refactor: Wire PreflightHelpers into 5 more transactors

Straight De Morgan swaps at 7 preflight/preclaim sites that were
manually duplicating logic covered by the helpers introduced earlier
in this PR:

- OfferCreate: isZeroId(*domainID); isPositiveAmount(saTakerPays/Gets)
- AMMClawback / AMMWithdraw / AMMDeposit: isPositiveAmount on optional
  LP/claw amounts
- Payment (preclaim): checkSize on outer path set and each inner path
- XChainCreateBridge / BridgeModify: isPositiveXRPAmount on
  MinAccountCreateAmount

Each swap is semantics-preserving. The reward/fee amounts in
XChainBridge and SponsorshipSet accept zero or negative values and are
therefore intentionally left as-is.

include/xrpl/tx/helpers/PreflightHelpers.h

@@ -0,0 +1,66 @@
+#pragma once
+
+#include <xrpl/beast/utility/Zero.h>
+#include <xrpl/protocol/STAmount.h>
+#include <xrpl/protocol/UintTypes.h>
+
+#include <cstddef>
+
+namespace xrpl {
+
+// Checks whether value is within [min, max], inclusive.
+template <class T>
+inline bool
+checkBounds(T const& value, T const& min, T const& max)
+{
+    return value >= min && value <= max;
+}
+
+// Checks whether a container's size is at most max.
+template <class T>
+inline bool
+checkSize(T const& value, std::size_t const max)
+{
+    return value.size() <= max;
+}
+
+// Checks whether a container is non-empty and its size is at most max.
+template <class T>
+inline bool
+checkSizeAndNonEmpty(T const& value, std::size_t const max)
+{
+    return !value.empty() && value.size() <= max;
+}
+
+// Checks whether a hash-like identifier field (e.g. a uint256 object ID) is
+// unset/zero.
+template <class T>
+inline bool
+isZeroId(T const& id)
+{
+    return id == beast::kZero;
+}
+
+// Checks whether an amount is a strictly positive XRP amount.
+inline bool
+isPositiveXRPAmount(STAmount const& amount)
+{
+    return isXRP(amount) && amount > beast::kZero;
+}
+
+// Checks whether an amount (of any asset type) is strictly positive.
+inline bool
+isPositiveAmount(STAmount const& amount)
+{
+    return amount > beast::kZero;
+}
+
+// Checks whether a currency code is the reserved "bad"/XRP currency code,
+// i.e. not a valid IOU currency.
+inline bool
+isBadCurrency(Currency const& currency)
+{
+    return badCurrency() == currency;
+}
+
+}  // namespace xrpl

src/libxrpl/tx/AGENTS.md

@@ -3,3 +3,7 @@
 See the repo-level [AGENTS.md](../../../AGENTS.md) for general build/test/style guidance.
 
 Any change to transaction-processing behavior must be gated behind an amendment. New amendments (and fixes, i.e. `fix*` amendments) are added to [`include/xrpl/protocol/detail/features.macro`](../../../include/xrpl/protocol/detail/features.macro), as an `XRPL_FEATURE(...)` or `XRPL_FIX(...)` entry added to the top of the list (the list is kept in reverse chronological order). Once the pre-amendment code path for a retired amendment is removed, move its entry to `XRPL_RETIRE_FEATURE(...)`/`XRPL_RETIRE_FIX(...)` instead of deleting it.
+
+## Preflight helpers
+
+When writing transactor preflight logic, prefer the helpers in [`include/xrpl/tx/helpers/PreflightHelpers.h`](../../../include/xrpl/tx/helpers/PreflightHelpers.h) over ad-hoc checks. If the same check pattern shows up in more than one transactor, add a new helper there rather than inlining it.

src/libxrpl/tx/transactors/account/SignerListSet.cpp

@@ -24,6 +24,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/SignerEntries.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <algorithm>
 #include <cstddef>
@@ -247,7 +248,7 @@ SignerListSet::validateQuorumAndSignerEntries(
     // Reject if there are too many or too few entries in the list.
     {
         std::size_t const signerCount = signers.size();
-        if (signerCount < STTx::kMinMultiSigners || signerCount > STTx::kMaxMultiSigners)
+        if (!checkBounds(signerCount, STTx::kMinMultiSigners, STTx::kMaxMultiSigners))
         {
             JLOG(j.trace()) << "Too many or too few signers in signer list.";
             return temMALFORMED;

src/libxrpl/tx/transactors/bridge/XChainBridge.cpp

@@ -35,6 +35,7 @@
 #include <xrpl/tx/ApplyContext.h>
 #include <xrpl/tx/SignerEntries.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 #include <xrpl/tx/paths/Flow.h>
 #include <xrpl/tx/paths/detail/Steps.h>
 
@@ -1369,8 +1370,8 @@ XChainCreateBridge::preflight(PreflightContext const& ctx)
     }
 
     if (minAccountCreate &&
-        ((!isXRP(*minAccountCreate) || minAccountCreate->signum() <= 0) ||
-         !isXRP(bridgeSpec.lockingChainIssue()) || !isXRP(bridgeSpec.issuingChainIssue())))
+        (!isPositiveXRPAmount(*minAccountCreate) || !isXRP(bridgeSpec.lockingChainIssue()) ||
+         !isXRP(bridgeSpec.issuingChainIssue())))
     {
         return temXCHAIN_BRIDGE_BAD_MIN_ACCOUNT_CREATE_AMOUNT;
     }
@@ -1540,8 +1541,8 @@ BridgeModify::preflight(PreflightContext const& ctx)
     }
 
     if (minAccountCreate &&
-        ((!isXRP(*minAccountCreate) || minAccountCreate->signum() <= 0) ||
-         !isXRP(bridgeSpec.lockingChainIssue()) || !isXRP(bridgeSpec.issuingChainIssue())))
+        (!isPositiveXRPAmount(*minAccountCreate) || !isXRP(bridgeSpec.lockingChainIssue()) ||
+         !isXRP(bridgeSpec.issuingChainIssue())))
     {
         return temXCHAIN_BRIDGE_BAD_MIN_ACCOUNT_CREATE_AMOUNT;
     }

src/libxrpl/tx/transactors/credentials/CredentialAccept.cpp

@@ -18,6 +18,7 @@
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstdint>
 namespace xrpl {
@@ -41,7 +42,7 @@ CredentialAccept::preflight(PreflightContext const& ctx)
     }
 
     auto const credType = ctx.tx[sfCredentialType];
-    if (credType.empty() || (credType.size() > kMaxCredentialTypeLength))
+    if (!checkSizeAndNonEmpty(credType, kMaxCredentialTypeLength))
     {
         JLOG(ctx.j.trace()) << "Malformed transaction: invalid size of CredentialType.";
         return temMALFORMED;

src/libxrpl/tx/transactors/credentials/CredentialCreate.cpp

@@ -20,6 +20,7 @@
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <chrono>
 #include <cstdint>
@@ -62,14 +63,14 @@ CredentialCreate::preflight(PreflightContext const& ctx)
     }
 
     auto const uri = tx[~sfURI];
-    if (uri && (uri->empty() || (uri->size() > kMaxCredentialUriLength)))
+    if (uri && !checkSizeAndNonEmpty(*uri, kMaxCredentialUriLength))
     {
         JLOG(j.trace()) << "Malformed transaction: invalid size of URI.";
         return temMALFORMED;
     }
 
     auto const credType = tx[sfCredentialType];
-    if (credType.empty() || (credType.size() > kMaxCredentialTypeLength))
+    if (!checkSizeAndNonEmpty(credType, kMaxCredentialTypeLength))
     {
         JLOG(j.trace()) << "Malformed transaction: invalid size of CredentialType.";
         return temMALFORMED;

src/libxrpl/tx/transactors/credentials/CredentialDelete.cpp

@@ -14,6 +14,7 @@
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstdint>
 namespace xrpl {
@@ -50,7 +51,7 @@ CredentialDelete::preflight(PreflightContext const& ctx)
     }
 
     auto const credType = ctx.tx[sfCredentialType];
-    if (credType.empty() || (credType.size() > kMaxCredentialTypeLength))
+    if (!checkSizeAndNonEmpty(credType, kMaxCredentialTypeLength))
     {
         JLOG(ctx.j.trace()) << "Malformed transaction: invalid size of CredentialType.";
         return temMALFORMED;

src/libxrpl/tx/transactors/delegate/DelegateSet.cpp

@@ -14,6 +14,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstdint>
 #include <memory>
@@ -25,7 +26,7 @@ NotTEC
 DelegateSet::preflight(PreflightContext const& ctx)
 {
     auto const& permissions = ctx.tx.getFieldArray(sfPermissions);
-    if (permissions.size() > kPermissionMaxSize)
+    if (!checkSize(permissions, kPermissionMaxSize))
         return temARRAY_TOO_LARGE;
 
     // can not authorize self

src/libxrpl/tx/transactors/dex/AMMBid.cpp

@@ -22,6 +22,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/ApplyContext.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <algorithm>
 #include <chrono>
@@ -76,7 +77,7 @@ AMMBid::preflight(PreflightContext const& ctx)
     if (ctx.tx.isFieldPresent(sfAuthAccounts))
     {
         auto const authAccounts = ctx.tx.getFieldArray(sfAuthAccounts);
-        if (authAccounts.size() > kAuctionSlotMaxAuthAccounts)
+        if (!checkSize(authAccounts, kAuctionSlotMaxAuthAccounts))
         {
             JLOG(ctx.j.debug()) << "AMM Bid: Invalid number of AuthAccounts.";
             return temMALFORMED;

src/libxrpl/tx/transactors/dex/AMMClawback.cpp

@@ -24,6 +24,7 @@
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 #include <xrpl/tx/transactors/dex/AMMWithdraw.h>
 
 #include <cstdint>
@@ -91,7 +92,7 @@ AMMClawback::preflight(PreflightContext const& ctx)
         return temBAD_AMOUNT;
     }
 
-    if (clawAmount && *clawAmount <= beast::kZero)
+    if (clawAmount && !isPositiveAmount(*clawAmount))
         return temBAD_AMOUNT;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/dex/AMMDeposit.cpp

@@ -23,6 +23,7 @@
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <bit>
 #include <cstdint>
@@ -123,7 +124,7 @@ AMMDeposit::preflight(PreflightContext const& ctx)
         return temBAD_AMM_TOKENS;
     }
 
-    if (lpTokens && *lpTokens <= beast::kZero)
+    if (lpTokens && !isPositiveAmount(*lpTokens))
     {
         JLOG(ctx.j.debug()) << "AMM Deposit: invalid LPTokens";
         return temBAD_AMM_TOKENS;

src/libxrpl/tx/transactors/dex/AMMWithdraw.cpp

@@ -29,6 +29,7 @@
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <algorithm>
 #include <bit>
@@ -129,7 +130,7 @@ AMMWithdraw::preflight(PreflightContext const& ctx)
         return temBAD_AMM_TOKENS;
     }
 
-    if (lpTokens && *lpTokens <= beast::kZero)
+    if (lpTokens && !isPositiveAmount(*lpTokens))
     {
         JLOG(ctx.j.debug()) << "AMM Withdraw: invalid tokens.";
         return temBAD_AMM_TOKENS;

src/libxrpl/tx/transactors/dex/OfferCreate.cpp

@@ -42,6 +42,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
 #include <xrpl/tx/applySteps.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 #include <xrpl/tx/paths/Flow.h>
 #include <xrpl/tx/paths/detail/Steps.h>
 
@@ -100,7 +101,7 @@ OfferCreate::preflight(PreflightContext const& ctx)
     // A zero DomainID is invalid for a PermissionedDomain ledger entry because
     // keylet::permissionedDomain(uint256) uses the DomainID as the ledger key.
     if (auto const domainID = tx[~sfDomainID];
-        ctx.rules.enabled(fixCleanup3_2_0) && domainID && *domainID == beast::kZero)
+        ctx.rules.enabled(fixCleanup3_2_0) && domainID && isZeroId(*domainID))
         return temMALFORMED;
 
     bool const bImmediateOrCancel(tx.isFlag(tfImmediateOrCancel));
@@ -137,7 +138,7 @@ OfferCreate::preflight(PreflightContext const& ctx)
         JLOG(j.debug()) << "Malformed offer: redundant (XRP for XRP)";
         return temBAD_OFFER;
     }
-    if (saTakerPays <= beast::kZero || saTakerGets <= beast::kZero)
+    if (!isPositiveAmount(saTakerPays) || !isPositiveAmount(saTakerGets))
     {
         JLOG(j.debug()) << "Malformed offer: bad amount";
         return temBAD_OFFER;

src/libxrpl/tx/transactors/escrow/EscrowCreate.cpp

@@ -28,10 +28,10 @@
 #include <xrpl/protocol/STLedgerEntry.h>
 #include <xrpl/protocol/STTx.h>
 #include <xrpl/protocol/TER.h>
-#include <xrpl/protocol/UintTypes.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
 #include <xrpl/tx/applySteps.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <memory>
 #include <system_error>
@@ -106,10 +106,10 @@ NotTEC
 escrowCreatePreflightHelper<Issue>(PreflightContext const& ctx)
 {
     STAmount const amount = ctx.tx[sfAmount];
-    if (amount.native() || amount <= beast::kZero)
+    if (amount.native() || !isPositiveAmount(amount))
         return temBAD_AMOUNT;
 
-    if (badCurrency() == amount.get<Issue>().currency)
+    if (isBadCurrency(amount.get<Issue>().currency))
         return temBAD_CURRENCY;
 
     return tesSUCCESS;
@@ -123,7 +123,7 @@ escrowCreatePreflightHelper<MPTIssue>(PreflightContext const& ctx)
         return temDISABLED;
 
     auto const amount = ctx.tx[sfAmount];
-    if (amount.native() || amount.mpt() > MPTAmount{kMaxMpTokenAmount} || amount <= beast::kZero)
+    if (amount.native() || amount.mpt() > MPTAmount{kMaxMpTokenAmount} || !isPositiveAmount(amount))
         return temBAD_AMOUNT;
 
     return tesSUCCESS;
@@ -146,7 +146,7 @@ EscrowCreate::preflight(PreflightContext const& ctx)
     }
     else
     {
-        if (amount <= beast::kZero)
+        if (!isPositiveXRPAmount(amount))
             return temBAD_AMOUNT;
     }
 

src/libxrpl/tx/transactors/lending/LoanBrokerCoverClawback.cpp

@@ -26,6 +26,7 @@
 #include <xrpl/protocol/Units.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <expected>
 #include <optional>
@@ -48,7 +49,7 @@ LoanBrokerCoverClawback::preflight(PreflightContext const& ctx)
     if (!brokerID && !amount)
         return temINVALID;
 
-    if (brokerID && *brokerID == beast::kZero)
+    if (brokerID && isZeroId(*brokerID))
         return temINVALID;
 
     if (amount)

src/libxrpl/tx/transactors/lending/LoanBrokerCoverDeposit.cpp

@@ -15,6 +15,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 namespace xrpl {
 
@@ -27,11 +28,11 @@ LoanBrokerCoverDeposit::checkExtraFeatures(PreflightContext const& ctx)
 NotTEC
 LoanBrokerCoverDeposit::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfLoanBrokerID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfLoanBrokerID]))
         return temINVALID;
 
     auto const dstAmount = ctx.tx[sfAmount];
-    if (dstAmount <= beast::kZero)
+    if (!isPositiveAmount(dstAmount))
         return temBAD_AMOUNT;
 
     if (!isLegalNet(dstAmount))

src/libxrpl/tx/transactors/lending/LoanBrokerCoverWithdraw.cpp

@@ -2,7 +2,6 @@
 
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/Number.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/ledger/View.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/CredentialHelpers.h>
@@ -20,6 +19,7 @@
 #include <xrpl/protocol/Units.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 namespace xrpl {
 
@@ -36,11 +36,11 @@ LoanBrokerCoverWithdraw::checkExtraFeatures(PreflightContext const& ctx)
 NotTEC
 LoanBrokerCoverWithdraw::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfLoanBrokerID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfLoanBrokerID]))
         return temINVALID;
 
     auto const dstAmount = ctx.tx[sfAmount];
-    if (dstAmount <= beast::kZero)
+    if (!isPositiveAmount(dstAmount))
         return temBAD_AMOUNT;
 
     if (!isLegalNet(dstAmount))
@@ -48,7 +48,7 @@ LoanBrokerCoverWithdraw::preflight(PreflightContext const& ctx)
 
     if (auto const destination = ctx.tx[~sfDestination])
     {
-        if (*destination == beast::kZero)
+        if (isZeroId(*destination))
         {
             return temMALFORMED;
         }

src/libxrpl/tx/transactors/lending/LoanBrokerDelete.cpp

@@ -16,6 +16,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 namespace xrpl {
 
@@ -28,7 +29,7 @@ LoanBrokerDelete::checkExtraFeatures(PreflightContext const& ctx)
 NotTEC
 LoanBrokerDelete::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfLoanBrokerID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfLoanBrokerID]))
         return temINVALID;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/lending/LoanBrokerSet.cpp

@@ -2,7 +2,6 @@
 
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/Number.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/View.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
@@ -21,6 +20,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <memory>
 #include <vector>
@@ -59,13 +59,13 @@ LoanBrokerSet::preflight(PreflightContext const& ctx)
             tx.isFieldPresent(sfCoverRateLiquidation))
             return temINVALID;
 
-        if (tx[sfLoanBrokerID] == beast::kZero)
+        if (isZeroId(tx[sfLoanBrokerID]))
             return temINVALID;
     }
 
     if (auto const vaultID = tx.at(~sfVaultID))
     {
-        if (*vaultID == beast::kZero)
+        if (isZeroId(*vaultID))
             return temINVALID;
     }
 

src/libxrpl/tx/transactors/lending/LoanDelete.cpp

@@ -15,6 +15,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 namespace xrpl {
 
@@ -27,7 +28,7 @@ LoanDelete::checkExtraFeatures(PreflightContext const& ctx)
 NotTEC
 LoanDelete::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfLoanID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfLoanID]))
         return temINVALID;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/lending/LoanManage.cpp

@@ -2,7 +2,6 @@
 
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/Number.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/View.h>
@@ -23,6 +22,7 @@
 #include <xrpl/protocol/Units.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <algorithm>
 #include <cstdint>
@@ -43,7 +43,7 @@ LoanManage::getFlagsMask(PreflightContext const& ctx)
 NotTEC
 LoanManage::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfLoanID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfLoanID]))
         return temINVALID;
 
     // Flags are mutually exclusive

src/libxrpl/tx/transactors/lending/LoanPay.cpp

@@ -25,6 +25,7 @@
 #include <xrpl/protocol/Units.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 #include <xrpl/tx/transactors/lending/LoanManage.h>
 
 #include <algorithm>
@@ -78,10 +79,10 @@ LoanPay::getFlagsMask(PreflightContext const& ctx)
 NotTEC
 LoanPay::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfLoanID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfLoanID]))
         return temINVALID;
 
-    if (ctx.tx[sfAmount] <= beast::kZero)
+    if (!isPositiveAmount(ctx.tx[sfAmount]))
         return temBAD_AMOUNT;
 
     // The loan payment flags are all mutually exclusive. If more than one is

src/libxrpl/tx/transactors/lending/LoanSet.cpp

@@ -29,6 +29,7 @@
 #include <xrpl/protocol/Units.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstddef>
 #include <cstdint>
@@ -146,7 +147,7 @@ LoanSet::preflight(PreflightContext const& ctx)
             return *ret;
     }
 
-    if (auto const brokerID = ctx.tx[~sfLoanBrokerID]; brokerID && *brokerID == beast::kZero)
+    if (auto const brokerID = ctx.tx[~sfLoanBrokerID]; brokerID && isZeroId(*brokerID))
         return temINVALID;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/nft/NFTokenCancelOffer.cpp

@@ -15,6 +15,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <algorithm>
 namespace xrpl {
@@ -24,7 +25,7 @@ NFTokenCancelOffer::preflight(PreflightContext const& ctx)
 {
     auto const& offerIds = ctx.tx[sfNFTokenOffers];
 
-    if (offerIds.empty() || (offerIds.size() > kMaxTokenOfferCancelCount))
+    if (!checkSizeAndNonEmpty(offerIds, kMaxTokenOfferCancelCount))
         return temMALFORMED;
 
     // Zero offer IDs cannot be passed as ledger entry keys.

src/libxrpl/tx/transactors/oracle/OracleSet.cpp

@@ -20,6 +20,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/ApplyContext.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <chrono>
 #include <cstddef>
@@ -46,7 +47,7 @@ OracleSet::preflight(PreflightContext const& ctx)
     auto const& dataSeries = ctx.tx.getFieldArray(sfPriceDataSeries);
     if (dataSeries.empty())
         return temARRAY_EMPTY;
-    if (dataSeries.size() > kMaxOracleDataSeries)
+    if (!checkSize(dataSeries, kMaxOracleDataSeries))
         return temARRAY_TOO_LARGE;
 
     auto isInvalidLength = [&](auto const& sField, std::size_t length) {

src/libxrpl/tx/transactors/payment/Payment.cpp

@@ -34,6 +34,7 @@
 #include <xrpl/protocol/jss.h>
 #include <xrpl/tx/Transactor.h>
 #include <xrpl/tx/applySteps.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 #include <xrpl/tx/paths/RippleCalc.h>
 
 #include <algorithm>
@@ -143,7 +144,7 @@ Payment::preflight(PreflightContext const& ctx)
     // A zero DomainID is invalid for a PermissionedDomain ledger entry because
     // keylet::permissionedDomain(uint256) uses the DomainID as the ledger key.
     if (auto const domainID = tx[~sfDomainID];
-        ctx.rules.enabled(fixCleanup3_2_0) && domainID && *domainID == beast::kZero)
+        ctx.rules.enabled(fixCleanup3_2_0) && domainID && isZeroId(*domainID))
         return temMALFORMED;
 
     bool const partialPaymentAllowed = tx.isFlag(tfPartialPayment);
@@ -183,13 +184,13 @@ Payment::preflight(PreflightContext const& ctx)
                         << "Payment destination account not specified.";
         return temDST_NEEDED;
     }
-    if (hasMax && maxSourceAmount <= beast::kZero)
+    if (hasMax && !isPositiveAmount(maxSourceAmount))
     {
         JLOG(j.trace()) << "Malformed transaction: bad max amount: "
                         << maxSourceAmount.getFullText();
         return temBAD_AMOUNT;
     }
-    if (dstAmount <= beast::kZero)
+    if (!isPositiveAmount(dstAmount))
     {
         JLOG(j.trace()) << "Malformed transaction: bad dst amount: " << dstAmount.getFullText();
         return temBAD_AMOUNT;
@@ -439,8 +440,8 @@ Payment::preclaim(PreclaimContext const& ctx)
     {
         STPathSet const& paths = ctx.tx.getFieldPathSet(sfPaths);
 
-        if (paths.size() > kMaxPathSize || std::ranges::any_of(paths, [](STPath const& path) {
-                return path.size() > kMaxPathLength;
+        if (!checkSize(paths, kMaxPathSize) || std::ranges::any_of(paths, [](STPath const& path) {
+                return !checkSize(path, kMaxPathLength);
             }))
         {
             // Open view: the soft tel (unchanged). Inner batch txns are claimed

src/libxrpl/tx/transactors/payment_channel/PaymentChannelClaim.cpp

@@ -21,6 +21,7 @@
 #include <xrpl/protocol/TxFlags.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstdint>
 #include <optional>
@@ -42,15 +43,15 @@ PaymentChannelClaim::getFlagsMask(PreflightContext const&)
 NotTEC
 PaymentChannelClaim::preflight(PreflightContext const& ctx)
 {
-    if (ctx.rules.enabled(fixCleanup3_2_0) && ctx.tx[sfChannel] == beast::kZero)
+    if (ctx.rules.enabled(fixCleanup3_2_0) && isZeroId(ctx.tx[sfChannel]))
         return temMALFORMED;
 
     auto const bal = ctx.tx[~sfBalance];
-    if (bal && (!isXRP(*bal) || *bal <= beast::kZero))
+    if (bal && !isPositiveXRPAmount(*bal))
         return temBAD_AMOUNT;
 
     auto const amt = ctx.tx[~sfAmount];
-    if (amt && (!isXRP(*amt) || *amt <= beast::kZero))
+    if (amt && !isPositiveXRPAmount(*amt))
         return temBAD_AMOUNT;
 
     if (bal && amt && *bal > *amt)

src/libxrpl/tx/transactors/payment_channel/PaymentChannelCreate.cpp

@@ -1,7 +1,6 @@
 #include <xrpl/tx/transactors/payment_channel/PaymentChannelCreate.h>
 
 #include <xrpl/basics/chrono.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/View.h>
@@ -21,6 +20,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
 #include <xrpl/tx/applySteps.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <memory>
 
@@ -57,7 +57,7 @@ PaymentChannelCreate::makeTxConsequences(PreflightContext const& ctx)
 NotTEC
 PaymentChannelCreate::preflight(PreflightContext const& ctx)
 {
-    if (!isXRP(ctx.tx[sfAmount]) || (ctx.tx[sfAmount] <= beast::kZero))
+    if (!isPositiveXRPAmount(ctx.tx[sfAmount]))
         return temBAD_AMOUNT;
 
     if (ctx.tx[sfAccount] == ctx.tx[sfDestination])

src/libxrpl/tx/transactors/payment_channel/PaymentChannelFund.cpp

@@ -1,7 +1,6 @@
 #include <xrpl/tx/transactors/payment_channel/PaymentChannelFund.h>
 
 #include <xrpl/beast/utility/Journal.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
@@ -19,6 +18,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
 #include <xrpl/tx/applySteps.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 namespace xrpl {
 
@@ -31,10 +31,10 @@ PaymentChannelFund::makeTxConsequences(PreflightContext const& ctx)
 NotTEC
 PaymentChannelFund::preflight(PreflightContext const& ctx)
 {
-    if (ctx.rules.enabled(fixCleanup3_2_0) && ctx.tx[sfChannel] == beast::kZero)
+    if (ctx.rules.enabled(fixCleanup3_2_0) && isZeroId(ctx.tx[sfChannel]))
         return temMALFORMED;
 
-    if (!isXRP(ctx.tx[sfAmount]) || (ctx.tx[sfAmount] <= beast::kZero))
+    if (!isPositiveXRPAmount(ctx.tx[sfAmount]))
         return temBAD_AMOUNT;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/permissioned_domain/PermissionedDomainDelete.cpp

@@ -1,7 +1,6 @@
 #include <xrpl/tx/transactors/permissioned_domain/PermissionedDomainDelete.h>
 
 #include <xrpl/basics/Log.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/protocol/Indexes.h>
@@ -11,6 +10,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 namespace xrpl {
 
@@ -18,7 +18,7 @@ NotTEC
 PermissionedDomainDelete::preflight(PreflightContext const& ctx)
 {
     auto const domain = ctx.tx.getFieldH256(sfDomainID);
-    if (domain == beast::kZero)
+    if (isZeroId(domain))
         return temMALFORMED;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/permissioned_domain/PermissionedDomainSet.cpp

@@ -1,6 +1,5 @@
 #include <xrpl/tx/transactors/permissioned_domain/PermissionedDomainSet.h>
 
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/CredentialHelpers.h>
@@ -17,6 +16,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <memory>
 #include <utility>
@@ -40,7 +40,7 @@ PermissionedDomainSet::preflight(PreflightContext const& ctx)
         return err;
 
     auto const domain = ctx.tx.at(~sfDomainID);
-    if (domain && *domain == beast::kZero)
+    if (domain && isZeroId(*domain))
         return temMALFORMED;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/system/Batch.cpp

@@ -21,6 +21,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
 #include <xrpl/tx/applySteps.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <algorithm>
 #include <bit>
@@ -236,7 +237,7 @@ Batch::preflight(PreflightContext const& ctx)
     }
 
     if (ctx.tx.isFieldPresent(sfBatchSigners) &&
-        ctx.tx.getFieldArray(sfBatchSigners).size() > kMaxBatchSigners)
+        !checkSize(ctx.tx.getFieldArray(sfBatchSigners), kMaxBatchSigners))
     {
         JLOG(ctx.j.debug()) << "BatchTrace[" << parentBatchId << "]:"
                             << "signers array exceeds " << kMaxBatchSigners << " entries.";

src/libxrpl/tx/transactors/system/TicketCreate.cpp

@@ -15,6 +15,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
 #include <xrpl/tx/applySteps.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstdint>
 #include <memory>
@@ -32,7 +33,7 @@ NotTEC
 TicketCreate::preflight(PreflightContext const& ctx)
 {
     if (std::uint32_t const count = ctx.tx[sfTicketCount];
-        count < kMinValidCount || count > kMaxValidCount)
+        !checkBounds(count, kMinValidCount, kMaxValidCount))
         return temINVALID_COUNT;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/token/Clawback.cpp

@@ -21,6 +21,7 @@
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/ApplyContext.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <algorithm>
 #include <variant>
@@ -44,7 +45,7 @@ preflightHelper<Issue>(PreflightContext const& ctx)
     // The issuer field is used for the token holder instead
     AccountID const& holder = clawAmount.getIssuer();
 
-    if (issuer == holder || isXRP(clawAmount) || clawAmount <= beast::kZero)
+    if (issuer == holder || isXRP(clawAmount) || !isPositiveAmount(clawAmount))
         return temBAD_AMOUNT;
 
     return tesSUCCESS;
@@ -67,7 +68,7 @@ preflightHelper<MPTIssue>(PreflightContext const& ctx)
     if (ctx.tx[sfAccount] == *mptHolder)
         return temMALFORMED;
 
-    if (clawAmount.mpt() > MPTAmount{kMaxMpTokenAmount} || clawAmount <= beast::kZero)
+    if (clawAmount.mpt() > MPTAmount{kMaxMpTokenAmount} || !isPositiveAmount(clawAmount))
         return temBAD_AMOUNT;
 
     return tesSUCCESS;

src/libxrpl/tx/transactors/token/MPTokenIssuanceCreate.cpp

@@ -1,7 +1,6 @@
 #include <xrpl/tx/transactors/token/MPTokenIssuanceCreate.h>
 
 #include <xrpl/beast/utility/Journal.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
@@ -20,6 +19,7 @@
 #include <xrpl/protocol/UintTypes.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstdint>
 #include <expected>
@@ -93,7 +93,7 @@ MPTokenIssuanceCreate::preflight(PreflightContext const& ctx)
 
     if (auto const domain = ctx.tx[~sfDomainID])
     {
-        if (*domain == beast::kZero)
+        if (isZeroId(*domain))
             return temMALFORMED;
 
         // Domain present implies that MPTokenIssuance is not public

src/libxrpl/tx/transactors/token/TrustSet.cpp

@@ -24,6 +24,7 @@
 #include <xrpl/protocol/UintTypes.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <cstdint>
 #include <unordered_set>
@@ -98,7 +99,7 @@ TrustSet::preflight(PreflightContext const& ctx)
         return temBAD_LIMIT;
     }
 
-    if (badCurrency() == saLimitAmount.get<Issue>().currency)
+    if (isBadCurrency(saLimitAmount.get<Issue>().currency))
     {
         JLOG(j.trace()) << "Malformed transaction: specifies XRP as IOU";
         return temBAD_CURRENCY;

src/libxrpl/tx/transactors/vault/VaultDelete.cpp

@@ -2,7 +2,6 @@
 
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/base_uint.h>
-#include <xrpl/beast/utility/Zero.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/MPTokenHelpers.h>
 #include <xrpl/ledger/helpers/TokenHelpers.h>
@@ -18,13 +17,14 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 namespace xrpl {
 
 NotTEC
 VaultDelete::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfVaultID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfVaultID]))
     {
         JLOG(ctx.j.debug()) << "VaultDelete: zero/empty vault ID.";
         return temMALFORMED;

src/libxrpl/tx/transactors/vault/VaultWithdraw.cpp

@@ -25,6 +25,7 @@
 #include <xrpl/protocol/TER.h>
 #include <xrpl/protocol/XRPAmount.h>
 #include <xrpl/tx/Transactor.h>
+#include <xrpl/tx/helpers/PreflightHelpers.h>
 
 #include <stdexcept>
 
@@ -52,18 +53,18 @@ shouldWaiveWithdrawal(ReadView const& view, AccountID const& account, SLE::const
 NotTEC
 VaultWithdraw::preflight(PreflightContext const& ctx)
 {
-    if (ctx.tx[sfVaultID] == beast::kZero)
+    if (isZeroId(ctx.tx[sfVaultID]))
     {
         JLOG(ctx.j.debug()) << "VaultWithdraw: zero/empty vault ID.";
         return temMALFORMED;
     }
 
-    if (ctx.tx[sfAmount] <= beast::kZero)
+    if (!isPositiveAmount(ctx.tx[sfAmount]))
         return temBAD_AMOUNT;
 
     if (auto const destination = ctx.tx[~sfDestination])
     {
-        if (*destination == beast::kZero)
+        if (isZeroId(*destination))
         {
             return temMALFORMED;
         }