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construct/matrix/room_origins.cc

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// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
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ircd::string_view
ircd::m::room::origins::random(const mutable_buffer &buf,
const closure_bool &proffer)
const
{
string_view ret;
const auto closure{[&buf, &proffer, &ret]
(const string_view &origin)
{
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ret = { data(buf), copy(buf, origin) };
}};
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random(closure, proffer);
return ret;
}
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bool
ircd::m::room::origins::random(const closure &view,
const closure_bool &proffer)
const
{
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return random(*this, view, proffer);
}
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bool
ircd::m::room::origins::random(const origins &origins,
const closure &view,
const closure_bool &proffer)
{
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bool ret{false};
const size_t max
{
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origins.count()
};
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if(unlikely(!max))
return ret;
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auto select
{
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ssize_t(rand::integer(0, max - 1))
};
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const closure_bool closure{[&proffer, &view, &select]
(const string_view &origin)
{
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if(select-- > 0)
return true;
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// Test if this random selection is "ok" e.g. the callback allows the
// user to test a blacklist for this origin. Skip to next if not.
if(proffer && !proffer(origin))
{
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++select;
return true;
}
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view(origin);
return false;
}};
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const auto iteration{[&origins, &closure, &ret]
{
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ret = !origins.for_each(closure);
}};
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// Attempt select on first iteration
iteration();
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// If nothing was OK between the random int and the end of the iteration
// then start again and pick the first OK.
if(!ret && select >= 0)
iteration();
return ret;
}
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bool
ircd::m::room::origins::empty()
const
{
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return for_each(closure_bool{[]
(const string_view &) noexcept
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{
// return false to break and return false.
return false;
}});
}
size_t
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ircd::m::room::origins::count()
const
{
size_t ret{0};
for_each([&ret]
(const string_view &) noexcept
{
++ret;
});
return ret;
}
size_t
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ircd::m::room::origins::count_error()
const
{
size_t ret{0};
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for_each([&ret](const string_view &server)
{
ret += fed::errant(server);
});
return ret;
}
size_t
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ircd::m::room::origins::count_online()
const
{
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ssize_t ret
{
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0 - ssize_t(count_error())
};
for_each([&ret](const string_view &server)
{
ret += bool(fed::exists(server));
});
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assert(ret >= 0L);
return std::max(ret, 0L);
}
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/// Tests if argument is the only origin in the room.
/// If a zero or more than one origins exist, returns false. If the only origin
/// in the room is the argument origin, returns true.
bool
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ircd::m::room::origins::only(const string_view &origin)
const
{
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ushort ret{2};
for_each(closure_bool{[&ret, &origin]
(const string_view &origin_) noexcept -> bool
{
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if(origin == origin_)
ret = 1;
else
ret = 0;
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return ret;
}});
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return ret == 1;
}
bool
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ircd::m::room::origins::has(const string_view &origin)
const
{
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db::domain &index
{
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dbs::room_joined
};
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char querybuf[dbs::ROOM_JOINED_KEY_MAX_SIZE];
const auto query
{
dbs::room_joined_key(querybuf, room.room_id, origin)
};
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auto it
{
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index.begin(query)
};
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if(!it)
return false;
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const string_view &key
{
lstrip(it->first, "\0"_sv)
};
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const string_view &key_origin
{
std::get<0>(dbs::room_joined_key(key))
};
return key_origin == origin;
}
void
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ircd::m::room::origins::for_each(const closure &view)
const
{
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for_each(closure_bool{[&view]
(const string_view &origin)
{
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view(origin);
return true;
}});
}
bool
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ircd::m::room::origins::for_each(const closure_bool &view)
const
{
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db::domain &index
{
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dbs::room_joined
};
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auto it
{
index.begin(room.room_id)
};
size_t repeat{0};
string_view last;
char lastbuf[rfc1035::NAME_BUFSIZE];
for(; bool(it); ++it)
{
const auto &[origin, user_id]
{
dbs::room_joined_key(it->first)
};
// This loop is about presenting unique origin strings to our user
// through the callback. Since we're iterating all members in the room
// we want to skip members from the same origin after the first member
// from that origin.
if(likely(origin != last))
{
if(!view(origin))
return false;
// Save the witnessed origin string in this buffer for the first
// member of each origin; also reset the repeat ctr (see below).
last = { lastbuf, copy(lastbuf, origin) };
repeat = 0;
continue;
};
// The threshold determines when to incur the cost of a logarithmic
// seek on a new key. Under this threshold we iterate normally which
// is a simple pointer-chase to the next record. If this threshold is
// low, we would pay the logarithmic cost even if every server only had
// one or two members joined to the room, etc.
static const size_t repeat_threshold
{
6
};
// Conditional branch that determines if we should generate a new key
// to skip many members from the same origin. We do this via increment
// of the last character of the current origin so the query key is just
// past the end of all the member records from the last origin.
if(repeat++ > repeat_threshold)
{
assert(!last.empty());
assert(last.size() < sizeof(lastbuf));
repeat = 0;
lastbuf[last.size() - 1]++;
char keybuf[dbs::ROOM_JOINED_KEY_MAX_SIZE];
if(!seek(it, dbs::room_joined_key(keybuf, room.room_id, last)))
break;
}
}
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return true;
}