Multithreaded Text Justification

Program that reads an array of words and generates an array of strings made up of the words fully justified such that each array element's length is set to the specified width.

The program works by reading words from the input array until the total width with spaces would exceed the specified line width. A thread is then created that fully justifies the words and creates a string. The process repeats for all lines excluding the last line. The last line is left justified in in a separate thread as well.

In addition to the words provided as input to the justification threads, the line number is also provided.

When the threads are finished justifying the line, the data is written to a channel.

Another thread waiting for input from the channel writes the justified lines to an array preserving the order by the provided line number. The array is pre-sized to the maximum number in order to handle asynchronous arrival of lines and to avoid the need for a synchronization primitive (i.e. mutex). This is an example of a lock free algorithm.

+------------------------------------------+
| ["foo", "bar", "baz", "foobar", ...]   G |
|                                          |
|                                          |
| FullJustifiy()                           |
+---------------------+--------------------+
                      |
                      +------------------------------------+
                                                           |
                                                           v
  +----------------------------------+       +--------------------------+
  | ["foo  bar", "baz     ", ...]  G |       | ["foo", "bar"]         G |-+
  |                                  |       |                          | |-+
  |                                  |<------+                          | | |
  | processIncomingLines()           |       | *JustifyLine()           | | |
  +----------------------------------+       +--------------------------+ | |
                                               +--------------------------+ |
                                                 +--------------------------+

G: Go Routine

Examples

words := []string{
    "Science", "is", "what", "we", "understand", "well", "enough", "to",
    "explain", "to", "a", "computer.", "Art", "is", "everything", "else",
    "we", "do",
}
width := 20
result := []string{
    "Science  is  what we",
    "understand      well",
    "enough to explain to",
    "a  computer.  Art is",
    "everything  else  we",
    "do                  ",
},