From b2cfc4e2e71d0f0a5113ddfbd93c8285cc4d74e4 Mon Sep 17 00:00:00 2001 From: rsc Date: Tue, 30 Sep 2003 17:47:41 +0000 Subject: Initial revision --- src/libfmt/pow10.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 src/libfmt/pow10.c (limited to 'src/libfmt/pow10.c') diff --git a/src/libfmt/pow10.c b/src/libfmt/pow10.c new file mode 100644 index 00000000..65a426c3 --- /dev/null +++ b/src/libfmt/pow10.c @@ -0,0 +1,57 @@ +/* + * The authors of this software are Rob Pike and Ken Thompson. + * Copyright (c) 2002 by Lucent Technologies. + * Permission to use, copy, modify, and distribute this software for any + * purpose without fee is hereby granted, provided that this entire notice + * is included in all copies of any software which is or includes a copy + * or modification of this software and in all copies of the supporting + * documentation for such software. + * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED + * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY + * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY + * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. + */ +#include +#include +#include "utf.h" +#include "fmt.h" +#include "fmtdef.h" + +/* + * this table might overflow 127-bit exponent representations. + * in that case, truncate it after 1.0e38. + * it is important to get all one can from this + * routine since it is used in atof to scale numbers. + * the presumption is that C converts fp numbers better + * than multipication of lower powers of 10. + */ + +static +double tab[] = +{ + 1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1.0e9, + 1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1.0e19, + 1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1.0e29, + 1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1.0e39, + 1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1.0e49, + 1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1.0e59, + 1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1.0e69, +}; + +double +__fmtpow10(int n) +{ + int m; + + if(n < 0) { + n = -n; + if(n < (int)(sizeof(tab)/sizeof(tab[0]))) + return 1/tab[n]; + m = n/2; + return __fmtpow10(-m) * __fmtpow10(m-n); + } + if(n < (int)(sizeof(tab)/sizeof(tab[0]))) + return tab[n]; + m = n/2; + return __fmtpow10(m) * __fmtpow10(n-m); +} -- cgit v1.2.3