resbuf的理解

resbuf(Result buffer structure:结果缓存区表)是用来处理所有AutoCAD的基本数据类型的.
struct resbuf {                                                 
        struct resbuf *rbnext;  //指向下一个resbuf的指针
        short restype;  //查询参数的种类,是一个DXF组码 
        union ads_u_val resval; //相应种类的匹配值
};
从定义上我们可以看出,结构resbuf是一个链表,每一个缓冲区指定一个检查参数和匹配的值;缓冲区的restype段是一个DXF组码,它指示要查询

的参数的种类,而缓冲区的resval域指定要匹配的值.
union ads_u_val {
   ads_real rreal;
   ads_real rpoint[3];
   short rint;
   char *rstring;
   long rlname[2];
   long rlong;  
   struct ads_binary rbinary;
   unsigned char ihandle[8];  //可能临时使用,目前仅仅为内部使用
};

 

//打印扩展数据列表,voidprintList(struct resbuf* pRb){int rt, i;char buf[133];for (i = 0;pRb != NULL;i++, pRb = pRb->rbnext) {if (pRb->restype < 1010) {rt = RTSTR;} else if (pRb->restype < 1040) {rt = RT3DPOINT;} else if (pRb->restype < 1060) {rt = RTREAL;} else if (pRb->restype < 1071) {rt = RTSHORT;} else if (pRb->restype == 1071) {rt = RTLONG;} else {/*记住,这里else可能为>1071的数,从而为后面的pRb->restype == RTSHORT做了工作,#define RTNONE 5000 #define RTREAL 5001 #define RTPOINT 5002 #define RTSHORT 5003 #define RTANG 5004 #define RTSTR 5005 #define RTENAME 5006 #define RTPICKS 5007 #define RTORINT 5008 #define RT3DPOINT 5009 #define RTLONG 5010 #define RTVOID 5014 */rt = pRb->restype; }switch (rt) {case RTSHORT:if (pRb->restype == RTSHORT) {acutPrintf("RTSHORT : %d/n", pRb->resval.rint);} else {acutPrintf("(%d . %d)/n", pRb->restype,pRb->resval.rint);};break;case RTREAL:if (pRb->restype == RTREAL) {acutPrintf("RTREAL : %0.3f/n",pRb->resval.rreal);} else {acutPrintf("(%d . %0.3f)/n", pRb->restype,pRb->resval.rreal);};break;case RTSTR:if (pRb->restype == RTSTR) {acutPrintf("RTSTR : %s/n",pRb->resval.rstring);} else {acutPrintf("(%d . /"%s/")/n", pRb->restype,pRb->resval.rstring);};break;case RT3DPOINT:if (pRb->restype == RT3DPOINT) {acutPrintf("RT3DPOINT : %0.3f, %0.3f, %0.3f/n",pRb->resval.rpoint[X],pRb->resval.rpoint[Y],pRb->resval.rpoint[Z]);} else {acutPrintf("(%d %0.3f %0.3f %0.3f)/n",pRb->restype,pRb->resval.rpoint[X],pRb->resval.rpoint[Y],pRb->resval.rpoint[Z]);}break;case RTLONG:acutPrintf("RTLONG : %dl/n", pRb->resval.rlong);break;}//这里为什么要有这个,主要是为了当记录多的时候,起到翻页功能,就要cmd dir /p类似if ((i == 23) && (pRb->rbnext != NULL)) {i = 0;acedGetString(0,"Press <ENTER> to continue...", buf);}}