Help Me
Bhuwan Shrestha
Project3-Introductionfol.pptxINFO-1156 Object-Oriented Programming with C++
Project 3 - Introduction
Beginning a Project
Read handout and read the rubric.
Run the executable to discover behaviours and error messages based on certain inputs.
What is acceptable input? What is unacceptable?
What happens if input is unacceptable?
Make a list of all possible test data!
Match your program to the executable.
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Test using: rle.exe
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Download rle.binaries.v2.0.0.zip from the Project folder
Unzip, type cmd in the address line, enter executable
Enter various input that will test the project requirements
Input Examples
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What happens if:
There is no input
Input file is not present
--debug switch is present
Run-length Encoding
Write a tool for encoding/decoding with run-length encoding
RLE is a very basic data compression algorithm used to compress digital data
The objective is to reduce the amount of data needed for storage or transmission
It is often used in digital signal processing (DSP) such as image processing and compression
RLE works by reducing the physical size of a repeating string of characters called a “run”
If all the values in the original data are exactly the same, RLE can reduce data to just two values
An Example:
The string “aaaaaaaaaaaaaaaa” after run-length encoding is 16a
RLE stores the encoding in bytes as 8-bit binary values
A hexadecimal representation looks like: x10x61
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https://www.fileformat.info/mirror/egff/ch09_03.htm
Examples
“hello” string, 5 bytes
rle encoded produces:
8 bytes
“aaaaaaaaaa” string, 9 bytes
rle encoded produces:
2 bytes
rle is best applied when there is a “run” of repeating characters
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| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| h | e | l | l | o | |||||
| 1 | h | 1 | e | 2 | l | 1 | o | ||
| x01 | x68 | x01 | x65 | x02 | x6c | x01 | x6f |
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| a | a | a | a | a | a | a | a | a | |
| 9 | a | ||||||||
| x09 | x61 |
Recall: ASCII Code Chart All keyboard characters have a corresponding decimal value between 0-255 . . . . and also corresponding hex, oct, bin values
© 2009-18, Santor, Wong, Manning
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http://www.getitwriteonline.com/archive/021806charactersnotonkeyboard.htm
rle – things to consider
rle compresses runs by writing the file information as:
byte count, followed by character byte
Where:
byte count is stored as uint8_t
character is stored as unsigned char
uint8_t
a typedef for a C unsigned char
guaranteed to be 8 bits
stream.get(ch) gets a char and will have to be cast to unsigned char
Files must be opened in binary mode to prevent conversions
\r, \n, ^D, ^Z could be changed
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Project 3 – Run-length encoding
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Program Interfaces
At the end of running rle, a file is encoded and a compressed file is created
At the end of running rld, an encoded file is decoded and restored to original file
| rle.exe | [--debug] | [--help] | inputfile.txt | [outputfile] |
| rld.exe | [--debug] | [--help] | inputfile.txt | [outputfile] |
Run-length encoding data compression algorithm
Compression in which runs of data are stored as a single data value and count, rather than as the original run
aaaaabbbbbcccdd
5a5b3c2d
Algorithm:
Look at a string, character by character
Compare c[n] == c[n+1]
If the same, increment a counter
Continue until c[n] != c[n+1]
Store the c[n] and count
Repeat
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Command line Input
No console input, only file input
If argc = 1, no file is provided, print “Help”
If argc >1, check for switches:
Is --debug present, set a bool to true,
Is --help, present, set a bool to true
If argc > 2, check for input file:
Create ifstream file
If argc > 3, check for output file:
Create ofstream file
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