basic_op40.c

EVRC是用于高通公司的语音编码

 |                                                                           |
 |   Perform an integer arithmetic shift on the double format value.         |
 |   If nbits > 0, arithmetically shift the value left nbits positions.      |
 |   Zero fill the nbits LSB of the value.                                   |
 |   If nbits < 0, arithmetically shift the value right by -nbits positions  |
 |   with sign extension.                                                    |
 |   No overflow control and saturation.                                     |
 |___________________________________________________________________________|
*/

static Word40 L_shift_left40(Word40 value, Word16 nbits)
{
  if (nbits > 40) nbits = 40;      /* to avoid needless loop after overflow */
  if (nbits < -40) nbits = -40;    

  if (nbits < 0)
  {
    for(; nbits<0; nbits++)
    {
      value = value * 0.5;         /* remove fraction bits */
    }
    value = floor(value);
  }
  else
  {
    value = floor(value);          /* remove fraction bits */
    for(; nbits>0; nbits--)
    {
      value = value * 2;
    }
  }

  return(value);
}

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_saturate40                                            |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |    Limit the value to the range of a 40 bit word.                         |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    var_out  40 bit short signed integer (Word40) whose value falls in the |
 |             range : MIN_40 <= var_out <= MAX_40.                          |
 |___________________________________________________________________________|
*/

static Word40 L_saturate40(Word40 value)
{
  Word40 L_var_out;

  L_var_out = value;
  
  if (L_var_out > MAX_40)
  {
    L_var_out = MAX_40;
    giOverflow = 1;
  }
  else if (L_var_out < MIN_40)
  {
    L_var_out = MIN_40;
    giOverflow = 1;
  }

  return(L_var_out);
}


//***************************************************************************
//***************************************************************************
//***************************************************************************
//***************************************************************************

// public functions for 40 bit accumulator	 
//    
// J. Klein, Conexant Systems   12/01/00

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_add40                                                 |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Add L_var1 by L_var2. Return a 40 bit result without saturation:        |
 |        L_add40 (L_var1, L_var2).                                          |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    L_var1   40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var1 <= MAX_40.                           |
 |                                                                           |
 |                                                                           |
 |    L_var2   32 bit long signed integer (Word32) whose value falls in      |
 |             the : MIN_32 <= L_var2 <= MAX_32.                             |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var_out <= MAX_40.                        |
 |___________________________________________________________________________|
*/

Word40 L_add40(Word40 L_var1, Word32 L_var2)
{
  Word40 L_var_out;

  L_var_out = L_var1 + (Word40)L_var2;

  L_var_out = L_saturate40(L_var_out);

#ifdef WMOPS_FX
  counter_fx.L_add40++;
#endif

  return(L_var_out);
}

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_sub40                                                 |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Substract L_var1 by L_var2. Return a 40 bit result without saturation:  |
 |        L_sub40 (L_var1, L_var2).                                          |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    L_var1   40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var1 <= MAX_40.                           |
 |                                                                           |
 |                                                                           |
 |    L_var2   32 bit long signed integer (Word32) whose value falls in      |
 |             the : MIN_32 <= L_var2 <= MAX_32.                             |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var_out <= MAX_40.                        |
 |___________________________________________________________________________|
*/

Word40 L_sub40(Word40 L_var1, Word32 L_var2)
{
  Word40 L_var_out;

  L_var_out = L_var1 - (Word40)L_var2;

  L_var_out = L_saturate40(L_var_out);

#ifdef WMOPS_FX
  counter_fx.L_sub40++;
#endif

  return(L_var_out);
}


/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_mac40                                                 |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Multiply var1 by var2 and shift the result left by 1. Add the 40 bit    |
 |   result to L_var3 with saturation, return a 40 bit result:               |
 |        L_mac(L_var3,var1,var2) = L_add(L_var3,(L_mult(var1,var2)).        |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    L_var3   40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var3 <= MAX_40.                           |
 |                                                                           |
 |    var1     16 bit short signed integer (Word16) whose value falls in  |
 |             the : MIN_16 <= var1 <= MAX_16.                               |
 |                                                                           |
 |    var2     16 bit short signed integer (Word16) whose value falls in  |
 |             the : MIN_16 <= var1 <= MAX_16.                               |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var_out <= MAX_40.                        |
 |___________________________________________________________________________|
*/

Word40 L_mac40(Word40 L_var3, Word16 var1, Word16 var2)
{
  Word40 L_var_out;

  L_var_out = L_var3 + ((Word40)var1 * (Word40)var2 * 2.0);

  L_var_out = L_saturate40(L_var_out);

#ifdef WMOPS_FX
  counter_fx.L_mac40++;
#endif

  return(L_var_out);
}


/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_msu40                                                 |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Multiply var1 by var2 and shift the result left by 1. Subtract the 40   |
 |   bit result to L_var3 with saturation, return a 40 bit result:           |
 |        L_msu(L_var3,var1,var2) = L_sub(L_var3,(L_mult(var1,var2)).        |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    L_var3   40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var3 <= MAX_40.                           |
 |                                                                           |
 |    var1     16 bit short signed integer (Word16) whose value falls in  |
 |             the range : MIN_16 <= var1 <= MAX_16.                         |
 |                                                                           |
 |    var2     16 bit short signed integer (Word16) whose value falls in  |
 |             therange : MIN_16 <= var1 <= MAX_16.                          |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             40 bit long signed integer (Word40) whose value falls in the  |
 |             range : MIN_40 <= L_var_out <= MAX_40.                        |
 |___________________________________________________________________________|
*/

Word40 L_msu40(Word40 L_var3, Word16 var1, Word16 var2)
{
  Word40 L_var_out;

  L_var_out = L_var3 - ((Word40)var1 * (Word40)var2 * 2.0);

  L_var_out = L_saturate40(L_var_out);

#ifdef WMOPS_FX
  counter_fx.L_msu40++;
#endif

  return(L_var_out);
}


/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_shr40                                                 |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Arithmetically shift the 40 bit input L_var1 right var2 positions with  |
 |   sign extension. If var2 is negative, arithmetically shift L_var1 left   |
 |   by -var2 and zero fill the var2 LSB of the result. Saturate the result  |
 |   in case of underflows or overflows.                                     |
 |                                                                           |
 |   Complexity weight : 2                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |