| /******************************************************************************* |
| * 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 |
| * Sergio R. Caprile - non-blocking packet read functions for stream transport |
| *******************************************************************************/ |
| |
| #include "StackTrace.h" |
| #include "MQTTPacket.h" |
| |
| #include <string.h> |
| |
| /** |
| * Encodes the message length according to the MQTT algorithm |
| * @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 buffer |
| */ |
| int MQTTPacket_encode(unsigned char* buf, int length) |
| { |
| int rc = 0; |
| |
| FUNC_ENTRY; |
| do |
| { |
| char d = length % 128; |
| length /= 128; |
| /* if there are more digits to encode, set the top bit of this digit */ |
| if (length > 0) |
| d |= 0x80; |
| buf[rc++] = d; |
| } while (length > 0); |
| FUNC_EXIT_RC(rc); |
| return rc; |
| } |
| |
| |
| /** |
| * Decodes the message length according to the MQTT algorithm |
| * @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 MQTTPacket_decode(int (*getcharfn)(unsigned char*, int), int* value) |
| { |
| unsigned char c; |
| int multiplier = 1; |
| int len = 0; |
| #define MAX_NO_OF_REMAINING_LENGTH_BYTES 4 |
| |
| FUNC_ENTRY; |
| *value = 0; |
| do |
| { |
| int rc = MQTTPACKET_READ_ERROR; |
| |
| if (++len > MAX_NO_OF_REMAINING_LENGTH_BYTES) |
| { |
| rc = MQTTPACKET_READ_ERROR; /* bad data */ |
| goto exit; |
| } |
| rc = (*getcharfn)(&c, 1); |
| if (rc != 1) |
| goto exit; |
| *value += (c & 127) * multiplier; |
| multiplier *= 128; |
| } while ((c & 128) != 0); |
| exit: |
| FUNC_EXIT_RC(len); |
| return len; |
| } |
| |
| |
| int MQTTPacket_len(int rem_len) |
| { |
| rem_len += 1; /* header byte */ |
| |
| /* now remaining_length field */ |
| if (rem_len < 128) |
| rem_len += 1; |
| else if (rem_len < 16384) |
| rem_len += 2; |
| else if (rem_len < 2097151) |
| rem_len += 3; |
| else |
| rem_len += 4; |
| return rem_len; |
| } |
| |
| |
| static unsigned char* bufptr; |
| |
| int bufchar(unsigned char* c, int count) |
| { |
| int i; |
| |
| for (i = 0; i < count; ++i) |
| *c = *bufptr++; |
| return count; |
| } |
| |
| |
| int MQTTPacket_decodeBuf(unsigned char* buf, int* value) |
| { |
| bufptr = buf; |
| return MQTTPacket_decode(bufchar, value); |
| } |
| |
| |
| /** |
| * 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*(*ptr) + (*(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 = 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 |
| */ |
| 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, const char* string) |
| { |
| int len = strlen(string); |
| writeInt(pptr, len); |
| memcpy(*pptr, string, len); |
| *pptr += len; |
| } |
| |
| |
| int getLenStringLen(char* ptr) |
| { |
| int len = 256*((unsigned char)(*ptr)) + (unsigned char)(*(ptr+1)); |
| return len; |
| } |
| |
| |
| void writeMQTTString(unsigned char** pptr, MQTTString mqttstring) |
| { |
| if (mqttstring.lenstring.len > 0) |
| { |
| writeInt(pptr, mqttstring.lenstring.len); |
| memcpy(*pptr, mqttstring.lenstring.data, mqttstring.lenstring.len); |
| *pptr += mqttstring.lenstring.len; |
| } |
| else if (mqttstring.cstring) |
| writeCString(pptr, mqttstring.cstring); |
| else |
| writeInt(pptr, 0); |
| } |
| |
| |
| /** |
| * @param mqttstring the MQTTString 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 readMQTTLenString(MQTTString* mqttstring, unsigned char** pptr, unsigned char* enddata) |
| { |
| int rc = 0; |
| |
| FUNC_ENTRY; |
| /* the first two bytes are the length of the string */ |
| if (enddata - (*pptr) > 1) /* enough length to read the integer? */ |
| { |
| mqttstring->lenstring.len = readInt(pptr); /* increments pptr to point past length */ |
| if (&(*pptr)[mqttstring->lenstring.len] <= enddata) |
| { |
| mqttstring->lenstring.data = (char*)*pptr; |
| *pptr += mqttstring->lenstring.len; |
| rc = 1; |
| } |
| } |
| mqttstring->cstring = NULL; |
| FUNC_EXIT_RC(rc); |
| return rc; |
| } |
| |
| |
| /** |
| * Return the length of the MQTTstring - C string if there is one, otherwise the length delimited string |
| * @param mqttstring the string to return the length of |
| * @return the length of the string |
| */ |
| int MQTTstrlen(MQTTString mqttstring) |
| { |
| int rc = 0; |
| |
| if (mqttstring.cstring) |
| rc = strlen(mqttstring.cstring); |
| else |
| rc = mqttstring.lenstring.len; |
| return rc; |
| } |
| |
| |
| /** |
| * Compares an MQTTString to a C string |
| * @param a the MQTTString to compare |
| * @param bptr the C string to compare |
| * @return boolean - equal or not |
| */ |
| int MQTTPacket_equals(MQTTString* a, char* bptr) |
| { |
| int alen = 0, |
| blen = 0; |
| char *aptr; |
| |
| if (a->cstring) |
| { |
| aptr = a->cstring; |
| alen = strlen(a->cstring); |
| } |
| else |
| { |
| aptr = a->lenstring.data; |
| alen = a->lenstring.len; |
| } |
| blen = strlen(bptr); |
| |
| return (alen == blen) && (strncmp(aptr, bptr, alen) == 0); |
| } |
| |
| |
| /** |
| * 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 -1 on error |
| * @note the whole message must fit into the caller's buffer |
| */ |
| int MQTTPacket_read(unsigned char* buf, int buflen, int (*getfn)(unsigned char*, int)) |
| { |
| int rc = -1; |
| MQTTHeader header = {0}; |
| int len = 0; |
| int rem_len = 0; |
| |
| /* 1. read the header byte. This has the packet type in it */ |
| if ((*getfn)(buf, 1) != 1) |
| goto exit; |
| |
| len = 1; |
| /* 2. read the remaining length. This is variable in itself */ |
| MQTTPacket_decode(getfn, &rem_len); |
| len += MQTTPacket_encode(buf + 1, rem_len); /* put the original remaining length back into the buffer */ |
| |
| /* 3. read the rest of the buffer using a callback to supply the rest of the data */ |
| if((rem_len + len) > buflen) |
| goto exit; |
| if ((*getfn)(buf + len, rem_len) != rem_len) |
| goto exit; |
| |
| header.byte = buf[0]; |
| rc = header.bits.type; |
| exit: |
| return rc; |
| } |
| |
| /** |
| * Decodes the message length according to the MQTT algorithm, non-blocking |
| * @param trp pointer to a transport structure holding what is needed to solve getting data from it |
| * @param value the decoded length returned |
| * @return integer the number of bytes read from the socket, 0 for call again, or -1 on error |
| */ |
| static int MQTTPacket_decodenb(MQTTTransport *trp) |
| { |
| unsigned char c; |
| int rc = MQTTPACKET_READ_ERROR; |
| |
| FUNC_ENTRY; |
| if(trp->len == 0){ /* initialize on first call */ |
| trp->multiplier = 1; |
| trp->rem_len = 0; |
| } |
| do { |
| int frc; |
| if (++(trp->len) > MAX_NO_OF_REMAINING_LENGTH_BYTES) |
| goto exit; |
| if ((frc=(*trp->getfn)(trp->sck, &c, 1)) == -1) |
| goto exit; |
| if (frc == 0){ |
| rc = 0; |
| goto exit; |
| } |
| trp->rem_len += (c & 127) * trp->multiplier; |
| trp->multiplier *= 128; |
| } while ((c & 128) != 0); |
| rc = trp->len; |
| exit: |
| FUNC_EXIT_RC(rc); |
| return rc; |
| } |
| |
| /** |
| * Helper function to read packet data from some source into a buffer, non-blocking |
| * @param buf the buffer into which the packet will be serialized |
| * @param buflen the length in bytes of the supplied buffer |
| * @param trp pointer to a transport structure holding what is needed to solve getting data from it |
| * @return integer MQTT packet type, 0 for call again, or -1 on error |
| * @note the whole message must fit into the caller's buffer |
| */ |
| int MQTTPacket_readnb(unsigned char* buf, int buflen, MQTTTransport *trp) |
| { |
| int rc = -1, frc; |
| MQTTHeader header = {0}; |
| |
| switch(trp->state){ |
| default: |
| trp->state = 0; |
| /*FALLTHROUGH*/ |
| case 0: |
| /* read the header byte. This has the packet type in it */ |
| if ((frc=(*trp->getfn)(trp->sck, buf, 1)) == -1) |
| goto exit; |
| if (frc == 0) |
| return 0; |
| trp->len = 0; |
| ++trp->state; |
| /*FALLTHROUGH*/ |
| /* read the remaining length. This is variable in itself */ |
| case 1: |
| if((frc=MQTTPacket_decodenb(trp)) == MQTTPACKET_READ_ERROR) |
| goto exit; |
| if(frc == 0) |
| return 0; |
| trp->len = 1 + MQTTPacket_encode(buf + 1, trp->rem_len); /* put the original remaining length back into the buffer */ |
| if((trp->rem_len + trp->len) > buflen) |
| goto exit; |
| ++trp->state; |
| /*FALLTHROUGH*/ |
| case 2: |
| /* read the rest of the buffer using a callback to supply the rest of the data */ |
| if ((frc=(*trp->getfn)(trp->sck, buf + trp->len, trp->rem_len)) == -1) |
| goto exit; |
| if (frc == 0) |
| return 0; |
| trp->rem_len -= frc; |
| trp->len += frc; |
| if(trp->rem_len) |
| return 0; |
| |
| header.byte = buf[0]; |
| rc = header.bits.type; |
| break; |
| } |
| |
| exit: |
| trp->state = 0; |
| return rc; |
| } |
| |