第 15 章 位操作（dualview）

 /*-----------------------------------

     dualview.c -- 位字段和按位运算符

 -----------------------------------*/

 #include <stdio.h>

 #include <limits.h>

 //边框线样式

 #define SOLID    0

 #define    DOTTED    1

 #define DASHED    2

 //三原色

 #define BLUE    4

 #define GREEN    2

 #define RED        1

 //混合颜色

 #define BLACK    (RED & GREEN & BLUE)

 #define YELLOW    (RED | GREEN)

 #define MAGENTA    (RED | BLUE)

 #define CYAN    (GREEN | BLUE)

 #define WHITE    (RED | BLUE | GREEN)

 //按位方法中用到的符号常量

 #define OPAQUE        0x1

 #define FILL_BLUE    0x8

 #define FILL_GREEN    0x4

 #define FILL_RED    0x2

 #define FILL_MASK    0xE        //掩码

 #define BORDER            0x100

 #define BORDER_BLUE        0x800

 #define BORDER_GREEN    0x400

 #define BORDER_RED        0x200

 #define BORDER_MASK        0xE00

 #define B_SOLID            0

 #define B_DOTTED        0x1000

 #define B_DASHED        0x2000

 #define STYLE_MASK        0x3000

 struct box_props

 {

     unsigned int opaque            : ;

     unsigned int fill_color        : ;

     unsigned int                : ;

     unsigned int show_border    : ;

     unsigned int border_color    : ;

     unsigned int border_style    : ;

     unsigned int                : ;

 };

 //把数据看作结构或 unsigned short 类型的变量

 union Views

 {

     struct box_props st_view;

     unsigned short us_view;

 };

 const char *color[] =

 {

     "black", "red", "green", "yellow", "blue", "magenta", "cyan", "white"

 };

 void show_settings(const struct box_props *pb);

 void show_setting1(unsigned short);

 char* itobs(int n, char *ps);

 void show_bstr(const char *str);

 int main()

 {

     printf("size of struct box_props is %d bit\n", CHAR_BIT * sizeof(struct box_props));

     printf("size of unsigned short is %d bit\n", CHAR_BIT * sizeof(unsigned short));

     //创建 Vies 联合，并初始化 initialize struct box view

     union Views box = {{true, YELLOW, true, GREEN, DASHED}};

     char bin_str[ * sizeof(unsigned int) + ];

     printf("\nOriginal box settings:\n");

     show_settings(&box.st_view);

     printf("\nBox settings using unsigned int view:\n");

     show_setting1(box.us_view);

     //printf("bits are %s\n", itobs(box.us_view, bin_str));

     printf("bits are:\n");

     show_bstr(itobs(box.us_view, bin_str));

     box.us_view &= ~FILL_MASK;        //把表示填充色的位清零

     box.us_view |= CYAN;            //重置填充色

     box.us_view ^= OPAQUE;            //切换透明位

     box.us_view &= ~BORDER_MASK;    //边框颜色位清零

     box.us_view |= BORDER_RED;

     box.us_view &= ~STYLE_MASK;        //样式位清零

     box.us_view |= B_DOTTED;        //边框样式设置为点

     printf("\nModified box settings:\n");

     show_settings(&box.st_view);

     printf("\nBox settings using unsigned int view:\n");

     show_setting1(box.us_view);

     //printf("bits are %s\n", itobs(box.us_view, bin_str));

     printf("bits are:\n");

     show_bstr(itobs(box.us_view, bin_str));

     return ;

 }

 void show_settings(const struct box_props *pb)

 {

     printf("Box is %s.\n", pb->opaque ? "opaque" : "transparent");

     printf("The fill color is %s.\n", color[pb->fill_color]);

     printf("Border %s.\n", pb->show_border ? "shown" : "not shown");

     printf("The border color is %s.\n", color[pb->border_color]);

     printf("The border style is ");

     switch (pb->border_style)

     {

     case SOLID:

         printf("solid.\n");

         break;

     case DOTTED:

         printf("dotted.\n");

         break;

     case DASHED:

         printf("dashed.\n");

         break;

     default:

         printf("unknown type.\n");

         break;

     }

 }

 void show_setting1(unsigned short us)

 {

     printf("Box is %s.\n", (us & OPAQUE) ? "opaque" : "transparent");

     printf("The fill color is %s.\n", color[(us >> ) & 0x07]);

     printf("Border %s.\n", (us & BORDER) == BORDER ? "shown" : "not shown");

     printf("The border color is %s.\n", color[us >>  & 0x07]);

     printf("The border style is ");

     switch (us & STYLE_MASK)

     {

     case B_SOLID:

         printf("solid.\n");

         break;

     case B_DOTTED:

         printf("dotted.\n");

         break;

     case B_DASHED:

         printf("dashed.\n");

         break;

     default:

         printf("unknown style");

         break;

     }

 }

 char* itobs(int n, char *ps)

 {

     const static int size = CHAR_BIT * sizeof(int);

     for (int i(size - ); i >= ; --i, n >>= )

         ps[i] = ( & n) + '';

     ps[size] = '\0';

     return ps;

 }

 //以 4 位为一组，显示二进制字符串

 void show_bstr(const char *str)

 {

     int i = ;

     while (str[i])        //str[i] 不是空字符

     {

         putchar(str[i]);

         if (++i %  ==  && str[i])

             putchar(' ');

     }

     putchar('\n');

 }

dualview.c