Diff: MQTTSNPacket.c

Revision:

0:c524a894b5e8

Child:

1:7fa362fa563f

--- /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;
+}
+
+
+