Do the simplest thing that can possibly work (2004) • Hacker News Board

Re: Do the simplest thing that can possibly work (2004)

#91

Post by madars » Wed, Mar 01, 2023, 7:31 PM UTC

addaon wrote: post #90

icedchai wrote: post #76

Earlier quoted context omitted.

Why reinvent the wheel? Just look at some older protocol, like SLIP.

SLIP uses byte stuffing to reserve its end-of-frame sequence, which leads to data-dependent packet transmission times, which is not acceptable in my application.

Is this a big deal? Say, if character 0 is reserved you can encode everything in base255 and transmit encoded bytes shifted by 1. (Or, for simpler encoding, transfer an appropriately encoded bitmask of which characters are 0, then a copy of that data where 0 is replaced by anything else.)

Edit: this HN comment by KMag suggests a much simpler encoding https://news.ycombinator.com/item?id=12550584 (you'd need to process your packets in 254 byte chunks)

> replace first null with 255. Every later null, replace with the index of the previous null. Make the final byte the index of the last null (or 255 if no nulls were replaced). In this way, you've replaced the nulls with a linked list of the locations where nulls used to be. To invert the transformation, just start at the final byte and walk the linked list backward until you hit a 255.

Looks like this is https://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuff...

Re: Do the simplest thing that can possibly work (2004)

#92

Post by tpoacher » Thu, Mar 02, 2023, 2:00 PM UTC

In practice, in most situations, the simplest thing would be to cheat.

So, grain of salt, and all that.

Re: Do the simplest thing that can possibly work (2004)

#93

Post by 7speter » Thu, Mar 02, 2023, 7:52 PM UTC

blippage wrote: post #72

7speter wrote: post #46

Earlier quoted context omitted.

I thought c was primarily developed for the initial purpose of being the language used to write Unix and that their developments were practically one after the other and that Ritchie and Thompson were colleagues at Bell? C was designed for portability in mind?

I could be wrong, but I think Unix was originally written in assembler, which isn't portable. Unix first appeared on a PDP-7 (not PDP-11). PDP-7 was pretty old even by the standards of the time. "Originally, UNIX was written in PDP-7 assembly, and then in PDP-11 assembly, but then when UNIX V4 began to be re-written in C in 1973 and was run mostly on the PDP-11. So far as I can tell, there is no Ancient C compiler th…

Thanks for painting a mire elaborate picture of how it all went. Of course c had to be compiled on some system, and there were probably a good variety of systems around back then.

Re: Do the simplest thing that can possibly work (2004)

#94

Post by addaon » Fri, Mar 03, 2023, 4:59 AM UTC

madars wrote: post #91

addaon wrote: post #90

Earlier quoted context omitted.

SLIP uses byte stuffing to reserve its end-of-frame sequence, which leads to data-dependent packet transmission times, which is not acceptable in my application.

Is this a big deal? Say, if character 0 is reserved you can encode everything in base255 and transmit encoded bytes shifted by 1. (Or, for simpler encoding, transfer an appropriately encoded bitmask of which characters are 0, then a copy of that data where 0 is replaced by anything else.) Edit: this HN comment by KMag suggests a much simpler encoding https://news.ycombinator.com/item?id=12550584 (you'd need to proces…

Yeah, COBS works. In my case, I can even go simpler, since messages are fixed size. But:

1) This is now part of the line code. And "uart + slip but modified" starts losing some of the "simplest thing" charm of "just do what everyone else does."

2) Looking at this without reference to previous work, it sure seems unlikely to be the simplest thing. Magic numbers everywhere -- 8N1 uses 8 bit bytes to support ~5% clock skew, which isn't reflective of the application; COBS forces sub-packets at 255-ish byte intervals, which doesn't match any inherent concept, etc. It can work, but does it make sense in isolation?

Re: Do the simplest thing that can possibly work (2004)

#95

Post by hattmall » Mon, Mar 06, 2023, 5:30 PM UTC

addaon wrote: post #4

This write-up is too light to provide any real insight. In particular, how do you assess simplicity? From an example I'm currently working through on a hobby project... do I use a RS-485 transceiver with a custom line code, or do I use a 10base-T1 PHY? Ethernet, especially one pair ethernet, is undoubtedly more /complex/, with echo cancellation, a complicated line code, etc; but if I use the PHY, then /I own/ that co…

Does simplicity equal time? In my mind it doesn't. As for your example I'm a software person and bringing external dependencies feels like adding layers of complexity. Simplicity is minimalist, if I need an external dependency I generally try to extract the actual part I need and understand it and have it my own code to streamline what I need. From my view external dependencies are the epitome of complexity.