Generic command parser wanted

Hi Gurus,

I would like to find a generic command parser for ascii lines containing variable string and number elements. Preferably it should be written in C++ and it should be very lean, using a minimum written code length, hopefully relying on use of STL.

Does anyone have a finished parser or a link to one?

Alternatively feel free to suggest a solution technique for writing my own simple and lean command parser using STL. I suppose just a few lines of the right code using stringstream's would be enough for the simple commands to be parsed.

Included is a sample of the commands to be parsed.
They are really quite simple.

Thanks for any help.

Sincerely,
Chris

Code:

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FA 0, 20000 C3                 
L  0,3FF0 ..\sample_files\Al01.hex         
L  4000,4000 ..\sample_files\Al01.hex 4000         
L  18000,8000 ..\sample_files\Al01.hex 18000
CC 0,3FF0 4000,4000 18000,7FFE 1FFFE               
HC 0,3FF0 ..\sample_files\Al01_flash.hex       
HA 4000,4000 ..\sample_files\Al01_flash.hex 4000       
HA 18000,8000 ..\sample_files\Al01_flash.hex 18000       
HE 0,0 ..\sample_files\Al01_flash.hex
Q

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Fine, Chris: I'll try to help you. Just give me some time.

Regards,

Here's a function that GNU put up on their gcc website a while back; I'm pretty sure you could use it to get what you want [if you want to]:

Code:

---

/*
 * stringtok.h -- Breaks a string into tokens.  This is an example for lib3.
 *
 * Template function looks like this:
 *
 *    template <typename Container>
 *    void stringtok (Container &l,
 *                    string const &s,
 *                    char const * const ws = " \t\n");
 *
 * A nondestructive version of strtok() that handles its own memory and can
 * be broken up by any character(s).  Does all the work at once rather than
 * in an invocation loop like strtok() requires.
 *
 * Container is any type that supports push_back(a_string), although using
 * list<string> and deque<string> are indicated due to their O(1) push_back.
 * (I prefer deque<> because op[]/at() is available as well.)  The first
 * parameter references an existing Container.
 *
 * s is the string to be tokenized.  From the parameter declaration, it can
 * be seen that s is not affected.  Since references-to-const may refer to
 * temporaries, you could use stringtok(some_container, readline("")) when
 * using the GNU readline library.
 *
 * The final parameter is an array of characters that serve as whitespace.
 * Whitespace characters default to one or more of tab, space, and newline,
 * in any combination.
 *
 * 'l' need not be empty on entry.  On return, 'l' will have the token
 * strings appended.
 *
 *
 * [Example:
 *      list<string>      ls;
 *      stringtok (ls, " this  \t is\t\n  a test  ");
 *      for (list<string>::const_iterator i = ls.begin();
 *            i != ls.end(); ++i)
 *      {
 *            cerr << ':' << (*i) << ":\n";
 *      }
 *
 *  would print
 *      :this:
 *      :is:
 *      :a:
 *      :test:
 * -end example]
 *
 * [email protected]  May 1999
*/


#include <string>
#include <cstring>    // for strchr


/*****************************************************************
 * This is the only part of the implementation that I don't like.
 * It can probably be improved upon by the reader...
*/
namespace {
    inline bool
    isws (char c, char const * const wstr)
    {
        return (strchr(wstr,c) != NULL);
    }
}


/*****************************************************************
 * Simplistic and quite Standard, but a bit slow.  This should be
 * templatized on basic_string instead, or on a more generic StringT
 * that just happens to support ::size_type, .substr(), and so on.
 * I had hoped that "whitespace" would be a trait, but it isn't, so
 * the user must supply it.  Enh, this lets them break up strings on
 * different things easier than traits would anyhow.
*/
template <typename Container>
void
stringtok (Container &l, string const &s, char const * const ws = " \t\n")
{
    const string::size_type  S = s.size();
          string::size_type  i = 0;

    while (i < S) {
        // eat leading whitespace
        while ((i < S) && (isws(s[i],ws)))  ++i;
        if (i == S)  return;  // nothing left but WS

        // find end of word
        string::size_type  j = i+1;
        while ((j < S) && (!isws(s[j],ws)))  ++j;

        // add word
        l.push_back(s.substr(i,j-i));

        // set up for next loop
        i = j+1;
    }
}

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It might not be able to help you, but it seems fairly generic; you could probably use it as a building block for what you need if you so desire.

--Paul

The syntax is not very clear. The code below is just quick written code and it is a starting point (I’m sure: not the best). I hope it’ll help you.

Code:

---

#include <string>
#include <fstream>
#include <iostream>
#include <vector>

using namespace std;

class Parser
{

public:
  Parser();
  bool run( istream& a_is = cin );

private:
  typedef struct
  {
    string m_string; // if string empty then it is number
    int m_number;
  } Argument;
  virtual void process( const string& a_cmd_name, const vector<Argument>& a_cmd_args );
  Parser( const Parser& ) : m_is(cin) {}
  enum { tkEOF, tkEnter, tkCommand, tkNumber, tkString, tkArgSeparator };
  int get_token();
  void command();
  istream& m_is;
  int m_last_token;
  int m_last_number;
  string m_last_string;
  int m_line_count;

};

Parser::Parser() : m_is(cin)
{
}

bool Parser::run( istream& a_is )
{
  // init
  m_line_count = 0;

  //
  try
  {
    while ( get_token() != tkEOF )
      command();
    return true;
  }
  catch( char* s )
  {
    cerr << "e r r o r :  " << s << endl;
    return false;
  }
}

void Parser::command()
{
  // get the command name
  if ( m_last_token != tkString )
    throw "command name expected"; // todo: your exception
  string cmd_name = m_last_string;

  // get the command arguments
  vector<Argument> cmd_args;
  while ( get_token() != tkEOF )
  {
    switch ( m_last_token )
    {
    case tkArgSeparator: // same as ws
      // nop
      break;
    case tkString:
      {
      Argument arg;
      arg.m_string = m_last_string;
      cmd_args.push_back( arg );
      }
    case tkNumber:
      {
      Argument arg;
      arg.m_number = m_last_number;
      cmd_args.push_back( arg );
      }
      break;
    case tkEnter:
      {
      process( cmd_name, cmd_args );
      }
      return;
    }
  }
}

void Parser:: process( const string& a_cmd_name, const vector<Argument>& a_cmd_args )
{
  cout << "p r o c e s s i n g . . . " << a_cmd_name << endl;
}

int Parser::get_token()
{
  // alias
  istream& is = m_is;

  // last char
  char c;

  // eat white
  do
  {
    if ( ! is.get(c) )
      return m_last_token = tkEOF;
  } while ( c != '\n' && isspace(c) );

  // analyze
  switch ( c )
  {

  case '\n':
    ++m_line_count;
    return m_last_token = tkEnter;

  case ',':
    return m_last_token = tkArgSeparator;

  case '0': case '1': case '2': case '3': case '4':
  case '5': case '6': case '7': case '8': case '9':
    is.putback(c);
    is >> hex >> m_last_number;
    return m_last_token = tkNumber;
   
  default: // todo: get path as well
    if ( ! isalpha(c) )
      throw "bad token"; // todo: your exception
    m_last_string = c;
    while ( is.get(c) && isalnum(c) )
      m_last_string += c;
    is.putback(c);
    return m_last_token = tkString;
  }
}

int main()
{
  Parser().run();
        return 0;
}

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Regards,

Thanks for the suggestions.
These are both good solutions.
Chris.

:)