?? basic_op.c
字號:
| |
| Inputs : |
| |
| var1 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| var2 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| Outputs : |
| |
| none |
| |
| Return Value : |
| |
| var_out |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var_out <= 0x0000 7fff. |
|___________________________________________________________________________|
*/
Word16 shl(Word16 var1,Word16 var2)
{
Word16 var_out;
Word32 resultat;
if (var2 < 0)
{
var_out = shr(var1,-var2);
}
else
{
resultat = (Word32) var1 * ((Word32) 1 << var2);
if ((var2 > 15 && var1 != 0) || (resultat != (Word32)((Word16) resultat)))
{
Overflow = 1;
var_out = (var1 > 0) ? MAX_16 : MIN_16;
}
else
{
var_out = extract_l(resultat);
}
}
return(var_out);
}
/*___________________________________________________________________________
| |
| Function Name : shr |
| |
| Purpose : |
| |
| Arithmetically shift the 16 bit input var1 right var2 positions with |
| sign extension. If var2 is negative, arithmetically shift var1 left by |
| -var2 with sign extension. Saturate the result in case of underflows or |
| overflows. |
| |
| Complexity weight : 1 |
| |
| Inputs : |
| |
| var1 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| var2 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| Outputs : |
| |
| none |
| |
| Return Value : |
| |
| var_out |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var_out <= 0x0000 7fff. |
|___________________________________________________________________________|
*/
Word16 shr(Word16 var1,Word16 var2)
{
Word16 var_out;
if (var2 < 0)
{
var_out = shl(var1,-var2);
}
else
{
if (var2 >= 15)
{
var_out = (var1 < 0) ? (Word16)(-1) : (Word16)0;
}
else
{
if (var1 < 0)
{
var_out = ~(( ~var1) >> var2 );
}
else
{
var_out = var1 >> var2;
}
}
}
return(var_out);
}
/*___________________________________________________________________________
| |
| Function Name : mult |
| |
| Purpose : |
| |
| Performs the multiplication of var1 by var2 and gives a 16 bit result |
| which is scaled i.e.: |
| mult(var1,var2) = shr((var1 times var2),15) and |
| mult(-32768,-32768) = 32767. |
| |
| Complexity weight : 1 |
| |
| Inputs : |
| |
| var1 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| var2 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| Outputs : |
| |
| none |
| |
| Return Value : |
| |
| var_out |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var_out <= 0x0000 7fff. |
|___________________________________________________________________________|
*/
Word16 mult(Word16 var1, Word16 var2)
{
Word16 var_out;
Word32 L_produit;
L_produit = (Word32)var1 * (Word32)var2;
L_produit = (L_produit & (Word32) 0xffff8000L) >> 15;
if (L_produit & (Word32) 0x00010000L)
L_produit = L_produit | (Word32) 0xffff0000L;
var_out = sature(L_produit);
return(var_out);
}
/*___________________________________________________________________________
| |
| Function Name : L_mult |
| |
| Purpose : |
| |
| L_mult is the 32 bit result of the multiplication of var1 times var2 |
| with one shift left i.e.: |
| L_mult(var1,var2) = shl((var1 times var2),1) and |
| L_mult(-32768,-32768) = 2147483647. |
| |
| Complexity weight : 1 |
| |
| Inputs : |
| |
| var1 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| var2 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| Outputs : |
| |
| none |
| |
| Return Value : |
| |
| L_var_out |
| 32 bit long signed integer (Word32) whose value falls in the |
| range : 0x8000 0000 <= L_var_out <= 0x7fff ffff. |
|___________________________________________________________________________|
*/
Word32 L_mult(Word16 var1,Word16 var2)
{
Word32 L_var_out;
L_var_out = (Word32)var1 * (Word32)var2;
if (L_var_out != (Word32)0x40000000L)
{
L_var_out *= 2;
}
else
{
Overflow = 1;
L_var_out = MAX_32;
}
return(L_var_out);
}
/*___________________________________________________________________________
| |
| Function Name : negate |
| |
| Purpose : |
| |
| Negate var1 with saturation, saturate in the case where input is -32768:|
| negate(var1) = sub(0,var1). |
| |
| Complexity weight : 1 |
| |
| Inputs : |
| |
| var1 |
| 16 bit short signed integer (Word16) whose value falls in the |
| range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| Outputs : |
| |
| none |
| |
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