//結構體相關的高級話題#include "stdio.h" #include "stdlib.h" #include "string.h" //定義一個結構體，就相當于各個變量的偏移量也定下來了 struct student {char name[32]; //32個字節int age; //4個字節char *na; //4個字節 };int main() {struct student s = {"Mr.right" , 24 , "Victory"};struct student *p = &s;p = p+1;p = 0; //p = p - p; //此時 p 相當于 ((struct student *)0)int i = (int )(&(p->name)); //0 int i = (int)(&(((struct student *)0)->name))int j = (int )(&(p->age)); //32 int j = (int)(&(((struct student *)0)->age))int k = (int )(&(p->na)); //36 int k = (int)(&(((struct student *)0)->na))int m = (int)&(((struct student *)0)->name);//把0地址空間進行類型轉換，轉換為struct student *的結構體指針；此處 //再指向結構體中的age； 此處->是一個尋址操作，就是計算age的地址在哪里，沒有往age所指向的內存空間讀寫數據//尋址操作對CPU來講，只不過是一個+-*/操作 //再取地址 ； //在把地址轉換成十進制 } ==================================================================================//【疑問】為什么講上面的知識：(int)&(((struct student *)0)->age)？ //【答】是為了引出“Linux內核鏈表了解”！Linux內核鏈表了解: //不是鏈表包含業務結點 //而是業務結點包含鏈表//如何從鏈表結點的位置找到業務結點的位置呢？#define offsetof(TYPE,MEMBER) ((size_t)&((TYPE*)0)->MEMBER) //求出MEMBER相對于TYPE結構體的偏移量offset#define container_of(ptr,type,member) (type*)((char*)ptr - offsetof(type,member)) //求整個結構體的偏移量

下圖是Linux內核鏈表的示意圖：可以通過鏈表結點，根據偏移量offset找到
業務結點的起始地址，對業務結點進行操作。

============================================================================

上述圖簡單介紹了公司的業務數據的設計，代碼如下：
實現：讓業務結點和鏈表結點進行有效的分離

#include<iostream> using namespace std;struct List //鏈表結點 {struct List *next; };struct student //業務結點（中有鏈表結點） {//數據元素int age;char name[100];//鏈表結點struct List node; };void insert_node(struct List *pNew,struct List *pHead) //插入鏈表結點 //注解：不用插入業務結點，實質上只要插入鏈表結點就可以（因為可以通過鏈表結點找到業務結點，并對業務結點進行訪問） {pNew->next = pHead->next; //此時用的是頭插法，打印時，輸出結果是逆序的pHead->next = pNew; }void printf_age(struct List *pHead) //打印業務結點 //就像上面說的那樣，遍歷鏈表結點，通過鏈表結點找到業務結點的入口，并對業務結點的數據元素進行訪問 {//計算偏移量int offset = (int)&(((struct student*)0)->node);//找到每一個結點的指針struct List *pCur = pHead->next;while(pCur){struct student* pCur_stu = (struct student*)((char*)pCur - offset);cout<<pCur_stu->age<<endl;pCur = pCur->next;} } int main() {struct List pHead; //定義一個鏈表頭結點pHead.next = NULL;struct student a,b,c,d;a.age = 20;b.age = 21;c.age = 22;d.age = 23;insert_node(&a.node,&pHead); //把鏈表結點插入到鏈表結點的頭結點上insert_node(&b.node,&pHead);insert_node(&c.node,&pHead);insert_node(&d.node,&pHead);printf_age(&pHead); //打印鏈表結點return 0; }

實質上可以進行“投機取巧，即永遠把鏈表結點放在業務結點的第一個位置，此時：鏈表結點相對于業務結點的偏移量offset為0.

struct List //鏈表結點 {struct List *next; };struct student //業務結點（中有鏈表結點） {//鏈表結點struct List node;//數據元素int age;char name[100]; }; 【1、企業級財富庫線性表之單鏈表開發和設計】 //linklist.h函數聲明 #ifndef _MYLINKLIST_H_ #define _MYLINKLIST_H_typedef void LinkList;typedef struct _tag_LinkListNode {struct _tag_LinkListNode* next; }LinkListNode;LinkList* LinkList_Create(); void LinkList_Destroy(LinkList* list); void LinkList_Clear(LinkList* list); int LinkList_Length(LinkList* list); int LinkList_Insert(LinkList* list, LinkListNode* node, int pos); LinkListNode* LinkList_Get(LinkList* list, int pos); LinkListNode* LinkList_Delete(LinkList* list, int pos); #endif ========================================================================= //linklist.cpp函數實現 #include "stdlib.h" #include "stdio.h" #include "string.h"#include "linklist.h"typedef struct _tag_LinkList {LinkListNode header;int length; }TLinkList;LinkList* LinkList_Create() {TLinkList *tList = (TLinkList *)malloc(sizeof(TLinkList));if (tList == NULL){return NULL;}tList->header.next = NULL;tList->length = 0;return tList; }void LinkList_Destroy(LinkList* list) {if (list != NULL){free(list);}return ; }void LinkList_Clear(LinkList* list) {TLinkList *tList = (TLinkList *)list;if (tList == NULL){return ;}tList->length = 0;tList->header.next = NULL;return ; }int LinkList_Length(LinkList* list) {TLinkList *tList = (TLinkList *)list;if (tList == NULL){return -1;}return tList->length; }int LinkList_Insert(LinkList* list, LinkListNode* pNew, int pos) {//將業務結點s中的s.node元素插入到單鏈表中int i = 0;TLinkList *tList = (TLinkList *)list;LinkListNode *current = NULL;if (tList == NULL || pNew == NULL || pos<0){return -1;}current = &tList->header; //環境初始化for (i=0; (i<pos)&&current->next!=NULL; i++ ) //尋找插入位置{current = current->next;} //插入新結點pNewpNew->next = current->next;current->next = pNew;tList->length ++;return 0; }LinkListNode* LinkList_Get(LinkList* list, int pos) {int i = 0;TLinkList *tList = (TLinkList *)list;LinkListNode *current = NULL;LinkListNode *ret = NULL;if (list==NULL || pos<0 || pos>=tList->length){return NULL;}current = &tList->header;for (i=0; i<pos; i++){current = current->next;}ret = current->next;return ret; }LinkListNode* LinkList_Delete(LinkList* list, int pos) {int i = 0;TLinkList *tList = (TLinkList *)list;LinkListNode *current = NULL;LinkListNode *ret = NULL;if (list==NULL || pos<0 || pos>=tList->length){return NULL;}//沒有初始化環境current = &tList->header;for (i=0; i<pos; i++){current = current->next;}ret = current->next;current->next = ret->next;tList->length --;return ret; } ========================================================================= //main.cpp測試程序 #include "linklist.h" #include <iostream> using namespace std;struct Student {LinkListNode node; //Linux內核原理：業務結點中有鏈表結點char name[100];int age; };void print_LinkList(void* list) //遍歷打印鏈表 {for (int i=0; i<LinkList_Length(list); i++){struct Student *tmp = (struct Student*)LinkList_Get(list, i);printf("name: %s , age: %d\n", tmp->name,tmp->age);} }int main() {Student s1; strcpy(s1.name,"Tom"); s1.age = 20;Student s2; strcpy(s2.name,"Tim"); s2.age = 21;Student s3; strcpy(s3.name,"Kim"); s3.age = 22;LinkList* list = list = LinkList_Create(); /************************************************************************/ //case1:LinkList_Insert(list,&s1.node,0); //把s1中的鏈表結點s1.node結點插入到鏈表listLinkList_Insert(list,&s2.node,0); //把s2中的鏈表結點s2.node結點插入到鏈表listLinkList_Insert(list,&s3.node,0); //把s3中的鏈表結點s3.node結點插入到鏈表list//LinkList_Insert(list,(LinkListNode*)(&s1.node),0);//LinkList_Insert(list,(LinkListNode*)(&s2.node),0);//LinkList_Insert(list,(LinkListNode*)(&s3.node),0); //case2://LinkList_Insert(list,(LinkListNode*)(&s1),0);//LinkList_Insert(list,(LinkListNode*)(&s2),0);//LinkList_Insert(list,(LinkListNode*)(&s3),0);print_LinkList(list); /************************************************************************/cout<<"刪除結點"<<endl;LinkList_Delete(list,1);print_LinkList(list);} /************************************************************************/ /************************************************************************/ 【2、企業級財富庫線性表之順序存儲開發和設計】 【核心問題】業務數據 和 鏈表算法（底層庫）是如何分離的？ //seqlist.h：函數聲明 #ifndef __MY_SEQLIST_H__ #define __MY_SEQLIST_H__typedef void SeqList; typedef void SeqListNode;//疑問：為什么傳入的形參類型、返回的類型為void* ？ //答：底層不想讓別人知道我是什么結構的，也沒有必要讓別人知道SeqList* SeqList_Create(int capacity); //創建容量為capacity的順序線性表 void SeqList_Destroy(SeqList* list); //釋放線性表list void SeqList_Clear(SeqList* list); //清空線性表list int SeqList_Length(SeqList* list); int SeqList_Capacity(SeqList* list); int SeqList_Insert(SeqList* list, SeqListNode* node, int pos); SeqListNode* SeqList_Get(SeqList* list, int pos); SeqListNode* SeqList_Delete(SeqList* list, int pos); int for_each(void (*CALLBACK_print)(void*),void* list); //回調函數循環遍歷 #endif //void* SeqList_Create(int capacity); //void SeqList_Destroy(void* list); //void SeqList_Clear(void* list); //int SeqList_Length(void* list); //int SeqList_Capacity(void* list); //int SeqList_Insert(void* list, void* node, int pos); //void* SeqList_Get(void* list, int pos); //void* SeqList_Delete(void* list, int pos);=============================================================================== //seqlist.cpp：函數實現 #include "seqlist.h" #include "stdlib.h" #include "stdio.h" #include "string.h"typedef struct _tag_SeqList {int capacity; //sizeof（數組），數組實際占有的內存大小int length; //strlen（數組），數組中存放著幾個數據unsigned int *node ; //數組的頭指針 }TSeqList;//typdef的意思 把void 重新命名成SeqList/* void * SeqList_Create2(int capacity) //分配兩次內存，惡心！ {TSeqList *ret = NULL;ret = (TSeqList *)malloc(sizeof(TSeqList));if (ret == NULL){return NULL;}ret->capacity = capacity;ret->node = (unsigned int *)malloc(sizeof(unsigned int ) * capacity);if (ret->node == NULL){return NULL;}ret->length = 0;return ret; } */void * SeqList_Create(int capacity) //創建一個長度為capacity的數組,數組的數據類型是unsigned int {TSeqList *ret = NULL;if (capacity <= 0){return NULL;}ret = (TSeqList *)malloc(sizeof(TSeqList) + sizeof(unsigned int ) * capacity );//一次性全部分配內存if (ret == NULL){return NULL;}ret->capacity = capacity; ret->length = 0;ret->node = (unsigned int *)(ret + 1);return ret; }void SeqList_Destroy(SeqList* list) {if (list == NULL){return ;}free(list);return ; }void SeqList_Clear(SeqList* list) //不是釋放內存，是直接把長度設為0 {TSeqList *tlist = NULL;if (list == NULL){return ;}tlist = (TSeqList *)list;tlist->length = 0;//直接把長度設為0return ; }int SeqList_Length(SeqList* list) {TSeqList *tlist = (TSeqList *)list;if (list == NULL){return -1;}return tlist->length; }int SeqList_Capacity(SeqList* list) {TSeqList *tlist = (TSeqList *)list;if (list == NULL){return -1;}return tlist->capacity; } //注解：實際位置和下標位置總是相差1 int SeqList_Insert(SeqList* list, SeqListNode* node, int pos) //插入位置：length+1>=pos>=1 {if(list == NULL||node == NULL)return -1;TSeqList *tlist = (TSeqList*)list; //capacity空間不夠if(tlist->length >= tlist->capacity) return -2; //容錯 //插入位置length+1>=pos>=1if(pos > tlist->length+1){pos = tlist->length;}if(pos < 1){pos = 1;} //插入操作int i = tlist->length-1; //最后一個有效元素的位置while(i>=pos-1) //循環后移{tlist->node[i+1] = tlist->node[i];i--;}tlist->node[pos-1] = (unsigned int)node; //插入tlist->length++;return 0; }SeqListNode* SeqList_Get(SeqList* list, int pos) //查找位置：length>=pos>=1 {TSeqList *tlist = (TSeqList *)list;if (list== NULL || pos<1 || pos>tlist->length){return NULL;}return (SeqListNode*)tlist->node[pos-1]; }SeqListNode* SeqList_Delete(SeqList* list, int pos) //刪除位置：length>=pos>=1 {int i = 0;TSeqList *tlist = (TSeqList *)list;SeqListNode* ret = NULL;if (list == NULL || pos<1 || pos>tlist->length){return NULL;} //緩存要刪除的結點ret = (SeqListNode*)tlist->node[pos-1]; //對鏈表元素值循環前移i = pos-1;while(i<=tlist->length-1){tlist->node[i] = tlist->node[i+1];i++;} //刪除后，長度-1tlist->length --;return ret; }int for_each(void (*CALLBACK_print)(void*),void* list) {if(list == NULL)return -1;(*CALLBACK_print)(list);return 0; } =============================================================================== //線性表順序存儲測試.cpp:測試代碼 #include "seqlist.h" #include "stdlib.h" #include "stdio.h" #include "string.h"typedef struct _Teacher //業務結點 {char name[64];int age ; }Teacher;void CALLBACK_print(void* list) //循環遍歷的回調函數 {printf("循環遍歷：\n");for (int i=1; i<=SeqList_Length(list); i++){Teacher *tmp = (Teacher *)SeqList_Get(list, i);printf("name:%s , age:%d \n", tmp->name,tmp->age);} }void main() { //創建業務數據，并初始化Teacher t1 = {"Kobe",20};Teacher t2 = {"James",19};Teacher t3 = {"Curry",16}; //環境準備int ret = 0, i = 0;SeqList* list = NULL; //創建線性表list = SeqList_Create(10);//仔細思考：業務數據 和 鏈表算法（底層庫）是如何分離的。。。。。。//業務數據結點的管理（內存的生命周期）甩給了上層應用（業務模型） //插入ret = SeqList_Insert(list, (SeqListNode*)&t1, 1);ret = SeqList_Insert(list, (SeqListNode*)&t2, 1);ret = SeqList_Insert(list, (SeqListNode*)&t3, 1); //循環遍歷for_each(CALLBACK_print,list); //刪除 SeqList_Delete(list, 2);for_each(CALLBACK_print,list); //銷毀線性表SeqList_Destroy(list);system("pause"); }

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