Rust bitwise function: Comment says reading hurts, writing it was even worse

Description

Screenshot of a light-themed code editor showing a Rust function definition: "fn load_maj_min(block: [u8; 4 * 15]) -> (u16, u32) {". The if-branch simply swaps bytes when block[0] or block[1] is non-zero. The else-branch contains a single-line comment in red highlight: "// if you think reading this is bad, I had to write it". Below, several tightly packed expressions combine block[5]-block[7] with masks "0b0000_1111" and "0b1111_0000" and multiple left/right shifts to construct u16 and u32 values. The snippet showcases painful bit-fiddling, byte ordering, and mask-and-shift logic that sacrifices readability, a common low-level programming headache that seasoned developers will recognize and laugh at

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DeveloperHumor Rust CodeReadability CodeQuality LowLevelProgramming CodeComplexity CodeComments

Comments

Anonymous ★ Top Pick Bit-twiddling in Rust is when I start missing C - at least in C the undefined behavior is upfront, not buried under four masks, two endiannesses, and a comment from past-me apologizing in advance

Anonymous ★ Top Pick

Bit-twiddling in Rust is when I start missing C - at least in C the undefined behavior is upfront, not buried under four masks, two endiannesses, and a comment from past-me apologizing in advance
Anonymous

This is what happens when you need to parse a binary format that was clearly designed by someone who measured memory in punch cards and thought endianness was a personality trait - now you're writing Rust that looks like you're defusing a bomb made of pointers while blindfolded
Anonymous

This is the code equivalent of 'I'm sorry you had to see that' - when your bit-twiddling logic becomes so gnarly that you preemptively apologize to future maintainers. The real tragedy? This is probably the *cleanest* way to parse major/minor device numbers from a byte array without pulling in a dependency. Welcome to systems programming, where the comments are apologies and the bit shifts are nested deeper than your call stack during a production incident
Anonymous

Semver packed across nibbles with endian roulette - Rust guarantees memory safety, not spec sanity
Anonymous

Optimizations so tight, they escaped the event horizon of readability - good luck grepping for bugs
Anonymous

Saving two bytes in the wire format costs three casts, four shifts, and a headcount for maintenance
@LonelyGayTiger 4y

What the actual fuck
@Kryvashek 4y

Look like some crypto calculations. Doesn't look terrible, looks usual.
@VolodymyrMeInyk 4y

sad but true
@LionElJonson 4y

Actual comment would be more useful
@dmytro_sukhariev 4y

Is it Rust Lisp?
1. @sylfn 4y
  
  https://t.me/dev_meme/3667 > Please use English in this chat. Fast translation (may be inaccurate): Is it Rust Lisp?
@cfyzium 4y

if 0 != block[0] || 0 != block[1] { These Yoda conditions are the most disturbing part of the snippet. Rust does not even compile misprints like block[0] = 0 =___=.
1. @sylfn 4y
  
  misprints like block[0] = 0 sometimes are not misprints
  
  @Agent1378 4y
  
  Yes, these are flaws of the language itself.
@cfyzium 4y

Still, neither Rust nor C++ with -Werror will let you make an unintentional mistake there (inside a condition expression).