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Diff: MQTTSNPacket.c
- Revision:
- 0:c524a894b5e8
- Child:
- 1:7fa362fa563f
diff -r 000000000000 -r c524a894b5e8 MQTTSNPacket.c --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/MQTTSNPacket.c Thu Feb 26 15:59:36 2015 +0000 @@ -0,0 +1,272 @@ +/******************************************************************************* + * Copyright (c) 2014 IBM Corp. + * + * All rights reserved. This program and the accompanying materials + * are made available under the terms of the Eclipse Public License v1.0 + * and Eclipse Distribution License v1.0 which accompany this distribution. + * + * The Eclipse Public License is available at + * http://www.eclipse.org/legal/epl-v10.html + * and the Eclipse Distribution License is available at + * http://www.eclipse.org/org/documents/edl-v10.php. + * + * Contributors: + * Ian Craggs - initial API and implementation and/or initial documentation + *******************************************************************************/ + +#include "StackTrace.h" +#include "MQTTSNPacket.h" + +#include <string.h> + +static char* packet_names[] = +{ + "ADVERTISE", "SEARCHGW", "GWINFO", "RESERVED", "CONNECT", "CONNACK", + "WILLTOPICREQ", "WILLTOPIC", "WILLMSGREQ", "WILLMSG", "REGISTER", "REGACK", + "PUBLISH", "PUBACK", "PUBCOMP", "PUBREC", "PUBREL", "RESERVED", + "SUBSCRIBE", "SUBACK", "UNSUBSCRIBE", "UNSUBACK", "PINGREQ", "PINGRESP", + "DISCONNECT", "RESERVED", "WILLTOPICUPD", "WILLTOPICRESP", "WILLMSGUPD", + "WILLMSGRESP" +}; + + +/** + * Returns a character string representing the packet name given a MsgType code + * @param code MsgType code + * @return the corresponding packet name + */ +char* MQTTSNPacket_name(int code) +{ + return (code >= 0 && code <= MQTTSN_WILLMSGRESP) ? packet_names[code] : "UNKNOWN"; +} + + +/** + * Calculates the full packet length including length field + * @param length the length of the MQTT-SN packet without the length field + * @return the total length of the MQTT-SN packet including the length field + */ +int MQTTSNPacket_len(int length) +{ + return (length > 255) ? length + 3 : length + 1; +} + + +/** + * Encodes the MQTT-SN message length + * @param buf the buffer into which the encoded data is written + * @param length the length to be encoded + * @return the number of bytes written to the buffer + */ +int MQTTSNPacket_encode(unsigned char* buf, int length) +{ + int rc = 0; + + FUNC_ENTRY; + if (length > 255) + { + buf[rc++] = 0x01; + writeInt(&buf, length); + rc += 2; + } + else + buf[rc++] = length; + + FUNC_EXIT_RC(rc); + return rc; +} + + +/** + * Obtains the MQTT-SN packet length from received data + * @param getcharfn pointer to function to read the next character from the data source + * @param value the decoded length returned + * @return the number of bytes read from the socket + */ +int MQTTSNPacket_decode(unsigned char* buf, int buflen, int* value) +{ + int len = MQTTSNPACKET_READ_ERROR; +#define MAX_NO_OF_LENGTH_BYTES 3 + + FUNC_ENTRY; + if (buflen <= 0) + goto exit; + + if (buf[0] == 1) + { + unsigned char* bufptr = &buf[1]; + if (buflen < 3) + goto exit; + *value = readInt(&bufptr); + len = 3; + } + else + { + *value = buf[0]; + len = 1; + } +exit: + FUNC_EXIT_RC(len); + return len; +} + + +/** + * Calculates an integer from two bytes read from the input buffer + * @param pptr pointer to the input buffer - incremented by the number of bytes used & returned + * @return the integer value calculated + */ +int readInt(unsigned char** pptr) +{ + unsigned char* ptr = *pptr; + int len = 256*((unsigned char)(*ptr)) + (unsigned char)(*(ptr+1)); + *pptr += 2; + return len; +} + + +/** + * Reads one character from the input buffer. + * @param pptr pointer to the input buffer - incremented by the number of bytes used & returned + * @return the character read + */ +char readChar(unsigned char** pptr) +{ + char c = **pptr; + (*pptr)++; + return c; +} + + +/** + * Writes one character to an output buffer. + * @param pptr pointer to the output buffer - incremented by the number of bytes used & returned + * @param c the character to write + */ +void writeChar(unsigned char** pptr, char c) +{ + **pptr = (unsigned char)c; + (*pptr)++; +} + + +/** + * Writes an integer as 2 bytes to an output buffer. + * @param pptr pointer to the output buffer - incremented by the number of bytes used & returned + * @param anInt the integer to write: 0 to 65535 + */ +void writeInt(unsigned char** pptr, int anInt) +{ + **pptr = (unsigned char)(anInt / 256); + (*pptr)++; + **pptr = (unsigned char)(anInt % 256); + (*pptr)++; +} + + +/** + * Writes a "UTF" string to an output buffer. Converts C string to length-delimited. + * @param pptr pointer to the output buffer - incremented by the number of bytes used & returned + * @param string the C string to write + */ +void writeCString(unsigned char** pptr, char* string) +{ + int len = strlen(string); + memcpy(*pptr, string, len); + *pptr += len; +} + + +int getLenStringLen(char* ptr) +{ + int len = 256*((unsigned char)(*ptr)) + (unsigned char)(*(ptr+1)); + return len; +} + + +void writeMQTTSNString(unsigned char** pptr, MQTTSNString MQTTSNString) +{ + if (MQTTSNString.lenstring.len > 0) + { + memcpy(*pptr, MQTTSNString.lenstring.data, MQTTSNString.lenstring.len); + *pptr += MQTTSNString.lenstring.len; + } + else if (MQTTSNString.cstring) + writeCString(pptr, MQTTSNString.cstring); +} + + +/** + * @param MQTTSNString the MQTTSNString structure into which the data is to be read + * @param pptr pointer to the output buffer - incremented by the number of bytes used & returned + * @param enddata pointer to the end of the data: do not read beyond + * @return 1 if successful, 0 if not + */ +int readMQTTSNString(MQTTSNString* MQTTSNString, unsigned char** pptr, unsigned char* enddata) +{ + int rc = 0; + + FUNC_ENTRY; + MQTTSNString->lenstring.len = enddata - *pptr; + if (MQTTSNString->lenstring.len > 0) + { + MQTTSNString->lenstring.data = (char*)*pptr; + *pptr += MQTTSNString->lenstring.len; + } + else + MQTTSNString->lenstring.data = NULL; + MQTTSNString->cstring = NULL; + rc = 1; + FUNC_EXIT_RC(rc); + return rc; +} + + +/** + * Return the length of the MQTTSNString - C string if there is one, otherwise the length delimited string + * @param MQTTSNString the string to return the length of + * @return the length of the string + */ +int MQTTSNstrlen(MQTTSNString MQTTSNString) +{ + int rc = 0; + + if (MQTTSNString.cstring) + rc = strlen(MQTTSNString.cstring); + else + rc = MQTTSNString.lenstring.len; + return rc; +} + + +/** + * Helper function to read packet data from some source into a buffer + * @param buf the buffer into which the packet will be serialized + * @param buflen the length in bytes of the supplied buffer + * @param getfn pointer to a function which will read any number of bytes from the needed source + * @return integer MQTT packet type, or MQTTSNPACKET_READ_ERROR on error + */ +int MQTTSNPacket_read(unsigned char* buf, int buflen, int (*getfn)(unsigned char*, int)) +{ + int rc = MQTTSNPACKET_READ_ERROR; + const int MQTTSN_MIN_PACKET_LENGTH = 3; + int len = 0; /* the length of the whole packet including length field */ + int lenlen = 0; + int datalen = 0; + + /* 1. read a packet - UDP style */ + if ((len = (*getfn)(buf, buflen)) < MQTTSN_MIN_PACKET_LENGTH) + goto exit; + + /* 2. read the length. This is variable in itself */ + lenlen = MQTTSNPacket_decode(buf, len, &datalen); + if (datalen != len) + goto exit; /* there was an error */ + + rc = buf[lenlen]; /* return the packet type */ +exit: + return rc; +} + + +