1 /* dualview.c -- bit fields and bitwise operators */ 2 #include <stdio.h> 3 /* BIT-FIELD CONSTANTS */ 4 /* opaque and show */ 5 #define YES 1 6 #define NO 0 7 /* line styles */ 8 #define SOLID 0 9 #define DOTTED 1 10 #define DASHED 2 11 /* primary colors */ 12 #define BLUE 4 13 #define GREEN 2 14 #define RED 1 15 /* mixed colors */ 16 #define BLACK 0 17 #define YELLOW (RED | GREEN) 18 #define MAGENTA (RED | BLUE) 19 #define CYAN (GREEN | BLUE) 20 #define WHITE (RED | GREEN | BLUE) 21 22 /* BITWISE CONSTANTS */ 23 #define OPAQUE 0x1 24 #define FILL_BLUE 0x8 25 #define FILL_GREEN 0x4 26 #define FILL_RED 0x2 27 #define FILL_MASK 0xE 28 #define BORDER 0x100 29 #define BORDER_BLUE 0x800 30 #define BORDER_GREEN 0x400 31 #define BORDER_RED 0x200 32 #define BORDER_MASK 0xE00 33 #define B_SOLID 0 34 #define B_DOTTED 0x1000 35 #define B_DASHED 0x2000 36 #define STYLE_MASK 0x3000 37 38 const char * colors[8] = {"black", "red", "green", "yellow", 39 "blue", "magenta", "cyan", "white"}; 40 struct box_props { 41 42 unsigned int opaque : 1; 43 unsigned int fill_color : 3; 44 unsigned int : 4; 45 unsigned int show_border : 1; 46 unsigned int border_color : 3; 47 unsigned int border_style : 2; 48 unsigned int : 2; 49 }; 50 51 union Views /* look at data as struct or as unsigned short */ 52 { 53 struct box_props st_view; 54 unsigned int ui_view; 55 }; 56 57 void show_settings(const struct box_props * pb); 58 void show_settings1(unsigned short); 59 char * itobs(unsigned int n, char * ps); 60 61 int main(void) 62 { 63 /* create Views object, initialize struct box view */ 64 union Views box = {{YES, YELLOW , YES, GREEN, DASHED}}; 65 char bin_str[8 * sizeof(unsigned int) + 1]; 66 67 printf("Original box settings: "); 68 show_settings(&box.st_view); 69 printf(" Box settings using unsigned int view: "); 70 show_settings1(box.ui_view); 71 72 printf("bits are %s ", 73 itobs(box.ui_view,bin_str)); 74 box.ui_view &= ~FILL_MASK; /* clear fill bits */ 75 box.ui_view |= (FILL_BLUE | FILL_GREEN); /* reset fill */ 76 box.ui_view ^= OPAQUE; /* toggle opacity */ 77 box.ui_view |= BORDER_RED; /* wrong approach */ 78 box.ui_view &= ~STYLE_MASK; /* clear style bits */ 79 box.ui_view |= B_DOTTED; /* set style to dotted*/ 80 printf(" Modified box settings: "); 81 show_settings(&box.st_view); 82 printf(" Box settings using unsigned int view: "); 83 show_settings1(box.ui_view); 84 printf("bits are %s ", 85 itobs(box.ui_view,bin_str)); 86 87 return 0; 88 } 89 90 void show_settings(const struct box_props * pb) 91 { 92 printf("Box is %s. ", 93 pb->opaque == YES? "opaque": "transparent"); 94 printf("The fill color is %s. ", colors[pb->fill_color]); 95 printf("Border %s. ", 96 pb->show_border == YES? "shown" : "not shown"); 97 printf("The border color is %s. ", colors[pb->border_color]); 98 printf ("The border style is "); 99 switch(pb->border_style) 100 { 101 case SOLID : printf("solid. "); break; 102 case DOTTED : printf("dotted. "); break; 103 case DASHED : printf("dashed. "); break; 104 default : printf("unknown type. "); 105 } 106 } 107 108 void show_settings1(unsigned short us) 109 { 110 printf("box is %s. ", 111 us & OPAQUE == OPAQUE? "opaque": "transparent"); 112 printf("The fill color is %s. ", 113 colors[(us >> 1) & 07]); 114 printf("Border %s. ", 115 us & BORDER == BORDER? "shown" : "not shown"); 116 printf ("The border style is "); 117 switch(us & STYLE_MASK) 118 { 119 case B_SOLID : printf("solid. "); break; 120 case B_DOTTED : printf("dotted. "); break; 121 case B_DASHED : printf("dashed. "); break; 122 default : printf("unknown type. "); 123 } 124 printf("The border color is %s. ", 125 colors[(us >> 9) & 07]); 126 127 } 128 129 /* convert int to binary string */ 130 char * itobs(unsigned int n, char * ps) 131 { 132 int i; 133 static int size = 8 * sizeof(unsigned int); 134 135 for (i = size - 1; i >= 0; i--, n >>= 1) 136 ps[i] = (01 & n) + '0'; 137 ps[size] = ' '; 138 139 return ps; 140 }