// The OS/K Team licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

#include "arch.h"

void scan_param(ctx_t *ctx, acc_t *p)
{
    ushort c;
    reg_t *r;
    
    assert(p != 0);

    c = ctx->get(ctx);

    if (c == A_MEM) {
        p->mem = 1;
        p->off = 0;
        c = ctx->get(ctx);
    }
    
    else if (c == A_OFF) {
        p->mem = 1;
        p->off = (short)ctx->get(ctx);
        c = ctx->get(ctx);
    }
        
    if (c >= A_IMM16) {
        assert(p->type == A_REG);
        p->type = c;
        c = ctx->get(ctx);
    }

    p->val = c;
        
    if (p->type == A_IMM32) {
        p->val = (p->val << 16) | ctx->get(ctx);
    }
        
    else if (p->type == A_IMM64) {
        p->val = (p->val << 16) | ctx->get(ctx);
        p->val = (p->val << 16) | ctx->get(ctx);
        p->val = (p->val << 16) | ctx->get(ctx);
    }
    
    else if (p->type == A_REG) {
        if (p->val > NREGS) {
            _except(ctx, E_ILL, "Inexistent REG");
        }

        r = &ctx->r[p->val];
        
        if (r->flags & (RES | CTL)) {
            _except(ctx, E_ACC, "Reserved REG");
        }
    }
}

void decode(ctx_t *ctx)
{
    instr_t *i;
    acc_t p1 = { 0 }, p2 = { 0 };

    ulong rip = ctx->r[RIP].val;
    ushort c = ctx->get(ctx);
    
    if (c == 0xFFFF) {
        log("0x%016lX: stop\n", rip);
        _except(ctx, E_SHT, "Shutdown INSTR");
    }

    else if (ISPREF(c)) {
        // nothing for now
    }
    
    else if (!ISINSTR(c)) {
        _except(ctx, E_ILL, "Bad opcode 0x%4hX", c);
    }

    // Scanning an instruction

    i = &ctx->i[c];
        
    // Scan for parameters
    if (i->prm1 != NOPRM) {
        scan_param(ctx, &p1);
        if (i->prm2 != NOPRM) {
            scan_param(ctx, &p2);
        }
    }
    
    dumpinstr(ctx, rip, c, &p1, &p2);
    i->func(ctx, &p1, &p2);
}