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mqtt: add comments in mqtt_parse_incoming

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goldsimon 2018-02-14 06:54:56 +01:00
parent 618a28fc53
commit 731336223f
1 changed files with 14 additions and 2 deletions
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16
src/apps/mqtt/mqtt.c
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@ -816,19 +816,29 @@ mqtt_parse_incoming(mqtt_client_t *client, struct pbuf *p)
u8_t b = 0;
while (p->tot_len > in_offset) {
/* We ALWAYS parse the header here first. Even if the header was not
included in this segment, we re-parse it here by buffering it in
client->rx_buffer. client->msg_idx keeps track of this. */
if ((fixed_hdr_idx < 2) || ((b & 0x80) != 0)) {
if (fixed_hdr_idx < client->msg_idx) {
/* parse header from old pbuf (buffered in client->rx_buffer) */
b = client->rx_buffer[fixed_hdr_idx];
} else {
/* parse header from this pbuf and save it in client->rx_buffer in case
it comes in segmented */
b = pbuf_get_at(p, in_offset++);
client->rx_buffer[client->msg_idx++] = b;
}
fixed_hdr_idx++;
if (fixed_hdr_idx >= 2) {
/* fixed header contains at least 2 bytes but can contain more, depending on
'remaining length'. All bytes but the last of this have 0x80 set to
indicate more bytes are coming. */
msg_rem_len |= (u32_t)(b & 0x7f) << ((fixed_hdr_idx - 2) * 7);
if ((b & 0x80) == 0) {
/* fixed header is done */
LWIP_DEBUGF(MQTT_DEBUG_TRACE, ("mqtt_parse_incoming: Remaining length after fixed header: %"U32_F"\n", msg_rem_len));
if (msg_rem_len == 0) {
/* Complete message with no extra headers of payload received */
@ -836,12 +846,14 @@ mqtt_parse_incoming(mqtt_client_t *client, struct pbuf *p)
client->msg_idx = 0;
fixed_hdr_idx = 0;
} else {
/* Bytes remaining in message */
/* Bytes remaining in message (changes remaining length if this is
not the first segment of this message) */
msg_rem_len = (msg_rem_len + fixed_hdr_idx) - client->msg_idx;
}
}
}
} else {
/* Fixed header has been parsed, parse variable header */
u16_t cpy_len, cpy_start, buffer_space;
cpy_start = (client->msg_idx - fixed_hdr_idx) % (MQTT_VAR_HEADER_BUFFER_LEN - fixed_hdr_idx) + fixed_hdr_idx;
@ -862,7 +874,7 @@ mqtt_parse_incoming(mqtt_client_t *client, struct pbuf *p)
msg_rem_len -= cpy_len;
LWIP_DEBUGF(MQTT_DEBUG_TRACE, ("mqtt_parse_incoming: msg_idx: %"U32_F", cpy_len: %"U16_F", remaining %"U32_F"\n", client->msg_idx, cpy_len, msg_rem_len));
if (msg_rem_len == 0 || cpy_len == buffer_space) {
if ((msg_rem_len == 0) || (cpy_len == buffer_space)) {
/* Whole message received or buffer is full */
mqtt_connection_status_t res = mqtt_message_received(client, fixed_hdr_idx, (cpy_start + cpy_len) - fixed_hdr_idx, msg_rem_len);
if (res != MQTT_CONNECT_ACCEPTED) {