SDL_hid_write(3)

💖 SDL_hid_write — bestie's guide to yelling at your HID device 💖

okay so you want to send an Output report to a HID device?? say less. this is the SDL_hid_write(3) page from the SDL3 functions era and I'm gonna walk you through it like we're texting at 2am 🦋

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✨ NAME ✨

SDL_hid_write — Write an Output report to a HID device. that's it. that's the job. 💅

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🌸 SYNOPSIS 🌸

#include <SDL3/SDL_hidapi.h>

int SDL_hid_write(SDL_hid_device *dev, const unsigned char *data, size_t length);

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🎀 DESCRIPTION 🎀

okay so the first byte of data MUST contain the Report ID. mandatory. non-negotiable. if your device only supports a single report, you set that first byte to 0x0. the bytes after that are the actual report data, no notes 💖

and because the Report ID is always required, calls to SDL_hid_write() will always carry one more byte than the report itself contains. like. always. it's giving "plus one" energy ✨

example time, because numbers make it click: if a hid report is 16 bytes long, you have to pass 17 bytes to SDL_hid_write() — that's the Report ID (or 0x0, for devices with a single report) followed by the report data (16 bytes). so in that example, the length you'd pass in would be 17. periodt. 👑

now, where does it actually go?? SDL_hid_write() will send the data on the first OUT endpoint, if one exists. and if it doesn't exist?? it sends the data through the Control Endpoint (Endpoint 0). main character finds a way, fr fr 🫶

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🌈 FUNCTION PARAMETERS 🌈

• dev — a device handle returned from SDL_hid_open(). you gotta have the handle, bestie, no handle no write 🙈
• data — the data to send, including the report number as the first byte. don't forget that first byte, I'm begging 😭
• length — the length in bytes of the data to send. yes, the whole thing, Report ID included 💜

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⭐ RETURN VALUE ⭐

it returns the actual number of bytes written, and -1 on failure 💀 — and if you get that -1, call SDL_GetError() for more information. she will tell you what went wrong, iykyk.

lowkey important: don't just assume it wrote everything, check the number it hands back. it's the actual count, not a vibe.

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🧚 AVAILABILITY 🧚

this function is available since SDL 3.2.0 🌟 so if you're on something older, bestie... it's not there. no cap.

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that's the whole page, you ate it 💅 go write some reports, you've got this 👑

— written with love by Simple Directmedia Layer, page from SDL 3.4.18, dated with the SDL_hid_write(3) energy. stay iconic, drink water, and always pass that extra byte 🍓✨