1 91c13e54 2004-02-29 devnull /*
 2 91c13e54 2004-02-29 devnull  * The authors of this software are Rob Pike and Ken Thompson.
 3 91c13e54 2004-02-29 devnull  *              Copyright (c) 2002 by Lucent Technologies.
 4 91c13e54 2004-02-29 devnull  * Permission to use, copy, modify, and distribute this software for any
 5 91c13e54 2004-02-29 devnull  * purpose without fee is hereby granted, provided that this entire notice
 6 91c13e54 2004-02-29 devnull  * is included in all copies of any software which is or includes a copy
 7 91c13e54 2004-02-29 devnull  * or modification of this software and in all copies of the supporting
 8 91c13e54 2004-02-29 devnull  * documentation for such software.
 9 91c13e54 2004-02-29 devnull  * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
10 c90dd38f 2004-12-29 devnull  * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
11 c90dd38f 2004-12-29 devnull  * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
12 91c13e54 2004-02-29 devnull  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
13 91c13e54 2004-02-29 devnull  */
14 91c13e54 2004-02-29 devnull #include <stdarg.h>
15 91c13e54 2004-02-29 devnull #include <string.h>
16 e5aa96ac 2004-12-26 devnull #include "plan9.h"
17 91c13e54 2004-02-29 devnull #include "fmt.h"
18 91c13e54 2004-02-29 devnull #include "fmtdef.h"
19 91c13e54 2004-02-29 devnull 
20 91c13e54 2004-02-29 devnull /*
21 91c13e54 2004-02-29 devnull  * this table might overflow 127-bit exponent representations.
22 91c13e54 2004-02-29 devnull  * in that case, truncate it after 1.0e38.
23 91c13e54 2004-02-29 devnull  * it is important to get all one can from this
24 91c13e54 2004-02-29 devnull  * routine since it is used in atof to scale numbers.
25 91c13e54 2004-02-29 devnull  * the presumption is that C converts fp numbers better
26 91c13e54 2004-02-29 devnull  * than multipication of lower powers of 10.
27 91c13e54 2004-02-29 devnull  */
28 91c13e54 2004-02-29 devnull 
29 91c13e54 2004-02-29 devnull static
30 91c13e54 2004-02-29 devnull double	tab[] =
31 91c13e54 2004-02-29 devnull {
32 91c13e54 2004-02-29 devnull 	1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1.0e9,
33 91c13e54 2004-02-29 devnull 	1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1.0e19,
34 91c13e54 2004-02-29 devnull 	1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1.0e29,
35 91c13e54 2004-02-29 devnull 	1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1.0e39,
36 91c13e54 2004-02-29 devnull 	1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1.0e49,
37 91c13e54 2004-02-29 devnull 	1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1.0e59,
38 91c13e54 2004-02-29 devnull 	1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1.0e69,
39 91c13e54 2004-02-29 devnull };
40 91c13e54 2004-02-29 devnull 
41 91c13e54 2004-02-29 devnull double
42 91c13e54 2004-02-29 devnull __fmtpow10(int n)
43 91c13e54 2004-02-29 devnull {
44 91c13e54 2004-02-29 devnull 	int m;
45 91c13e54 2004-02-29 devnull 
46 91c13e54 2004-02-29 devnull 	if(n < 0) {
47 91c13e54 2004-02-29 devnull 		n = -n;
48 91c13e54 2004-02-29 devnull 		if(n < (int)(sizeof(tab)/sizeof(tab[0])))
49 91c13e54 2004-02-29 devnull 			return 1/tab[n];
50 91c13e54 2004-02-29 devnull 		m = n/2;
51 91c13e54 2004-02-29 devnull 		return __fmtpow10(-m) * __fmtpow10(m-n);
52 91c13e54 2004-02-29 devnull 	}
53 91c13e54 2004-02-29 devnull 	if(n < (int)(sizeof(tab)/sizeof(tab[0])))
54 91c13e54 2004-02-29 devnull 		return tab[n];
55 91c13e54 2004-02-29 devnull 	m = n/2;
56 91c13e54 2004-02-29 devnull 	return __fmtpow10(m) * __fmtpow10(n-m);
57 91c13e54 2004-02-29 devnull }