在 C 语言中可以用结构体代替类，用函数指针代替成员方法，实现数据成员与成员方法的封装，在客户端写出的程序与 C++ 类似，唯一的不同是 C 语言中调用函数指针成员时必须将本对象的地址传给函数，因为 C 语言中各函数的地位是相同的。
本文以模仿 STL 中的 vector 类写了一个 C 语言的 vector 结构体，程序如下：
1. vector 的接口
/********************************************************************
created: 2013/08/19
created: 19:8:2013 0:09
file base: vector
file ext: h
author: Justme0 (http://blog.csdn.net/Justme0)
purpose: vector 结构体的定义
*********************************************************************/
#ifndef _VECTOR_H_
#define _VECTOR_H_
typedef struct vector vector;
typedef char vec_value_type;
typedef vec_value_type* vec_pointer;
typedef vec_value_type* vec_iterator;
typedef unsigned int vec_size_type;
struct vector {
/*
** 获取下标为 index 的元素
*/
vec_value_type (*get_at)(vector *pvec, const int index);
/*
** 设置下标为 index 处的元素为 elem
*/
void (*set_at)(vector *pvec, const int index, const vec_value_type elem);
vec_iterator (*begin)(vector *pvec);
vec_iterator (*end)(vector *pvec);
vec_value_type (*front)(vector *pvec);
vec_value_type (*back)(vector *pvec);
int (*size)(vector *pvec);
int (*capacity)(vector *pvec);
int (*empty)(vector *pvec);
void (*insert_n)(vector *pvec, const vec_iterator position, const vec_size_type n, const vec_value_type elem);
vec_iterator (*earse_pos)(vector *pvec, const vec_iterator position);
vec_iterator (*earse_int)(vector *pvec, const vec_iterator first, const vec_iterator last);
void (*clear)(vector *pvec);
void (*push_back)(vector *pvec, const vec_value_type elem);
void (*pop_back)(vector *pvec);
vec_iterator _start;
vec_iterator _finish;
vec_iterator _end_of_storage;
};
void vec_construct(vector *pvec);
void vec_construct_n(vector *pvec, const int size);
void vec_destruct(vector *pvec);
#endif
2. vector 的实现
/********************************************************************
created: 2013/08/19
created: 19:8:2013 0:09
file base: vector
file ext: c
author: Justme0 (http://blog.csdn.net/Justme0)
purpose: vector 的实现
*********************************************************************/
#include "vector.h"
#include <math.h>
#include <stdlib.h>
#include <assert.h>
#define CHECK_BORDER assert(pvec->_finish >= pvec->_start && pvec->_end_of_storage >= pvec->_start)
static vec_iterator copy(vec_iterator first, vec_iterator last, vec_iterator result) {
vec_iterator src = first;
vec_iterator dst = result;
for (; src != last; ++src, ++dst) {
*dst = *src;
}
return dst;
}
static vec_value_type _get_at(vector *pvec, int index) {
return *(pvec->begin(pvec) + index);
}
static void _set_at(vector *pvec, int index, vec_value_type elem) {
pvec->_start[index] = elem;
}
static vec_iterator _begin(vector *pvec) {
return pvec->_start;
}
static vec_iterator _end(vector *pvec) {
return pvec->_finish;
}
static vec_value_type _front(vector *pvec) {
return *pvec->begin(pvec);
}
static vec_value_type _back(vector *pvec) {
return *(pvec->end(pvec) - 1);
}
static int _size(vector *pvec) {
return pvec->end(pvec) - pvec->begin(pvec);
}
static int _capacity(vector *pvec) {
return pvec->_end_of_storage - pvec->begin(pvec);
}
static int _empty(vector *pvec) {
return pvec->begin(pvec) == pvec->end(pvec);
}
static void _insert_n(vector *pvec, vec_iterator position, vec_size_type n, const vec_value_type elem) {
vec_size_type old_size = 0;
vec_size_type new_size = 0;
int inset_index = 0;
vec_iterator ite = NULL;
assert(pvec->_start <= position && position <= pvec->end(pvec));
CHECK_BORDER;
if (0 == n) {
return ;
}
inset_index = position - pvec->_start;
old_size = pvec->size(pvec);
new_size = old_size + n;
// 先检查剩余空间是否足够，不够则扩容
if ((vec_size_type)(pvec->_end_of_storage - pvec->_finish) < n) {
const vec_size_type new_capacity = old_size + __max(old_size, n);
vec_value_type *new_base = (vec_value_type *)realloc(pvec->_start, new_capacity * sizeof(vec_value_type));
if (NULL == new_base) {
exit(OVERFLOW); // 此时原来的空间将发生内存泄漏
}
pvec->_start = new_base;
pvec->_end_of_storage = pvec->_start + new_capacity;
}
pvec->_finish = pvec->_start + new_size;
position = pvec->_start + inset_index;
// 移动元素
for (ite = pvec->_finish; ite >= position + n; --ite) {
*ite = *(ite - n);
}
// 插入n个新元素
for (; ite >= position; --ite) {
*ite = elem;
}
}
static vec_iterator _earse_pos(vector *pvec, const vec_iterator position) {
if (position + 1 != pvec->end(pvec)) {
copy(position + 1, pvec->_finish, position);
}
--pvec->_finish;
return position;
}
static vec_iterator _earse_int(vector *pvec, const vec_iterator first, const vec_iterator last) {
vec_iterator i = copy(last, pvec->_finish, first);
pvec->_finish -= last - first;
return first;
}
static void _clear(vector *pvec) {
pvec->earse_int(pvec, pvec->begin(pvec), pvec->end(pvec));
}
static void _push_back(vector *pvec, const vec_value_type elem) {
CHECK_BORDER;
_insert_n(pvec, pvec->end(pvec), 1, elem);
}
static void _pop_back(vector *pvec) {
pvec->earse_pos(pvec, pvec->end(pvec) - 1);
}
static void set(vector *pvec) {
pvec->_finish = NULL;
pvec->_start = NULL;
pvec->_end_of_storage = NULL;
pvec->get_at = _get_at;
pvec->set_at = _set_at;
pvec->begin = _begin;
pvec->end = _end;
pvec->front = _front;
pvec->back = _back;
pvec->size = _size;
pvec->capacity = _capacity;
pvec->empty = _empty;
pvec->insert_n = _insert_n;
pvec->earse_pos = _earse_pos;
pvec->earse_int = _earse_int;
pvec->clear = _clear;
pvec->push_back = _push_back;
pvec->pop_back = _pop_back;
}
static void reset(vector *pvec) {
pvec->_finish = NULL;
pvec->_start = NULL;
pvec->_end_of_storage = NULL;
pvec->get_at = NULL;
pvec->set_at = NULL;
pvec->begin = NULL;
pvec->end = NULL;
pvec->front = NULL;
pvec->back = NULL;
pvec->size = NULL;
pvec->capacity = NULL;
pvec->empty = NULL;
pvec->insert_n = NULL;
pvec->earse_pos = NULL;
pvec->earse_int = NULL;
pvec->clear = NULL;
pvec->push_back = NULL;
pvec->pop_back = NULL;
}
void vec_construct(vector *pvec) {
set(pvec);
}
void vec_construct_n(vector *pvec, const int size) {
set(pvec);
pvec->_start = (vec_iterator)malloc(size * sizeof(*pvec->_start));
if (NULL == pvec->_start) {
// TODO:
exit(OVERFLOW);
}
pvec->_finish = pvec->_start + size;
pvec->_end_of_storage = pvec->_finish;
}
void vec_destruct(vector *pvec) {
free(pvec->_start);
reset(pvec);
}
3. 测试程序
/********************************************************************
created: 2013/08/19
created: 19:8:2013 0:10
file base: test
file ext: c
author: Justme0 (http://blog.csdn.net/Justme0)
purpose: vector 的测试程序
*********************************************************************/
#include "vector.h"
#include <stdio.h>
void output(vector *pvec) {
vec_iterator iter;
for (iter = pvec->begin(pvec); iter != pvec->end(pvec); ++iter) {
printf("%c\n", *iter);
}
}
int main(int argc, char **argv) {
char ch = 'A';
int cnt = 5;
vector my_vec;
vec_construct(&my_vec);
while (cnt--) {
my_vec.push_back(&my_vec, ch++);
}
output(&my_vec);
puts("set [2]: '2'");
my_vec.set_at(&my_vec, 2, '2');
output(&my_vec);
my_vec.empty(&my_vec) ? puts("empty") : puts("not empty");
puts("pop_back...");
my_vec.pop_back(&my_vec);
output(&my_vec);
printf("size is %d\n", my_vec.size(&my_vec));
printf("back is '%c'\n", my_vec.back(&my_vec));
puts("clear...");
my_vec.clear(&my_vec);
my_vec.empty(&my_vec) ? puts("empty") : puts("not empty");
vec_destruct(&my_vec);
return 0;
}
4. 运行结果
A B C D E set [2]: '2' A B 2 D E not empty pop_back... A B 2 D size is 4 back is 'D' clear... empty 请按任意键继续. . .
1、在测试程序中可以看到，定义一个结构体后，必须紧跟着用函数 construct 将对象的成员赋值以初始化，我称这个过程为“构造”。
2、最后必须显示调用 destruct 函数将对象“析构”，释放对象 malloc 的空间。
我将这个程序给某个 C++ 游戏程序员看，被他一阵批，说我的程序最大的缺点就是 不是面向对象；没有一个企业会让这份程序通过；“你写的是 Objective-C 形式”。桑心啊，我只好贴在这独自欣赏了。