Next()'s result is a tri-state - failed, more to go, complete. Replace
the way that this is returned with an enum with values FAIL, MORE, and
DONE rather than with two booleans.
Instead of having DatabaseBatch deal with opening and closing database
cursors, have a separate RAII class that deals with those.
For now, DatabaseBatch manages DatabaseCursor, but this will change
later.
No change in behavior. Just remove a little bit of code, reduce macro usage,
remove duplicative functions, and make BDB and SQLite implementations more
consistent with each other.
This commit does not change to any code and behavior. It it is easily reviewed
with the --color-moved=dimmed_zebra git diff option.
Motivation for this change is to:
- Consolidate redundant functions
IsBDBFile /ExistsBerkeleyDatabase / SplitWalletPath, and
IsSQLiteFile / ExistsSQLiteDatabase in the next commits
- Detect SQLite wallets consistently regardless whether bitcoin is built with
SQLite support in the next commits
- Avoid attempting to open SQLite databases with the BDB library when bitcoin
is built without SQLite support in the next commits
sqlite3 recommends that sqlite3_initialize be called when the
application starts, and sqlite3_shutdown when it stops. Since we don't
always use sqlite3, we initialize it when a SQLiteDatabse is constructed
(calling sqlite3_initialize after initialized is a no-op). We call
sqlite3_shutdown when we see that there are no databases opened. The
number of open databases is tracked by an atomic g_dbs_open.
