Imported Upstream version 1.3.14

[debian/gzip] / lib / printf-frexp.c

diff --git a/lib/printf-frexp.c b/lib/printf-frexp.c
new file mode 100644 (file)
index 0000000..da5c9c3
--- /dev/null
+++ b/lib/printf-frexp.c
@@ -0,0 +1,188 @@
+/* Split a double into fraction and mantissa, for hexadecimal printf.
+   Copyright (C) 2007 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#ifdef USE_LONG_DOUBLE
+# include "printf-frexpl.h"
+#else
+# include "printf-frexp.h"
+#endif
+
+#include <float.h>
+#include <math.h>
+#ifdef USE_LONG_DOUBLE
+# include "fpucw.h"
+#endif
+
+/* This file assumes FLT_RADIX = 2.  If FLT_RADIX is a power of 2 greater
+   than 2, or not even a power of 2, some rounding errors can occur, so that
+   then the returned mantissa is only guaranteed to be <= 2.0, not < 2.0.  */
+
+#ifdef USE_LONG_DOUBLE
+# define FUNC printf_frexpl
+# define DOUBLE long double
+# define MIN_EXP LDBL_MIN_EXP
+# if HAVE_FREXPL_IN_LIBC && HAVE_LDEXPL_IN_LIBC
+#  define USE_FREXP_LDEXP
+#  define FREXP frexpl
+#  define LDEXP ldexpl
+# endif
+# define DECL_ROUNDING DECL_LONG_DOUBLE_ROUNDING
+# define BEGIN_ROUNDING() BEGIN_LONG_DOUBLE_ROUNDING ()
+# define END_ROUNDING() END_LONG_DOUBLE_ROUNDING ()
+# define L_(literal) literal##L
+#else
+# define FUNC printf_frexp
+# define DOUBLE double
+# define MIN_EXP DBL_MIN_EXP
+# if HAVE_FREXP_IN_LIBC && HAVE_LDEXP_IN_LIBC
+#  define USE_FREXP_LDEXP
+#  define FREXP frexp
+#  define LDEXP ldexp
+# endif
+# define DECL_ROUNDING
+# define BEGIN_ROUNDING()
+# define END_ROUNDING()
+# define L_(literal) literal
+#endif
+
+DOUBLE
+FUNC (DOUBLE x, int *expptr)
+{
+  int exponent;
+  DECL_ROUNDING
+
+  BEGIN_ROUNDING ();
+
+#ifdef USE_FREXP_LDEXP
+  /* frexp and ldexp are usually faster than the loop below.  */
+  x = FREXP (x, &exponent);
+
+  x = x + x;
+  exponent -= 1;
+
+  if (exponent < MIN_EXP - 1)
+    {
+      x = LDEXP (x, exponent - (MIN_EXP - 1));
+      exponent = MIN_EXP - 1;
+    }
+#else
+  {
+    /* Since the exponent is an 'int', it fits in 64 bits.  Therefore the
+       loops are executed no more than 64 times.  */
+    DOUBLE pow2[64]; /* pow2[i] = 2^2^i */
+    DOUBLE powh[64]; /* powh[i] = 2^-2^i */
+    int i;
+
+    exponent = 0;
+    if (x >= L_(1.0))
+      {
+       /* A nonnegative exponent.  */
+       {
+         DOUBLE pow2_i; /* = pow2[i] */
+         DOUBLE powh_i; /* = powh[i] */
+
+         /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
+            x * 2^exponent = argument, x >= 1.0.  */
+         for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
+              ;
+              i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
+           {
+             if (x >= pow2_i)
+               {
+                 exponent += (1 << i);
+                 x *= powh_i;
+               }
+             else
+               break;
+
+             pow2[i] = pow2_i;
+             powh[i] = powh_i;
+           }
+       }
+       /* Here 1.0 <= x < 2^2^i.  */
+      }
+    else
+      {
+       /* A negative exponent.  */
+       {
+         DOUBLE pow2_i; /* = pow2[i] */
+         DOUBLE powh_i; /* = powh[i] */
+
+         /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
+            x * 2^exponent = argument, x < 1.0, exponent >= MIN_EXP - 1.  */
+         for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
+              ;
+              i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
+           {
+             if (exponent - (1 << i) < MIN_EXP - 1)
+               break;
+
+             exponent -= (1 << i);
+             x *= pow2_i;
+             if (x >= L_(1.0))
+               break;
+
+             pow2[i] = pow2_i;
+             powh[i] = powh_i;
+           }
+       }
+       /* Here either x < 1.0 and exponent - 2^i < MIN_EXP - 1 <= exponent,
+          or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1.  */
+
+       if (x < L_(1.0))
+         /* Invariants: x * 2^exponent = argument, x < 1.0 and
+            exponent - 2^i < MIN_EXP - 1 <= exponent.  */
+         while (i > 0)
+           {
+             i--;
+             if (exponent - (1 << i) >= MIN_EXP - 1)
+               {
+                 exponent -= (1 << i);
+                 x *= pow2[i];
+                 if (x >= L_(1.0))
+                   break;
+               }
+           }
+
+       /* Here either x < 1.0 and exponent = MIN_EXP - 1,
+          or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1.  */
+      }
+
+    /* Invariants: x * 2^exponent = argument, and
+       either x < 1.0 and exponent = MIN_EXP - 1,
+       or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1.  */
+    while (i > 0)
+      {
+       i--;
+       if (x >= pow2[i])
+         {
+           exponent += (1 << i);
+           x *= powh[i];
+         }
+      }
+    /* Here either x < 1.0 and exponent = MIN_EXP - 1,
+       or 1.0 <= x < 2.0 and exponent >= MIN_EXP - 1.  */
+  }
+#endif
+
+  END_ROUNDING ();
+
+  *expptr = exponent;
+  return x;
+}