?? basic_op.c
字號:
/* Version 3.3 Last modified: December 26, 1995 */
/*___________________________________________________________________________
| |
| Basics operators. |
|___________________________________________________________________________|
*/
/*___________________________________________________________________________
| |
| Include-Files |
|___________________________________________________________________________|
*/
#include <stdio.h>
#include <stdlib.h>
#include "typedef.h"
#include "basic_op.h"
/*___________________________________________________________________________
| |
| Local Functions |
|___________________________________________________________________________|
*/
Word16 sature(Word32 L_var1);
/*___________________________________________________________________________
| |
| Constants and Globals |
|___________________________________________________________________________|
*/
Flag Overflow =0;
Flag Carry =0;
/*___________________________________________________________________________
| |
| Functions |
|___________________________________________________________________________|
*/
/*___________________________________________________________________________
| |
| Function Name : sature |
| |
| Purpose : |
| |
| Limit the 32 bit input to the range of a 16 bit word. |
| |
| Inputs : |
| |
| L_var1 |
| 32 bit long signed integer (Word32) whose value falls in the |
| range : 0x8000 0000 <= L_var1 <= 0x7fff ffff. |
| |
| 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 sature(Word32 L_var1)
{
Word16 var_out;
if (L_var1 > 0X00007fffL)
{
Overflow = 1;
var_out = MAX_16;
}
else if (L_var1 < (Word32)0xffff8000L)
{
Overflow = 1;
var_out = MIN_16;
}
else
{
Overflow = 0;
var_out = extract_l(L_var1);
}
return(var_out);
}
/*___________________________________________________________________________
| |
| Function Name : add |
| |
| Purpose : |
| |
| Performs the addition (var1+var2) with overflow control and saturation;|
| the 16 bit result is set at +32767 when overflow occurs or at -32768 |
| when underflow occurs. |
| |
| 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 add(Word16 var1,Word16 var2)
{
Word16 var_out;
Word32 L_somme;
L_somme = (Word32) var1 + var2;
var_out = sature(L_somme);
return(var_out);
}
/*___________________________________________________________________________
| |
| Function Name : sub |
| |
| Purpose : |
| |
| Performs the subtraction (var1+var2) with overflow control and satu- |
| ration; the 16 bit result is set at +32767 when overflow occurs or at |
| -32768 when underflow occurs. |
| |
| 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 sub(Word16 var1,Word16 var2)
{
Word16 var_out;
Word32 L_diff;
L_diff = (Word32) var1 - var2;
var_out = sature(L_diff);
return(var_out);
}
/*___________________________________________________________________________
| |
| Function Name : abs_s |
| |
| Purpose : |
| |
| Absolute value of var1; abs_s(-32768) = 32767. |
| |
| Complexity weight : 1 |
| |
| Inputs : |
| |
| var1 |
| 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 : 0x0000 0000 <= var_out <= 0x0000 7fff. |
|___________________________________________________________________________|
*/
Word16 abs_s(Word16 var1)
{
Word16 var_out;
if (var1 == (Word16)0X8000 )
{
var_out = MAX_16;
}
else
{
if (var1 < 0)
{
var_out = -var1;
}
else
{
var_out = var1;
}
}
return(var_out);
}
/*___________________________________________________________________________
| |
| Function Name : shl |
| |
| Purpose : |
| |
| Arithmetically shift the 16 bit input var1 left var2 positions.Zero fill|
| the var2 LSB of the result. If var2 is negative, arithmetically shift |
| var1 right by -var2 with sign extension. Saturate the result in case of |
| underflows or overflows. |
| |
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