public static IEnumerable <T> Seek <T>(this DB db, ReadOptions options, byte[] prefix, SeekDirection direction, Func <byte[], byte[], T> resultSelector)
{
using Iterator it = db.NewIterator(options);
if (direction == SeekDirection.Forward)
{
for (it.Seek(prefix); it.Valid(); it.Next())
{
yield return(resultSelector(it.Key(), it.Value()));
}
}
else
{
// SeekForPrev
it.Seek(prefix);
if (!it.Valid())
{
it.SeekToLast();
}
else if (it.Key().AsSpan().SequenceCompareTo(prefix) > 0)
{
it.Prev();
}
for (; it.Valid(); it.Prev())
{
yield return(resultSelector(it.Key(), it.Value()));
}
}
}
public static IEnumerable <T> Seek <T>(this DB db, ReadOptions options, byte table, byte[] prefix, SeekDirection direction, Func <byte[], byte[], T> resultSelector)
{
using Iterator it = db.NewIterator(options);
byte[] target = CreateKey(table, prefix);
if (direction == SeekDirection.Forward)
{
for (it.Seek(target); it.Valid(); it.Next())
{
var key = it.Key();
if (key.Length < 1 || key[0] != table)
{
break;
}
yield return(resultSelector(it.Key(), it.Value()));
}
}
else
{
// SeekForPrev
it.Seek(target);
if (!it.Valid())
{
it.SeekToLast();
}
else if (it.Key().AsSpan().SequenceCompareTo(target) > 0)
{
it.Prev();
}
for (; it.Valid(); it.Prev())
{
var key = it.Key();
if (key.Length < 1 || key[0] != table)
{
break;
}
yield return(resultSelector(it.Key(), it.Value()));
}
}
}
public static IEnumerable <T> Seek <T>(this DB db, ReadOptions options, byte table, byte[] prefix, SeekDirection direction, Func <byte[], byte[], T> resultSelector)
{
using Iterator it = db.NewIterator(options);
for (it.Seek(CreateKey(table, prefix)); it.Valid();)
{
var key = it.Key();
if (key.Length < 1 || key[0] != table)
{
break;
}
yield return(resultSelector(it.Key(), it.Value()));
if (direction == SeekDirection.Forward)
{
it.Next();
}
else
{
it.Prev();
}
}
}