qthread_writeEF(3)

✨ qthread_writeEF(3) ✨

okay bestie, pull up a chair, we're reading the libqthread manual together and this one is genuinely iconic 🫶 it's the qthread_writeEF page, and yes there's a _const twin, they're a package deal 💅

🌸 NAME 🌸

qthread_writeEF, qthread_writeEF_const — waits for the dest to be empty, then fills it. that's it. that's the whole vibe. wait for empty, then fill. 💖

🦋 SYNOPSIS 🦋

#include <qthread.h>

int
qthread_writeEF (aligned_t * restrict dest, const aligned_t * restrict
src);

int
qthread_writeEF_const (aligned_t *dest, aligned_t src);

🎀 DESCRIPTION 🎀

so like, these functions wait for memory to become empty, and then fill it. the way that works is: when the memory becomes empty, only one thread that's blocked like this gets awoken. not two, not a crowd, one. main character energy only 👑

data is read from src and written to dest. simple. slay.

the semantics of writeEF are, in order, no skipping:

1. dest's FEB state must be "empty"
2. data is copied from src to dest
3. dest's FEB state gets changed from "empty" to "full"

periodt. that's the whole pipeline. 🌈

💀 WARNING 💀

okay so this is the part where I hold your hand, because it's giving "read this or perish" 🙈

This, and all other FEB-related functions currently operate exclusively on aligned data. This is to simulate the behavior of the MTA as closely as possible. If the library was compiled for a 32-bit architecture, it will require 4-byte alignment and reads/writes will operate on four bytes at a time; if the library was compiled for a 64-bit architecture, it will require 8-byte alignment and reads/writes will operate on eight bytes at a time.

bestie. alignment is not a suggestion here, it's a personality requirement. get it wrong and you're on your own 😭

⭐ RETURN VALUE ⭐

On success, the memory address dest is marked full, the address dest is filled with the contents of src, and 0 is returned. 🎉

On error, a non-zero error code is returned. that's the "we don't talk about it" branch. 💅

🍓 ERRORS 🍓

• ENOMEM — Not enough memory could be allocated for bookkeeping structures. lowkey tragic. the bookkeeping could not be booked. 😭

🧚 SEE ALSO 🧚

• qthread_empty(3)
• qthread_fill(3)
• qthread_writeF(3)
• qthread_readFF(3)
• qthread_readFE(3)
• qthread_lock(3)
• qthread_unlock(3)

go read those too, they're all in the same friend group 💜

and that's the page!! this whole thing came out of libqthread, dated APRIL 2011 — shoutout to the source and the version and the date, they ate and left no crumbs 👑💖 byeeee, go write to your dest responsibly 🫶✨