X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=lib%2Ffrexp.c;fp=lib%2Ffrexp.c;h=e139885c338fe34aec03ce8b78f5a31eaa7498f3;hb=a2016c1de6e4884f6c8ed5cc498f3bf821c25ca4;hp=7e1f5d1ad48e07de95943f3fd6d3664dda8df109;hpb=c7e61475680fa226bd9b8bdd469cd66914e630f5;p=debian%2Fgzip diff --git a/lib/frexp.c b/lib/frexp.c index 7e1f5d1..e139885 100644 --- a/lib/frexp.c +++ b/lib/frexp.c @@ -1,5 +1,5 @@ /* Split a double into fraction and mantissa. - Copyright (C) 2007-2008 Free Software Foundation, Inc. + Copyright (C) 2007-2010 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 @@ -85,73 +85,73 @@ FUNC (DOUBLE x, int *expptr) exponent = 0; if (x >= L_(1.0)) { - /* A positive 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; - } - /* Avoid making x too small, as it could become a denormalized - number and thus lose precision. */ - while (i > 0 && x < pow2[i - 1]) - { - i--; - powh_i = powh[i]; - } - exponent += (1 << i); - x *= powh_i; - /* Here 2^-2^i <= x < 1.0. */ + /* A positive 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; + } + /* Avoid making x too small, as it could become a denormalized + number and thus lose precision. */ + while (i > 0 && x < pow2[i - 1]) + { + i--; + powh_i = powh[i]; + } + exponent += (1 << i); + x *= powh_i; + /* Here 2^-2^i <= x < 1.0. */ } else { - /* A negative or zero 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 < powh_i) - { - exponent -= (1 << i); - x *= pow2_i; - } - else - break; - - pow2[i] = pow2_i; - powh[i] = powh_i; - } - /* Here 2^-2^i <= x < 1.0. */ + /* A negative or zero 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 < powh_i) + { + exponent -= (1 << i); + x *= pow2_i; + } + else + break; + + pow2[i] = pow2_i; + powh[i] = powh_i; + } + /* Here 2^-2^i <= x < 1.0. */ } /* Invariants: x * 2^exponent = argument, and 2^-2^i <= x < 1.0. */ while (i > 0) { - i--; - if (x < powh[i]) - { - exponent -= (1 << i); - x *= pow2[i]; - } + i--; + if (x < powh[i]) + { + exponent -= (1 << i); + x *= pow2[i]; + } } /* Here 0.5 <= x < 1.0. */ }