mirror of
https://github.com/RobTillaart/Arduino.git
synced 2024-09-20 00:55:58 -04:00
180 lines
5.3 KiB
Markdown
180 lines
5.3 KiB
Markdown
|
|
[](https://github.com/marketplace/actions/arduino_ci)
|
|
[](https://github.com/RobTillaart/UUID/actions/workflows/arduino-lint.yml)
|
|
[](https://github.com/RobTillaart/UUID/actions/workflows/jsoncheck.yml)
|
|
[](https://github.com/RobTillaart/UUID/blob/master/LICENSE)
|
|
[](https://github.com/RobTillaart/UUID/releases)
|
|
|
|
|
|
# UUID
|
|
|
|
Arduino library for generating UUID strings.
|
|
|
|
|
|
## Description
|
|
|
|
This **experimental** library provides a UUID generator.
|
|
A UUID is an Universally Unique IDentifier of 128 bits.
|
|
These are typically written in the following format, defined in RFC 4122.
|
|
|
|
```
|
|
0ac82d02-002b-4ccb-b96c-1c7839cbc4c0
|
|
^ ^
|
|
```
|
|
|
|
The length is 32 hexadecimal digits + four hyphens = 36 characters.
|
|
Note that the hexadecimal digits are lower case.
|
|
|
|
The 0.1.1 version of the lib tries to follow the RFC4122,
|
|
for version 4 (random generated) and variant 1.
|
|
In the format above the version 4 is indicated by the first arrow and must be 4.
|
|
The variant 1 is at the position of the second arrow.
|
|
This nibble must be 8,9, a or b.
|
|
All the remaining bits are random.
|
|
|
|
The basis for the UUID class is a Marsaglia pseudo random number generator.
|
|
This PRNG must be seeded with two real random uint32_t to get real random UUID's.
|
|
|
|
Often one sees also the term GUID = Globally Unique Identifier.
|
|
|
|
Tested on Arduino UNO only.
|
|
|
|
- https://en.wikipedia.org/wiki/Universally_unique_identifier
|
|
- https://www.ietf.org/rfc/rfc4122.txt
|
|
|
|
|
|
## Interface
|
|
|
|
|
|
### UUID class
|
|
|
|
Use **\#include "UUID.h"**
|
|
|
|
The UUID class has only a few methods.
|
|
|
|
- **UUID()** Constructor, initializes internals an generates a default UUID.
|
|
- **void seed(uint32_t s1, uint32_t s2 = 0)** reseeds the internal
|
|
pseudo random number generator.
|
|
It is mandatory to set s1 while s2 is optional.
|
|
The combination {0, 0} is not allowed and overruled in software.
|
|
- **void generate()** generates a new UUID depending on the mode.
|
|
- **UUID_MODE_RANDOM**: all UUID bits are random.
|
|
- **UUID_MODE_VARIANT4**: the UUID (tries to) conform to version 4 variant 1. See above.
|
|
- **char \* toCharArray()** returns a pointer to a char buffer
|
|
representing the last generated UUID.
|
|
Multiple subsequent calls to **toCharArray()** gives the same UUID
|
|
until **generate()** is called again.
|
|
|
|
|
|
### Mode
|
|
|
|
Only two modi are supported. Default is the **UUID_MODE_VARIANT4**.
|
|
|
|
- **void setVariant4Mode()** set mode to **UUID_MODE_VARIANT4**.
|
|
- **void setRandomMode()** set mode to **UUID_MODE_RANDOM**.
|
|
- **uint8_t getMode()** returns mode set.
|
|
|
|
|
|
### Printable
|
|
|
|
The UUID class implements the printable interface.
|
|
This allows one to print the UUID object directly over Serial and any other
|
|
stream implementing the Print interface. Think Ethernet or SD card.
|
|
|
|
```cpp
|
|
UUID uuid;
|
|
|
|
Serial.println(uuid);
|
|
|
|
// gives same output as
|
|
|
|
Serial.println(uuid.toCharArray());
|
|
```
|
|
|
|
|
|
## Performance
|
|
|
|
Not tested ESP32 (and many other platforms) yet.
|
|
|
|
Performance measured with **UUID_test.ino** shows the following times:
|
|
|
|
|
|
#### microseconds per byte
|
|
|
|
| Version | Function | UNO 16 MHz | ESP32 240 MHz |
|
|
|:-------:|:------------|:----------:|:-------------:|
|
|
| 0.1.0 | seed | 4 us | |
|
|
| 0.1.0 | generate | 412 us | |
|
|
| 0.1.0 | toCharArray | 4 us | |
|
|
| 0.1.1 | seed | 4 us | |
|
|
| 0.1.1 | generate | 248 us | |
|
|
| 0.1.1 | toCharArray | 4 us | |
|
|
| 0.1.2 | generate | 156 us | |
|
|
| 0.1.3 | generate | 120 us | |
|
|
|
|
Note: generating the 16 random bytes already takes ~40 us.
|
|
|
|
|
|
#### UUID's per second
|
|
|
|
| Version | UNO 16 MHz | ESP32 240 MHz | notes |
|
|
|:-------:|:------------:|:---------------:|:------:|
|
|
| 0.1.0 | 2000++ | |
|
|
| 0.1.1 | 4000++ | | generate both modes
|
|
| 0.1.2 | 6400++ | | generate both modes
|
|
| 0.1.3 | 8200++ | | generate both modes
|
|
|
|
|
|
Note that this maximum is not realistic e.g. for a server where also
|
|
other tasks need to be done (listening, transfer etc).
|
|
|
|
|
|
## Operation
|
|
|
|
See examples.
|
|
|
|
|
|
## Future
|
|
|
|
### General
|
|
|
|
- improve documentation
|
|
- external random input needed
|
|
- background
|
|
- test other platforms
|
|
- investigate entropy harvesting
|
|
- freeRAM, micros, timers, RAM, USB-ID, ...
|
|
- compile constants __DATE__ and __TIME__
|
|
- GUID as derived class?
|
|
- (further identical?)
|
|
|
|
### Functions
|
|
|
|
- add **setUpperCase()** and **setLowerCase()**, **isUpperCase()**
|
|
- one bool flag
|
|
- binary output in a byte array
|
|
- **getBinary(uint8_t \* array)**
|
|
- need to store them from generate.
|
|
|
|
|
|
### Examples
|
|
|
|
- ESP32 UUID server
|
|
- using timing of the calls as entropy !
|
|
- RTC for entropy
|
|
- EEPROM to store last seeds?
|
|
|
|
### Fixes / optimizations
|
|
|
|
- reduce footprint
|
|
- can the buffer be reduced?
|
|
- smaller random generator?
|
|
|
|
### Won't
|
|
|
|
- support for { and }
|
|
- add **setSeparator(char)** and **getSeparator()** ?
|
|
- minus is the specification.
|
|
|
|
|