Merge pull request #6 from xyb/prefix

iterating with special prefix or range

src/leveldb.nim

@@ -1,4 +1,4 @@
-import options, leveldb/raw
+import options, strutils, leveldb/raw
 
 type
   LevelDb* = ref object
@@ -122,6 +122,24 @@ iterator iter*(self: LevelDb, seek: string = "", reverse: bool = false): (
     else:
       leveldb_iter_next(iterPtr)
 
+iterator iterPrefix*(self: LevelDb, prefix: string): (string, string) =
+  for (key, value) in iter(self, prefix, reverse = false):
+    if key.startsWith(prefix):
+      yield (key, value)
+    else:
+      break
+
+iterator iterRange*(self: LevelDb, start, limit: string): (string, string) =
+  let reverse: bool = limit < start
+  for (key, value) in iter(self, start, reverse = reverse):
+    if reverse:
+      if key < limit:
+        break
+    else:
+      if key > limit:
+        break
+    yield (key, value)
+
 proc removeDb*(name: string) =
   var err: cstring = nil
   let options = leveldb_options_create()

tests/test.nim

@@ -52,3 +52,18 @@ suite "leveldb":
     initData(db)
     check(toSeq(db.iter(seek = "ab", reverse = true)) ==
           @[("ba", "2"), ("aa", "1")])
+
+  test "iter prefix":
+    initData(db)
+    check(toSeq(db.iterPrefix(prefix = "b")) ==
+          @[("ba", "2"), ("bb", "3")])
+
+  test "iter range":
+    initData(db)
+    check(toSeq(db.iterRange(start = "a", limit = "ba")) ==
+          @[("aa", "1"), ("ba", "2")])
+
+  test "iter range reverse":
+    initData(db)
+    check(toSeq(db.iterRange(start = "bb", limit = "b")) ==
+          @[("bb", "3"), ("ba", "2")])