151 lines
3.0 KiB
C++
151 lines
3.0 KiB
C++
/* Copyright (C) 2010 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "precompiled.h"
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#include "Fixed.h"
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#include "ps/CStr.h"
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template<>
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CFixed_15_16 CFixed_15_16::FromString(const CStr8& s)
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{
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// Parse a superset of the xsd:decimal syntax: [-+]?\d*(\.\d*)?
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// TODO: this could be made more precise
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if (s.empty())
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return CFixed_15_16::Zero();
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bool neg = false;
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CFixed_15_16 r;
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const char* c = &s[0];
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if (*c == '+')
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{
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++c;
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}
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else if (*c == '-')
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{
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++c;
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neg = true;
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}
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// Integer part
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while (true)
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{
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if (*c == '.')
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{
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++c;
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// Fractional part
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u32 frac = 0;
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u32 div = 1;
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while (true)
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{
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if (*c >= '0' && *c <= '9')
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{
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frac *= 10;
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frac += (*c - '0');
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div *= 10;
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++c;
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if (div >= 100000)
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{
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// any further digits will be too small to have any effect
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r += CFixed_15_16(((u64)frac << 16) / div);
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break;
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}
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}
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else
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{
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// invalid character or end of string
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r += CFixed_15_16(((u64)frac << 16) / div);
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break;
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}
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}
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break;
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}
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else if (*c >= '0' && *c <= '9')
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{
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r = r * 10; // TODO: handle overflow gracefully, maybe
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r += CFixed_15_16::FromInt(*c - '0');
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++c;
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}
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else
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{
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// invalid character or end of string
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break;
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}
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}
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return (neg ? -r : r);
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}
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template<>
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CFixed_15_16 CFixed_15_16::FromString(const CStrW& s)
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{
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return FromString(CStr8(s));
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}
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// Based on http://www.dspguru.com/dsp/tricks/fixed-point-atan2-with-self-normalization
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CFixed_15_16 atan2_approx(CFixed_15_16 y, CFixed_15_16 x)
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{
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CFixed_15_16 zero;
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// Special case to avoid division-by-zero
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if (x.IsZero() && y.IsZero())
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return zero;
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CFixed_15_16 c1;
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c1.SetInternalValue(51472); // pi/4 << 16
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CFixed_15_16 c2;
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c2.SetInternalValue(154415); // 3*pi/4 << 16
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CFixed_15_16 abs_y = y.Absolute();
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CFixed_15_16 angle;
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if (x >= zero)
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{
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CFixed_15_16 r = (x - abs_y) / (x + abs_y);
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angle = c1 - c1.Multiply(r);
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}
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else
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{
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CFixed_15_16 r = (x + abs_y) / (abs_y - x);
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angle = c2 - c1.Multiply(r);
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}
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if (y < zero)
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return -angle;
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else
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return angle;
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}
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template<>
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CFixed_15_16 CFixed_15_16::Pi()
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{
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return CFixed_15_16(205887); // = pi << 16
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}
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void sincos_approx(CFixed_15_16 a, CFixed_15_16& sin_out, CFixed_15_16& cos_out)
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{
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// XXX: mustn't use floating-point here - need a fixed-point emulation
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sin_out = CFixed_15_16::FromDouble(sin(a.ToDouble()));
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cos_out = CFixed_15_16::FromDouble(cos(a.ToDouble()));
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}
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