parser.c

00001 /*
00002  *
00003  */
00004 
00005 #include "mbed.h"
00006 #include "parser.h"
00007 
00008 int wrap_protocol(char *c, string *message, list<string> *messages, char header, char footer, char dle ) {
00009 
00010     static int state = 0;
00011     static int dle_state = 0;
00012     static int index;
00013     static int size;
00014 
00015 
00016     switch (state) {
00017         case 0: // start sending a header if there is a valid message available
00018             if (!messages->empty()) {
00019                 *message =  messages->front();
00020                 messages->pop_front();      // now that we have the message, delete it from the list
00021                 index = 0;                  // initialize sending the actual message
00022                 size = message->size();
00023                 state = 1;
00024                 *c = header;
00025                 return WRAP_SEND;
00026             }
00027             return WRAP_ABORT;
00028 
00029         case 1:
00030             if ((size == 0) || (index==size)) {
00031                 *c = footer;
00032                 state = 0;
00033                 return WRAP_FINISHED;
00034             }
00035 
00036             *c = (*message)[index];
00037 
00038             if ( dle_state == 1 ) {
00039                 dle_state = 0;
00040                 index++;
00041                 return WRAP_SEND;
00042             }
00043 
00044             if ( (*c == header) || (*c == footer) || (*c == dle) ) {
00045                 dle_state = 1;
00046                 *c = dle;
00047                 return WRAP_SEND;
00048             }
00049 
00050             index++;
00051             return WRAP_SEND;
00052     }
00053 
00054     // if we reach this point, something went wrong!
00055     return WRAP_ABORT;
00056 }
00057 
00058 void unwrap_protocol(char *c, string *buffer, list<string> *messages, unsigned int max_message_size,
00059                      unsigned int max_messages, char header, char footer, char dle ) {
00060 
00061     // these are needed for the internal state of the function
00062     // they are also the reaseon, why this function can only be used in exactly one location
00063     // i.e. the interrupt routine for receiving characters from the RS232
00064     static int state = 0;
00065     static int dle_state = 0;
00066 
00067     switch (state) {
00068         case 0:
00069             if (*c == header) {
00070                 message_led=!message_led;
00071                 state = 1;
00072             }
00073             return;
00074 
00075         case 1:
00076             if (*c== header && dle_state==0) {
00077                 // new header that is not escaped will set e new message start
00078                 buffer->clear();
00079                 return;
00080             }
00081             if (*c == footer && dle_state==0 ) {
00082                 // a frame end is only a frame end, if the footer is not escaped
00083                 messages->push_back( *buffer );
00084                 buffer->clear();
00085                 state = 0;
00086                 message_led=!message_led;
00087                 return;
00088             }
00089 
00090             // check length of buffer; clear, if too large; restart search for header!
00091             if (buffer->length() > max_message_size) {
00092                 // prevent buffer overflows if someone is flooding us with characters
00093                 buffer->clear();
00094                 state=0;
00095                 return;
00096             }
00097 
00098             if (*c == dle && dle_state==0) {
00099                 // the next character is "escaped" and is part of the message
00100                 dle_state = 1;
00101                 return;
00102             }
00103 
00104             // probably the easiest and quickest way of resetting the dle_state
00105             dle_state = 0;
00106 
00107             // in all other cases, we found a new character and append it to the buffer
00108             *buffer += *c;
00109     }
00110 }
00111 
00112 
00113