03.openssl编程——堆栈-白红宇

03.openssl编程——堆栈

阅读量：2243 次

发布时间：2019-05-09

本文共 5431 字，大约阅读时间需要 18 分钟。

3.1    openssl堆栈

    堆栈是一种先进先出的数据结构。openssl大量采用堆栈来存放数据。他实现一个通用的堆栈，可以方便的存储任意数据。他实现了许多基本的堆栈操作。主要有： 

    a.堆栈拷贝(sk_dup) 

    b.构建新堆栈(sk_new_null, sk_new) 

    c.插入数据(sk_insert) 

    d.删除数据(sk_delete) 

    e.查找数据(sk_find,sk_find_ex) 

    f.入栈(sk_push) 

    h.出栈(sk_pop) 

    i.获取堆栈元素个数(sk_num) 

    j.获取堆栈值(sk_value) 

    k.设置堆栈值(sk_set) 

    l.堆栈排序(sk_sort) 

3.2 数据结构

    openssl堆栈数据结构在stack.h中定义 

    typedef struct stack_st 

{

    int num; 堆栈中存放数据的个数 

    char **data; 用于存放数据地址，每个数据地址存放在data[0]到data[num-1]中 

    int sorted; 堆栈是否已排序，如果排序则为1，否则为0，堆栈数据一般是无序的，只有当用户调用了sk_sort操作，其值才为1. 

    int num_alloc; 

    int (*comp)(const char *const *, const char *const *); 堆栈内存放数据的比较函数地址，此函数用于排序和查找操作；当用户生成一个新堆栈时，可以指定comp为函数实现的一个比较函数；或当堆栈已经存在时通过调用sk_set_cmp_func函数来重新指定比较函数。 

}

    备注：用户不需要调用底层的堆栈函数(sk_sort\sk_set_comp_func等)，而是调用他通过宏实现的各个函数。 

3.3 源码

    openssl堆栈实现源码位于crypto/stack目录下。 

    1)sk_set_cmp_func 

    此函数用于设置堆栈存放数据的比较函数。由于堆栈不知道用户存放的是什么数据，所以，比较函数必须由用户自己实现。 

    2)sk_find 

    根据数据地址来查找它在堆栈中的位置。当堆栈设置比较函数时，他首先对堆栈进行排序，然后通过二分法进行查找。如果堆栈没有设置比较半数，他只是简单的比较数据地址来查找。 

    3)sk_sort 

    本函数对堆栈数据排序。他首先根据sorted来判断是否已经排序，如果未排序则调用了C函数qsort进行快速排序 

    4)sk_pop_free 

    本函数用于释放堆栈内存放的数据以堆栈本身，他需要一个由用户指定的针对具体数据的释放函数。如果用户仅调用sk_free函数，则只会释放堆栈本身所用的内存，而不会释放数据内存。 

3.4 定义用户自己的堆栈函数 

    用户直接调用最底层的堆栈操作函数。用户可以参考safesstack.h来定义自己上层堆栈操作函数 

    #define sk_GENERAL_NAMES_new(st) SKM_sk_new(GENERAL_NAME, (st)) 

    #define sk_GENERAL_NAMES_new_null() SKM_sk_new_new_null(GENERAL_NAME) 

    #define sk_GENERAL_NAMES_free(st) SKM_sk_free(GENERAL_NAME, (st)) 

    #define sk_GENERAL_NAMES_num(st) SKM_sk_num(GENERAL_NAMES, (st)) 

    #define sk_GENERAL_NAMES_value(st, i) SKM_sk_value(GENERAL_NAMES, (st), (i)) 

    #define sk_GENERAL_NAMES_set(st, i, val) SKM_sk_set(GENERAL_NAMES, (st), (i), (val)) 

    #define sk_GENERAL_NAMES_zero(st) SKM_sk_zero(GENERAL_NAMES, (st)) 

    #define sk_GENERAL_NAMES_push(st, val) SKM_sk_push(GENERAL_NAMES, (st)) 

    #define sk_GENERAL_NAMES_unshift(st, val) SKM_sk_unshift(GENERAL_NAMES, (st), (val)) 

    #define sk_GENERAL_NAMES_find(st, val) SKM_sk_find(GENERAL_NAMES, (st), (val)) 

    #define sk_GENERAL_NAMES_find_ex(st, val) SKM_sk_find_ex(GENERAL_NAMES, (st), (val)) 

    #define sk_GENERAL_NAMES_delete(st, i) SKM_sk_delete(GENERAL_NAMES, (st), (i)) 

    #define sk_GENERAL_NAMES_delete_ptr(st, ptr) SKM_sk_delete_ptr(GENERAL_NAMES, (st), (ptr)) 

    #define sk_GENERAL_NAMES_insert(st, val, i) SKM_sk_insert(GENERAL_NAMES, (st), (val), (i)) 

    #define sk_GENERAL_NAMES_set_cmp_func(st, cmp) SKM_sk_set_cmp_func(GENERAL_NAMES, (st), (cmp)) 

    #define sk_GENERAL_NAMES_dup(st) SKM_sk_dup(GENERAL_NAMES, st) 

    #define sk_GENERAL_NAMES_pop_free(st, free_func) SKM_sk_pop_free(GENERAL_NAMES,(st), (free_func)) 

    #define sk_GENERAL_NAMES_deep_copy(st, copy_func, free_func) SKM_sk_deep_copy(GENERAL_NAMES, (st), (copy_func), (free_func)) 

    #define sk_GENERAL_NAMES_shift(st) SKM_sk_shift(GENERAL_NAMES, (st)) 

    #define sk_GENERAL_NAMES_pop(st) SKM_sk_pop(GENERAL_NAMES, (st)) 

    #define sk_GENERAL_NAMES_is_sorted(st) SKM_sk_is_sorted(GENERAL_NAMES, (st)) 

3.5 编程示例

1 #include 
     
       2 #include 
      
        3 #include 
       
         4 #include 
        
          5   6 #define sk_student_new(st) SKM_sk_new(student, (st)) 7 #define sk_student_new_null() SKM_sk_new_null(student) 8 #define sk_student_free(st) SKM_sk_free(student, (st)) 9 #define sk_student_num(st) SKM_sk_num(student, (st))10 #define sk_student_value(st, i) SKM_sk_value(student, (st), (i))11 #define sk_student_set(st, i, val) SKM_sk_set(student, (st), (i), (val))12 #define sk_student_zero(st) SKM_sk_zero(student, (st))13 #define sk_student_push(st, val) SKM_sk_push(student, (st), (val))14 #define sk_student_unshift(st, val) SKM_sk_unshift(student, (st), (val))15 #define sk_student_find(st, val) SKM_sk_find(student, (st), (val))16 #define sk_student_delete(st, i) SKM_sk_delete(student, (st), (i))17 #define sk_student_delete_ptr(st, ptr) SKM_sk_delete_ptr(student, (st), (ptr))18 #define sk_student_insert(st, val, i) SKM_sk_insert(student, (st), (val), (i))19 #define sk_student_set_cmp_func(st, cmp) SKM_sk_set_cmp_func(student, (st), (cmp))20 #define sk_student_dup(st) SKM_sk_dup(student, st)21 #define sk_student_pop_free(st, free_func) SKM_sk_pop_free(student, (st), (free_func))22 #define sk_student_shift(st) SKM_sk_shift(student, (st))23 #define sk_student_pop(st) SKM_sk_pop(student, (st))24 #define sk_student_sort(st) SKM_sk_sort(student, (st))25  26  27 typedef struct student_st28 {29 char *name;30 int age;31 char *otherInfo;32 }student;33  34 typedef STACK_OF(student) students;35  36 student *student_malloc()37 {38 student *a = malloc(sizeof(student));39 a->name = malloc(20);40 strcpy(a->name, "zcp");41 a->otherInfo = malloc(20);42 strcpy(a->otherInfo, "no info");43 return a;44 }45  46  47 void student_free(student *a)48 {49 free(a->name);50 free(a->otherInfo);51 free(a);52 }53  54 static int student_cmp(student *a, student *b)55 {56 int ret;57 ret = strcmp(a->name, b->name);58 return ret;59 }60  61 int main(int argc, char *argv)62 {63 students *s, *snew;64 student *s1, *one, *s2;65 int i, num;66  67 s = sk_student_new_null();68 s2 = student_malloc();69 sk_student_push(snew, s2);70 i = sk_student_find(snew, s2);71 s1 = student_malloc();72 sk_student_push(s, s1);73 num = sk_student_num(s);74  75 for (i = 0; i < num; i++)76 {77 one = sk_student_value(s,i);78 printf("student name: %s \n", one->name);79 printf("student age: %d \n", one->age);80 printf("student otherinfo: %s\n\n\n", one->otherInfo);81 }82  83 sk_student_pop_free(s, student_free);84 sk_student_pop_free(snew, student_free);85 return 0;86 }