your list.
*/
#define list_for_each_prev(pos, head) \
for (pos = (head)->prev; prefetch(pos->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 counter.
* @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_entry - iterate over list of given type
* @pos: the type * to use as a loop counter.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry(pos, head, member) \
for (pos = list_entry((head)->next, typeof(*pos), member); \
pos->member != (head); \
pos = list_entry(pos->member->next, typeof(*pos), member))
/**
* list_for_each_entry_reverse - iterate backwards over list of given type.
* @pos: the type * to use as a loop counter.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_reverse(pos, head, member) \
for (pos = list_entry((head)->prev, typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.prev, typeof(*pos), member))
/**
* list_prepare_entry - prepare a pos entry for use as a start point 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_struct within the struct.
*/
#define list_prepare_entry(pos, head, member) \
((pos) ? : list_entry(head, typeof(*pos), member))
/**
* list_for_each_entry_continue - iterate over list of given type
* continuing after existing point
* @pos: the type * to use as a loop counter.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_continue(pos, head, member) \
for (pos = list_entry(pos->member.next, typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*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 counter.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_safe(pos, n, head, member) \
for (pos = list_entry((head)->next, typeof(*pos), member), \
n = list_entry(pos->member.next, typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, typeof(*n), member))
/**
* list_for_each_entry_safe_continue - iterate over list of given type
* continuing after existing point safe against removal of list entry
* @pos: the type * to use as a loop counter.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_safe_continue(pos, n, head, member) \
for (pos = list_entry(pos->member.next, typeof(*pos), member), \
n = list_entry(pos->member.next, typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, typeof(*n), member))
/**
* list_for_each_entry_safe_reverse - iterate backwards over list of given type safe against
* removal of list entry
* @pos: the type * to use as a loop counter.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_safe_reverse(pos, n, head, member) \
for (pos = list_entry((head)->prev, typeof(*pos), member), \
n = list_entry(pos->member.prev, typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.prev, typeof(*n), 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_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
#define INIT_HLIST_NODE(ptr) ((ptr)->next = NULL, (ptr)->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 = LIST_POISON1;
n->pprev = LIST_POISON2;
}
static inline void hlist_del_init(struct hlist_node *n)
{
if (n->pprev) {
__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_after(struct hlist_node *n,
struct hlist_node *next)
{
next->next = n->next;
n->next = next;
next->pprev = &n->next;
if(next->next)
next->next->pprev = &next->next;
}
#define hlist_entry(ptr, type, member) container_of(ptr,type,member)
#define hlist_for_each(pos, head) \
for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
pos = pos->next)
#define hlist_for_each_safe(pos, n, head) \
for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
pos = n)
/**
* hlist_for_each_entry - iterate over list of given type
* @tpos: the type * to use as a loop counter.
* @pos: the &struct hlist_node to use as a loop counter.
* @head: the head for your list.
* @member: the name of the hlist_node within the struct.
*/
#define hlist_for_each_entry(tpos, pos, head, member) \
for (pos = (head)->first; \
pos && ({ prefetch(pos->next); 1;}) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
pos = pos->next)
/**
* hlist_for_each_entry_continue - iterate over a hlist continuing after existing point
* @tpos: the type * to use as a loop counter.
* @pos: the &struct hlist_node to use as a loop counter.
* @member: the name of the hlist_node within the struct.
*/
#define hlist_for_each_entry_continue(tpos, pos, member) \
for (pos = (pos)->next; \
pos && ({ prefetch(pos->next); 1;}) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
pos = pos->next)
/**
* hlist_for_each_entry_from - iterate over a hlist continuing from existing point
* @tpos: the type * to use as a loop counter.
* @pos: the &struct hlist_node to use as a loop counter.
* @member: the name of the hlist_node within the struct.
*/
#define hlist_for_each_entry_from(tpos, pos, member) \
for (; pos && ({ prefetch(pos->next); 1;}) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
pos = pos->next)
/**
* hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
* @tpos: the type * to use as a loop counter.
* @pos: the &struct hlist_node to use as a loop counter.
* @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(tpos, pos, n, head, member) \
for (pos = (head)->first; \
pos && ({ n = pos->next; 1; }) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
pos = n)
#endif
答案 0 :(得分：0)
您的第一步应该是创建malloc()和free()（也可能是realloc()）的代理，这些代理可以从共享内存而不是普通堆内存管理内存分配。您可以与大多数其余代码分开调试它们。他们需要知道共享内存块的总体大小，并且需要记录分配的内容或者空闲内容（或两者）。如果内存在进程之间共享，则控制信息也需要在共享内存中（否则只有一个进程可以修改内存分配），并且需要适当的并发控制（互斥等）来保护它。如果进程之间没有共享内存，则不应该首先使用共享内存。
使用这些原语后，您可以修改代码，以便在需要分配空间时将它们用于代码中的内存分配。
请注意，您的代码会为unsigned long val成员分配一个struct a_list。这是毫无意义的。您只是使用指针而不是直接存储在结构中的unsigned long来浪费空间。如果它是unsigned long的数组，那将是另一回事，但这不是你所展示的。
您的问题还会显示对index struct a_list成员的访问权限，该成员未在结构定义中显示。而且您没有显示struct list_head类型。这意味着人们无法编译您的代码以观察是否存在其他问题。制作可编译的代码是个好主意。值得花时间创建MCVE（How to create a Minimal, Complete, and Verifiable Example?）或SSCCE（Short, Self-Contained, Correct Example） - 两个名称和链接用于相同的基本想法。
答案 1 :(得分：0)
这是我的解决方法：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/shm.h>
#define MAX_SHM_ID_NUM 100
typedef struct node
{
int val;
struct node * next;
} node;
int shm_id_arr[MAX_SHM_ID_NUM];
int current_index = -1 ;
void insert_at_tail (int num);
node * my_head = NULL;
int * num_of_elements = NULL ;
key_t key_first = 5681;
key_t key_current;
void * my_malloc(int size)
{
void * ptr = NULL;
key_current = key_first ++;
int shm_id;
if ((shm_id = shmget(key_current, size , IPC_CREAT | 0666)) < 0) {
perror("shmget error.");printf("errno= %d EINVAL=%d \n ", errno , EINVAL);
return NULL;
}
if ((ptr = shmat(shm_id, NULL, 0)) == (void *) - 1) {
perror("shmat error");
//exit(1);
return NULL;
}
current_index ++ ;
shm_id_arr[current_index] = shm_id ;
return ptr;
}
void insert_at_tail (int num)
{
if(my_head == NULL)
{
my_head = my_malloc(sizeof(node));
my_head->val = num;
my_head->next = NULL;
}else
{
node * tmp = my_head;
while(tmp->next != NULL)
tmp = tmp->next;
tmp->next = my_malloc(sizeof(node));
tmp->next->val = num;
tmp->next->next = NULL;
}
(* num_of_elements) ++;
}
/* deAttach the shared memory without removing. */
void deattach_shared_mem()
{
if (shmdt(num_of_elements) < 0) { /* deAttach num_of_elements */
perror("shmdt error num_of_elements\n");
}
if (shmdt(my_head) < 0) {
perror("shmdt error my_head\n");
}
//how to deattach all pointers in list?
}
void remove_shared_mem()
{
int i;
for(i = 0 ; i < current_index ; i ++)
{
if (shmctl(shm_id_arr[i], IPC_RMID, NULL) < 0) { /* remove the shared memory segment. */
perror("shmctl error.\n");
}
}
}
void print_it()
{
node * tmp = my_head;
while(tmp != NULL)
{
printf("%d\n" , tmp->val);
tmp = tmp->next;
}
}
int main()
{
num_of_elements = (int *)my_malloc(sizeof(int));
(* num_of_elements) = 0 ;
insert_at_tail(10);
insert_at_tail(8);
insert_at_tail(6);
insert_at_tail(4);
insert_at_tail(2);
printf("we have %d elements.\n" , (*num_of_elements));
print_it();
deattach_shared_mem();
remove_shared_mem();
return 0 ;
}