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61 lines
2.0 KiB
C
61 lines
2.0 KiB
C
/*
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* The authors of this software are Rob Pike and Ken Thompson,
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* with contributions from Mike Burrows and Sean Dorward.
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*
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* Copyright (c) 2002-2006 by Lucent Technologies.
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* Portions Copyright (c) 2004 Google Inc.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose without fee is hereby granted, provided that this entire notice
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* is included in all copies of any software which is or includes a copy
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* or modification of this software and in all copies of the supporting
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* documentation for such software.
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* THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
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* WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES
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* NOR GOOGLE INC MAKE ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING
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* THE MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
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*/
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#include <u.h>
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#include <libc.h>
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#include "fmtdef.h"
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/*
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* this table might overflow 127-bit exponent representations.
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* in that case, truncate it after 1.0e38.
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* it is important to get all one can from this
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* routine since it is used in atof to scale numbers.
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* the presumption is that C converts fp numbers better
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* than multipication of lower powers of 10.
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*/
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static
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double tab[] =
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{
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1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1.0e9,
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1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1.0e19,
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1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1.0e29,
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1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1.0e39,
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1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1.0e49,
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1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1.0e59,
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1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1.0e69,
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};
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double
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__fmtpow10(int n)
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{
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int m;
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if(n < 0) {
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n = -n;
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if(n < (int)(sizeof(tab)/sizeof(tab[0])))
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return 1/tab[n];
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m = n/2;
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return __fmtpow10(-m) * __fmtpow10(m-n);
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}
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if(n < (int)(sizeof(tab)/sizeof(tab[0])))
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return tab[n];
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m = n/2;
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return __fmtpow10(m) * __fmtpow10(n-m);
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}
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