Bit Field - Examples

Examples

Declaring a bit field in C:

#include // opaque and show #define YES 1 #define NO 0 // line styles #define SOLID 1 #define DOTTED 2 #define DASHED 3 // primary colors #define BLUE 4 // 100 #define GREEN 2 // 010 #define RED 1 // 001 // mixed colors #define BLACK 0 // 000 #define YELLOW (RED | GREEN) // 011 #define MAGENTA (RED | BLUE) // 101 #define CYAN (GREEN | BLUE) // 110 #define WHITE (RED | GREEN | BLUE) // 111 const char * colors = {"Black", "Red", "Green", "Yellow", "Blue", " Magenta", "Cyan", "White"}; // bit field box properties struct box_props { unsigned int opaque : 1; unsigned int fill_color : 3; unsigned int : 4; // fill to 8 bits unsigned int show_border : 1; unsigned int border_color : 3; unsigned int border_style : 2; unsigned int : 2; // fill to 16 bits };


Example of emulating bit fields with a primitive and bit operators in C:

/* Each prepocessor directive defines a single bit */ #define KEY_UP (1 << 0) // 000001 #define KEY_RIGHT (1 << 1) // 000010 #define KEY_DOWN (1 << 2) // 000100 #define KEY_LEFT (1 << 3) // 001000 #define KEY_BUTTON1 (1 << 4) // 010000 #define KEY_BUTTON2 (1 << 5) // 100000 int gameControllerStatus = 0; /* Sets the gameCtrollerStatus using OR */ void keyPressed(int key) { gameControllerStatus |= key; } /* Turns the key in gameControllerStatus off using AND and ~ */ void keyReleased(int key) { gameControllerStatus &= ~key; } /* Tests whether a bit is set using AND */ int isPressed(int key) { return gameControllerStatus & key; }

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