From f63abb769a5ef820381b09da59a6c024ef2f31a7 Mon Sep 17 00:00:00 2001
From: Xie Yanbo <xieyanbo@gmail.com>
Date: Sat, 16 Nov 2019 17:42:40 +0800
Subject: [PATCH 1/3] Iterates with the prefix of keys

---
 src/leveldb.nim | 7 ++++++-
 tests/test.nim  | 5 +++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/leveldb.nim b/src/leveldb.nim
index e50eddd..508ad3d 100644
--- a/src/leveldb.nim
+++ b/src/leveldb.nim
@@ -1,4 +1,4 @@
-import options, leveldb/raw
+import options, strutils, leveldb/raw
 
 type
   LevelDb* = ref object
@@ -122,6 +122,11 @@ 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):
+    if key.startsWith(prefix):
+      yield (key, value)
+
 proc removeDb*(name: string) =
   var err: cstring = nil
   let options = leveldb_options_create()
diff --git a/tests/test.nim b/tests/test.nim
index 8bb8f3d..5d587cb 100644
--- a/tests/test.nim
+++ b/tests/test.nim
@@ -52,3 +52,8 @@ 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")])

From 177190b3118a9eb6fcd2f331877949b03e1a47cc Mon Sep 17 00:00:00 2001
From: Xie Yanbo <xieyanbo@gmail.com>
Date: Sat, 16 Nov 2019 17:42:48 +0800
Subject: [PATCH 2/3] Iterates with range of keys

---
 src/leveldb.nim | 15 +++++++++++++--
 tests/test.nim  | 10 ++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/leveldb.nim b/src/leveldb.nim
index 508ad3d..fe1b4ea 100644
--- a/src/leveldb.nim
+++ b/src/leveldb.nim
@@ -122,11 +122,22 @@ 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):
+iterator iterPrefix*(self: LevelDb, prefix: string): (string, string) =
+  for (key, value) in iter(self, prefix, reverse = false):
     if key.startsWith(prefix):
       yield (key, value)
 
+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()
diff --git a/tests/test.nim b/tests/test.nim
index 5d587cb..6b614b1 100644
--- a/tests/test.nim
+++ b/tests/test.nim
@@ -57,3 +57,13 @@ suite "leveldb":
     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")])

From 9d67cd79c8bc87ad890befc76e9bc40cded880cb Mon Sep 17 00:00:00 2001
From: Xie Yanbo <xieyanbo@gmail.com>
Date: Sat, 16 Nov 2019 19:35:02 +0800
Subject: [PATCH 3/3] fix: stop iter if prefix not matched

---
 src/leveldb.nim | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/leveldb.nim b/src/leveldb.nim
index fe1b4ea..c82618b 100644
--- a/src/leveldb.nim
+++ b/src/leveldb.nim
@@ -126,6 +126,8 @@ 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