ngth * stk->elemsize;
memcpy(target, elemaddr, stk->elemsize);
stk->loglength++;
}
/* Delete the top element off the stack */
void
stack_pop(Stack stk)
{
ElementAddr target;
if ( stack_is_empty(stk) ) {
fprintf(stderr, "Empty stack\n");
exit(1);
}
if ( stk->freefn ) {
target = (char *)stk->array +
(stk->loglength-1) * stk->elemsize;
stk->freefn(target);
}
stk->loglength--;
}
/* Fetch the top element from the stack */
void
stack_top(Stack stk, ElementAddr elemaddr)
{
void *target = (char *)stk->array +
(stk->loglength-1) * stk->elemsize;
memcpy(elemaddr, target, stk->elemsize);
}
/* Fetch & Delete the top element from the stack */
void
stack_top_and_pop(Stack stk, ElementAddr elemaddr)
{
ElementAddr target;
if ( stack_is_empty(stk) ) {
fprintf(stderr, "Empty stack\n");
exit(1);
}
target = (char *)stk->array +
(stk->loglength-1) * stk->elemsize;
memcpy(elemaddr, target, stk->elemsize);
stk->loglength--;
}
使用和测试
------------------------------------------------------------------------------------------------------------------------
测试代码:
[cpp]
#include
#include
#include
#include "generic-stack.h"
void strfreefn(ElementAddr elemaddr)
{
free(*(char **)elemaddr);
}
int
main(int argc, char **argv)
{
Stack int_stk, str_stk;
int i;
char *names[] = {
"C", "
C++", "Jave", "C#", "Python",
"
PHP", "Basic", "Objective C", "Matlab", "Golang"
};
/* test integer stack */
printf("Test integer stack\n");
int_stk = stack_create(sizeof(int), NULL);
for ( i = 0; i < 10; ++i ) {
stack_push(int_stk, &i);
}
while ( !stack_is_empty(int_stk) ) {
int val;
stack_top_and_pop(int_stk, &val);
printf("%d\n", val);
}
stack_dispose(int_stk);
/* test string stack */
printf("Test string stack\n");
str_stk = stack_create(sizeof(char *), strfreefn);
for ( i = 0; i < 10; ++i ) {
char *copy = strdup(names[i]);
char *dest;
stack_push(str_stk, );
}
while ( !stack_is_empty(str_stk) ) {
char *dest;
stack_top_and_pop(str_stk, &dest);
printf("%s\n", dest);
free(dest);
}
stack_dispose(str_stk);
return 0;
}
分析:
(1). int_stack (存放对象)
(2). str_stack(存放指针)
array存放的是一系列指针,这些指针指向的实际对象需要在堆中分配.那么最初放入stack进行管理的对象来源不定,可能是堆,栈,甚至是常量区.为了便于管理,应该先在堆中分配这些对象(来源对象的副本:上述的strdup操作)."一个元素一旦入栈,这个元素的控制权就交由栈进行管理,一旦出栈,这个元素的控制权就交由用户管理".
