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