Code Review or Root Canal? Hmmm…

I don’t particularly care for line-by-line code reviews. I don’t think they convey much meaning, even to people who think like computers. But you have to understand the inner workings of the software published earlier before I turn you loose on society. Thankfully, there are only about ten lines of code in the software and three major areas, so covering them should be a breeze for both you and me. So, copy the source code from the last article into your favorite text editor and follow along. Trust me, this won’t hurt a bit.

The three major sections are the setup data, the chunkifier and the rendering engine.

The Setup
The setup data consists of the necessary string literals to enable the rendering engine to draw the images using base-64 converted PNG files. This front matter takes up almost 1800 bytes and consists of the declaration for the JavaScript arrays array5bit_A, array5bit_B, stringStart, stringMid and stringEnd. Once these arrays are defined any barcode symbology can use them. So they are pretty important and well worth the space they take up.

The Chunkifier
Sounds like a subtitle for a good slasher movie, eh? The chunkifier is the four lines of code starting with the initialization of the intRawmod variable and ending with the for loop that populates the arraySeq array. In short, what the chunkifier does is break down a long string of ones and zeroes into a sequence of 5-bit integers.

The Rendering Engine
The rendering engine takes the sequence of 5-bit integers created by the chunkifier and builds the <img> elements necessary to render the array. This is a very simple loop and uses the integers found in the sequence to look up the unique text found in array5bit_A and array5bit_B and patch it together with the start, middle and end string constants so we have an <img> element that parses and scales to display a series of bars and spaces.

The Output
What you would see, if you used the rendering engine to output to a text file from the demonstration at the end of the last article is:


There are no line feeds or carriage returns embedded in the output text for a very good reason covered earlier. The text consists only of HTML entities. So, it takes six HTML images to render that very simple pseudo-barcode we saw last time (near the anti-climactic “ta-da!”). Next time we are going to demonstrate doing something non-trivial with the rendering engine by hooking it up to some code that actually generates valid barcodes. Until next time, thanks for tuning in.