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author | Igor Pashev <pashev.igor@gmail.com> | 2012-06-24 22:28:35 +0000 |
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committer | Igor Pashev <pashev.igor@gmail.com> | 2012-06-24 22:28:35 +0000 |
commit | 3950ffe2a485479f6561c27364d3d7df5a21d124 (patch) | |
tree | 468c6e14449d1b1e279222ec32f676b0311917d2 /src/lib/libast/comp/frexpl.c | |
download | ksh-upstream.tar.gz |
Imported Upstream version 93u+upstream
Diffstat (limited to 'src/lib/libast/comp/frexpl.c')
-rw-r--r-- | src/lib/libast/comp/frexpl.c | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/src/lib/libast/comp/frexpl.c b/src/lib/libast/comp/frexpl.c new file mode 100644 index 0000000..5d90ad9 --- /dev/null +++ b/src/lib/libast/comp/frexpl.c @@ -0,0 +1,161 @@ +/*********************************************************************** +* * +* This software is part of the ast package * +* Copyright (c) 1985-2011 AT&T Intellectual Property * +* and is licensed under the * +* Eclipse Public License, Version 1.0 * +* by AT&T Intellectual Property * +* * +* A copy of the License is available at * +* http://www.eclipse.org/org/documents/epl-v10.html * +* (with md5 checksum b35adb5213ca9657e911e9befb180842) * +* * +* Information and Software Systems Research * +* AT&T Research * +* Florham Park NJ * +* * +* Glenn Fowler <gsf@research.att.com> * +* David Korn <dgk@research.att.com> * +* Phong Vo <kpv@research.att.com> * +* * +***********************************************************************/ +#pragma prototyped + +/* + * frexpl/ldexpl implementation + */ + +#include <ast.h> + +#include "FEATURE/float" + +#if _lib_frexpl && _lib_ldexpl + +NoN(frexpl) + +#else + +#ifndef LDBL_MAX_EXP +#define LDBL_MAX_EXP DBL_MAX_EXP +#endif + +#if defined(_ast_fltmax_exp_index) && defined(_ast_fltmax_exp_shift) + +#define INIT() _ast_fltmax_exp_t _pow_ +#define pow2(i) (_pow_.f=1,_pow_.e[_ast_fltmax_exp_index]+=((i)<<_ast_fltmax_exp_shift),_pow_.f) + +#else + +static _ast_fltmax_t pow2tab[LDBL_MAX_EXP + 1]; + +static int +init(void) +{ + register int x; + _ast_fltmax_t g; + + g = 1; + for (x = 0; x < elementsof(pow2tab); x++) + { + pow2tab[x] = g; + g *= 2; + } + return 0; +} + +#define INIT() (pow2tab[0]?0:init()) + +#define pow2(i) (pow2tab[i]) + +#endif + +#if !_lib_frexpl + +#undef frexpl + +extern _ast_fltmax_t +frexpl(_ast_fltmax_t f, int* p) +{ + register int k; + register int x; + _ast_fltmax_t g; + + INIT(); + + /* + * normalize + */ + + x = k = LDBL_MAX_EXP / 2; + if (f < 1) + { + g = 1.0L / f; + for (;;) + { + k = (k + 1) / 2; + if (g < pow2(x)) + x -= k; + else if (k == 1 && g < pow2(x+1)) + break; + else + x += k; + } + if (g == pow2(x)) + x--; + x = -x; + } + else if (f > 1) + { + for (;;) + { + k = (k + 1) / 2; + if (f > pow2(x)) + x += k; + else if (k == 1 && f > pow2(x-1)) + break; + else + x -= k; + } + if (f == pow2(x)) + x++; + } + else + x = 1; + *p = x; + + /* + * shift + */ + + x = -x; + if (x < 0) + f /= pow2(-x); + else if (x < LDBL_MAX_EXP) + f *= pow2(x); + else + f = (f * pow2(LDBL_MAX_EXP - 1)) * pow2(x - (LDBL_MAX_EXP - 1)); + return f; +} + +#endif + +#if !_lib_ldexpl + +#undef ldexpl + +extern _ast_fltmax_t +ldexpl(_ast_fltmax_t f, register int x) +{ + INIT(); + if (x < 0) + f /= pow2(-x); + else if (x < LDBL_MAX_EXP) + f *= pow2(x); + else + f = (f * pow2(LDBL_MAX_EXP - 1)) * pow2(x - (LDBL_MAX_EXP - 1)); + return f; +} + +#endif + +#endif |