5. Compute/Tick

A single instruction is read through a command called compute. A tick will compute until a halt is reached.

int seqvm_compute(seqvm *svm, seqvm_cell *c);
int seqvm_tick(seqvm *svm, int blkpos);
int seqvm_retick(seqvm *svm, int *start);

int seqvm_compute(seqvm *svm, seqvm_cell *c)
{
    int pos;

    pos = svm->pos;

    switch (c->cmd) {
<<compute>>
        default:
            pos++;
            break;
    }

    return pos;
}

int seqvm_tick(seqvm *svm, int blkpos)
{
    int i;

    svm->blkpos = blkpos;

    svm->halt = 0;
    for (i = 0; i < 128; i++) {
        seqvm_cell *c;

        if (svm->halt) {
            return 0;
        }

        c = &svm->pool[svm->pos];
        svm->pos = seqvm_compute(svm, c);
    }

    return -1;
}

int seqvm_retick(seqvm *svm, int *start)
{
    int i;
    int save;

    svm->halt = 0;

    save = svm->pos;
    svm->pos = *start;
    for (i = 0; i < 128; i++) {
        seqvm_cell *c;

        if (svm->halt) {
            *start = svm->pos;
            svm->pos = save;
            return 0;
        }

        c = &svm->pool[svm->pos];
        svm->pos = seqvm_compute(svm, c);
    }

    *start = svm->pos;
    svm->pos = save;
    return -1;
}

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