FIDO_DEV_INFO_MANIFEST(3)

💖 FIDO_DEV_INFO_MANIFEST — the FIDO2 device discovery functions, bestie edition 💖

okay so this is the FIDO_DEV_INFO_MANIFEST(3) page from the Library Functions Manual, and it's literally all about finding your FIDO2 devices and poking at their little info cards. sit down, grab a boba, we're doing this 🧋✨

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✨ NAME ✨

fido_dev_info_manifest, fido_dev_info_new, fido_dev_info_free, fido_dev_info_ptr, fido_dev_info_path, fido_dev_info_product, fido_dev_info_vendor, fido_dev_info_manufacturer_string, fido_dev_info_product_string, fido_dev_info_set — FIDO2 device discovery functions 🦋

like. the whole friend group. all ten of them. slay.

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🌸 SYNOPSIS 🌸

#include <fido.h>

int
fido_dev_info_manifest(fido_dev_info_t *devlist, size_t ilen,
    size_t *olen);

fido_dev_info_t *
fido_dev_info_new(size_t n);

void
fido_dev_info_free(fido_dev_info_t **devlist_p, size_t n);

const fido_dev_info_t *
fido_dev_info_ptr(const fido_dev_info_t *devlist, size_t i);

const char *
fido_dev_info_path(const fido_dev_info_t *di);

int16_t
fido_dev_info_product(const fido_dev_info_t *di);

int16_t
fido_dev_info_vendor(const fido_dev_info_t *di);

const char *
fido_dev_info_manufacturer_string(const fido_dev_info_t *di);

const char *
fido_dev_info_product_string(const fido_dev_info_t *di);

int
fido_dev_info_set(fido_dev_info_t *devlist, size_t i, const char *path,
    const char *manufacturer, const char *product,
    const fido_dev_io_t *io, const fido_dev_transport_t *transport);

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👑 DESCRIPTION 👑

🔍 finding devices: fido_dev_info_manifest()

okay so fido_dev_info_manifest() fills up devlist with up to ilen FIDO2 devices that the underlying operating system managed to find. and rn? only USB HID devices are supported. that's it. that's the roster. 💅

the number of discovered devices comes back in olen, and olen has to be an addressable pointer. no cap.

🎀 making a list: fido_dev_info_new()

fido_dev_info_new() returns a pointer to a freshly allocated, empty device list with n available slots. and if memory isn't available? it returns NULL. tragic. 😭

🧹 cleaning up: fido_dev_info_free()

fido_dev_info_free() releases the memory backing *devlist_p, where *devlist_p must have been previously allocated by fido_dev_info_new(). you also gotta hand over the number n of allocated slots. on return, *devlist_p gets set to NULL.

and here's the cute part: either devlist_p or *devlist_p may be NULL, and in that case fido_dev_info_free() is a NOP. it just... doesn't do anything. iconic, honestly. 🫶

🦋 grabbing a slot: fido_dev_info_ptr()

fido_dev_info_ptr() returns a pointer to slot number i of devlist. and it is the caller's responsibility to ensure that i is bounded. that's on you, bestie. also pls note: the first slot has index 0. zero-indexed, as the universe intended. ✨

📍 the getters 📍

• fido_dev_info_path() returns the filesystem path or subsystem-specific identification string of di.
• fido_dev_info_product() returns the product ID of di.
• fido_dev_info_vendor() returns the vendor ID of di.
• fido_dev_info_manufacturer_string() returns the manufacturer string of di. if di does not have an associated manufacturer string, fido_dev_info_manufacturer_string() returns an empty string. (an empty string, not a sad little NULL. she's polite.)
• fido_dev_info_product_string() returns the product string of di. and same vibe — if di does not have an associated product string, fido_dev_info_product_string() returns an empty string.

💫 the example

an example of how to use the functions described in this document can be found in the examples/manifest.c file shipped with libfido2. go read it, it's giving tutorial energy. 📖

🧚 setting it up yourself: fido_dev_info_set()

fido_dev_info_set() initializes an entry in a device list allocated by fido_dev_info_new() with the specified path, manufacturer, and product strings, and with the specified I/O handlers and, optionally, transport functions, as described in fido_dev_set_io_functions(3).

the io argument must be specified; the transport argument may be NULL.

the path, I/O handlers, and transport functions will be used automatically by fido_dev_new_with_info(3) and fido_dev_open_with_info(3). so an application can use this, for example, to substitute mock FIDO2 devices in testing for the real ones that fido_dev_info_manifest() would discover. fake devices in the group chat. pretending. it's a bit of a moment. 🙈

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⭐ RETURN VALUES ⭐

fido_dev_info_manifest() always returns FIDO_OK. and if a discovery error occurs? the olen pointer is set to 0. that's your little signal. 🚨

fido_dev_info_set() returns FIDO_OK on success. on error, a different error code defined in <fido/err.h> is returned. check the header, bestie.

and the pointers returned by fido_dev_info_ptr(), fido_dev_info_path(), fido_dev_info_manufacturer_string(), and fido_dev_info_product_string() are guaranteed to exist until fido_dev_info_free() is called on the corresponding device list. so like, don't free the list and then go poking at the pointers. that would be a vibe check you fail. 💀

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friendly lil reminder: keep that i bounded, keep your olen addressable, and free your lists. main character energy requires memory hygiene. 💜

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and that's the whole page, bestie!! this one came from the Debian build, dated March 30, 2022 🎀 go manifest some devices, you're gonna do great. mwah. 💖✨🦋