genau(1) - Linux man page

Name

genau - Generate automata function.

Synopsis

genau [<filename>]

Description

The program reads a lookup-table-based automata description and creates a C function to simulate the automata.

Return Value

The program returns exit status code 0 on success, any other value indicates an error.

Example

In the example we want to write a function to check whether a string is a valid identifier in the C programming language. Identifiers are started by a character or underscore and followed by an optional sequence of characters, underscores and digits.

The function check_string() processes the string character by character. Each character is classified by the classify_char() function, the classification result is the input to the state machine. After processing all characters we tell the state machine about the end of input data, output in this step shows whether the string is acceptable or not.

The check_string() function looks like this:

#include "testid.h"

int check_string(char *str)
{
  int state_machine;
  int input;
  int output;
  char *ptr;

  ptr = str;
  reset_decide(&state_machine);
  while(*ptr) {
    input = classify_char(*ptr);
    (void)decide(&state_machine, input);
    ptr++;
  }
  output = decide(&state_machine, I_FINISHED);
  return output;
}

int classify_char(char c)
{
  int back = I_ANY;
  if((c >= 'a') && (c <= 'z')) {
    back = I_CHARACTER;
  } else {
    if((c >= 'A') && (c <= 'Z')) {
      back = I_CHARACTER;
    } else {
      if((c >= '1') && (c <= '9')) {
        back = I_DIGIT;
      } else {
        if(c == '0') {
          back = I_DIGIT;
        } else {
          if(c == '_') {
            back = I_UNDERSCORE;
          }
        }
      }
    }
  }
}

[options]
  c file              = testid.c
  h file              = testid.h
  reduced file        = testid2.au
  transition function = decide
  reset function      = reset_decide
[states]
  S_START
  S_OK
  S_ERROR
[inputs]
  I_ANY          # Any character not mentioned below
  I_UNDERSCORE   # Input byte is '_'
  I_CHARACTER    # Input byte is a character
  I_DIGIT        # Input byte is a digit
  I_FINISHED     # Notification about the end of string
[outputs]
  O_OK           # The string is acceptable
  O_ERROR        # The string is not an identifier
[rules]
  *       *            S_ERROR O_ERROR
  *       I_FINISHED   S_START O_ERROR
  S_START I_UNDERSCORE S_OK    O_OK
  S_START I_CHARACTER  S_OK    O_OK
  S_OK    I_UNDERSCORE S_OK    O_OK
  S_OK    I_CHARACTER  S_OK    O_OK
  S_OK    I_DIGIT      S_OK    O_OK
  S_OK    I_FINISHED   S_START O_OK

Input File Structure

OVERVIEW

Comments in the file are started by ''#''.

The input file consists of the following sections: ''options'', ''states'', ''inputs'', ''outputs'', and ''rules''.

OPTIONS SECTION

The options section is started by ''[options]'' standing alone in the line. In the section there are key/value pairs, key and value are separated by ''=''.

The following keys can be used:

c file

Name of the *.c file to produce.

h file

Name of the *.h file to produce.

prototypes

Specify whether to use prototypes in the *.h file (''yes''), K&R function declarations (''no'') or the DK_PR () notation used by DK libs (''dk'').

transition function

Name of the function doing the transitions, must be a C identifier.

reset function

Name of the function to reset the state machine, must be a C identifier.

reduced file

Write reduced state machine file to this file name.

reduce

Allow (''yes'') or deny (''no'') a state machine reduction.

include protect

Specify a C identifier used to prevent multiple inclusion of the header file.

c define

Specify a C identifier used to separate between the .c module generated by genau and other C modules.

test file

Name of a C file to generate. This C file will test all possible state/input combinations.

doxygen comments

Boolean to control whether or not to write comments for doxygen to output.

squeezed

Boolean to control whether output is squeezed (less spaces and empty lines) or normal.

States section

The states section is started by ''[states]'' standing alone in a line. The following lines contain a state name each, optionally followed by an integer number. The state names must be C identifiers.

Inputs section

The inputs section is started by ''[inputs]'' standing alone in a line. The following lines contain input value names, optionally followed by an integer number. The input names must be C identifiers

Outputs section

The outputs section is started by ''[outputs]'' standing alone in a line. The following lines contain output value names, optionally followed by an integer number. The output names must be C identifiers.

Rules section

The rules section is started by ''[rules]'' standing alone in a line. Each line in the section contains one transition rule consisting of four items: current state, input to process, new state, output.

Each of the items must be a name as defined in the sections above.

The wildcard symbol ''*'' can be used for current state and input.

When using wildcards, priority for the rules is as follows:

Exact rule

An exact rule (not containing wildcards) has highest priority.

One wildcard

If no exact rule matches current state and input, rules containing one wildcard are considered next. The first rule found in the file is used.

Two wildcards

The general rule (two wildcards) is used only if there was no matching exact rule and no matching rule containing one wildcard found.

Implicit rule

If no matching rule was found in the tests above the state machine remains in the current state and issues the default output (the first output name declared in the outputs section).

See Also

http://dktools.sourceforge.net/genau.html

Author

Dirk Krause

Copyright And License

Copyright © 2010, Dirk Krause All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above
  copyright notice, this list of conditions and the
  following disclaimer.

* Redistributions in binary form must reproduce the above
  copyright notice, this list of conditions and the following
  disclaimer in the documentation and/or other materials
  provided with the distribution.

* Neither the name of the Dirk Krause nor the names of
  contributors may be used to endorse or promote products
  derived from this software without specific prior written
  permission.