Top all-time · #24916
pyokagan
Personal blog · pyokagan.name/blogprogrammingsystems
pyokagan is a personal blog at pyokagan.name about programming and systems. Since 2021, 3 different Hacker News readers have linked it 3 times. No feed was found, so read it on the site itself.
Too few sampled comments (2) to say how often HN recommends it.?
Why HN links it
HN readers link this post as an overview of PNG chunk structure, which explains how APNG files and their frame control chunks are laid out.
Summarised by Claude from a sample of 2 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
What Hacker News says?
Pretty neat. That sent me on a brief hunt out to see how it might work. It seems that PNG (including APNG) has a fairly easy to follow pattern of chunks. So this could be a fairly simple cgi-bin type script that just does a "sleep(2)" or similar when it encounters a fcTL (frame control) chunk. See https://pyokagan.name/blog/2019-10-14-png/ for a good overview of how you might walk over PNG chunks.
Comment linking /blog/2019-10-14-png/
on “PNG files can be animated via network latency”Submitted Let's Implement Zlib.decompress() as a story · 3 points
HN discussionIn x86, a basic immediate instruction with a 1 Byte immediate value is encoded like this: <op> (1 Byte opcode), <Registers> (1 Byte), <immediate value> (1 Byte) While xor eax, eax only uses 2 bytes. Since there are only 8 registers, meaning they can be encoded with 3 bits, you can pack two values into the <Registers> field (ModR/M). Making mov eax, 0 only take two bytes would require significant changes of the ISA t…
Comment linking /blog/2019-09-20-x86encoding/
on “XOR'ing a register with itself is the idiom for zeroing it out. Why not sub?”