CSCI 4061 Lab03: Input and Expanding Buffers

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                            LAB 03 QUESTIONS
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Lab Instructions
================

  Follow the instructions below to experiment with topics related to
  this lab.
  - For sections marked QUIZ, fill in an (X) for the appropriate
    response in this file. Use the command `make test-quiz' to see if
    all of your answers are correct.
  - For sections marked CODE, complete the code indicated. Use the
    command `make test-code' to check if your code is complete.
  - DO NOT CHANGE any parts of this file except the QUIZ sections as it
    may interfere with the tests otherwise.
  - If your `QUESTIONS.txt' file seems corrupted, restore it by copying
    over the `QUESTIONS.txt.bk' backup file.
  - When you complete the exercises, check your answers with `make test'
    and if all is well, create a zip file with `make zip' and upload it
    to Gradescope. Ensure that the Autograder there reflects your local
    results.
  - IF YOU WORK IN A GROUP only one member needs to submit and then add
    the names of their group.


QUIZ Questions on print_reverse.c
=================================

  Analyze the `print_reverse.c' application. Compile and run it as shown
  below
  ,----
  | // DEMO:
  | > make print_reverse
  | gcc -Wall -Werror -g  -o print_reverse print_reverse.c
  | 
  | > ./print_reverse               # interactive run
  | hello world                     # typed input
  |                                 # press Ctrl-d to end input
  | dlrow olleh                     # output from program
  | 
  | # non-interactive runs via pipes
  | > printf "0123456789" | ./print_reverse
  | ...
  | 
  | > printf "here is everything I have" | ./print_reverse
  | ...
  `----

  Answer the following Questions about the techniques used in this
  program. You may need to consult the Manual Page / Documentation on
  some functions to answer confidently.


Location of buf
~~~~~~~~~~~~~~~

  The variable `buf' is used to store character data that is read from
  standard input in `print_reverse'.  Which part of memory are these
  characters stored?

  - ( ) The Stack: `buf' is declared as a local array near the top of
    `main()' so exists in `main()''s stack frame.
  - ( ) The Heap: `buf' points to an array that is `malloc()''d on the
    heap near the start of main.
  - ( ) Globals: `buf' is declared outside of any function and is
    therefore in the Globa/Static/Data portion of program memory.
  - ( ) Based on the way that `buf' is declared, it is impossible to say
    where in memory it exists.


Expansion of buf
~~~~~~~~~~~~~~~~

  The `realloc()' function is used to change the size of the memory area
  associated with `buf'.  According to your read of the code and the
  manual page for this function, which of the following is returned by
  `realloc()'?

  - ( ) It will return `NULL' if it is not possible to find a larger
    space for `buf'
  - ( ) It will return the same pointer `buf' if that space can be
    expanded in place.
  - ( ) It will return a pointer to a new memory of the requested size
    where the contents of `buf' have already been copied with the old
    pointer being automatically `free()''d.
  - ( ) `realloc()' could return any of these.


Resizing Rate
~~~~~~~~~~~~~

  Which of the following is used as the "rate" of expansion for the
  buffer?
  - ( ) If there is insufficient space in `buf', it is resized to be 1
    character larger than its previous size.
  - ( ) If there is insufficient space in `buf', it is resized to be 10
    characters larger than its previous size.
  - ( ) If there is insufficient space in `buf', it is resized to be
    150% of its previous size.
  - ( ) If there is insufficient space in `buf', it is resized to be
    200% of its previous size.

  Note that expanding by 150% or 200% each iteration leads to an "append
  item" operation that has an Amortized computation complexity O(1).
  This approach is often used in data structures such as Python Lists,
  Java's ArrayList / StringBuffer, or other "dynamic array" data
  structures. <https://en.wikipedia.org/wiki/Dynamic_array>


CODE Adapt to file_reverse.c
============================

  Create a new file called `file_reverse.c' and adapt the approach taken
  in `print_reverse.c' to print the contents of a file in reverse order,
  character by character.

  1. The provided `Makefile' will compile `file_reverse.c' to the
     program `file_reverse'
  2. `file_reverse' should take a command line argument which is the
     name of a file to print in reverse order.
  3. If no command line argument is given, print a usage message and
     exit with code 1 as demonstrated below.
  4. Open the file provided on the command line using the C standard
     library. Scan data into a character array and expand the array as
     needed using the techniques demoed in print_reverse.
  5. When the entire file has been read in, print the contents in
     reverse order.
  6. Make sure to clean up any memory used through heap allocation or
     opening files.

  NOTE: If you are not familiar with how to use `argc / argv' to deal
  with command line arguments, get help from a colleague or staff member
  to review this technique.

  The tests provided via `make test-code' use the files `alphabet.txt'
  and `nums.txt'. A correctly written program will behave as
  demonstrated below.

  ,----
  | >> ./file_reverse               # run with no args
  | usage: file_reverse <file>      # print usage message
  | 
  | >> echo $?                      # show return code
  | 1                               # 1 - error while running program
  | 
  | >> ./file_reverse alphabet.txt  # print alphabet.txt in reverse
  | 
  | z y x w v u t s r q p o n m l k j i h g f e d c b a
  | Z Y X W V U T S R Q P O N M L K J I H G F E D C B A
  | 
  | >> echo $?                      # check return code
  | 0                               # 0 for no problems
  | 
  | >> ./file_reverse nums.txt      # print nums.txt in reverse
  | 
  | 52
  | 42
  | 32
  | 22
  | 12
  | 02
  | 91
  | 81
  | 71
  | 61
  | 51
  | 41
  | 31
  | 21
  | 11
  | 01
  | 9
  | 8
  | 7
  | 6
  | 5
  | 4
  | 3
  | 2
  | 1
  `----