add delete and iter procedures

leveldb.nim

@@ -11,6 +11,10 @@ type
 
   LevelDbException* = object of Exception
 
+const
+  levelDbTrue = cuchar(1)
+  levelDbFalse = cuchar(0)
+
 proc checkError(errPtr: cstring) =
   if errPtr != nil:
     defer: free(errPtr)
@@ -18,7 +22,7 @@ proc checkError(errPtr: cstring) =
 
 proc close*(self: LevelDb) =
   if self.db == nil:
-     return
+    return
   leveldb_close(self.db)
   leveldb_writeoptions_destroy(self.syncWriteOptions)
   leveldb_writeoptions_destroy(self.asyncWriteOptions)
@@ -29,20 +33,20 @@ proc open*(path: string): LevelDb =
   new(result, close)
 
   let options = leveldb_options_create()
-  leveldb_options_set_create_if_missing(options, 1.cuchar)
+  leveldb_options_set_create_if_missing(options, levelDbTrue)
   defer: leveldb_options_destroy(options)
 
   result.syncWriteOptions = leveldb_writeoptions_create()
-  leveldb_writeoptions_set_sync(result.syncWriteOptions, cuchar(1))
+  leveldb_writeoptions_set_sync(result.syncWriteOptions, levelDbTrue)
   result.asyncWriteOptions = leveldb_writeoptions_create()
-  leveldb_writeoptions_set_sync(result.asyncWriteOptions, cuchar(0))
+  leveldb_writeoptions_set_sync(result.asyncWriteOptions, levelDbFalse)
   result.readOptions = leveldb_readoptions_create()
 
   var errPtr: cstring = nil
   result.db = leveldb_open(options, path, addr errPtr)
   checkError(errPtr)
 
-proc put*(self: LevelDb, key: string, value: string, sync=true) =
+proc put*(self: LevelDb, key: string, value: string, sync = true) =
   assert self.db != nil
   var errPtr: cstring = nil
   let writeOptions = if sync: self.syncWriteOptions else: self.asyncWriteOptions
@@ -62,8 +66,80 @@ proc get*(self: LevelDb, key: string): Option[string] =
     result = some($s)
     free(s)
 
+proc delete*(self: LevelDb, key: string, sync = true) =
+  var errPtr: cstring = nil
+  let writeOptions = if sync: self.syncWriteOptions else: self.asyncWriteOptions
+  leveldb_delete(self.db, writeOptions, key, key.len, addr errPtr)
+  checkError(errPtr)
+
+proc getIterData(iterPtr: ptr leveldb_iterator_t): (Option[string], Option[string]) =
+  var len: csize
+  var str: cstring
+
+  str = leveldb_iter_key(iterPtr, addr len)
+  if len > 0:
+    result[0] = some ($str)[0..<len]
+  else:
+    result[0] = none string
+
+  str = leveldb_iter_value(iterPtr, addr len)
+  if len > 0:
+    result[1] = some ($str)[0..<len]
+  else:
+    result[1] = none string
+
+iterator iter*(self: LevelDb, seek: string = "", reverse: bool = false): (
+    string, string) =
+  var iterPtr = leveldb_create_iterator(self.db, self.readOptions)
+  defer: leveldb_iter_destroy(iterPtr)
+
+  if seek.len > 0:
+    leveldb_iter_seek(iterPtr, seek, seek.len)
+  else:
+    if reverse:
+      leveldb_iter_seek_to_last(iterPtr)
+    else:
+      leveldb_iter_seek_to_first(iterPtr)
+
+  while true:
+    if leveldb_iter_valid(iterPtr) == levelDbFalse:
+      break
+
+    var (key, value) = getIterData(iterPtr)
+    var err: cstring = nil
+    leveldb_iter_get_error(iterPtr, addr err)
+    checkError(err)
+    yield (key.get(), value.get())
+
+    if reverse:
+      leveldb_iter_prev(iterPtr)
+    else:
+      leveldb_iter_next(iterPtr)
+
 when isMainModule:
   let db = leveldb.open("test.db")
   db.put("hello", "world")
-  echo db.get("one")
+  echo db.get("nothing")
   echo db.get("hello")
+  db.delete("hello")
+  echo db.get("hello")
+
+  db.put("aaa", "1")
+  db.put("aba", "2")
+  db.put("abb", "3")
+
+  echo ">> iter"
+  for i in db.iter:
+    echo i
+
+  echo ">> iter reverse"
+  for i in db.iter(reverse = true):
+    echo i
+
+  echo ">> iter seek ab"
+  for i in db.iter(seek = "ab"):
+    echo i
+
+  echo ">> iter seek ab reverse"
+  for i in db.iter(seek = "ab", reverse = true):
+    echo i