refactor: Use LedgerHashesEntry everywhere (#8369)

include/xrpl/ledger/entries/LedgerHashesEntry.h

@@ -1,11 +1,17 @@
 #pragma once
 
+#include <xrpl/basics/base_uint.h>
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
 #include <xrpl/ledger/entries/SLEBase.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/LedgerFormats.h>
+#include <xrpl/protocol/SField.h>
+#include <xrpl/protocol/STVector256.h>
+
+#include <cstddef>
+#include <optional>
 
 namespace xrpl {
 
@@ -25,6 +31,31 @@ public:
         : Base(keylet::skip(), view, j)
     {
     }
+
+    /**
+     * Looks up a hash `diff` slots back from the most recent entry in the
+     * sfHashes vector (diff == 0 is the most recent entry).
+     *
+     * Callers decide which skip list entry to read and how to translate a
+     * target ledger sequence into `diff`; this only does the bounds check
+     * and vector indexing shared by both the recent (stride 1) and distant
+     * (stride 256) skip lists.
+     *
+     * @param diff how many slots back from the most recent hash to look up;
+     * 0 is the most recent hash.
+     * @return the hash at that slot, or std::nullopt if the entry does not
+     * exist or `diff` is out of range.
+     */
+    [[nodiscard]] std::optional<UInt256>
+    hashAt(std::size_t diff) const
+    {
+        if (!this->exists())
+            return std::nullopt;
+        STVector256 const vec = (*this)->getFieldV256(sfHashes);
+        if (vec.size() > diff)
+            return vec[vec.size() - diff - 1];
+        return std::nullopt;
+    }
 };
 
 using LedgerHashesEntryR = LedgerHashesEntry<ReadView>;

src/libxrpl/ledger/View.cpp

@@ -9,6 +9,7 @@
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
+#include <xrpl/ledger/entries/LedgerHashesEntry.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/CredentialHelpers.h>
 #include <xrpl/ledger/helpers/DirectoryHelpers.h>
@@ -361,17 +362,16 @@ hashOfSeq(ReadView const& ledger, LedgerIndex seq, beast::Journal journal)
     if (int const diff = ledger.seq() - seq; diff <= 256)
     {
         // Within 256...
-        auto const hashIndex = ledger.read(keylet::skip());
+        LedgerHashesEntryR const hashIndex(ledger, journal);
         if (hashIndex)
         {
             XRPL_ASSERT(
                 hashIndex->getFieldU32(sfLastLedgerSequence) == (ledger.seq() - 1),
                 "xrpl::hashOfSeq : matching ledger sequence");
-            STVector256 vec = hashIndex->getFieldV256(sfHashes);
-            if (vec.size() >= diff)
-                return vec[vec.size() - diff];
+            if (auto const hash = hashIndex.hashAt(diff - 1))
+                return hash;
             JLOG(journal.warn()) << "Ledger " << ledger.seq() << " missing hash for " << seq << " ("
-                                 << vec.size() << "," << diff << ")";
+                                 << hashIndex->getFieldV256(sfHashes).size() << "," << diff << ")";
         }
         else
         {
@@ -387,16 +387,14 @@ hashOfSeq(ReadView const& ledger, LedgerIndex seq, beast::Journal journal)
     }
 
     // in skiplist
-    auto const hashIndex = ledger.read(keylet::skip(seq));
+    LedgerHashesEntryR const hashIndex(keylet::skip(seq), ledger, journal);
     if (hashIndex)
     {
         auto const lastSeq = hashIndex->getFieldU32(sfLastLedgerSequence);
         XRPL_ASSERT(lastSeq >= seq, "xrpl::hashOfSeq : minimum last ledger");
         XRPL_ASSERT((lastSeq & 0xff) == 0, "xrpl::hashOfSeq : valid last ledger");
-        auto const diff = (lastSeq - seq) >> 8;
-        STVector256 vec = hashIndex->getFieldV256(sfHashes);
-        if (vec.size() > diff)
-            return vec[vec.size() - diff - 1];
+        if (auto const hash = hashIndex.hashAt((lastSeq - seq) >> 8))
+            return hash;
     }
     JLOG(journal.warn()) << "Can't get seq " << seq << " from " << ledger.seq() << " error";
     return std::nullopt;

src/xrpld/app/consensus/RCLValidations.cpp

@@ -14,7 +14,7 @@
 #include <xrpl/core/Job.h>
 #include <xrpl/core/JobQueue.h>
 #include <xrpl/core/PerfLog.h>
-#include <xrpl/protocol/Indexes.h>
+#include <xrpl/ledger/entries/LedgerHashesEntry.h>
 #include <xrpl/protocol/PublicKey.h>
 #include <xrpl/protocol/RippleLedgerHash.h>
 #include <xrpl/protocol/SField.h>
@@ -36,7 +36,7 @@ RCLValidatedLedger::RCLValidatedLedger(
     beast::Journal j)
     : ledgerID_{ledger->header().hash}, ledgerSeq_{ledger->seq()}, j_{j}
 {
-    auto const hashIndex = ledger->read(keylet::skip());
+    LedgerHashesEntryR const hashIndex(*ledger, j_);
     if (hashIndex)
     {
         XRPL_ASSERT(

src/xrpld/app/ledger/detail/SkipListAcquire.cpp

@@ -13,6 +13,7 @@
 #include <xrpl/basics/base_uint.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/core/Job.h>
+#include <xrpl/ledger/entries/LedgerHashesEntry.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/SField.h>
 #include <xrpl/shamap/SHAMapItem.h>
@@ -183,7 +184,7 @@ SkipListAcquire::getData() const
 void
 SkipListAcquire::retrieveSkipList(std::shared_ptr<Ledger const> const& ledger, ScopedLockType& sl)
 {
-    if (auto const hashIndex = ledger->read(keylet::skip());
+    if (LedgerHashesEntryR const hashIndex(*ledger, journal_);
         hashIndex && hashIndex->isFieldPresent(sfHashes))
     {
         auto const& slist = hashIndex->getFieldV256(sfHashes).value();

src/xrpld/app/misc/NegativeUNLVote.cpp

@@ -8,7 +8,7 @@
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/Ledger.h>
-#include <xrpl/protocol/Indexes.h>
+#include <xrpl/ledger/entries/LedgerHashesEntry.h>
 #include <xrpl/protocol/Protocol.h>
 #include <xrpl/protocol/PublicKey.h>
 #include <xrpl/protocol/SField.h>
@@ -170,7 +170,7 @@ NegativeUNLVote::buildScoreTable(
     validations.setSeqToKeep(seq - 1, seq + kFlagLedgerInterval);
 
     // Find FLAG_LEDGER_INTERVAL (i.e. 256) previous ledger hashes
-    auto const hashIndex = prevLedger->read(keylet::skip());
+    LedgerHashesEntryR const hashIndex(*prevLedger, j_);
     if (!hashIndex || !hashIndex->isFieldPresent(sfHashes))
     {
         JLOG(j_.debug()) << "N-UNL: ledger " << seq << " no history.";