Using the programming language C

Write a program that creates 4 threads to process input from standard input as follows

1. Thread 1, called the Input Thread, reads in lines of characters from the standard input.
2. Thread 2, called the Line Separator Thread, replaces every line separator in the input by a space.
3. Thread, 3 called the Plus Sign thread, replaces every pair of plus signs, i.e., "++", by a "^".
4. Thread 4, called the Output Thread, write this processed data to standard output as lines of exactly 80 characters.

Furthermore, in your program these 4 threads must communicate with each other using the Producer-Consumer approach.

INPUT:

• A line of input is
  • A sequence of the allowed characters (see below) that does not include a line separator
  • Followed by a line separator.
• Line separator
  • The line separator is the newline character, i.e., ' '
  • Note that line separator may not be the newline character on Windows or Mac, but that's irrelevant.
• Allowed characters
  • Other than the line separator, the input will only consist of ASCII characters from space (decimal 32) to tilde (decimal 126). These are sometimes termed printable characters.
• Stop-processing line
  • Your program must process input lines until it receives an input line that contains only the characters STOP, i.e., STOP followed immediately by the line separator.
  • Examples: The following input lines must not cause the program to stop processing the input
    • STOP!
    • ISTOP
    • stop
    • Stop
• If there are any more lines in the input after the stop-processing line, the program must not process them.
• The input will not contain any empty lines, i.e., lines that only have space characters or no characters except the line separator.
• An input line will never be longer than 1000 characters (including the line separator).
• The input for the program will never have more than 49 lines before the stop-processing line.
• Program does not need to check the input for correctness.

OUTPUT:

• The 80 character line to be written to standard output is defined as 80 non-line separator characters plus a line separator.
• Your program must not wait to produce the output only when the stop-processing line is received.
  • Whenever your program has sufficient data for an output line, the output line must be produced.
• After the program receives the stop-processing line and before it terminates, the program must produce all 80 character lines it can still produce based on the input lines which were received before the stop-processing line and which have not yet been processed to produce output.
• No part of the stop-processing line must be written to the output.
• In addition, your program must not output any user prompts, debugging information, status messages, etc.
• Your program must output only lines with 80 characters (with a line separator after each line).

• For the second replacement requirement, pairs of plus signs must be replaced as they are seen.
  • Examples:
    • The string abc+++def contains only one pair of plus signs and must be converted to the string "abc^+def".
    • The string abc++++def contains two pairs of plus signs and must be converted to the string "abc^^def".
  • Thus, whenever the Plus Sign thread replaces a pair of plus signs by a caret, the number of characters produced by the Plus Sign thread decreases by one compared to the number characters consumed by this thread.