/* node.c -- the v4 node.  See node.h. */
#include "v4/node.h"

void v4_node_reset(v4_node *n)
{
    n->p = 0;
    n->a = 0;
    n->b = 0;
    for (unsigned i = 0; i < V4_NODE_WORDS; i++) n->mem[i] = 0;
    v4_guard_fill(n->mem_guard_head, V4_MEM_BOUND, V4_GUARD_PATTERN_HEAD);
    v4_guard_fill(n->mem_guard_tail, V4_MEM_BOUND, V4_GUARD_PATTERN_TAIL);
    v4_dstack_reset(&n->ds);
    v4_rstack_reset(&n->rs);
    v4_node_console_attach(n, -1);
}

int v4_node_guards_intact(const v4_node *n)
{
    return v4_guard_intact(n->mem_guard_head, V4_MEM_BOUND, V4_GUARD_PATTERN_HEAD)
        && v4_guard_intact(n->mem_guard_tail, V4_MEM_BOUND, V4_GUARD_PATTERN_TAIL)
        && v4_dstack_guards_intact(&n->ds)
        && v4_rstack_guards_intact(&n->rs);
}

v4_cell v4_node_load(const v4_node *n, v4_cell addr)
{
    /* Precondition checked by the caller; see node.h.  The unsigned compare is
     * deliberate: `addr` is signed, and a negative address must not wrap into
     * a large positive one and read the top of memory instead. */
    return n->mem[(unsigned)addr];
}

void v4_node_store(v4_node *n, v4_cell addr, v4_cell value)
{
    /* CONSOLE-TX: capture the character, leave memory alone.  console_tx is
     * -1 when no console is attached, which no valid address equals. */
    if (addr == n->console_tx) {
        if (n->console_len < V4_CONSOLE_CAP)
            n->console[n->console_len++] = (unsigned char)((v4_ucell)value & 0xFFu);
        else
            n->console_dropped++;
        return;
    }
    n->mem[(unsigned)addr] = value;
}

void v4_node_console_attach(v4_node *n, v4_cell addr)
{
    n->console_tx = addr;
    n->console_len = 0;
    n->console_dropped = 0;
}