Add support for XLS-85 Token Escrow (#5185)

- Specification: https://github.com/XRPLF/XRPL-Standards/pull/272
- Amendment: `TokenEscrow`
- Enables escrowing of IOU and MPT tokens in addition to native XRP.
- Allows accounts to lock issued tokens (IOU/MPT) in escrow objects, with support for freeze, authorization, and transfer rates.
- Adds new ledger fields (`sfLockedAmount`, `sfIssuerNode`, etc.) to track locked balances for IOU and MPT escrows.
- Updates EscrowCreate, EscrowFinish, and EscrowCancel transaction logic to support IOU and MPT assets, including proper handling of trustlines and MPT authorization, transfer rates, and locked balances.
- Enforces invariant checks for escrowed IOU/MPT amounts.
- Extends GatewayBalances RPC to report locked (escrowed) balances.

src/test/jtx/impl/Env.cpp

@@ -199,6 +199,48 @@ Env::balance(Account const& account, Issue const& issue) const
     return {amount, lookup(issue.account).name()};
 }
 
+PrettyAmount
+Env::balance(Account const& account, MPTIssue const& mptIssue) const
+{
+    MPTID const id = mptIssue.getMptID();
+    if (!id)
+        return {STAmount(mptIssue, 0), account.name()};
+
+    AccountID const issuer = mptIssue.getIssuer();
+    if (account.id() == issuer)
+    {
+        // Issuer balance
+        auto const sle = le(keylet::mptIssuance(id));
+        if (!sle)
+            return {STAmount(mptIssue, 0), account.name()};
+
+        STAmount const amount{mptIssue, sle->getFieldU64(sfOutstandingAmount)};
+        return {amount, lookup(issuer).name()};
+    }
+    else
+    {
+        // Holder balance
+        auto const sle = le(keylet::mptoken(id, account));
+        if (!sle)
+            return {STAmount(mptIssue, 0), account.name()};
+
+        STAmount const amount{mptIssue, sle->getFieldU64(sfMPTAmount)};
+        return {amount, lookup(issuer).name()};
+    }
+}
+
+PrettyAmount
+Env::limit(Account const& account, Issue const& issue) const
+{
+    auto const sle = le(keylet::line(account.id(), issue));
+    if (!sle)
+        return {STAmount(issue, 0), account.name()};
+    auto const aHigh = account.id() > issue.account;
+    if (sle && sle->isFieldPresent(aHigh ? sfLowLimit : sfHighLimit))
+        return {(*sle)[aHigh ? sfLowLimit : sfHighLimit], account.name()};
+    return {STAmount(issue, 0), account.name()};
+}
+
 std::uint32_t
 Env::ownerCount(Account const& account) const
 {

src/test/jtx/impl/TestHelpers.cpp

@@ -211,42 +211,6 @@ expectLedgerEntryRoot(
     return accountBalance(env, acct) == to_string(expectedValue.xrp());
 }
 
-/* Escrow */
-/******************************************************************************/
-
-Json::Value
-escrow(AccountID const& account, AccountID const& to, STAmount const& amount)
-{
-    Json::Value jv;
-    jv[jss::TransactionType] = jss::EscrowCreate;
-    jv[jss::Account] = to_string(account);
-    jv[jss::Destination] = to_string(to);
-    jv[jss::Amount] = amount.getJson(JsonOptions::none);
-    return jv;
-}
-
-Json::Value
-finish(AccountID const& account, AccountID const& from, std::uint32_t seq)
-{
-    Json::Value jv;
-    jv[jss::TransactionType] = jss::EscrowFinish;
-    jv[jss::Account] = to_string(account);
-    jv[sfOwner.jsonName] = to_string(from);
-    jv[sfOfferSequence.jsonName] = seq;
-    return jv;
-}
-
-Json::Value
-cancel(AccountID const& account, Account const& from, std::uint32_t seq)
-{
-    Json::Value jv;
-    jv[jss::TransactionType] = jss::EscrowCancel;
-    jv[jss::Account] = to_string(account);
-    jv[sfOwner.jsonName] = from.human();
-    jv[sfOfferSequence.jsonName] = seq;
-    return jv;
-}
-
 /* Payment Channel */
 /******************************************************************************/
 Json::Value

src/test/jtx/impl/escrow.cpp

@@ -0,0 +1,82 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2019 Ripple Labs Inc.
+
+    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 appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include <test/jtx/escrow.h>
+
+#include <xrpl/protocol/TxFlags.h>
+#include <xrpl/protocol/jss.h>
+
+namespace ripple {
+namespace test {
+namespace jtx {
+
+/** Escrow operations. */
+namespace escrow {
+
+Json::Value
+create(AccountID const& account, AccountID const& to, STAmount const& amount)
+{
+    Json::Value jv;
+    jv[jss::TransactionType] = jss::EscrowCreate;
+    jv[jss::Flags] = tfFullyCanonicalSig;
+    jv[jss::Account] = to_string(account);
+    jv[jss::Destination] = to_string(to);
+    jv[jss::Amount] = amount.getJson(JsonOptions::none);
+    return jv;
+}
+
+Json::Value
+finish(AccountID const& account, AccountID const& from, std::uint32_t seq)
+{
+    Json::Value jv;
+    jv[jss::TransactionType] = jss::EscrowFinish;
+    jv[jss::Flags] = tfFullyCanonicalSig;
+    jv[jss::Account] = to_string(account);
+    jv[sfOwner.jsonName] = to_string(from);
+    jv[sfOfferSequence.jsonName] = seq;
+    return jv;
+}
+
+Json::Value
+cancel(AccountID const& account, Account const& from, std::uint32_t seq)
+{
+    Json::Value jv;
+    jv[jss::TransactionType] = jss::EscrowCancel;
+    jv[jss::Flags] = tfFullyCanonicalSig;
+    jv[jss::Account] = to_string(account);
+    jv[sfOwner.jsonName] = from.human();
+    jv[sfOfferSequence.jsonName] = seq;
+    return jv;
+}
+
+Rate
+rate(Env& env, Account const& account, std::uint32_t const& seq)
+{
+    auto const sle = env.le(keylet::escrow(account.id(), seq));
+    if (sle->isFieldPresent(sfTransferRate))
+        return ripple::Rate((*sle)[sfTransferRate]);
+    return Rate{0};
+}
+
+}  // namespace escrow
+
+}  // namespace jtx
+
+}  // namespace test
+}  // namespace ripple