庖丁解牛——代码段分析

下面这段代码来源于opencv的头文件。

#define CV_TREE_NODE_FIELDS(node_type) \

    int       flags;             /* Miscellaneous flags.     */      \

    int       header_size;       /* Size of sequence header. */      \

    struct    node_type* h_prev; /* Previous sequence.       */      \

    struct    node_type* h_next; /* Next sequence.           */      \

    struct    node_type* v_prev; /* 2nd previous sequence.   */      \

    struct    node_type* v_next  /* 2nd next sequence.       */

/*

   Read/Write sequence.

   Elements can be dynamically inserted to or deleted from the sequence.

*/

#define CV_SEQUENCE_FIELDS()                                              \

    CV_TREE_NODE_FIELDS(CvSeq);                                           \

    int       total;          /* Total number of elements.            */  \

    int       elem_size;      /* Size of sequence element in bytes.   */  \

    schar*    block_max;      /* Maximal bound of the last block.     */  \

    schar*    ptr;            /* Current write pointer.               */  \

    int       delta_elems;    /* Grow seq this many at a time.        */  \

    CvMemStorage* storage;    /* Where the seq is stored.             */  \

    CvSeqBlock* free_blocks;  /* Free blocks list.                    */  \

    CvSeqBlock* first;        /* Pointer to the first sequence block. */

typedef struct CvSeq

{

    CV_SEQUENCE_FIELDS()

}

CvSeq;

这段代码的精妙之处在于将指针进行了封装  CV_TREE_NODE_FIELDS(node_type)  从而让指针的定义无区别化，只要更改node_type就能将这个指针节点用在别的定义中。