/* Author      : Rick van der Zwet
 * S-number    : 0433373
 * Version     : $Id: alu.c 364 2007-12-03 07:23:37Z rick $
 * Copyright   : FreeBSD Licence
 * Description : ALU unit
 */

#include <stdlib.h>
#include <stdio.h>
#include <sysexits.h>
#include "alu.h"

word
alu_sra(const word in1, const word in2)
{
    word out = 0;
    out = in1 >> in2;
    /* Find out wether high order bit was set */
    if (in1 >> (BITSIZE(out) - 1) == 0x1) {
        /* Set bit in2 till high-order to 1 */
        int i = BITSIZE(out) - in2;
        for (; i < BITSIZE(out); i++)
            out = out | (1 << i);
    }
    return (out);
}

word
alu(word in1, word in2, alu_control_t action)
{
    word out = 0;
    switch (action) {
    case ADD:
        out = in1 + in2;
        break;
    case AND:
        out = in1 & in2;
        break;
    case NOR:
        out = ~(in1 | in2);
        break;
    case OR:
        out = in1 | in2;
        break;
    case PassS1:
        out = in1;
        break;
    case PassS2:
        out = in2;
        break;
    case SLL:
        out = in1 << in2;
        break;
    case SRA:
        out = alu_sra(in1, in2);
        break;
    case SRL:
        out = in1 >> in2;
        break;
    case SUB:
        out = in1 - in2;
        break;
    case XOR:
        out = in1 ^ in2;
        break;
    default:
        fprintf(stderr,"Requested alu-action not implemented\n");
        exit(EX_SOFTWARE);
        break;
    };

    /* Set signals */
    if (out < 0) {
        zero = FALSE;
        negative = TRUE;
    } else if (out == 0) {
        zero = TRUE;
        negative = FALSE;
    } else {
        zero = FALSE;
        negative = FALSE;
    }

    return(out);
}