/* message.c -- a message, as it is written to a port and read from one.
 * See message.h.  Nothing here uses the C library.
 */
#include "v4/message.h"

unsigned v4_message_text(v4_message *m, v4_cell to, v4_cell from, v4_cell type, const char *chars, unsigned len)
{
    unsigned i, words;

    if (len > V4_MSG_MAX_CHARS) return 0;
    words = (len + 3u) / 4u;
    m->word[0] = to;
    m->word[1] = from;
    m->word[2] = type;
    m->word[3] = 0;
    m->word[4] = 0;
    m->word[5] = 0;
    m->word[6] = (v4_cell)len;
    for (i = 0; i < words; i++) m->word[V4_MSG_HEADER + i] = 0;
    for (i = 0; i < len; i++)
        m->word[V4_MSG_HEADER + i / 4u] = (v4_cell)((v4_ucell)m->word[V4_MSG_HEADER + i / 4u]
                                                    | ((v4_ucell)(unsigned char)chars[i] << (8u * (i % 4u))));
    m->count = V4_MSG_HEADER + words;
    return m->count;
}

unsigned v4_message_length(const v4_message *m)
{
    v4_cell len = m->word[6];
    return (len < 0 || len > (v4_cell)V4_MSG_MAX_CHARS) ? 0u : (unsigned)len;
}

char v4_message_char(const v4_message *m, unsigned i)
{
    return (char)(((v4_ucell)m->word[V4_MSG_HEADER + i / 4u] >> (8u * (i % 4u))) & 0xFFu);
}

int v4_message_word(v4_message *m, v4_cell word)
{
    if (m->count < V4_MSG_MAX_WORDS) m->word[m->count] = word;
    m->count++;
    if (m->count < V4_MSG_HEADER) return 0;
    return m->count >= V4_MSG_HEADER + (v4_message_length(m) + 3u) / 4u;
}