From 712708f87c968b2c7b2c8f9e5bf0189668588848 Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Fri, 22 Aug 2014 22:26:03 +0200
Subject: [PATCH] Added transcoder functions to LevelDB backend.

---
 common/coords.go |  5 +++++
 leveldb.go       | 43 +++++++++++++++++++++++++++++--------------
 main.go          |  6 +++++-
 3 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/common/coords.go b/common/coords.go
index 2ca3189..e7c3490 100644
--- a/common/coords.go
+++ b/common/coords.go
@@ -24,6 +24,7 @@ type (
 	KeyTransformer func(int64) int64
 	KeyEncoder     func(int64) ([]byte, error)
 	KeyDecoder     func([]byte) (int64, error)
+	KeyTranscoder  func([]byte) ([]byte, error)
 	KeySplitter    func(int64) Coord
 	KeyJoiner      func(Coord) int64
 )
@@ -156,6 +157,10 @@ func EncodeStringToBytesFromInterleaved(key int64) ([]byte, error) {
 	return EncodeStringToBytes(TransformInterleavedToPlain(key))
 }
 
+func IdentityTranscoder(key []byte) ([]byte, error) {
+	return key, nil
+}
+
 func SelectKeySplitter(interleaved bool) KeySplitter {
 	if interleaved {
 		return InterleavedToCoord
diff --git a/leveldb.go b/leveldb.go
index 64cf1d5..b0715a1 100644
--- a/leveldb.go
+++ b/leveldb.go
@@ -8,13 +8,17 @@ import (
 	"log"
 	"sync"
 
+	"bitbucket.org/s_l_teichmann/mtredisalize/common"
+
 	leveldb "github.com/jmhodges/levigo"
 )
 
 type LevelDBBackend struct {
-	cache *leveldb.Cache
-	db    *leveldb.DB
-	mutex sync.RWMutex
+	cache   *leveldb.Cache
+	db      *leveldb.DB
+	encoder common.KeyTranscoder
+	decoder common.KeyTranscoder
+	mutex   sync.RWMutex
 }
 
 type LevelDBSession struct {
@@ -22,7 +26,11 @@ type LevelDBSession struct {
 	tx      *leveldb.WriteBatch
 }
 
-func NewLeveDBBackend(path string, cacheSize int) (ldb *LevelDBBackend, err error) {
+func NewLeveDBBackend(
+	path string,
+	encoder common.KeyTranscoder,
+	decoder common.KeyTranscoder,
+	cacheSize int) (ldb *LevelDBBackend, err error) {
 	opts := leveldb.NewOptions()
 
 	var cache *leveldb.Cache
@@ -41,8 +49,10 @@ func NewLeveDBBackend(path string, cacheSize int) (ldb *LevelDBBackend, err erro
 		return
 	}
 	ldb = &LevelDBBackend{
-		cache: cache,
-		db:    db}
+		cache:   cache,
+		db:      db,
+		encoder: encoder,
+		decoder: decoder}
 	return
 }
 
@@ -78,7 +88,9 @@ func (ldb *LevelDBBackend) Shutdown() error {
 }
 
 func (ldbs *LevelDBSession) Fetch(hash, key []byte) (value []byte, err error) {
-
+	if key, err = ldbs.backend.decoder(key); err != nil {
+		return
+	}
 	ldbs.backend.doRead(func(db *leveldb.DB) {
 		ro := leveldb.NewReadOptions()
 		value, err = ldbs.backend.db.Get(ro, key)
@@ -108,24 +120,21 @@ func keyExists(db *leveldb.DB, key []byte) (exists bool, err error) {
 }
 
 func (ldbs *LevelDBSession) Store(hash, key, value []byte) (exists bool, err error) {
-
+	if key, err = ldbs.backend.decoder(key); err != nil {
+		return
+	}
 	ldbs.backend.doWrite(func(db *leveldb.DB) {
 		if exists, err = keyExists(db, key); err != nil {
 			return
 		}
-
 		if ldbs.tx != nil {
-			//log.Printf("Stored in tx: key = '%s' len(value) = %d\n", key, len(value))
 			ldbs.tx.Put(key, value)
 			return
 		}
-
-		//log.Printf("Stored: key = '%s' len(value) = %d\n", key, len(value))
 		wo := leveldb.NewWriteOptions()
 		err = ldbs.backend.db.Put(wo, key, value)
 		wo.Close()
 	})
-
 	return
 }
 
@@ -178,8 +187,14 @@ func (ldbs *LevelDBSession) AllKeys(hash []byte) (keys chan []byte, n int, err e
 		defer close(keys)
 		defer it.Close()
 		it.SeekToFirst()
+		encoder := ldbs.backend.encoder
 		for ; it.Valid(); it.Next() {
-			keys <- it.Key()
+			if key, err := encoder(it.Key()); err == nil {
+				keys <- key
+			} else {
+				log.Printf("WARN: %s\n", err)
+				return
+			}
 		}
 		if err := it.GetError(); err != nil {
 			log.Printf("WARN: %s\n", err)
diff --git a/main.go b/main.go
index bdf38df..17ffa9b 100644
--- a/main.go
+++ b/main.go
@@ -70,7 +70,11 @@ func main() {
 			log.Fatal(err)
 		}
 	} else {
-		if backend, err = NewLeveDBBackend(args[0], cacheSize); err != nil {
+		if backend, err = NewLeveDBBackend(
+			args[0],
+			common.IdentityTranscoder,
+			common.IdentityTranscoder,
+			cacheSize); err != nil {
 			log.Fatal(err)
 		}
 	}