03.openssl编程——堆栈

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

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/safestack.h>
 
#define sk_student_new(st) SKM_sk_new(student, (st))
#define sk_student_new_null() SKM_sk_new_null(student)
#define sk_student_free(st) SKM_sk_free(student, (st))
#define sk_student_num(st) SKM_sk_num(student, (st))
#define sk_student_value(st, i) SKM_sk_value(student, (st), (i))
#define sk_student_set(st, i, val) SKM_sk_set(student, (st), (i), (val))
#define sk_student_zero(st) SKM_sk_zero(student, (st))
#define sk_student_push(st, val) SKM_sk_push(student, (st), (val))
#define sk_student_unshift(st, val) SKM_sk_unshift(student, (st), (val))
#define sk_student_find(st, val) SKM_sk_find(student, (st), (val))
#define sk_student_delete(st, i) SKM_sk_delete(student, (st), (i))
#define sk_student_delete_ptr(st, ptr) SKM_sk_delete_ptr(student, (st), (ptr))
#define sk_student_insert(st, val, i) SKM_sk_insert(student, (st), (val), (i))
#define sk_student_set_cmp_func(st, cmp) SKM_sk_set_cmp_func(student, (st), (cmp))
#define sk_student_dup(st) SKM_sk_dup(student, st)
#define sk_student_pop_free(st, free_func) SKM_sk_pop_free(student, (st), (free_func))
#define sk_student_shift(st) SKM_sk_shift(student, (st))
#define sk_student_pop(st) SKM_sk_pop(student, (st))
#define sk_student_sort(st) SKM_sk_sort(student, (st))
 
 
typedef struct student_st
{
char *name;
int age;
char *otherInfo;
}student;
 
typedef STACK_OF(student) students;
 
student *student_malloc()
{
student *a = malloc(sizeof(student));
a->name = malloc(20);
strcpy(a->name, "zcp");
a->otherInfo = malloc(20);
strcpy(a->otherInfo, "no info");
return a;
}
 
 
void student_free(student *a)
{
free(a->name);
free(a->otherInfo);
free(a);
}
 
static int student_cmp(student *a, student *b)
{
int ret;
ret = strcmp(a->name, b->name);
return ret;
}
 
int main(int argc, char *argv)
{
students *s, *snew;
student *s1, *one, *s2;
int i, num;
 
s = sk_student_new_null();
s2 = student_malloc();
sk_student_push(snew, s2);
i = sk_student_find(snew, s2);
s1 = student_malloc();
sk_student_push(s, s1);
num = sk_student_num(s);
 
for (i = 0; i < num; i++)
{
one = sk_student_value(s,i);
printf("student name: %s \n", one->name);
printf("student age: %d \n", one->age);
printf("student otherinfo: %s\n\n\n", one->otherInfo);
}
 
sk_student_pop_free(s, student_free);
sk_student_pop_free(snew, student_free);
return 0;
}