wallet: Add GetPrefixCursor to DatabaseBatch

In order to get records beginning with a prefix, we will need a cursor
specifically for that prefix. So add a GetPrefixCursor function and
DatabaseCursor classes for dealing with those prefixes.

Tested on each supported db engine.

1) Write two different key->value elements to db.
2) Create a new prefix cursor and walk-through every returned element,
   verifying that it gets parsed properly.
3) Try to move the cursor outside the filtered range: expect failure
   and flag complete=true.

Co-Authored-By: Ryan Ofsky <ryan@ofsky.org>
Co-Authored-By: furszy <matiasfurszyfer@protonmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/wallet/db.h b/src/wallet/db.h
index b4ccd13a9a..9d684225c3 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -113,6 +113,7 @@ public:
     virtual bool ErasePrefix(Span<const std::byte> prefix) = 0;
 
     virtual std::unique_ptr<DatabaseCursor> GetNewCursor() = 0;
+    virtual std::unique_ptr<DatabaseCursor> GetNewPrefixCursor(Span<const std::byte> prefix) = 0;
     virtual bool TxnBegin() = 0;
     virtual bool TxnCommit() = 0;
     virtual bool TxnAbort() = 0;