1*0d601874SDavid du Colombier /* 2*0d601874SDavid du Colombier * The authors of this software are Rob Pike and Ken Thompson. 3*0d601874SDavid du Colombier * Copyright (c) 2002 by Lucent Technologies. 4*0d601874SDavid du Colombier * Permission to use, copy, modify, and distribute this software for any 5*0d601874SDavid du Colombier * purpose without fee is hereby granted, provided that this entire notice 6*0d601874SDavid du Colombier * is included in all copies of any software which is or includes a copy 7*0d601874SDavid du Colombier * or modification of this software and in all copies of the supporting 8*0d601874SDavid du Colombier * documentation for such software. 9*0d601874SDavid du Colombier * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED 10*0d601874SDavid du Colombier * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE 11*0d601874SDavid du Colombier * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY 12*0d601874SDavid du Colombier * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. 13*0d601874SDavid du Colombier */ 148ccd4a63SDavid du Colombier #include <u.h> 158ccd4a63SDavid du Colombier #include <libc.h> 16*0d601874SDavid du Colombier #include "fmtdef.h" 178ccd4a63SDavid du Colombier 188ccd4a63SDavid du Colombier /* 198ccd4a63SDavid du Colombier * this table might overflow 127-bit exponent representations. 208ccd4a63SDavid du Colombier * in that case, truncate it after 1.0e38. 218ccd4a63SDavid du Colombier * it is important to get all one can from this 228ccd4a63SDavid du Colombier * routine since it is used in atof to scale numbers. 238ccd4a63SDavid du Colombier * the presumption is that C converts fp numbers better 248ccd4a63SDavid du Colombier * than multipication of lower powers of 10. 258ccd4a63SDavid du Colombier */ 26*0d601874SDavid du Colombier 278ccd4a63SDavid du Colombier static 288ccd4a63SDavid du Colombier double tab[] = 298ccd4a63SDavid du Colombier { 308ccd4a63SDavid du Colombier 1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1.0e9, 318ccd4a63SDavid du Colombier 1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1.0e19, 328ccd4a63SDavid du Colombier 1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1.0e29, 338ccd4a63SDavid du Colombier 1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1.0e39, 348ccd4a63SDavid du Colombier 1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1.0e49, 358ccd4a63SDavid du Colombier 1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1.0e59, 368ccd4a63SDavid du Colombier 1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1.0e69, 378ccd4a63SDavid du Colombier }; 388ccd4a63SDavid du Colombier 398ccd4a63SDavid du Colombier double 40*0d601874SDavid du Colombier __fmtpow10(int n) 418ccd4a63SDavid du Colombier { 428ccd4a63SDavid du Colombier int m; 438ccd4a63SDavid du Colombier 448ccd4a63SDavid du Colombier if(n < 0) { 458ccd4a63SDavid du Colombier n = -n; 46*0d601874SDavid du Colombier if(n < (int)(sizeof(tab)/sizeof(tab[0]))) 478ccd4a63SDavid du Colombier return 1/tab[n]; 488ccd4a63SDavid du Colombier m = n/2; 49*0d601874SDavid du Colombier return __fmtpow10(-m) * __fmtpow10(m-n); 508ccd4a63SDavid du Colombier } 51*0d601874SDavid du Colombier if(n < (int)(sizeof(tab)/sizeof(tab[0]))) 528ccd4a63SDavid du Colombier return tab[n]; 538ccd4a63SDavid du Colombier m = n/2; 54*0d601874SDavid du Colombier return __fmtpow10(m) * __fmtpow10(n-m); 558ccd4a63SDavid du Colombier } 56