Is it correct to use column precedence in arrays in C language?

(*-*)浩
Release: 2019-11-18 14:45:30
Original
2782 people have browsed it

Is it correct to use column precedence in arrays in C language?

If we store it in the way of C language, that is, row-first storage, then in memory, its shape is like this:

Is it correct to use column precedence in arrays in C language?

This storage method is also called C contiguous array.                                                                                                                                                   (Recommended learning: web front-end video tutorial)

Implementation of column-major order storage of array structures in C language (GCC compilation).

Convert from row-major to column-major storage. Compared with row-major, the difference is that the order of the array dimension base addresses is changed, thereby changing the image function constant base address.

/**
 * @brief C语言 数组 列优先 实现
 * @author wid
 * @date 2013-11-02
 *
 * @note 若代码存在 bug 或程序缺陷, 请留言反馈, 谢谢!
 */
 
 #include 
 #include 
 #include 
 #include 
 
 #define OK 1
 #define ERROR -1
 
 #define MAX_DIM 8       ///允许的最大数组维数
 
 typedef int ElemType;
 
 typedef struct
 {
     ElemType *base;         ///数组元素基址
     int dim;                ///数组维数
     int *bounds;            ///数组维界基址
     int *constants;         ///数组映像函数常量基址
 }Array;     ///数组结构
 
 ///数组方法声明
 int InitArray( Array *pArr, int nDim, ... );        ///初始化数组 pArr
 void DestroyArray( Array *pArr );                   ///销毁数组 pArr
 int Locate( Array *pArr, int nDim, va_list ap );                     ///定位下标指向的元素在数组中的位置
 int Assign( Array *pArr, ElemType *elm, ... );      ///数组赋值
 int Value( Array *pArr, ElemType *elm, ... );       ///数组取值
 
 ///数组方法实现
 
 /**
 * @brief 初始化数组
 *
 * @param pArr 指向待初始化的数组
 * @param nDim 数组的维数
 * @param ... 数组各维数的长度
 *
 * @return 初始化成功返回OK, 否则返回ERROR
 */
 int InitArray( Array *pArr, int nDim, ... )
 {
      || nDim > MAX_DIM )
         return ERROR;
 
     ///初始化 pArr 数组维数属性
     pArr->dim = nDim;
 
     ///构造数组维界基址
     pArr->bounds = (int *)malloc( nDim * sizeof(int) );
     if( !pArr->bounds )
         return ERROR;
 
     , nElemCount = ;
     va_list ap;
     va_start( ap, nDim );
 
     /// i = nDim - 1, 使列优先
     ; i >= ; --i )
     {
         pArr->bounds[i] = va_arg( ap, int );
          )
             return ERROR;
 
         nElemCount *= pArr->bounds[i];
     }
     va_end(ap);
 
     ///初始化元素基址
     pArr->base = (ElemType *)malloc( nElemCount * sizeof(ElemType) );
     if( !pArr->base )
         return ERROR;
 
     ///初始化函数映像常数基址
     pArr->constants = (int *)malloc( nDim * sizeof(int) );
 
     ///递推求常量基址, 列优先
     pArr->constants[nDim-] = ;
      ; i >= ; --i )
     {
         pArr->constants[i] = pArr->bounds[i+] * pArr->constants[i+];
     }
 
     return OK;
 }
 
 /**
 * @brief 销毁数组 pArr
 *
 * @param pArr 指向待销毁的数组
 */
 void DestroyArray( Array *pArr )
 {
     if( pArr->base )
         free( pArr->base );
 
     if( pArr->bounds )
         free( pArr->bounds );
 
     if( pArr->constants )
         free( pArr->constants );
 }
 
 /**
 * @brief 定位数组下标指向的元素在数组中的位置
 *
 * @param 指向的数组
 * @param ... 数组的下标
 *
 * @return 若下标合法, 返回下标在数组中的位置, 否则返回 ERROR
 */
 int Locate( Array *pArr, int nDim, va_list ap )
 {
     , ind = , i = ;
 
     ///列优先求地址
     ; i >= ; --i )
     {
         ind = va_arg( ap, int );
 
         ///使用断言, 确保下标合法
         assert( ind >=  && ind < pArr->bounds[i] );
 
         nPos += pArr->constants[i] * ind;
     }
     va_end(ap);
 
     return nPos;
 }
 
 /**
 * @brief 数组赋值
 *
 * @param pArr 指向待赋值的数组
 * @param elm 指向赋值元素
 * @param nDim 数组维数
 * @param ... 数组下标
 *
 * @param 赋值成功返回 OK, 否则返回 ERROR
 */
 int Assign( Array *pArr, ElemType *elm, ... )
 {
     ;
     va_list ap;
     va_start( ap, elm );
     nPos = Locate( pArr, pArr->dim, ap );
     *(pArr->base + nPos) = *elm;
 
     return OK;
 }
 
 /**
 * @brief 数组取值
 
 */
 int Value( Array *pArr, ElemType *elm, ... )
 {
     ;
     va_list ap;
     va_start( ap, elm );
     nPos = Locate( pArr, pArr->dim, ap );
     *elm = *(pArr->base + nPos);
     printf( "addr = 0x%X\n", pArr->base + nPos );
 
     return OK;
 }
 
 int main()
 {
     Array arr;
 
     ///初始化一个三维数组, 大小为 2x3x5
     InitArray( &arr, , , ,  );
 
     ;
     ///赋值测试
     , m = , n = ;
     ; i < ; ++i )
         ; m < ; ++m )
             ; n < ; ++n )
             {
                 a = i + m + n;
                 Assign( &arr, &a, i, m, n );
             }
 
     ;
     ///取值测试
     ; i < ; ++i )
         ; m < ; ++m )
             ; n < ; ++n )
             {
                  Value( &arr, &b, i, m, n );
                  printf( "[%d][%d][%d]=%d\n", i, m, n, b );
             }
 
     ///销毁数组
     DestroyArray( &arr );
 
     ;
 }
Copy after login

Run the test:

Is it correct to use column precedence in arrays in C language?

The above is the detailed content of Is it correct to use column precedence in arrays in C language?. For more information, please follow other related articles on the PHP Chinese website!

Related labels:
source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template
About us Disclaimer Sitemap
php.cn:Public welfare online PHP training,Help PHP learners grow quickly!