From 87b34d123e67cfc45d44259f4a4a2658310209d2 Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Wed, 20 Aug 2014 16:21:44 +0200
Subject: [PATCH] Added block producer for LevelDB in interleaver.

---
 interleaver/leveldb.go | 92 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 87 insertions(+), 5 deletions(-)

diff --git a/interleaver/leveldb.go b/interleaver/leveldb.go
index 4941697..6a854cf 100644
--- a/interleaver/leveldb.go
+++ b/interleaver/leveldb.go
@@ -5,16 +5,96 @@
 package main
 
 import (
+	"os"
+
 	"bitbucket.org/s_l_teichmann/mtredisalize/common"
 
 	leveldb "github.com/jmhodges/levigo"
 )
 
-type LevelDBBlockConsumer struct {
-	db      *leveldb.DB
-	wo      *leveldb.WriteOptions
-	joiner  common.KeyJoiner
-	encoder common.KeyEncoder
+type (
+	LevelDBBlockProducer struct {
+		db       *leveldb.DB
+		opts     *leveldb.Options
+		ro       *leveldb.ReadOptions
+		iterator *leveldb.Iterator
+		splitter common.KeySplitter
+		decoder  common.KeyDecoder
+	}
+
+	LevelDBBlockConsumer struct {
+		db      *leveldb.DB
+		opts    *leveldb.Options
+		wo      *leveldb.WriteOptions
+		joiner  common.KeyJoiner
+		encoder common.KeyEncoder
+	}
+)
+
+func NewLevelDBlockProducer(path string,
+	splitter common.KeySplitter,
+	decoder common.KeyDecoder) (ldbp *LevelDBBlockProducer, err error) {
+
+	// check if we can stat it -> exists.
+	if _, err = os.Stat(path); err != nil {
+		return
+	}
+
+	opts := leveldb.NewOptions()
+	opts.SetCreateIfMissing(false)
+
+	var db *leveldb.DB
+	if db, err = leveldb.Open(path, opts); err != nil {
+		opts.Close()
+		return
+	}
+
+	ro := leveldb.NewReadOptions()
+	ro.SetFillCache(false)
+
+	iterator := db.NewIterator(ro)
+	iterator.SeekToFirst()
+
+	ldbp = &LevelDBBlockProducer{
+		db:       db,
+		opts:     opts,
+		ro:       ro,
+		iterator: iterator,
+		splitter: splitter,
+		decoder:  decoder}
+	return
+}
+
+func (ldbp *LevelDBBlockProducer) Close() error {
+	if ldbp.iterator != nil {
+		ldbp.iterator.Close()
+	}
+	ldbp.ro.Close()
+	ldbp.db.Close()
+	ldbp.opts.Close()
+	return nil
+}
+
+func (ldbp *LevelDBBlockProducer) Next(block *Block) (err error) {
+	if ldbp.iterator == nil {
+		err = NoMoreBlocksErr
+		return
+	}
+	if !ldbp.iterator.Valid() {
+		if err = ldbp.iterator.GetError(); err == nil {
+			err = NoMoreBlocksErr
+		}
+		ldbp.iterator.Close()
+		ldbp.iterator = nil
+		return
+	}
+	var key int64
+	if key, err = ldbp.decoder(ldbp.iterator.Key()); err != nil {
+		return
+	}
+	block.Coord = ldbp.splitter(key)
+	block.Data = ldbp.iterator.Value()
+	return
 }
 
 func NewLevelDBBlockConsumer(
@@ -32,6 +112,7 @@ func NewLevelDBBlockConsumer(
 
 	ldbc = &LevelDBBlockConsumer{
 		db:      db,
+		opts:    opts,
 		wo:      leveldb.NewWriteOptions(),
 		joiner:  joiner,
 		encoder: encoder}
@@ -41,6 +122,7 @@ func NewLevelDBBlockConsumer(
 func (ldbc *LevelDBBlockConsumer) Close() error {
 	ldbc.wo.Close()
 	ldbc.db.Close()
+	ldbc.opts.Close()
 	return nil
 }