/** Calculate the amount particular user could get through an offer.
@param amount the maximum flow that is available to the taker.
@param offer the offer to flow through.
@param taker the person taking the offer.
@return the maximum amount that can flow through this offer.
*/
Amounts
Taker::flow (Amounts amount, Offer const& offer, Account const& taker)
{
// Limit taker's input by available funds less fees
Amount const taker_funds (view ().accountFunds (
taker, amount.in, fhZERO_IF_FROZEN));
// Get fee rate paid by taker
std::uint32_t const taker_charge_rate (rippleTransferRate (view (),
taker, offer.account (), amount.in.getIssuer()));
// Skip some math when there's no fee
if (taker_charge_rate == QUALITY_ONE)
{
amount = offer.quality ().ceil_in (amount, taker_funds);
}
else
{
Amount const taker_charge (amountFromRate (taker_charge_rate));
amount = offer.quality ().ceil_in (amount,
divide (taker_funds, taker_charge, taker_funds.issue ()));
}
// Best flow the owner can get.
// Start out assuming entire offer will flow.
Amounts owner_amount (amount);
// Limit owner's output by available funds less fees
Amount const owner_funds (view ().accountFunds (
offer.account (), owner_amount.out, fhZERO_IF_FROZEN));
// Get fee rate paid by owner
std::uint32_t const owner_charge_rate (rippleTransferRate (view (),
offer.account (), taker, amount.out.getIssuer()));
if (owner_charge_rate == QUALITY_ONE)
{
// Skip some math when there's no fee
owner_amount = offer.quality ().ceil_out (owner_amount, owner_funds);
}
else
{
Amount const owner_charge (amountFromRate (owner_charge_rate));
owner_amount = offer.quality ().ceil_out (owner_amount,
divide (owner_funds, owner_charge, owner_funds.issue ()));
}
// Calculate the amount that will flow through the offer
// This does not include the fees.
return (owner_amount.in < amount.in)
? owner_amount
: amount;
}
std::uint32_t
Taker::calculateRate (
LedgerView& view, AccountID const& issuer, AccountID const& account)
{
return isXRP (issuer) || (account == issuer)
? QUALITY_ONE
: rippleTransferRate (view, issuer);
}
TER PathCursor::reverseLiquidity () const
{
// Every account has a transfer rate for its issuances.
// TOMOVE: The account charges
// a fee when third parties transfer that account's own issuances.
// node.transferRate_ caches the output transfer rate for this node.
node().transferRate_ = amountFromRate (
rippleTransferRate (view(), node().issue_.account));
if (node().isAccount ())
return reverseLiquidityForAccount ();
// Otherwise the node is an Offer.
if (isXRP (nextNode().account_))
{
WriteLog (lsTRACE, RippleCalc)
<< "reverseLiquidityForOffer: "
<< "OFFER --> offer: nodeIndex_=" << nodeIndex_;
return tesSUCCESS;
// This control structure ensures deliverNodeReverse is only called for the
// rightmost offer in a chain of offers - which means that
// deliverNodeReverse has to take all of those offers into consideration.
}
// Next is an account node, resolve current offer node's deliver.
STAmount saDeliverAct;
WriteLog (lsTRACE, RippleCalc)
<< "reverseLiquidityForOffer: OFFER --> account:"
<< " nodeIndex_=" << nodeIndex_
<< " saRevDeliver=" << node().saRevDeliver;
// The next node wants the current node to deliver this much:
return deliverNodeReverse (
nextNode().account_,
node().saRevDeliver,
saDeliverAct);
}
// The reverse pass has been narrowing by credit available and inflating by fees
// as it worked backwards. Now, for the current account node, take the actual
// amount from previous and adjust forward balances.
//
// Perform balance adjustments between previous and current node.
// - The previous node: specifies what to push through to current.
// - All of previous output is consumed.
//
// Then, compute current node's output for next node.
// - Current node: specify what to push through to next.
// - Output to next node is computed as input minus quality or transfer fee.
// - If next node is an offer and output is non-XRP then we are the issuer and
// do not need to push funds.
// - If next node is an offer and output is XRP then we need to deliver funds to
// limbo.
TER PathCursor::forwardLiquidityForAccount () const
{
TER resultCode = tesSUCCESS;
auto const lastNodeIndex = pathState_.nodes().size () - 1;
auto viewJ = rippleCalc_.logs_.journal ("View");
std::uint64_t uRateMax = 0;
AccountID const& previousAccountID =
previousNode().isAccount() ? previousNode().account_ :
node().account_;
// Offers are always issue.
AccountID const& nextAccountID =
nextNode().isAccount() ? nextNode().account_ : node().account_;
std::uint32_t uQualityIn = nodeIndex_
? quality_in (view(),
node().account_,
previousAccountID,
node().issue_.currency)
: QUALITY_ONE;
std::uint32_t uQualityOut = (nodeIndex_ == lastNodeIndex)
? quality_out (view(),
node().account_,
nextAccountID,
node().issue_.currency)
: QUALITY_ONE;
// When looking backward (prv) for req we care about what we just
// calculated: use fwd.
// When looking forward (cur) for req we care about what was desired: use
// rev.
// For nextNode().isAccount()
auto saPrvRedeemAct = previousNode().saFwdRedeem.zeroed();
auto saPrvIssueAct = previousNode().saFwdIssue.zeroed();
// For !previousNode().isAccount()
auto saPrvDeliverAct = previousNode().saFwdDeliver.zeroed ();
JLOG (j_.trace)
<< "forwardLiquidityForAccount> "
<< "nodeIndex_=" << nodeIndex_ << "/" << lastNodeIndex
<< " previousNode.saFwdRedeem:" << previousNode().saFwdRedeem
<< " saPrvIssueReq:" << previousNode().saFwdIssue
<< " previousNode.saFwdDeliver:" << previousNode().saFwdDeliver
<< " node.saRevRedeem:" << node().saRevRedeem
<< " node.saRevIssue:" << node().saRevIssue
<< " node.saRevDeliver:" << node().saRevDeliver;
// Ripple through account.
if (previousNode().isAccount() && nextNode().isAccount())
{
// Next is an account, must be rippling.
if (!nodeIndex_)
{
// ^ --> ACCOUNT --> account
// For the first node, calculate amount to ripple based on what is
// available.
node().saFwdRedeem = node().saRevRedeem;
if (pathState_.inReq() >= zero)
{
// Limit by send max.
node().saFwdRedeem = std::min (
node().saFwdRedeem, pathState_.inReq() - pathState_.inAct());
}
pathState_.setInPass (node().saFwdRedeem);
node().saFwdIssue = node().saFwdRedeem == node().saRevRedeem
// Fully redeemed.
? node().saRevIssue : STAmount (node().saRevIssue);
if (node().saFwdIssue && pathState_.inReq() >= zero)
{
// Limit by send max.
node().saFwdIssue = std::min (
node().saFwdIssue,
pathState_.inReq() - pathState_.inAct() - node().saFwdRedeem);
}
pathState_.setInPass (pathState_.inPass() + node().saFwdIssue);
JLOG (j_.trace)
<< "forwardLiquidityForAccount: ^ --> "
<< "ACCOUNT --> account :"
<< " saInReq=" << pathState_.inReq()
<< " saInAct=" << pathState_.inAct()
<< " node.saFwdRedeem:" << node().saFwdRedeem
<< " node.saRevIssue:" << node().saRevIssue
<< " node.saFwdIssue:" << node().saFwdIssue
<< " pathState_.saInPass:"******"forwardLiquidityForAccount: account --> "
<< "ACCOUNT --> $ :"
<< " previousAccountID="
<< to_string (previousAccountID)
<< " node.account_="
<< to_string (node().account_)
<< " previousNode.saFwdRedeem:" << previousNode().saFwdRedeem
<< " previousNode.saFwdIssue:" << previousNode().saFwdIssue;
// Last node. Accept all funds. Calculate amount actually to credit.
auto& saCurReceive = pathState_.outPass();
STAmount saIssueCrd = uQualityIn >= QUALITY_ONE
? previousNode().saFwdIssue // No fee.
: mulRound (
previousNode().saFwdIssue,
amountFromRate (uQualityIn),
previousNode().saFwdIssue.issue (),
true); // Amount to credit.
// Amount to credit. Credit for less than received as a surcharge.
pathState_.setOutPass (previousNode().saFwdRedeem + saIssueCrd);
if (saCurReceive)
{
// Actually receive.
resultCode = rippleCredit(view(),
previousAccountID,
node().account_,
previousNode().saFwdRedeem + previousNode().saFwdIssue,
false, viewJ);
}
else
{
// After applying quality, total payment was microscopic.
resultCode = tecPATH_DRY;
}
}
else
{
// account --> ACCOUNT --> account
JLOG (j_.trace)
<< "forwardLiquidityForAccount: account --> "
<< "ACCOUNT --> account";
node().saFwdRedeem.clear (node().saRevRedeem);
node().saFwdIssue.clear (node().saRevIssue);
// Previous redeem part 1: redeem -> redeem
if (previousNode().saFwdRedeem && node().saRevRedeem)
// Previous wants to redeem.
{
// Rate : 1.0 : quality out
rippleLiquidity (
rippleCalc_,
QUALITY_ONE,
uQualityOut,
previousNode().saFwdRedeem,
node().saRevRedeem,
saPrvRedeemAct,
node().saFwdRedeem,
uRateMax);
}
// Previous issue part 1: issue -> redeem
if (previousNode().saFwdIssue != saPrvIssueAct
// Previous wants to issue.
&& node().saRevRedeem != node().saFwdRedeem)
// Current has more to redeem to next.
{
// Rate: quality in : quality out
rippleLiquidity (
rippleCalc_,
uQualityIn,
uQualityOut,
previousNode().saFwdIssue,
node().saRevRedeem,
saPrvIssueAct,
node().saFwdRedeem,
uRateMax);
}
// Previous redeem part 2: redeem -> issue.
if (previousNode().saFwdRedeem != saPrvRedeemAct
// Previous still wants to redeem.
&& node().saRevRedeem == node().saFwdRedeem
// Current redeeming is done can issue.
&& node().saRevIssue)
// Current wants to issue.
{
// Rate : 1.0 : transfer_rate
rippleLiquidity (
rippleCalc_,
QUALITY_ONE,
rippleTransferRate (view(), node().account_),
previousNode().saFwdRedeem,
node().saRevIssue,
saPrvRedeemAct,
node().saFwdIssue,
uRateMax);
}
// Previous issue part 2 : issue -> issue
if (previousNode().saFwdIssue != saPrvIssueAct
// Previous wants to issue.
&& node().saRevRedeem == node().saFwdRedeem
// Current redeeming is done can issue.
&& node().saRevIssue)
// Current wants to issue.
{
// Rate: quality in : 1.0
rippleLiquidity (
rippleCalc_,
uQualityIn,
QUALITY_ONE,
previousNode().saFwdIssue,
node().saRevIssue,
saPrvIssueAct,
node().saFwdIssue,
uRateMax);
}
STAmount saProvide = node().saFwdRedeem + node().saFwdIssue;
// Adjust prv --> cur balance : take all inbound
resultCode = saProvide
? rippleCredit(view(),
previousAccountID,
node().account_,
previousNode().saFwdRedeem + previousNode().saFwdIssue,
false, viewJ)
: tecPATH_DRY;
}
}
else if (previousNode().isAccount() && !nextNode().isAccount())
{
// Current account is issuer to next offer.
// Determine deliver to offer amount.
// Don't adjust outbound balances- keep funds with issuer as limbo.
// If issuer hold's an offer owners inbound IOUs, there is no fee and
// redeem/issue will transparently happen.
if (nodeIndex_)
{
// Non-XRP, current node is the issuer.
JLOG (j_.trace)
<< "forwardLiquidityForAccount: account --> "
<< "ACCOUNT --> offer";
node().saFwdDeliver.clear (node().saRevDeliver);
// redeem -> issue/deliver.
// Previous wants to redeem.
// Current is issuing to an offer so leave funds in account as
// "limbo".
if (previousNode().saFwdRedeem)
// Previous wants to redeem.
{
// Rate : 1.0 : transfer_rate
// XXX Is having the transfer rate here correct?
rippleLiquidity (
rippleCalc_,
QUALITY_ONE,
rippleTransferRate (view(), node().account_),
previousNode().saFwdRedeem,
node().saRevDeliver,
saPrvRedeemAct,
node().saFwdDeliver,
uRateMax);
}
// issue -> issue/deliver
if (previousNode().saFwdRedeem == saPrvRedeemAct
// Previous done redeeming: Previous has no IOUs.
&& previousNode().saFwdIssue)
// Previous wants to issue. To next must be ok.
{
// Rate: quality in : 1.0
rippleLiquidity (
rippleCalc_,
uQualityIn,
QUALITY_ONE,
previousNode().saFwdIssue,
node().saRevDeliver,
saPrvIssueAct,
node().saFwdDeliver,
uRateMax);
}
// Adjust prv --> cur balance : take all inbound
resultCode = node().saFwdDeliver
? rippleCredit(view(),
previousAccountID, node().account_,
previousNode().saFwdRedeem + previousNode().saFwdIssue,
false, viewJ)
: tecPATH_DRY; // Didn't actually deliver anything.
}
else
{
// Delivering amount requested from downstream.
node().saFwdDeliver = node().saRevDeliver;
// If limited, then limit by send max and available.
if (pathState_.inReq() >= zero)
{
// Limit by send max.
node().saFwdDeliver = std::min (
node().saFwdDeliver, pathState_.inReq() - pathState_.inAct());
// Limit XRP by available. No limit for non-XRP as issuer.
if (isXRP (node().issue_))
node().saFwdDeliver = std::min (
node().saFwdDeliver,
accountHolds(view(),
node().account_,
xrpCurrency(),
xrpAccount(),
fhIGNORE_FREEZE, viewJ)); // XRP can't be frozen
}
// Record amount sent for pass.
pathState_.setInPass (node().saFwdDeliver);
if (!node().saFwdDeliver)
{
resultCode = tecPATH_DRY;
}
else if (!isXRP (node().issue_))
{
// Non-XRP, current node is the issuer.
// We could be delivering to multiple accounts, so we don't know
// which ripple balance will be adjusted. Assume just issuing.
JLOG (j_.trace)
<< "forwardLiquidityForAccount: ^ --> "
<< "ACCOUNT -- !XRP --> offer";
// As the issuer, would only issue.
// Don't need to actually deliver. As from delivering leave in
// the issuer as limbo.
}
else
{
JLOG (j_.trace)
<< "forwardLiquidityForAccount: ^ --> "
<< "ACCOUNT -- XRP --> offer";
// Deliver XRP to limbo.
resultCode = accountSend(view(),
node().account_, xrpAccount(), node().saFwdDeliver, viewJ);
}
}
}
else if (!previousNode().isAccount() && nextNode().isAccount())
{
if (nodeIndex_ == lastNodeIndex)
{
// offer --> ACCOUNT --> $
JLOG (j_.trace)
<< "forwardLiquidityForAccount: offer --> "
<< "ACCOUNT --> $ : "
<< previousNode().saFwdDeliver;
// Amount to credit.
pathState_.setOutPass (previousNode().saFwdDeliver);
// No income balance adjustments necessary. The paying side inside
// the offer paid to this account.
}
else
{
// offer --> ACCOUNT --> account
JLOG (j_.trace)
<< "forwardLiquidityForAccount: offer --> "
<< "ACCOUNT --> account";
node().saFwdRedeem.clear (node().saRevRedeem);
node().saFwdIssue.clear (node().saRevIssue);
// deliver -> redeem
if (previousNode().saFwdDeliver && node().saRevRedeem)
// Previous wants to deliver and can current redeem.
{
// Rate : 1.0 : quality out
rippleLiquidity (
rippleCalc_,
QUALITY_ONE,
uQualityOut,
previousNode().saFwdDeliver,
node().saRevRedeem,
saPrvDeliverAct,
node().saFwdRedeem,
uRateMax);
}
// deliver -> issue
// Wants to redeem and current would and can issue.
if (previousNode().saFwdDeliver != saPrvDeliverAct
// Previous still wants to deliver.
&& node().saRevRedeem == node().saFwdRedeem
// Current has more to redeem to next.
&& node().saRevIssue)
// Current wants issue.
{
// Rate : 1.0 : transfer_rate
rippleLiquidity (
rippleCalc_,
QUALITY_ONE,
rippleTransferRate (view(), node().account_),
previousNode().saFwdDeliver,
node().saRevIssue,
saPrvDeliverAct,
node().saFwdIssue,
uRateMax);
}
// No income balance adjustments necessary. The paying side inside
// the offer paid and the next link will receive.
STAmount saProvide = node().saFwdRedeem + node().saFwdIssue;
if (!saProvide)
resultCode = tecPATH_DRY;
}
}
else
{
// offer --> ACCOUNT --> offer
// deliver/redeem -> deliver/issue.
JLOG (j_.trace)
<< "forwardLiquidityForAccount: offer --> ACCOUNT --> offer";
node().saFwdDeliver.clear (node().saRevDeliver);
if (previousNode().saFwdDeliver && node().saRevDeliver)
{
// Rate : 1.0 : transfer_rate
rippleLiquidity (
rippleCalc_,
QUALITY_ONE,
rippleTransferRate (view(), node().account_),
previousNode().saFwdDeliver,
node().saRevDeliver,
saPrvDeliverAct,
node().saFwdDeliver,
uRateMax);
}
// No income balance adjustments necessary. The paying side inside the
// offer paid and the next link will receive.
if (!node().saFwdDeliver)
resultCode = tecPATH_DRY;
}
return resultCode;
}
