MQTTSerializePublish.c

00001 /*******************************************************************************
00002  * Copyright (c) 2014 IBM Corp.
00003  *
00004  * All rights reserved. This program and the accompanying materials
00005  * are made available under the terms of the Eclipse Public License v1.0
00006  * and Eclipse Distribution License v1.0 which accompany this distribution.
00007  *
00008  * The Eclipse Public License is available at
00009  *    http://www.eclipse.org/legal/epl-v10.html
00010  * and the Eclipse Distribution License is available at
00011  *   http://www.eclipse.org/org/documents/edl-v10.php.
00012  *
00013  * Contributors:
00014  *    Ian Craggs - initial API and implementation and/or initial documentation
00015  *    Ian Craggs - fix for https://bugs.eclipse.org/bugs/show_bug.cgi?id=453144
00016  *******************************************************************************/
00017 
00018 #include "MQTTPacket.h"
00019 
00020 #include <string.h>
00021 
00022 
00023 /**
00024   * Determines the length of the MQTT publish packet that would be produced using the supplied parameters
00025   * @param qos the MQTT QoS of the publish (packetid is omitted for QoS 0)
00026   * @param topicName the topic name to be used in the publish  
00027   * @param payloadlen the length of the payload to be sent
00028   * @return the length of buffer needed to contain the serialized version of the packet
00029   */
00030 size_t MQTTSerialize_publishLength(int qos, MQTTString topicName, size_t payloadlen)
00031 {
00032     size_t len = 0;
00033 
00034     len += 2 + MQTTstrlen(topicName) + payloadlen;
00035     if (qos > 0)
00036         len += 2; /* packetid */
00037     return len;
00038 }
00039 
00040 
00041 /**
00042   * Serializes the supplied publish data into the supplied buffer, ready for sending
00043   * @param buf the buffer into which the packet will be serialized
00044   * @param buflen the length in bytes of the supplied buffer
00045   * @param dup integer - the MQTT dup flag
00046   * @param qos integer - the MQTT QoS value
00047   * @param retained integer - the MQTT retained flag
00048   * @param packetid integer - the MQTT packet identifier
00049   * @param topicName MQTTString - the MQTT topic in the publish
00050   * @param payload byte buffer - the MQTT publish payload
00051   * @param payloadlen integer - the length of the MQTT payload
00052   * @return the length of the serialized data.  <= 0 indicates error
00053   */
00054 int MQTTSerialize_publish(unsigned char* buf, size_t buflen, unsigned char dup, int qos, unsigned char retained, unsigned short packetid,
00055         MQTTString topicName, unsigned char* payload, size_t payloadlen)
00056 {
00057     unsigned char *ptr = buf;
00058     MQTTHeader header = {0};
00059     size_t rem_len = 0;
00060     int rc = 0;
00061 
00062     if (MQTTPacket_len(rem_len = MQTTSerialize_publishLength(qos, topicName, payloadlen)) > buflen)
00063     {
00064         rc = MQTTPACKET_BUFFER_TOO_SHORT;
00065         goto exit;
00066     }
00067 
00068     header.bits.type = PUBLISH_MSG;
00069     header.bits.dup = dup;
00070     header.bits.qos = qos;
00071     header.bits.retain = retained;
00072     writeChar(&ptr, header.byte); /* write header */
00073 
00074     ptr += MQTTPacket_encode(ptr, rem_len); /* write remaining length */;
00075 
00076     writeMQTTString(&ptr, topicName);
00077 
00078     if (qos > 0)
00079         writeInt(&ptr, packetid);
00080 
00081     memcpy(ptr, payload, payloadlen);
00082     ptr += payloadlen;
00083 
00084     rc = (int)(ptr - buf);
00085 
00086 exit:
00087     return rc;
00088 }
00089 
00090 
00091 
00092 /**
00093   * Serializes the ack packet into the supplied buffer.
00094   * @param buf the buffer into which the packet will be serialized
00095   * @param buflen the length in bytes of the supplied buffer
00096   * @param type the MQTT packet type
00097   * @param dup the MQTT dup flag
00098   * @param packetid the MQTT packet identifier
00099   * @return serialized length, or error if 0
00100   */
00101 int MQTTSerialize_ack(unsigned char* buf, size_t buflen, unsigned char packettype, unsigned char dup, unsigned short packetid)
00102 {
00103     MQTTHeader header = {0};
00104     int rc = 0;
00105     unsigned char *ptr = buf;
00106 
00107     if (buflen < 4)
00108     {
00109         rc = MQTTPACKET_BUFFER_TOO_SHORT;
00110         goto exit;
00111     }
00112     header.bits.type = packettype;
00113     header.bits.dup = dup;
00114     header.bits.qos = (packettype == PUBREL_MSG) ? 1 : 0;
00115     writeChar(&ptr, header.byte); /* write header */
00116 
00117     ptr += MQTTPacket_encode(ptr, 2); /* write remaining length */
00118     writeInt(&ptr, packetid);
00119     rc = (int)(ptr - buf);
00120 exit:
00121     return rc;
00122 }
00123 
00124 
00125 /**
00126   * Serializes a puback packet into the supplied buffer.
00127   * @param buf the buffer into which the packet will be serialized
00128   * @param buflen the length in bytes of the supplied buffer
00129   * @param packetid integer - the MQTT packet identifier
00130   * @return serialized length, or error if 0
00131   */
00132 int MQTTSerialize_puback(unsigned char* buf, size_t buflen, unsigned short packetid)
00133 {
00134     return MQTTSerialize_ack(buf, buflen, PUBACK_MSG, 0, packetid);
00135 }
00136 
00137 
00138 /**
00139   * Serializes a pubrel packet into the supplied buffer.
00140   * @param buf the buffer into which the packet will be serialized
00141   * @param buflen the length in bytes of the supplied buffer
00142   * @param dup integer - the MQTT dup flag
00143   * @param packetid integer - the MQTT packet identifier
00144   * @return serialized length, or error if 0
00145   */
00146 int MQTTSerialize_pubrel(unsigned char* buf, size_t buflen, unsigned char dup, unsigned short packetid)
00147 {
00148     return MQTTSerialize_ack(buf, buflen, PUBREL_MSG, dup, packetid);
00149 }
00150 
00151 
00152 /**
00153   * Serializes a pubrel packet into the supplied buffer.
00154   * @param buf the buffer into which the packet will be serialized
00155   * @param buflen the length in bytes of the supplied buffer
00156   * @param packetid integer - the MQTT packet identifier
00157   * @return serialized length, or error if 0
00158   */
00159 int MQTTSerialize_pubcomp(unsigned char* buf, size_t buflen, unsigned short packetid)
00160 {
00161     return MQTTSerialize_ack(buf, buflen, PUBCOMP_MSG, 0, packetid);
00162 }
00163 
00164