basop.c

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/*___________________________________________________________________________
 |                                                                           |
 | Basics operators.                                                         |
 |___________________________________________________________________________|
*/

/*___________________________________________________________________________
 |                                                                           |
 |   Include-Files                                                           |
 |___________________________________________________________________________|
*/

#include <stdio.h>
#include <stdlib.h>
#include "typedef.h"
#include "basop.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 + (Word32) 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 -  (Word32) 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.                                                |
 |                                                                           |