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mqtt support for sending fragmented messages and full mqtt message length support

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This commit is contained in:
David Cermak
2018-10-25 16:38:25 +02:00
parent cf5b8eda89
commit e0bbbebc08
5 changed files with 142 additions and 39 deletions
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68
lib/mqtt_msg.c
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@@ -34,7 +34,7 @@
#include "mqtt_config.h"
#include "platform.h"
#define MQTT_MAX_FIXED_HEADER_SIZE 3
#define MQTT_MAX_FIXED_HEADER_SIZE 5
enum mqtt_connect_flag
{
@@ -105,22 +105,42 @@ static mqtt_message_t* fail_message(mqtt_connection_t* connection)
static mqtt_message_t* fini_message(mqtt_connection_t* connection, int type, int dup, int qos, int retain)
{
int remaining_length = connection->message.length - MQTT_MAX_FIXED_HEADER_SIZE;
if (remaining_length > 127)
{
connection->buffer[0] = ((type & 0x0f) << 4) | ((dup & 1) << 3) | ((qos & 3) << 1) | (retain & 1);
connection->buffer[1] = 0x80 | (remaining_length % 128);
connection->buffer[2] = remaining_length / 128;
connection->message.length = remaining_length + 3;
connection->message.data = connection->buffer;
int message_length = connection->message.length - MQTT_MAX_FIXED_HEADER_SIZE;
int total_length = message_length;
int encoded_length = 0;
uint8_t encoded_lens[4] = {0};
// Check if we have fragmented message and update total_len
if (connection->message.fragmented_msg_total_length) {
total_length = connection->message.fragmented_msg_total_length - MQTT_MAX_FIXED_HEADER_SIZE;
}
else
{
connection->buffer[1] = ((type & 0x0f) << 4) | ((dup & 1) << 3) | ((qos & 3) << 1) | (retain & 1);
connection->buffer[2] = remaining_length;
connection->message.length = remaining_length + 2;
connection->message.data = connection->buffer + 1;
// Encode MQTT message length
int len_bytes = 0; // size of encoded message length
do {
encoded_length = total_length % 128;
total_length /= 128;
if (total_length > 0) {
encoded_length |= 0x80;
}
encoded_lens[len_bytes] = encoded_length;
len_bytes++;
} while (total_length > 0);
// Sanity check for MQTT header
if (len_bytes + 1 > MQTT_MAX_FIXED_HEADER_SIZE) {
return fail_message(connection);
}
// Save the header bytes
connection->message.length = message_length + len_bytes + 1; // msg len + encoded_size len + type (1 byte)
int offs = MQTT_MAX_FIXED_HEADER_SIZE - 1 - len_bytes;
connection->message.data = connection->buffer + offs;
connection->message.fragmented_msg_data_offset -= offs;
// type byte
connection->buffer[offs++] = ((type & 0x0f) << 4) | ((dup & 1) << 3) | ((qos & 3) << 1) | (retain & 1);
// length bytes
for (int j = 0; j<len_bytes; j++) {
connection->buffer[offs++] = encoded_lens[j];
}
return &connection->message;
@@ -377,11 +397,17 @@ mqtt_message_t* mqtt_msg_publish(mqtt_connection_t* connection, const char* topi
else
*message_id = 0;
if (connection->message.length + data_length > connection->buffer_length)
return fail_message(connection);
memcpy(connection->buffer + connection->message.length, data, data_length);
connection->message.length += data_length;
if (connection->message.length + data_length > connection->buffer_length) {
// Not enough size in buffer -> fragment this message
connection->message.fragmented_msg_data_offset = connection->message.length;
memcpy(connection->buffer + connection->message.length, data, connection->buffer_length - connection->message.length);
connection->message.length = connection->buffer_length;
connection->message.fragmented_msg_total_length = data_length + connection->message.fragmented_msg_data_offset;
} else {
memcpy(connection->buffer + connection->message.length, data, data_length);
connection->message.length += data_length;
connection->message.fragmented_msg_total_length = 0;
}
return fini_message(connection, MQTT_MSG_TYPE_PUBLISH, 0, qos, retain);
}