[WIP] Generic Select for IO #3595
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| def self.select(actions : Tuple | Array, has_else = false) | ||
| pollfds = Array(LibC::Pollfd).new | ||
| fdmap = Hash(Int32, Int32).new # Map of poll file descriptor to action index |
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I would like to get rid of these malloc calls in select. Unfortunately it seems that allocating variable size arrays on the stack isn't possible.
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Maybe one could recycle the pollfds and fdmap variables? Chances are good, that a Fiber is always running the same select in a loop, with the same arguments, thus the sizes of both would never change and no sub-sequent allocations will be done. That, or we need to introduce VLAs :)
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| select | ||
| when byte = reader.read_byte | ||
| byte.should eq(10_u8) | ||
| end |
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Will not fail if line 10 is never reached
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Expanding nodoc to comments which simply end in :nodoc: means that technical documentation for implementors can be attached to lower-level classes while keeping the docs free of their presence.
Resume tokens allows the resuming fiber to send a pointer to the resumed fiber. This is useful in the case when there are multiple possible resume events, as the resumed fiber can work out which event resumed it by checking the received token.
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Select.select is a more generic select variant which can select over anything which can resume the fiber once the action is ready. It also provides optimisations for actions which can be tested for readiness cheaply, and actions which can provide a pollfd struct compatible with poll().
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| # :nodoc: | ||
| def read_token | ||
| self.as(Void*) + 1 |
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I've implemented differentiating read/write tokens by adding a constant to the self pointer. This means now you can select over read/write on the same channel/IO.
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Closing because this PR is out of date and the conversation here. Hopefully this will be useful reference code for the future though. |
See extended commit messages for more details.
This is WIP, as some things like selecting read/write from a single IO, and selecting on
sleepare not yet implemented. I wanted to get this up for discussion early as there may be a better way to implement this, especially resume tokens.