et_name.c

Linux下的多协议即时通讯程序源代码

/*
 * Copyright 1987 by MIT Student Information Processing Board
 *
 * For copyright info, see mit-sipb-copyright.h.
 */

#include <sysdep.h>


#define	ERRCODE_RANGE	8	/* # of bits to shift table number */
#define	BITS_PER_CHAR	6	/* # bits to shift per character in name */


static const char char_set[] =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_";

/* Prototypes for -Wmissing-prototypes */
const char * error_table_name(int num);
const char * error_table_name_r(int num, char *buf);

const char * error_table_name_r(int num, char *buf)
{
    int ch;
    int i;
    char *p;

    /* num = aa aaa abb bbb bcc ccc cdd ddd d?? ??? ??? */
    p = buf;
    num >>= ERRCODE_RANGE;
    /* num = ?? ??? ??? aaa aaa bbb bbb ccc ccc ddd ddd */
    num &= 077777777;
    /* num = 00 000 000 aaa aaa bbb bbb ccc ccc ddd ddd */
    for (i = 4; i >= 0; i--) {
	ch = (num >> BITS_PER_CHAR * i) & ((1 << BITS_PER_CHAR) - 1);
	if (ch != 0)
	    *p++ = char_set[ch-1];
    }
    *p = '\0';
    return(buf);
}

const char * error_table_name(int num)
{
    static char buf[6];

    return(error_table_name_r(num, buf));
}