c vector

这是一个类似于std::vector可增长数组的实现，但采用纯 C89 代码。结果是一个类型安全、易于使用的动态数组，具有一组熟悉的操作。

它的工作原理是使用与许多分配器相同的技巧，即稍微分配比请求更多的数据，并使用前面的额外填充作为元数据的存储。因此，任何非空向量在内存中看起来都是这样的：

 +-----------------+------+----------+---------+
| elem_destructor | size | capacity | data... |
+-----------------+------+----------+---------+
                                    ^
                                    | user's pointer

其中向用户提供指向data第一个元素的指针。这样，代码可以轻松访问必要的元数据，但用户无需关心这些细节。每个向量的总开销为2 * sizeof(size_t) + sizeof(void (*)(void *)) 。

为了使代码最大限度地通用，它被实现为所有宏，因此仅是标头。用法很简单：

 /* if this is defined, then the vector will double in capacity each
 * time it runs out of space. if it is not defined, then the vector will
 * be conservative, and will have a capcity no larger than necessary.
 * having this defined will minimize how often realloc gets called.
 */
#define CVECTOR_LOGARITHMIC_GROWTH

#include "cvector.h"
#include <stdio.h>

int main ( int argc , char * argv []) {

	/* this is the variable that will store the array, you can have
	 * a vector of any type! For example, you may write float *v = NULL,
	 * and you'd have a vector of floats :-). NULL will have a size
	 * and capacity of 0. Additionally, vector_begin and vector_end will
	 * return NULL on a NULL vector. Alternatively, for clarity of writing
	 * you can use the cvector_vector_type macro to define a vector of a
	 * given type.
	 */
	cvector_vector_type ( int ) v = NULL ;

	( void ) argc ;
	( void ) argv ;

	/* add some elements to the back */
	cvector_push_back ( v , 10 );
	cvector_push_back ( v , 20 );
	cvector_push_back ( v , 30 );
	cvector_push_back ( v , 40 );

	/* remove an element by specifying an array subscript */
	cvector_erase ( v , 2 );

	/* remove an element from the back */
	cvector_pop_back ( v );

	/* print out some stats about the vector */
	printf ( "pointer : %pn" , ( void * ) v );
	printf ( "capacity: %lun" , cvector_capacity ( v ));
	printf ( "size    : %lun" , cvector_size ( v ));

	/* iterator over the vector using "iterator" style */
	if ( v ) {
		int * it ;
		int i = 0 ;
		for ( it = cvector_begin ( v ); it != cvector_end ( v ); ++ it ) {
			printf ( "v[%d] = %dn" , i , * it );
			++ i ;
		}
	}

	/* iterator over the vector standard indexing too! */
	if ( v ) {
		size_t i ;
		for ( i = 0 ; i < cvector_size ( v ); ++ i ) {
			printf ( "v[%lu] = %dn" , i , v [ i ]);
		}
	}

	/* well, we don't have destructors, so let's clean things up */
	cvector_free ( v );

	return 0 ;
}

应用程序编程接口

std::vector	cvector
std::vector<int> v	cvector(int) v
析构函数	cvector_free(v)
v.at(3)	cvector_at(v, 3)
v[3]	v[3]
v.front()	cvector_front(v)
v.back()	cvector_back(v)
v.begin()	cvector_begin(v)
v.end()	cvector_end(v)
v.empty()	cvector_empty(v)
v.size()	cvector_size(v)
v.capacity()	cvector_capacity(v)
v.shrink_to_fit()	cvector_shrink_to_fit(v)
v.clear()	cvector_clear(v)
v.insert(pos, value)	cvector_insert(v, pos, value)
v.erase(v.begin() + 2)	cvector_erase(v, 2)
v.push_back(value)	cvector_push_back(v, value)
v.pop_back()	cvector_pop_back(v)
v.reserve(new_cap)	cvector_reserve(v, new_cap)
v.resize(count)	cvector_resize(v, count)
v.swap(other)	cvector_swap(v, other)
std::vector<int> other = v;	cvector(int) other; cvector_copy(v, other);