add sfLockCount and isAddable

src/ripple/app/tx/impl/Escrow.cpp

@@ -267,6 +267,7 @@ EscrowCreate::doApply()
                     ctx_.view(),
                     sleLine,
                     amount,
+                    1,
                     ctx_.journal,
                     DryRun);
             
@@ -345,6 +346,7 @@ EscrowCreate::doApply()
                 ctx_.view(),
                 sleLine,
                 amount,
+                1,
                 ctx_.journal,
                 WetRun);
                 
@@ -570,6 +572,7 @@ EscrowFinish::doApply()
                 sle,        // src account
                 sled,       // dst account
                 amount,     // xfer amount
+                -1,
                 j_,
                 DryRun      // dry run
             );
@@ -620,6 +623,7 @@ EscrowFinish::doApply()
                 sle,        // src account
                 sled,       // dst account
                 amount,     // xfer amount
+                -1,
                 j_,
                 WetRun      // wet run;
             );
@@ -708,6 +712,7 @@ EscrowCancel::doApply()
                 ctx_.view(),
                 sleLine,
                 -amount,
+                -1,
                 ctx_.journal,
                 DryRun);
             result != tesSUCCESS)
@@ -753,6 +758,7 @@ EscrowCancel::doApply()
                 ctx_.view(),
                 sleLine,
                 -amount,
+                -1,
                 ctx_.journal,
                 WetRun);
 

src/ripple/app/tx/impl/PayChan.cpp

@@ -138,6 +138,7 @@ closeChannel(
                 view,
                 sleLine,
                 -amount,
+                -1,
                 j,
                 DryRun);
 
@@ -189,6 +190,7 @@ closeChannel(
                 view,
                 sleLine,
                 -amount,
+                -1,
                 j,
                 WetRun);
 
@@ -312,6 +314,7 @@ PayChanCreate::preclaim(PreclaimContext const& ctx)
                     ctx.view,
                     sleLine,
                     amount,
+                    1,
                     ctx.j,
                     DryRun);
             
@@ -417,6 +420,7 @@ PayChanCreate::doApply()
                 ctx_.view(),
                 sleLine,
                 amount,
+                1,
                 ctx_.journal,
                 WetRun);
 
@@ -506,6 +510,7 @@ PayChanFund::doApply()
                 ctx_.view(),
                 sleLine,
                 amount,
+                1,
                 ctx_.journal,
                 DryRun);
 
@@ -587,6 +592,7 @@ PayChanFund::doApply()
                 ctx_.view(),
                 sleLine,
                 amount,
+                1,
                 ctx_.journal,
                 WetRun);
         
@@ -776,6 +782,7 @@ PayChanClaim::doApply()
                     sleSrcAcc,
                     sled,
                     reqDelta,
+                    0,
                     ctx_.journal,
                     WetRun);
             

src/ripple/ledger/View.h

@@ -475,6 +475,7 @@ trustAdjustLockedBalance(
     V& view,
     S& sleLine,
     STAmount const& deltaAmt,
+    int deltaLockCount,                // if +1 lockCount is increased, -1 is decreased, 0 unchanged
     beast::Journal const& j,
     R dryRun)
 {
@@ -542,26 +543,43 @@ trustAdjustLockedBalance(
         return tecUNFUNDED_PAYMENT;
     }
 
-    STAmount lockedBalance {sfLockedBalance, deltaAmt.issue()};
+    STAmount priorLockedBalance {sfLockedBalance, deltaAmt.issue()};
     if (sleLine->isFieldPresent(sfLockedBalance))
-        lockedBalance = 
+        priorLockedBalance = 
             high ? -(*sleLine)[sfLockedBalance] : (*sleLine)[sfLockedBalance];
 
-    lockedBalance += deltaAmt;
+    uint32_t priorLockCount = 0;
+    if (sleLine->isFieldPresent(sfLockCount))
+        priorLockCount = sleLine->getFieldU32(sfLockCount);
 
-    if (lockedBalance > balance)
+    uint32_t finalLockCount = priorLockCount + deltaLockCount;
+    STAmount finalLockedBalance = priorLockedBalance + deltaAmt;
+
+    if (finalLockedBalance > balance)
     {
         JLOG(j.trace())
             << "trustAdjustLockedBalance: "
             << "lockedBalance("
-            << lockedBalance
+            << finalLockedBalance
             << ") > balance("
             << balance
             << ") = true\n";
         return tecUNFUNDED_PAYMENT;
     }
 
-    if (lockedBalance < beast::zero)
+    if (finalLockedBalance < beast::zero)
+        return tecINTERNAL;
+   
+    // check if there is significant precision loss
+    if (!isAddable(balance, deltaAmt) ||
+        !isAddable(priorLockedBalance, deltaAmt) ||
+        !isAddable(finalLockedBalance, balance))
+        return tecPRECISION_LOSS;
+
+    // sanity check possible overflows on the lock counter
+    if ((deltaLockCount > 0 && priorLockCount > finalLockCount) ||
+        (deltaLockCount < 0 && priorLockCount < finalLockCount) ||
+        (deltaLockCount == 0 && priorLockCount != finalLockCount))
         return tecINTERNAL;
 
     // we won't update any SLEs if it is a dry run
@@ -570,11 +588,17 @@ trustAdjustLockedBalance(
 
     if constexpr(std::is_same<V, ApplyView>::value && std::is_same<S, std::shared_ptr<SLE>>::value)
     {
-        if (lockedBalance == beast::zero)
+        if (finalLockedBalance == beast::zero || finalLockCount == 0)
+        {
             sleLine->makeFieldAbsent(sfLockedBalance);
+            sleLine->makeFieldAbsent(sfLockCount);
+        }
         else
+        {
             sleLine->
-                setFieldAmount(sfLockedBalance, high ? -lockedBalance : lockedBalance);
+                setFieldAmount(sfLockedBalance, high ? -finalLockedBalance : finalLockedBalance);
+            sleLine->setFieldU32(sfLockCount, finalLockCount);
+        }
     
         view.update(sleLine);
     }
@@ -752,6 +776,7 @@ trustTransferLockedBalance(
     S& sleSrcAcc,
     S& sleDstAcc,
     STAmount const& amount,     // issuer, currency are in this field
+    int deltaLockCount,         // -1 decrement, +1 increment, 0 unchanged
     beast::Journal const& j,
     R dryRun)
 {
@@ -820,10 +845,10 @@ trustTransferLockedBalance(
         return tecNO_LINE;
 
     // can't transfer a locked balance that does not exist
-    if (!sleSrcLine->isFieldPresent(sfLockedBalance))
+    if (!sleSrcLine->isFieldPresent(sfLockedBalance) || !sleSrcLine->isFieldPresent(sfLockCount))
     {
         JLOG(j.trace())
-            << "trustTransferLockedBalance could not find sfLockedBalance on source line";
+            << "trustTransferLockedBalance could not find sfLockedBalance/sfLockCount on source line";
         return tecUNFUNDED_PAYMENT;
     }
 
@@ -836,6 +861,8 @@ trustTransferLockedBalance(
         STAmount priorLockedBalance =
             srcHigh ? -((*sleSrcLine)[sfLockedBalance]) : (*sleSrcLine)[sfLockedBalance];
 
+        uint32_t priorLockCount = (*sleSrcLine)[sfLockCount];
+
         AccountID srcIssuerAccID = 
                 sleSrcLine->getFieldAmount(srcHigh ? sfLowLimit : sfHighLimit).getIssuer();
 
@@ -853,6 +880,19 @@ trustTransferLockedBalance(
 
         STAmount finalLockedBalance = priorLockedBalance - amount;
 
+        uint32_t finalLockCount = priorLockCount + deltaLockCount;
+
+        // check if there is significant precision loss
+        if (!isAddable(priorBalance, amount) ||
+            !isAddable(priorLockedBalance, amount))
+            return tecPRECISION_LOSS;
+
+        // sanity check possible overflows on the lock counter
+        if ((deltaLockCount > 0 && priorLockCount > finalLockCount) ||
+            (deltaLockCount < 0 && priorLockCount < finalLockCount) ||
+            (deltaLockCount == 0 && priorLockCount != finalLockCount))
+            return tecINTERNAL;
+        
         // this should never happen but defensively check it here before updating sle
         if (finalBalance < beast::zero || finalLockedBalance < beast::zero)
         {
@@ -865,10 +905,16 @@ trustTransferLockedBalance(
         {
             sleSrcLine->setFieldAmount(sfBalance, srcHigh ? -finalBalance : finalBalance);
 
-            if (finalLockedBalance == beast::zero)
+            if (finalLockedBalance == beast::zero || finalLockCount == 0)
+            {
                 sleSrcLine->makeFieldAbsent(sfLockedBalance);
+                sleSrcLine->makeFieldAbsent(sfLockCount);
+            }
             else
+            {
                 sleSrcLine->setFieldAmount(sfLockedBalance, srcHigh ? -finalLockedBalance : finalLockedBalance);
+                sleSrcLine->setFieldU32(sfLockCount, finalLockCount);
+            }
         }
 
     }
@@ -959,6 +1005,10 @@ trustTransferLockedBalance(
             return tecPATH_DRY;
         }
         
+        // check if there is significant precision loss
+        if (!isAddable(priorBalance, dstAmt))
+            return tecPRECISION_LOSS;
+
         if constexpr(!dryRun)
             sleDstLine->setFieldAmount(sfBalance, dstHigh ? -finalBalance : finalBalance);
     }

src/ripple/protocol/SField.h

@@ -400,6 +400,7 @@ extern SF_UINT32 const sfMintedNFTokens;
 extern SF_UINT32 const sfBurnedNFTokens;
 extern SF_UINT32 const sfHookStateCount;
 extern SF_UINT32 const sfEmitGeneration;
+extern SF_UINT32 const sfLockCount;
 
 // 64-bit integers (common)
 extern SF_UINT64 const sfIndexNext;

src/ripple/protocol/STAmount.h

@@ -526,6 +526,29 @@ isFakeXRP(STAmount const& amount)
     return isFakeXRP(amount.issue().currency);
 }    
 
+/** returns true iff adding or subtracting results in less than or equal to 0.01% precision loss **/
+inline bool
+isAddable(STAmount const& amt1, STAmount const& amt2)
+{
+    if (amt1 == beast::zero || amt2 == beast::zero)
+        return true;
+
+    static const STAmount one {IOUAmount{1, 0}, noIssue()};
+    static const STAmount maxLoss {IOUAmount{1, -4}, noIssue()};
+
+    STAmount A = amt1;
+    STAmount B = amt2;
+
+    A.setIssue(noIssue());
+    B.setIssue(noIssue());
+
+    STAmount lhs = divide((A - B) + B, A, noIssue()) - one;
+    STAmount rhs = divide((B - A) + A, B, noIssue()) - one;
+
+    return ((rhs.negative() ? -rhs : rhs) + (lhs.negative() ? -lhs : lhs)) <= maxLoss;
+}
+
+
 // Since `canonicalize` does not have access to a ledger, this is needed to put
 // the low-level routine stAmountCanonicalize on an amendment switch. Only
 // transactions need to use this switchover. Outside of a transaction it's safe

src/ripple/protocol/TER.h

@@ -289,6 +289,7 @@ enum TECcodes : TERUnderlyingType {
     tecINSUFFICIENT_FUNDS = 159,
     tecOBJECT_NOT_FOUND = 160,
     tecINSUFFICIENT_PAYMENT = 161,
+    tecPRECISION_LOSS = 162,
 };
 
 //------------------------------------------------------------------------------

src/ripple/protocol/impl/LedgerFormats.cpp

@@ -106,6 +106,7 @@ LedgerFormats::LedgerFormats()
             {sfHighQualityIn,        soeOPTIONAL},
             {sfHighQualityOut,       soeOPTIONAL},
             {sfLockedBalance,        soeOPTIONAL},
+            {sfLockCount,            soeOPTIONAL},
         },
         commonFields);
 

src/ripple/protocol/impl/SField.cpp

@@ -150,6 +150,7 @@ CONSTRUCT_TYPED_SFIELD(sfMintedNFTokens,        "MintedNFTokens",       UINT32,
 CONSTRUCT_TYPED_SFIELD(sfBurnedNFTokens,        "BurnedNFTokens",       UINT32,    44);
 CONSTRUCT_TYPED_SFIELD(sfHookStateCount,        "HookStateCount",       UINT32,    45);
 CONSTRUCT_TYPED_SFIELD(sfEmitGeneration,        "EmitGeneration",       UINT32,    46);
+CONSTRUCT_TYPED_SFIELD(sfLockCount,             "LockCount",            UINT32,    47);
 
 // 64-bit integers (common)
 CONSTRUCT_TYPED_SFIELD(sfIndexNext,             "IndexNext",            UINT64,     1);