git ssb

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'use strict'
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//Question: can I use req to reliably track how many
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//messages we are expecting to receive?
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//Math.max(null, null) is zero, but we want null
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function max (a, b) {
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  return a == null ? b : b == null ? a : Math.max(a, b)
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}
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function process(data, state) {
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  var local = state.local
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  var remote = state.remote
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  var _seq = remote.req == -1 ? -1 : max(remote.seq, remote.req)
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  var seq = local.req == -1 ? -1 : max(local.seq, local.req)
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  //don't count this feed, because we do not expect
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  //to exchange anything.
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  //this should only happen when there are many connections.
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  if(!local.tx && seq > _seq) return data
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  //req represents what they _know_ we have because
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  //we have either mentioned it in a note or sent it.
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  if(seq == null) {
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    //we havn't decided if we want this feed yet
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    data.unknown ++
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  } else if(seq === -1) {
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    //we have decided we do not want this feed. don't count it.
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  } else {
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    if(_seq == null) {
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      data.unknown ++
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    } else if(_seq === -1) {
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      //they have told us they do not want it.
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      //this means we do not expect to send anything.
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      //so don't count this feed.
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    } else {
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      data.feeds ++
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      if(seq == _seq)
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        data.sync ++
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      data.total += Math.max(
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        seq - remote.req,
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        _seq - (local.req || local.seq)
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      )
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      if(seq > _seq && local.tx)
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        data.send += seq - _seq
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      else if(seq < _seq && remote.tx)
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        data.recv += _seq - seq
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    }
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  }
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  return data
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}
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module.exports = function (states) {
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  var data = {
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    sync: 0, feeds: 0,
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    recv: 0, send: 0, total: 0,
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    unknown: 0,
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  }
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  for(var k in states)
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    //Only count this as an out of sync feed if we either can send
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    //to it or receive from it.
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    data = process(data, states[k])
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  return data
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}
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