mathevrc.c

EVRC是用于高通公司的语音编码

 *     Perform a fractional multipy of the two 16 bit input numbers
 *     with saturation.  Output a 32 bit number.
 *
 *   INPUTS:
 *
 *     var1
 *                     16 bit short signed integer (Shortword) whose value
 *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
 *     var2
 *                     16 bit short signed integer (Shortword) whose value
 *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
 *
 *   OUTPUTS:
 *
 *     none
 *
 *   RETURN VALUE:
 *
 *     L_Out
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *
 *   IMPLEMENTATION:
 *
 *     Multiply the two the two 16 bit input numbers. If the
 *     result is within this range, left shift the result by one
 *     and output the 32 bit number.  The only possible overflow
 *     occurs when var1==var2==-0x8000.  In this case output
 *     0x7fff ffff.
 *
 *   KEYWORDS: multiply, mult, mpy
 *
 *************************************************************************/

Longword L_mult(Shortword var1, Shortword var2)
{
	Longword L_product;

    OP_COUNT(1);        /* Complexity Count -- LT 6/96 */

    if (var1 == SW_MIN && var2 == SW_MIN)
	{
		L_product = LW_MAX;		/* overflow */
		giOverflow = 1;
	}
	else
	{
		L_product = (Longword) var1 *var2;	/* integer multiply */

		L_product = L_product << 1;
	}
	return (L_product);
}

/***************************************************************************
 *
 *   FUNCTION NAME: L_negate
 *
 *   PURPOSE:
 *
 *     Negate the 32 bit input. 0x8000 0000's negated value is
 *     0x7fff ffff.
 *
 *   INPUTS:
 *
 *     L_var1
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *
 *   OUTPUTS:
 *
 *     none
 *
 *   RETURN VALUE:
 *
 *     L_Out
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0001 <= L_var1 <= 0x7fff ffff.
 *
 *   KEYWORDS: negate, negative
 *
 *************************************************************************/

Longword L_negate(Longword L_var1)
{
	Longword L_Out;

    OP_COUNT(2);        /* Complexity Count -- LT 6/96 */

    if (L_var1 == LW_MIN)
	{
		L_Out = LW_MAX;
		giOverflow = 1;
	}
	else
		L_Out = -L_var1;
	return (L_Out);
}

/***************************************************************************
 *
 *   FUNCTION NAME: L_shift_r
 *
 *   PURPOSE:
 *
 *     Shift and round.  Perform a shift right. After shifting, use
 *     the last bit shifted out of the LSB to round the result up
 *     or down.
 *
 *   INPUTS:
 *
 *     L_var1
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *     var2
 *                     16 bit short signed integer (Shortword) whose value
 *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
 *
 *   OUTPUTS:
 *
 *     none
 *
 *   RETURN VALUE:
 *
 *     L_var1
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *
 *
 *   IMPLEMENTATION:
 *
 *     Shift and round.  Perform a shift right. After shifting, use
 *     the last bit shifted out of the LSB to round the result up
 *     or down.  This is just like shift_r above except that the
 *     input/output is 32 bits as opposed to 16.
 *
 *     if var2 is positve perform a arithmetic left shift
 *     with saturation (see L_shl() above).
 *
 *     If var2 is zero simply return L_var1.
 *
 *     If var2 is negative perform a arithmetic right shift (L_shr)
 *     of L_var1 by (-var2)+1.  Add the LS bit of the result to
 *     L_var1 shifted right (L_shr) by -var2.
 *
 *     Note that there is no constraint on var2, so if var2 is
 *     -0xffff 8000 then -var2 is 0x0000 8000, not 0x0000 7fff.
 *     This is the reason the L_shl function is used.
 *
 *
 *   KEYWORDS:
 *
 *************************************************************************/

Longword L_shift_r(Longword L_var1, Shortword var2)
{
	Longword L_Out, L_rnd;

    OP_COUNT(3);        /* Complexity Count -- LT 6/96 */

    if (var2 < -31)
	{
		L_Out = 0;
	}
	else if (var2 < 0)
	{
		/* right shift */
        L_rnd = L_shl(L_var1, var2 + 1) & 0x1;      OP_COUNT(-2);   /* LT 6/96 */
        L_Out = L_add(L_shl(L_var1, var2), L_rnd);  OP_COUNT(-2);   /* LT 6/96 */
	}
	else
    {
        L_Out = L_shl(L_var1, var2);                OP_COUNT(-2);   /* LT 6/96 */
    }

	return (L_Out);
}

/***************************************************************************
 *
 *   FUNCTION NAME: L_shl
 *
 *   PURPOSE:
 *
 *     Arithmetic shift left (or right).
 *     Arithmetically shift the input left by var2.   If var2 is
 *     negative then an arithmetic shift right (L_shr) of L_var1 by
 *     -var2 is performed.
 *
 *   INPUTS:
 *
 *     var2
 *                     16 bit short signed integer (Shortword) whose value
 *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
 *     L_var1
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *   OUTPUTS:
 *
 *     none
 *
 *   RETURN VALUE:
 *
 *     L_Out
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *
 *
 *   IMPLEMENTATION:
 *
 *     Arithmetically shift the 32 bit input left by var2.  This
 *     operation maintains the sign of the input number. If var2 is
 *     negative then an arithmetic shift right (L_shr) of L_var1 by
 *     -var2 is performed.  See description of L_shr for details.
 *
 *     Equivalent to the Full-Rate GSM ">> n" operation.  Note that
 *     ANSI-C does not guarantee operation of the C ">>" or "<<"
 *     operator for negative numbers.
 *
 *   KEYWORDS: shift, arithmetic shift left,
 *
 *************************************************************************/

Longword L_shl(Longword L_var1, Shortword var2)
{

	Longword L_Mask, L_Out;
	int i, iOverflow = 0;

    OP_COUNT(2);        /* Complexity Count -- LT 6/96 */

	if (var2 == 0 || L_var1 == 0)
	{
		L_Out = L_var1;
	}
	else if (var2 < 0)
	{
		if (var2 <= -31)
		{
			if (L_var1 > 0)
				L_Out = 0;
			else
				L_Out = 0xffffffffL;
		}
		else
        {
            L_Out = L_shr(L_var1, -var2);
            OP_COUNT(-2);        /* Complexity Count -- LT 6/96 */
        }
	}
	else
	{

		if (var2 >= 31)
			iOverflow = 1;

		else
		{

			if (L_var1 < 0)
				L_Mask = LW_SIGN;	/* sign bit mask */
			else
				L_Mask = 0x0;
			L_Out = L_var1;
			for (i = 0; i < var2 && !iOverflow; i++)
			{
				/* check the sign bit */
				L_Out = (L_Out & 0x7fffffffL) << 1;
				if ((L_Mask ^ L_Out) & LW_SIGN)
					iOverflow = 1;
			}
		}

		if (iOverflow)
		{
			/* saturate */
			if (L_var1 > 0)
				L_Out = LW_MAX;
			else
				L_Out = LW_MIN;

			giOverflow = 1;
		}
	}

	return (L_Out);
}

/***************************************************************************
 *
 *   FUNCTION NAME: L_shr
 *
 *   PURPOSE:
 *
 *     Arithmetic shift right (or left).
 *     Arithmetically shift the input right by var2.   If var2 is
 *     negative then an arithmetic shift left (shl) of var1 by
 *     -var2 is performed.
 *
 *   INPUTS:
 *
 *     var2
 *                     16 bit short signed integer (Shortword) whose value
 *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
 *     L_var1
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *   OUTPUTS:
 *
 *     none
 *
 *   RETURN VALUE:
 *
 *     L_Out
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *
 *
 *   IMPLEMENTATION:
 *
 *     Arithmetically shift the input right by var2.  This
 *     operation maintains the sign of the input number. If var2 is
 *     negative then an arithmetic shift left (shl) of L_var1 by
 *     -var2 is performed.  See description of L_shl for details.
 *
 *     The input is a 32 bit number, as is the output.
 *
 *     Equivalent to the Full-Rate GSM ">> n" operation.  Note that
 *     ANSI-C does not guarantee operation of the C ">>" or "<<"
 *     operator for negative numbers.
 *
 *   KEYWORDS: shift, arithmetic shift right,
 *
 *************************************************************************/

Longword L_shr(Longword L_var1, Shortword var2)
{

	Longword L_Mask, L_Out;

    OP_COUNT(2);        /* Complexity Count -- LT 6/96 */

	if (var2 == 0 || L_var1 == 0)
	{
		L_Out = L_var1;
	}
	else if (var2 < 0)
	{
		/* perform a left shift */
        /*----------------------*/
		if (var2 <= -31)
		{
			/* saturate */
			if (L_var1 > 0)
			{
				L_Out = LW_MAX;
				giOverflow = 1;
			}
			else
			{
				L_Out = LW_MIN;
				giOverflow = 1;
			}
		}
		else
        {
            L_Out = L_shl(L_var1, -var2);
            OP_COUNT(-2);        /* Complexity Count -- LT 6/96 */
        }
	}
	else
	{

		if (var2 >= 31)
		{
			if (L_var1 > 0)
				L_Out = 0;
			else
				L_Out = 0xffffffffL;
		}
		else
		{
			L_Mask = 0;
			if (L_var1 < 0)
			{
				L_Mask = ~L_Mask << (32 - var2);
			}
			L_var1 >>= var2;
			L_Out = L_Mask | L_var1;
		}
	}
	return (L_Out);
}

/***************************************************************************
 *
 *   FUNCTION NAME: L_sub
 *
 *   PURPOSE:
 *
 *     Perform the subtraction of the two 32 bit input variables with
 *     saturation.
 *
 *   INPUTS:
 *
 *     L_var1
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *     L_var2
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var2 <= 0x7fff ffff.
 *
 *   OUTPUTS:
 *
 *     none
 *
 *   RETURN VALUE:
 *
 *     L_Out
 *                     32 bit long signed integer (Longword) whose value
 *                     falls in the range
 *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
 *
 *   IMPLEMENTATION:
 *
 *     Perform the subtraction of the two 32 bit input variables with
 *     saturation.
 *
 *     L_Out = L_var1 - L_var2
 *
 *     L_Out is set to 0x7fff ffff if the operation results in an
 *     overflow.  L_Out is set to 0x8000 0000 if the operation
 *     results in an underflow.
 *
 *   KEYWORDS: sub, subtraction
 *
 *************************************************************************/
Longword L_sub(Longword L_var1, Longword L_var2)
{
    Longword L_Sum;
	double dSum;

    OP_COUNT(2);        /* Complexity Count -- LT 6/96 */

	dSum = (double) L_var1 - (double) L_var2;
	L_Sum = L_var1 - L_var2;