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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [s_trunc.c] - Blame information for rev 207

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/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */
/*
FUNCTION
<<trunc>>, <<truncf>>--round to integer, towards zero
INDEX
        trunc
INDEX
        truncf
 
ANSI_SYNOPSIS
        #include <math.h>
        double trunc(double <[x]>);
        float truncf(float <[x]>);
 
DESCRIPTION
        The <<trunc>> functions round their argument to the integer value, in
        floating format, nearest to but no larger in magnitude than the
        argument, regardless of the current rounding direction.  (While the
        "inexact" floating-point exception behavior is unspecified by the C
        standard, the <<trunc>> functions are written so that "inexact" is not
        raised if the result does not equal the argument, which behavior is as
        recommended by IEEE 754 for its related functions.)
 
RETURNS
<[x]> truncated to an integral value.
 
PORTABILITY
ANSI C, POSIX
 
*/
 
#include "fdlibm.h"
 
#ifndef _DOUBLE_IS_32BITS
 
#ifdef __STDC__
        double trunc(double x)
#else
        double trunc(x)
        double x;
#endif
{
  int signbit;
  /* Most significant word, least significant word. */
  int msw;
  unsigned int lsw;
  int exponent_less_1023;
 
  EXTRACT_WORDS(msw, lsw, x);
 
  /* Extract sign bit. */
  signbit = msw & 0x80000000;
 
  /* Extract exponent field. */
  exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;
 
  if (exponent_less_1023 < 20)
    {
      /* All significant digits are in msw. */
      if (exponent_less_1023 < 0)
        {
          /* -1 < x < 1, so result is +0 or -0. */
          INSERT_WORDS(x, signbit, 0);
        }
      else
        {
          /* All relevant fraction bits are in msw, so lsw of the result is 0. */
          INSERT_WORDS(x, signbit | (msw & ~(0x000fffff >> exponent_less_1023)), 0);
        }
    }
  else if (exponent_less_1023 > 51)
    {
      if (exponent_less_1023 == 1024)
        {
          /* x is infinite, or not a number, so trigger an exception. */
          return x + x;
        }
      /* All bits in the fraction fields of the msw and lsw are needed in the result. */
    }
  else
    {
      /* All fraction bits in msw are relevant.  Truncate irrelevant
         bits from lsw. */
      INSERT_WORDS(x, msw, lsw & ~(0xffffffffu >> (exponent_less_1023 - 20)));
    }
  return x;
}
 
#endif /* _DOUBLE_IS_32BITS */

Line No.	Rev	Author	Line
1	207	jeremybenn	`/*`
2			`* ====================================================`
3			`* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.`
4			`*`
5			`* Developed at SunPro, a Sun Microsystems, Inc. business.`
6			`* Permission to use, copy, modify, and distribute this`
7			`* software is freely granted, provided that this notice`
8			`* is preserved.`
9			`* ====================================================`
10			`*/`
11			`/*`
12			`FUNCTION`
13			`<<trunc>>, <<truncf>>--round to integer, towards zero`
14			`INDEX`
15			`trunc`
16			`INDEX`
17			`truncf`
18
19			`ANSI_SYNOPSIS`
20			`#include <math.h>`
21			`double trunc(double <[x]>);`
22			`float truncf(float <[x]>);`
23
24			`DESCRIPTION`
25			`The <<trunc>> functions round their argument to the integer value, in`
26			`floating format, nearest to but no larger in magnitude than the`
27			`argument, regardless of the current rounding direction. (While the`
28			`"inexact" floating-point exception behavior is unspecified by the C`
29			`standard, the <<trunc>> functions are written so that "inexact" is not`
30			`raised if the result does not equal the argument, which behavior is as`
31			`recommended by IEEE 754 for its related functions.)`
32
33			`RETURNS`
34			`<[x]> truncated to an integral value.`
35
36			`PORTABILITY`
37			`ANSI C, POSIX`
38
39			`*/`
40
41			`#include "fdlibm.h"`
42
43			`#ifndef _DOUBLE_IS_32BITS`
44
45			`#ifdef __STDC__`
46			`double trunc(double x)`
47			`#else`
48			`double trunc(x)`
49			`double x;`
50			`#endif`
51			`{`
52			`int signbit;`
53			`/* Most significant word, least significant word. */`
54			`int msw;`
55			`unsigned int lsw;`
56			`int exponent_less_1023;`
57
58			`EXTRACT_WORDS(msw, lsw, x);`
59
60			`/* Extract sign bit. */`
61			`signbit = msw & 0x80000000;`
62
63			`/* Extract exponent field. */`
64			`exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;`
65
66			`if (exponent_less_1023 < 20)`
67			`{`
68			`/* All significant digits are in msw. */`
69			`if (exponent_less_1023 < 0)`
70			`{`
71			`/* -1 < x < 1, so result is +0 or -0. */`
72			`INSERT_WORDS(x, signbit, 0);`
73			`}`
74			`else`
75			`{`
76			`/* All relevant fraction bits are in msw, so lsw of the result is 0. */`
77			`INSERT_WORDS(x, signbit \| (msw & ~(0x000fffff >> exponent_less_1023)), 0);`
78			`}`
79			`}`
80			`else if (exponent_less_1023 > 51)`
81			`{`
82			`if (exponent_less_1023 == 1024)`
83			`{`
84			`/* x is infinite, or not a number, so trigger an exception. */`
85			`return x + x;`
86			`}`
87			`/* All bits in the fraction fields of the msw and lsw are needed in the result. */`
88			`}`
89			`else`
90			`{`
91			`/* All fraction bits in msw are relevant. Truncate irrelevant`
92			`bits from lsw. */`
93			`INSERT_WORDS(x, msw, lsw & ~(0xffffffffu >> (exponent_less_1023 - 20)));`
94			`}`
95			`return x;`
96			`}`
97
98			`#endif /* _DOUBLE_IS_32BITS */`

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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [s_trunc.c] - Blame information for rev 207