CST 8152 - Assignment 2

Due 12 noon Monday June 2, 1997

• Assigned: Wednesday, May 14 in class

  Content last revised: 12noon Tuesday, May 20

  Due date changed: Wednesday, May 28

Purpose

• This is a review of C coding style, memory management, and a further introduction to basic Lexical Analysis.
  You should be able to use most of the skeleton from Assignment One in this program.

Instructions

• Design, write, and thoroughly test the following C program:

• • Allocate dynamic memory to hold a character string.
  • Pass the file pointer of an open input file and sufficient information to manage the dynamic memory to a function.
  • The function reads from the open input file. It returns to the calling function a pointer to the (possibly newly allocated) memory containing the longest identifier in the input file, and also the line number on which it occurs.
  • Definition of an identifier:
  • • An identifier starts with a letter and is followed by zero or more letters, digits, and underscores.
    • For this assignment, identifiers need not be separated by blanks from preceding numbers. An identifier starts with a letter, even if the letter immediately follows a digit, e.g. 1234567This_Is_An_Identifier
    • If two identifiers are equally the "longest", locate the one closest to the end of the file.
  • The function itself prints nothing except error messages. (Bonus points: Instead of having the function print its own error messages, have the function return numeric error codes that the calling function can decode and print.)
  • Output: On return from the function, generate the output file:
  • • Write out your name and Student Number.
    • Write out the file name of the input file.
    • Write out the line number.
    • Write out the longest identifier.
  • Repeatedly get new input files and call the function for as many input files as the user wants to process.
  • All the output should go to the same output file.
  • Example: The output should look something like this:

  • Name: Ian Allen
    Student Number: 000 000 000
    
    Input file: Assignment Two Data-1.txt
    Line number: 23
    Longest identifier: antidisestablishmentarianism
    
    Input file: Assignment Two Data-2.txt
    Line number: 523
    Longest identifier: plinth
    
    Input file: Empty File.txt
    Line number: 0
    Longest identifier: 
    

Important Notes

• • Use the string prompting routine you wrote in Assignment One to obtain each file name.
  • You may only read the input file in one place. Do not spread multiple calls to fgetc() or fgets() throughout your function. See the code fragment contained in this assignment for an example of how to use a state flag to handle the input.
  • Use realloc() to handle identifiers of any length.
  • Make sure you detect identifiers that are followed immediately by end-of-file.
  • Do the initial memory allocation and final freeing in the function that calls the identifier-finding function. The identifier-finding function must only use realloc().
  • No global variables. All data passing must be via function arguments and return values.
  • • Consider returning a structure that contains all the needed function return values, rather than using multiple function output arguments passed by reference.
  • Follow the C Programming Style guidelines carefully.
  • • Do not duplicate code!
    • De-allocate any dynamic storage used.
    • Close all files opened.
    • Check all the return codes of function calls.
    • Issue appropriate messages if any operation in your program fails.
    • Where possible, use perror() to find out from the operating system why the operation failed.
      (E.g. "no permission", "file not found", "I/O error", "disk full", etc.)

  The deliverables for your assignment are due in the Ian Allen assignment box before 12 noon Friday, May 30, 1997.

Deliverables for this assignment

1. The fully documented source listing of your program (including your own .h files).
   The submission must follow the online course submission guidelines.
2. A description or listing of your input test file(s) (and output, if appropriate) showing how you tested your input routine and your counting function. (Do not print out large test files. Describe them instead.)
3. I will show you how to deposit your assignment source code into a directory on the Algonquin server when the server is ready. All assignment source code will be collected for analysis later in the term.

Evaluation

1. The aggregate of all assignment marks comprises 20% of your final mark.
   All assignments must be completed satisfactorily to get credit for the course.

   Please review the C Programming Style guidelines.
   Assignments are marked for clarity and simplicity as well as correctness.

   Late assignments are handled according to the policy given in the course outline.

   “Inside every big program is a little program struggling to get out.”

Code Fragment

• Only read input in one place in your code. Use a state flag to decide whether you are ignoring characters while looking for a letter that begins an identifier. For example:

• while( not end of file )
     switch( currentState )
     case ST_IGNORING_INPUT:
        if( input begins an identifier  )
           currentState = ST_COLLECTING_ID;
           ...
        break;
     case ST_COLLECTING_ID:
        if( input ends an identifier  )
           currentState = ST_IGNORING_INPUT;
           ...
        else
           ...
        break;
     default:
        ...
  }
  

Ian D. Allen CST8152 Home Page - Summer 1997