bounce_aio.c

unix linux 编程实践源代码

/* bounce_aio.c
 *	purpose	animation with user control, using aio_read() etc
 *	note	set_ticker() sends SIGALRM, handler does animation
 *		keyboard sends SIGIO, main only calls pause()
 *	compile cc bounce_aio.c set_ticker.c -lrt  -lcurses -o bounce_aio
 */
#include	<stdio.h>
#include	<curses.h>
#include	<signal.h>
#include	<aio.h>

/* The state of the game 			*/

#define	MESSAGE	"hello"
#define	BLANK	"     "

int	row   = 10;	/* current row		*/
int	col   =  0;	/* current column	*/
int	dir   =  1;	/* where we are going	*/
int	delay = 200;	/* how long to wait	*/
int	done  = 0;

struct aiocb kbcbuf;	/* an aio control buf   */

main()
{
	void	on_alarm(int);	/* handler for alarm	*/
	void	on_input(int);	/* handler for keybd    */
	void	setup_aio_buffer();

	initscr();		/* set up screen */
	crmode();
	noecho();
	clear();

	signal(SIGIO, on_input);          /* install a handler        */
	setup_aio_buffer();	  	  /* initialize aio ctrl buff */
	aio_read(&kbcbuf);		  /* place a read request     */

	signal(SIGALRM, on_alarm);        /* install alarm handler    */
	set_ticker(delay);		  /* start ticking	      */

	mvaddstr( row, col, MESSAGE );    /* draw initial image       */

	while( !done )			  /* the main loop */
		pause();
	endwin();
}
/*
 * handler called when aio_read() has stuff to read
 *   First check for any error codes, and if ok, then get the return code
 */
void on_input()
{
	int  c;
	char *cp = (char *) kbcbuf.aio_buf;	/* cast to char * */

	/* check for errors */
	if ( aio_error(&kbcbuf) != 0 )
		perror("reading failed");
	else 
		/* get number of chars read */
		if ( aio_return(&kbcbuf) == 1 )
		{
			c = *cp;
			if ( c == 'Q' || c == EOF )
				done = 1;
			else if ( c == ' ' )
				dir = -dir;
		}

	/* place a new request */
	aio_read(&kbcbuf);
}

void on_alarm()
{
	signal(SIGALRM, on_alarm);	/* reset, just in case	*/
	mvaddstr( row, col, BLANK );	/* clear old string	*/
	col += dir;			/* move to new column	*/
	mvaddstr( row, col, MESSAGE );	/* draw new string	*/
	refresh();			/* and show it		*/
	/*
	 * now handle borders
	 */
	if ( dir == -1 && col <= 0 )
		dir = 1;
	else if ( dir == 1 && col+strlen(MESSAGE) >= COLS )
		dir = -1;
}
/*
 * set members of struct.  
 *   First specify args like those for read(fd, buf, num)  and offset
 *   Then  specify what to do (send signal) and what signal (SIGIO)
 */
void setup_aio_buffer()
{
	static char input[1];		      /* 1 char of input */

	/* describe what to read */
	kbcbuf.aio_fildes     = 0;	      /* standard intput */
	kbcbuf.aio_buf        = input;	      /* buffer          */
	kbcbuf.aio_nbytes     = 1;             /* number to read  */
	kbcbuf.aio_offset     = 0;             /* offset in file  */

	/* describe what to do when read is ready */
	kbcbuf.aio_sigevent.sigev_notify = SIGEV_SIGNAL;
	kbcbuf.aio_sigevent.sigev_signo  = SIGIO;  /* send sIGIO   */
}