CS253 HW2: More datatypes, tagging

Description

Write a C++ program called hw2 that behaves as the program from from HW1, except that it:

reads from multiple files given as command-line arguments
reads chars and strings, in addition to integers
produces tagged output
does not echo the original value, just the serialized version.

Tagged Output

Now, instead of simply producing vnums, the program will produce tagged output. Each vnum will be preceded by an identifying character:

s: short (fits in a signed 16-bit integer)
i: int (fits in a signed 32-bit integer)
l: long (fits in a signed 64-bit integer)
c: char (a single eight-bit character)
S: string (a string of characters)

The program must figure out which category (short/int/long) a number should go into.

For example, the number three, since it fits into a short, would be tagged with an s, thus: 73 03

The number one billion, which fits into an int, would be tagged with an i, thus: 69 40 3b 9a ca 00

The serialized output for a character is simply a c followed by the character. For example, 'x' would be serialized as: 63 78

A string is serialized as follows:

a capital S
an untagged vnum that represents the length of the string in bytes
the bytes of the string

For example, "Jack" would be serialized as: 53 04 4a 61 63 6b
Don’t be fooled by 04. That is not a simple byte containing the value 4. That is a vnum that happens to be a single byte, because 4 (the length of “Jack”) fits into the bottom four bits of a vnum. A longer string might have a multibyte vnum representing its length.

Sample Run

Here is a sample run. “%” is my prompt:

    % cat sample-input 
    5 300 -1

    1
    2 -3 40 500 -6000 70000
    1000000000

    'a'
    'b' ' '
    "Jack Applin"
    % ./hw2 sample-input 
    73 05
    73 11 2c
    73 0f
    73 01
    73 02
    73 0d
    73 10 28
    73 11 f4
    73 2f e8 90
    69 21 11 70
    69 40 3b 9a ca 00
    63 61
    63 62
    63 20
    53 10 0b 4a 61 63 6b 20 41 70 70 6c 69 6e
    %

char→int conversion

// Here’s how to convert a char to an int:
int n = 'S';        // It’s just that easy.
cout << hex << n;

or via the shell:

% echo -n silcS | xxd
00000000: 7369 6c63 53                             silcS

or going from hex to characters:

% echo -e '\u4a\u61\u63\u6b'
Jack

Requirements

The requirements are the same as those for HW1, plus:

Read from files given as arguments, not stdin.
All error messages must go to stderr, and include the name of the program, as determined at runtime.
Produce a usage message to stderr if no arguments are given.
Produce an error message, including the file name, if a file can’t be opened.
If the input is not a number, or 'single-char', or "any-number-of-chars", emit an error message and terminate the program.
You may assume that:
- input items will be separated by whitespace
- if an integer is given to the program, that it will fit into a C++ long.
- a char constant will not contain a single quote, backslash, or a newline.
- a string constant will not contain a double quote, backslash, or a newline.

Ask

If you have any questions about the requirements, ask. In the real world, your programming tasks will almost always be vague and incompletely specified. Same here.

Tar file

The tar file for this assignment must be called: hw2.tar
It must contain:
- source files (*.cc)
- header files (*.h) (if any)
- Makefile (Makefile, with a capital M)
The Makefile’s default target must create the executable file hw2.
Your Makefile must use at least -Wall when compiling.

How to submit your homework:

Use web checkin, or Linux checkin:

    ~cs253/bin/checkin HW2 hw2.tar

How to receive negative points:

Turn in someone else’s work.

CS253: Software Development with C++

Spring 2018

HW 2