function fulfill_order($our_orderid)
{
$our = fetch_order_info($our_orderid);
if ($our->status != 'OPEN') {
return;
}
if ($our->processed) {
throw new Error('Unprocessed', "Shouldn't be here for {$our_orderid}");
}
// Dividing two bignum(20) values only gives us 4 decimal places in the result
// this can cause us to process the matching orders out of sequence unless we arrange
// for the quotient to be greater than 1 by putting the bigger value on top.
//
// With BTC at around 10 GBP each, I just saw the previous version of this query
// process 2 orders out of sequence because the values of initial_want_amount / initial_amount
// for the two orders were 0.09348 and 0.09346, which compare equal to 4 decimal places
if ($our->initial_amount > $our->initial_want_amount) {
$order_by = "initial_want_amount / initial_amount ASC";
} else {
$order_by = "initial_amount / initial_want_amount DESC";
}
$query = "\n SELECT orderid, uid\n FROM orderbook\n WHERE\n status='OPEN'\n AND processed=TRUE\n AND type='{$our->want_type}'\n AND want_type='{$our->type}'\n AND initial_amount * '{$our->initial_amount}' >= initial_want_amount * '{$our->initial_want_amount}'\n AND uid!='{$our->uid}'\n ORDER BY {$order_by}, timest ASC;\n ";
wait_for_lock($our->uid);
$result = b_query($query);
while ($row = mysql_fetch_array($result)) {
echo "Found matching ", $row['orderid'], " from user ", $row['uid'], ".\n";
wait_for_lock($row['uid']);
// lock their account
$them = fetch_order_info($row['orderid']);
// re-fetch their order now that they're locked
if ($them->status != 'OPEN') {
echo "order {$them->orderid} was cancelled on us\n";
release_lock($them->uid);
continue;
}
printf("old order: has %s; wants %s\n", internal_to_numstr($them->amount), internal_to_numstr($them->want_amount));
if ($them->type != $our->want_type || $our->type != $them->want_type) {
throw Error('Problem', 'Urgent problem. Contact the site owner IMMEDIATELY.');
}
// echo " them: orderid {$them->orderid}, uid {$them->uid}, have {$them->amount} {$them->type}, want {$them->want_amount}\n";
// echo " us: orderid {$our->orderid}, uid {$our->uid }, have: {$our->amount} {$our->type}, want {$our->want_amount}\n";
// echo " them->initial_amount = {$them->initial_amount}, them->initial_want_amount = {$them->initial_want_amount}\n";
$left = gmp_mul($our->amount, $them->initial_amount);
$right = gmp_mul($them->amount, $them->initial_want_amount);
if (gmp_cmp($left, $right) >= 0) {
// We need to calculate how much of our stuff they can afford at their price
// we ignore the remainder - it's totally insignificant.
list($them->new_want, $remainder) = gmp_div_qr($right, $them->initial_amount);
if (gmp_cmp($remainder, 0) != 0) {
$them->new_want = gmp_add($them->new_want, 1);
}
$them->new_want = gmp_strval($them->new_want);
echo " we swallow them; they can afford {$them->new_want} from us\n";
pacman($them->orderid, $them->uid, $them->amount, $them->type, $them->commission, $our->orderid, $our->uid, $them->new_want, $our->type, $our->commission, $our->amount, $our->initial_amount, $our->initial_want_amount);
release_lock($them->uid);
// re-update as still haven't finished...
// info needed for any further transactions
$our = fetch_order_info($our->orderid);
// order was closed and our job is done.
if ($our->status != 'OPEN') {
break;
}
} else {
// We need to calculate how much of their stuff we can afford at their price
// we ignore the remainder - it's totally insignificant.
list($our->new_want, $remainder) = gmp_div_qr($left, $them->initial_want_amount);
if (gmp_cmp($remainder, 0) != 0) {
$our->new_want = gmp_add($our->new_want, 1);
}
$our->new_want = gmp_strval($our->new_want);
echo " they swallow us; we can afford {$our->new_want} from them\n";
pacman($our->orderid, $our->uid, $our->amount, $our->type, $our->commission, $them->orderid, $them->uid, $our->new_want, $our->want_type, $them->commission, $them->amount, $them->initial_amount, $them->initial_want_amount);
release_lock($them->uid);
break;
}
}
release_lock($our->uid);
}
<ul>
<li><a href="http://code.google.com/p/googlechartphplib/">Project home on Google Code</a></li>
<li><a href="http://code.google.com/p/googlechartphplib/issues/list">Issue Tracker</a></li>
<li><code>remi at cloudconnected dot fr</code></li>
</ul>
</div>
<div class="clear"></div>
</div>
<div id="footer">
<h3>About</h3>
<p>I'm Rémi Lanvin, and you can contact me by email at <code>remi at cloudconnected dot fr</code></p>
<p>Sometimes I have enough free time to write an article <a href="http://cloudconnected.fr">on my dev blog</a>, or something <a href="http://twitter.com/rlanvin">on my Twitter account</a>.</p>
<p id="pacman"><img src="<?php
echo pacman();
?>
" alt="Tribute to Pacman with a Pie Chart" title="Tribute to Pacman with a Pie Chart"></p>
</div>
</div>
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