// $Id: fix24.cpp 1282 2006-06-09 09:46:49Z alex $ /* @@tag:xara-cn@@ DO NOT MODIFY THIS LINE ================================XARAHEADERSTART=========================== Xara LX, a vector drawing and manipulation program. Copyright (C) 1993-2006 Xara Group Ltd. Copyright on certain contributions may be held in joint with their respective authors. See AUTHORS file for details. LICENSE TO USE AND MODIFY SOFTWARE ---------------------------------- This file is part of Xara LX. Xara LX is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation. Xara LX and its component source files are 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. 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Captain's Log - supplementary // ==================================================== // // Pirated fixed16 code to base fixed24 upon // This was from revision 1.24 of fixed16.cpp // Jason #include "camtypes.h" //#include "fixed24.h" - in camtypes.h [AUTOMATICALLY REMOVED] //#include "fix24.h" - in camtypes.h [AUTOMATICALLY REMOVED] /******************************************************************************************** > FIXED24 Fixed24Mul(FIXED24 arg1, FIXED24 arg2) Author: Gavin_Theobald (Xara Group Ltd) Created: 15/6/2005 Inputs: two fixed24s Outputs: None Returns: FIXED24 result (arg1 * arg2) Scope: Only to be used in the FIXED24 class. Purpose: signed multiplication Errors: None (no overflow checks). Rounds ********************************************************************************************/ fixed24 Fixed24Mul( fixed24 a, fixed24 b ) { fixed24 result; result.all = INT32((Int32x32To64(a.all,b.all)+0x800000)>>24) ; return result; } /******************************************************************************************** > FIXED24 Fixed24Div(FIXED24 arg1, FIXED24 arg2) Author: Gavin_Theobald (Xara Group Ltd) Created: 15/6/2005 Inputs: two fixed24s Outputs: None Returns: FIXED24 result (arg1 / arg2) Scope: Only to be used in the FIXED24 class. Purpose: signed division Errors: None (no overflow checks). No rounding either (should it?) Overflow will cause a DIV0 exception, as will divide by zero Note that this is not very efficient as it forces a multiply that could instead be performed by a shift. The alternative is to use int64s but this would then compile as a 64bit/64bit division which is worse. Why isn't there a Int64div32to32 function? ********************************************************************************************/ fixed24 Fixed24Div(fixed24 a,fixed24 b) { fixed24 result ; result.all = MulDiv(a.all,1<<24,b.all) ; return result ; } /******************************************************************************************** > double Fixed24ToDouble( FIXED24 arg ) Author: Gavin_Theobald (Xara Group Ltd) Created: 15/6/2005 Inputs: FIXED24 argument Outputs: None Returns: double-precision value Scope: Only to be used in the FIXED24 class. Purpose: General type conversion Errors: None This code relies on the compiler efficiently replacing the division by a multiplication of the reciprical. ********************************************************************************************/ double Fixed24ToDouble( fixed24 a ) { return (double)a.all/(1<<24) ; } /******************************************************************************************** > fixed24 DoubleToFixed24( double arg ) Author: Gavin_Theobald (Xara Group Ltd) Created: 15/6/2005 Inputs: double-precision argument Outputs: None Returns: FIXED24 value Purpose: General type conversion Errors: None (overflow will cause exception) ********************************************************************************************/ fixed24 DoubleToFixed24( double arg ) { fixed24 result ; #if 0 //defined(_M_IX86) // // This avoids the slow fix operation. Add a large number so that // the double always has the same exponent and the mantissa becomes, // in affect, a fixed point value with the value we want in the // bottom 32 bits. // // Note that we are relying on the compiler to convert this to // efficient code. // // TODO: Test! // static const double fFix = (XLONG)3<<(DBL_MANT_DIG-24-2); double F = arg+fFix; result.all = (INT32&)F ; #else result.all = INT32(arg*(1<<24)) ; #endif return result ; }