Locally Unique ID Generator

Generate system wide (locally) unique IDs.

This module generates system wide, variable length unique IDs based on on the cpuid module. If the cpuid module is not present, the module falls back to a pre-defined, constant seed for creating unique IDs.

The main purpose of this module is to have a unified way for e.g. creating hardware addresses and similar.

The IDs generated by this module are base created from a constant base part and a dynamic portion, which is XORed into the base ID. If the cpuid module is present, the base ID is created from the CPU’s unique ID. If not, the base ID is created by simple ‘memsetting’ the base ID with the defined backup seed value.

Once the base ID is generated, a LUID is generated by (i) XORing a counter value with the LSB of the base ID, or (ii) by XORing the least significant byes with a value given by the user.

Example: Calling luid_base(&buf, 8) will always yield an identical value, independent how often the function is called. But calling luid_base(&buf, 2) afterwards will results in a different value, if the cpuid module is present, and in the same (but shorter) value if not.

Example: Calling luid_get(&buf, 8) four times in a row, will yield four different IDs, differing in their LSB.

Example: Calling luid_custom(&buf, 8, 123) will always yield the same value, but calling luid_custom(&buf, 8, 124) will differ.

Note

This module generates locally unique IDs without any guarantees on their structure. These LUIDs are not compatible nor conform to UUIDs as defined in RFC4122.

void luid_get(void * buf, msp430_types.h::size_t len)

Get a unique ID.

The resulting ID is built from the base ID generated with luid.h::luid_base(), which isXORed with an 8-bit incrementing counter value into the most significant byte.

Note

The resulting LUID will repeat after 255 calls.

Parameters

buf:memory location to copy the LUID into. MUST be able to hold at least len bytes
len:length of the LUID in bytes

void luid_custom(void * buf, msp430_types.h::size_t len, int gen)

Get a custom unique ID based on a user given generator value.

The resulting ID is built from the base ID XORed with gen in the base ID’s most significant bytes.

Note

Calling this function with identical values for gen and len will always result in identical LUIDs.

Parameters

buf:memory location to copy the LUID into. MUST be able to hold at least len bytes
len:length of the LUID in bytes
gen:custom LUID generator value

void luid_base(void * buf, msp430_types.h::size_t len)

Get a LUID base value.

The luid module creates the value dependent on the given len value using the cpuid module if present or a static seed value (luid.h::LUID_BACKUP_SEED) if not.

Parameters

buf:memory location to copy the LUID into. MUST be able to hold at least len bytes
len:length of the LUID in bytes

LUID_BACKUP_SEED

Value used as based for the LUIDs in case the cpuid module is not present. 

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