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189 lines
6.3 KiB
Markdown
189 lines
6.3 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/Multiplex/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/Multiplex/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/Multiplex/blob/master/LICENSE)
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[](https://github.com/RobTillaart/Multiplex/releases)
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# Multiplex
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Arduino Library implementing a (Print) stream multiplexer.
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## Description
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Multiplex is a library in which one can add multiple Print streams.
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If one prints to the multiplexer the data is sent to all the streams that were added and are enabled.
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Streams can be enabled or disabled by calling `enable()/disable()` passing either an index (based on the order
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in which `add()` was called; 0 is first) or a pointer to the `Print`
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object that was passed to `add(Print *)` by calling `enableStream()/disableStream()`
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Default all streams are enabled.
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### Number of streams
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The maximum number of streams to add is default 4.
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This value is defined in the **multiplex.h file** and can be overruled on the command line.
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```cpp
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#define MAX_MULTIPLEX 4
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```
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This value can be set to 254 MAX as the number 255 / 0xFF is used as a NOT_FOUND flag.
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### Removal of streams
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Since 0.2.2 the library has **experimental** remove support.
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The effect of the current implementation of removal is that the order in which the streams are handled
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can change as the indices are affected.
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If you want to prevent this effect, you should use **reset()** and repopulate the multiplexer.
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## Interface
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### Constructor
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- **Multiplex()** constructor,
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sets the maximum number of streams to MAX_MULTIPLEX == 4 by default.
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MAX number is 254 as 255 (0xFF) is used as a flag for **NOT FOUND**.
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- **~Multiplex()** destructor
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- **void reset()** resets the count in the multiplexer to zero streams.
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Effectively a remove all.
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### Core
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- **bool add(Print \* stream)** add another Print stream.
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Returns true on success.
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Returns false if no space left, or when stream already in multiplex.
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Use the **index(Stream)** to get the actual index of the stream.
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- **size_t write(uint8_t c)** workhorse of the Print interface.
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Writes a character to all enabled streams.
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- **size_t write(const uint8_t \* buffer, size_t size)**
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Writes a buffer of size characters to all enabled streams.
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- **virtual void flush() override** flushes all enabled streams.
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With respect to the two **write()** functions:
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The performance will be affected by the number of streams and their performance.
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One slow stream can hold them all.
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Note: the different streams will get the data in order of addition,
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and therefore they will get the data at different times.
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### Remove - experimental
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(since 0.2.2)
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Removing a stream is still experimental. Feedback is welcome.
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Removing a stream changes the internal indices used.
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So if you want to use **remove()** in your sketch,
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only use the functions with a stream as parameter as these will always work correctly.
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Alternative is to request the **uint8_t index(Stream)** after you called
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**remove()** and update your own used indices.
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- **bool remove(Print \* stream)** remove a Print stream.
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Returns false if the stream is not in the multiplexer.
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- **bool remove(uint8_t index)** remove a stream by its internal index.
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Returns false if index is out of range.
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### Control
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#### Info
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- **uint8_t count()** returns number of streams added, MAX 4 in initial release
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- **uint8_t size()** returns size which is 4 in the current release.
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- **uint8_t free()** returns number of free slots, 0 .. 4.
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#### enable / disable
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Note: the index based functions are (slightly) faster than the stream based functions.
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How much faster depends on **MAX_MULTIPLEX** as the stream based functions do a lookup in every call.
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- **bool enable(uint8_t index)** enable the stream at index.
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Returns true on success, false otherwise.
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- **bool enableStream(Stream \* stream)** enable the stream.
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Returns true on success, false otherwise.
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- **bool disable(uint8_t index)** disable the stream at index.
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Returns true on success, false otherwise.
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- **bool disableStream(Stream \* stream)** disable the stream.
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Returns true on success, false otherwise.
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- **bool isEnabled(uint8_t index)** returns true if the stream at index is enabled,
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false otherwise.
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- **bool isEnabledStream(Stream \* stream)** returns true if the stream is enabled,
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false otherwise.
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- **bool isEnabledAny()** returns true if at least one stream is enabled.
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If false is returned it makes no sense to print anything.
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#### Lookup functions
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- **uint8_t index(Print \*stream)** returns the index of the stream if it was added,
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otherwise it returns 0xFF == 255.
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Can be used to check if a stream is added to the multiplexer.
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- **Print \* stream(uint8_t index)** returns the stream at index or NULL otherwise.
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Convenience function.
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### OutputCount - experimental
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(since 0.2.4)
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The output count function was added for diagnostic tests.
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It is kept in the library for now, however it might be removed in the future.
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Footprint is minimal.
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- **uint32_t getOutputCount()** returns number of bytes multiplexed.
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So if 6 bytes are sent to 3 streams the output byte count is 3 x 6 = 18.
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For diagnostic purpose.
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- **void resetOutputCount()** set internal counter to 0.
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## Operation
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See examples
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## Future
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#### Must
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#### Should
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- set size in constructor
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- dynamic memory for all internal arrays
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- breaking change ==> 0.3.0
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- should **int add()** return the index? Or -1 if fails.
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- usable idea
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- breaking change ==> 0.3.0
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- add **removeAll()** ==> reset()
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#### Could
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- error handling
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- add an error flag if one of the streams does not **write()**
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correctly and returns 0 or less than it should.
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- add more examples.
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- add performance measurement
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- KB / second
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- move all code to .cpp
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#### Wont
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- pack enabled flag in one or more bytes.
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(not much faster + need to encode/decode)
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- add names?
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(too much memory)
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- test to prevent circular addition of streams?
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- no, is risk of the user.
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