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//! A "receive-only" view of a circuit, as a placeholder for circuits
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//! that have closed.
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use crate::{Error, Result};

            

        

            

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/// A HalfCirc represents the receive-only aspects of a circuit, for

            

        

            

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/// use to represent closed circuits and make sure that only

            

        

            

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/// acceptable data is received there.

            

        

            

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// TODO: This should probably have an expiration time too.

            

        

            

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#[derive(Debug, Clone)]

            

        

            

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pub(crate) struct HalfCirc {

            

        

            

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    /// How many RELAY cells will we accept on this circuit before we

            

        

            

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    /// conclude that somebody is violating the protocols?

            

        

            

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    allow_relay_cells: u16,

            

        

            

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}

            

        

            

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impl HalfCirc {

            

        

            

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    /// Create a new HalfCirc that will allow `total_windows` RELAY cells.

            

        

            

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    pub(crate) fn new(total_windows: u16) -> Self {

            

        

            

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        HalfCirc {

            

        

            

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            allow_relay_cells: total_windows,

            

        

            

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        }

            

        

            

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    }

            

        

            

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    /// Try receiving a relay cell on this circuit. Give an error if there

            

        

            

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    /// have been too many such cells to believe.

            

        

            

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    pub(crate) fn receive_cell(&mut self) -> Result<()> {

            

        

            

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        if let Some(n) = self.allow_relay_cells.checked_sub(1) {

            

        

            

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            self.allow_relay_cells = n;

            

        

            

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            Ok(())

            

        

            

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        } else {

            

        

            

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            Err(Error::ChanProto(

            

        

            

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                "Too many cells received on destroyed circuit".into(),

            

        

            

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            ))

            

        

            

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        }

            

        

            

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    }

            

        

            

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}