pe15-7.c

C Primer Plus(第五版)中文版,不用多说了

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define ID_MASK     0xFF
#define SIZE_MASK   0x7F00
#define LEFT		0x00000
#define CENTER      0x08000
#define RIGHT       0x10000
#define ALIGN_MASK  0x18000
#define REGULAR     0x00000
#define BOLD        0x20000
#define ITALIC      0x40000
#define UNDERLINE   0x80000
#define STYLE_MASK  0xE0000
#define SIZE_SHIFT  8

typedef unsigned long font;


char do_menu(font * f);
char get_choice(const char *);
void show_menu(void);
void show_font(font f);
void eatline(void);
void get_id(font * f);
void get_size(font * f);
void get_align(font * f);

int main(void)
{
    font sample = 1 | (12 <<SIZE_SHIFT) | LEFT | ITALIC;
    
    while (do_menu(&sample) != 'q')
    	continue;
	puts("Bye!");
    return 0;
}

char do_menu(font * f)
{
    char response;
    
	show_font(*f);
	show_menu();
	response = get_choice("fsabiuq");
	switch(response)
	{
		case 'f' : get_id(f); break;
		case 's' : get_size(f); break;
		case 'a' : get_align(f); break;
		case 'b' : *f ^= BOLD; break;
		case 'i' : *f ^= ITALIC; break;
		case 'u' : *f ^= UNDERLINE; break;
		case 'q' : break;
		default  : fprintf(stderr, "menu problem\n");
	}
	
	return response;
}

char get_choice(const char * str)
{
	char ch;
	
	ch = getchar();
	ch = tolower(ch);
	eatline();
	while (strchr(str, ch) == NULL)
	{
		printf("Please enter one of the following: %s\n",
		       str);
		ch = tolower(getchar());
		eatline();
	}
	return ch;
}

void eatline(void)
{
	while (getchar() != '\n')
		continue;
}


void show_menu(void)
{
	puts("f)change font    s)change size    a)change alignment");
	puts("b)toggle bold    i)toggle italic  u)toggle underline");
	puts("q)quit");
}


void show_font(font f)
{
	printf("\n%4s %4s %9s %3s %3s %3s\n", 
	       "ID", "SIZE", "ALIGNMENT", "B", "I", "U");
	printf("%4d %4d", f & ID_MASK, (f & SIZE_MASK) >> SIZE_SHIFT);
	switch(f & ALIGN_MASK)
	{
		case LEFT   : printf("%7s", "left"); break;
		case RIGHT  : printf("%7s", "right"); break;
		case CENTER : printf("%7s", "center"); break;
		default     : printf("%7s", "unknown"); break;
	}
	printf("%8s %3s %3s\n\n", (f & BOLD) == BOLD? "on" : "off",
	       (f & ITALIC) == ITALIC ? "on" : "off",
	       (f & UNDERLINE) == UNDERLINE ? "on" : "off");	       
}

void get_id(font * f)
{
	int id;
	
	printf("Enter font ID (0-255): ");
	scanf("%d", &id);
	id = id & ID_MASK;
	*f |= id;
	eatline();
}

void get_size(font * f)
{
	int size;
	
	printf("Enter font size (0-127): ");
	scanf("%d", &size);
	*f |= (size << SIZE_SHIFT) & SIZE_MASK;
	eatline();
}

void get_align(font * f)
{
	puts("Select alignment:");
	puts("l)left   c)center   r)right");
    switch (get_choice("lcr"))
    {
    	case 'l' : *f &= ~ALIGN_MASK; *f |= LEFT; break;
    	case 'c' : *f &= ~ALIGN_MASK; *f |= CENTER; break;
      	case 'r' : *f &= ~ALIGN_MASK; *f |= RIGHT; break;
      	default  : fprintf(stderr, "alignment problem\n");
    }
}