u16.h(3)

✨ NAME ✨

u16.h — it's giving 16-bit words, bestie. (In the original tongue: 16-разрядные слова. Same vibe. 💅)

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🦋 SYNOPSIS 🦋

#include 'bee2/defs.h'
#include 'bee2/core/safe.h'

🎀 Macros

• #define u16RotHi(w, d) — cyclic shift of a u16 word by d positions toward the higher (most significant) bits 💫
• #define u16RotLo(w, d) — cyclic shift of a u16 word by d positions toward the lower (least significant) bits 💫

🎀 Functions

• u16 u16Rev (register u16 w) — reverse the octets
• void u16Rev2 (u16 buf[], size_t count) — reverse the octets of an array of words
• u16 u16Bitrev (register u16 w) — reverse the bits
• size_t u16Weight (register u16 w) — weight
• bool_t u16Parity (register u16 w) — parity
• size_t u16CTZ (register u16 w) — count of trailing zero bits
• size_t u16CLZ (register u16 w) — count of leading zero bits
• u16 u16Shuffle (register u16 w) — shuffle the bits
• u16 u16Deshuffle (register u16 w) — un-shuffle the bits
• u16 u16NegInv (register u16 w) — additive-multiplicative inversion
• void u16From (u16 dest[], const void *src, size_t count) — load from a memory buffer
• void u16To (void *dest, size_t count, const u16 src[]) — store into a memory buffer

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📖 DESCRIPTION 📖

Okay so this header is where the operations on 16-bit words live — and not just one word, whole arrays of them. Main character energy for a little integer type, honestly. 👑

Precondition: correct memory buffers get passed into the functions. Like, actual valid buffers. Don't hand it chaos and then act surprised. 🙈

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💖 MACROS 💖

#define u16RotHi(w, d)

The macro definition, verbatim, no notes:

((u16)((w) << (d) | (w) >> (16 - (d))))

Precondition: 0 < d < 16. (Yes, strictly. Read it. 😌)

#define u16RotLo(w, d)

Same deal, other direction:

((u16)((w) >> (d) | (w) << (16 - (d))))

Precondition: 0 < d < 16. Periodt.

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🌸 FUNCTIONS 🌸

u16 u16Bitrev (register u16 w)

Flips the bits of the u16 word w all the way around. Little bit reversed, big bit first. 🪞

Returns: the word with its bits rearranged.

Arguments:

• w — word

size_t FAST u16CLZ (register u16 w)

Works out the length of the run of zero bits at the leading (top) end of the machine word w.

Returns: the length of that run.

Note: CLZ == Count of Leading Zeros. Iykyk. ✨

Regularity: there is a faster irregular version available.

Arguments:

• w — word

Cross-references: u16CLZ().

Used in: u16CLZ().

size_t FAST u16CTZ (register u16 w)

Same but the other end: the length of the run of zero bits at the trailing (bottom) end of the u16 word w.

Returns: the length of that run.

Note: CTZ == Count of Trailing Zeros. 💅

Regularity: there is a faster irregular version available.

Arguments:

• w — word

Cross-references: u16CTZ().

Used in: u16CTZ().

u16 u16Deshuffle (register u16 w)

The even bits of the u16 word w get grouped together in its lower half, and the odd bits go into the upper half.

Returns: the word with its bits grouped up.

Arguments:

• w — word

void u16From (u16 dest[], const void * src, size_t count)

The buffer [count]src gets turned into an array [(count + 1) / 2]dest of u16 words. Loading arc. 📥

Arguments:

• dest — destination
• src — source
• count — number of octets

u16 u16NegInv (register u16 w)

Additive and multiplicative inversion of the u16 word-as-a-number w, modulo 2^16.

Precondition: w is odd. (Not even. Not negotiable. 🫠)

Returns: - w^{-1} \mod 2^16.

Note: the computed word is used in Montgomery reduction.

Arguments:

• w — word

bool_t u16Parity (register u16 w)

Computes the sum modulo 2 of the bits of the u16 word w.

Returns: the sum of the bits.

Arguments:

• w — word

u16 u16Rev (register u16 w)

Reverses the octets of the u16 word w.

Returns: the word with its octets rearranged.

Arguments:

• w — word

void u16Rev2 (u16 buf[], size_t count)

Reverses the octets of the array [count]buf of u16 words. Whole squad, flipped. 🔄

Arguments:

• buf — destination
• count — number of elements

u16 u16Shuffle (register u16 w)

The bits of the lower half of the u16 word w move into the even positions, and the bits of the upper half move into the odd positions.

Returns: the word with its bits shuffled apart.

Arguments:

• w — word

void u16To (void * dest, size_t count, const u16 src[])

The buffer [count]dest is formed from the array [(count + 1) / 2]src of u16 words. Writing arc. 📤

Arguments:

• dest — destination
• count — number of octets
• src — source

size_t u16Weight (register u16 w)

Counts how many nonzero bits live in the u16 word w. Every bit that showed up gets counted, no cap. 🔥

Returns: the number of nonzero bits.

Arguments:

• w — word

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👑 AUTHOR 👑

Automatically generated by Doxygen for the Bee2 Library from the source text. (Not a human author, just a very diligent robot. Respect. 🎀)

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Bee2 Library — Sun 25 Jan 2026 00:00:00. That's the version-and-date tea, bestie, and that's the whole u16.h(3) page. Slay, go shift some bits. 💖✨🦋