Source code of Windows XP (NT5)
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/*-----------------------------------------------------------------------------+
| MATH.C || || Written to provide MulDiv32 for the Win32 version of MPlayer2 || || Multiplies two 32 bit values and then divides the result by a third || 32 bit value with full 64 bit precision || N.B. NOT TRUE. However it is good enough for general MPlayer use. || || lResult = (lNumber * lNumerator) / lDenominator with correct rounding || || Entry: || lNumber = number to multiply by nNumerator || lNumerator = number to multiply by nNumber || lDenominator = number to divide the multiplication result by. || || Returns: || result of multiplication and division. || || (This is less accurate than the Win16 ASM version as it cannot be written in || ASM (for portability reasons) and NT doesn't yet support 64 bit arithmetic) || This file houses the discardable code used at initialisation time. Among || other things, this code reads .INI information and looks for MCI devices. || || || NOTE: This code is NOT safe when the intermediate result becomes negative || or overflows. However it is simple, quick, and safe for a wide || number of uses within MPLayer. || || (C) Copyright Microsoft Corporation 1991. All rights reserved. || || Revision History || 21-Oct-1992 MikeTri Created by "cloning" MATH.ASM || |+------------------------------------------------------------------------------+| || Original MulDiv32 PseudoCode || ============================ || || long FAR PASCAL muldiv32(long, long, long) || long l; || long Numer; || long Denom; || { || || Sign = sign of Denom; // Sign will keep track of final sign // |
| || || if (Denom < 0) || { || negate Denom; // make sure Denom is positive // |
| } || || if (l < 0) || { || negate l; // make sure l is positive // |
| } || || make Sign reflect any sign change; || || || if (Numer < 0) || { || negate Numer; // make sure Numer is positive // |
| } || || make Sign reflect any sign change; || || Numer *= l; || Numer += (Denom/2); // adjust for rounding // |
| || if (overflow) // check for overflow, and handle divide by zero //|
| { || jump to md5; || } || || result = Numer/Denom; || || if (overflow) // check again to see if overflow occured // |
| { || jump to md5; || } || || if (Sign is negative) // put sign on the result // |
| { || negate result; || } || ||md6: || return(result); || ||md5: || DX = 7FFF; // indicate overflow by // |
| AX = 0xFFFF // return largest integer // |
| if (Sign is negative) || { || DX = 0x8000; // with correct sign // |
| AX = 0x0000; || } || || jump to md6; || } |\-----------------------------------------------------------------------------*/
#include <windows.h>
LONG FAR PASCAL muldiv32(long l, long Numer, long Denom){ return( (l*Numer)/Denom);}
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