From c14e7c3dd03c0824faba70c5709f155e8acb1c09 Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Tue, 19 Aug 2014 12:07:57 +0200
Subject: [PATCH] Added first stubs of SQLite producer for interleaver.

---
 interleaver/interfaces.go | 10 ++++--
 interleaver/main.go       |  9 +++++
 interleaver/sqlite.go     | 75 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+), 2 deletions(-)
 create mode 100644 interleaver/main.go
 create mode 100644 interleaver/sqlite.go

diff --git a/interleaver/interfaces.go b/interleaver/interfaces.go
index dd2c1b5..a83dd76 100644
--- a/interleaver/interfaces.go
+++ b/interleaver/interfaces.go
@@ -4,7 +4,12 @@
 
 package main
 
-import "bitbucket.org/s_l_teichmann/mtredisalize/common"
+import (
+    "fmt"
+    "bitbucket.org/s_l_teichmann/mtredisalize/common"
+)
+
+var NoMoreBlocksErr = fmt.Errorf("No more blocks.")
 
 type (
 	Block struct {
@@ -13,8 +18,9 @@ type (
 	}
 
 	BlocKProducer interface {
+        // Returns next block.
+        // error is NoMoreBlocksErr if it run out of blocks.
 		Next() (Block, error)
-		HasNext() bool
 		Close() error
 	}
 
diff --git a/interleaver/main.go b/interleaver/main.go
new file mode 100644
index 0000000..0f2c2a1
--- /dev/null
+++ b/interleaver/main.go
@@ -0,0 +1,9 @@
+// Copyright 2014 by Sascha L. Teichmann
+// Use of this source code is governed by the MIT license
+// that can be found in the LICENSE file.
+
+package main
+
+func main() {
+    // TODO: Implement me!
+}
diff --git a/interleaver/sqlite.go b/interleaver/sqlite.go
new file mode 100644
index 0000000..6ed5f5e
--- /dev/null
+++ b/interleaver/sqlite.go
@@ -0,0 +1,75 @@
+// Copyright 2014 by Sascha L. Teichmann
+// Use of this source code is governed by the MIT license
+// that can be found in the LICENSE file.
+
+package main
+
+import (
+	"database/sql"
+	"os"
+
+	"bitbucket.org/s_l_teichmann/mtredisalize/common"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+const (
+	fetchSql = "SELECT pos, data FROM blocks"
+)
+
+type SQLiteBlockProducer struct {
+	db       *sql.DB
+	rows     *sql.Rows
+	splitter common.KeySplitter
+}
+
+func NewSQLiteBlockProducer(path string, splitter common.KeySplitter) (sbp *SQLiteBlockProducer, err error) {
+
+	// check if we can stat it -> exists.
+	if _, err = os.Stat(path); err != nil {
+		return
+	}
+
+	var db *sql.DB
+	if db, err = sql.Open("sqlite3", path); err != nil {
+		return
+	}
+
+	var rows *sql.Rows
+	if rows, err = db.Query(fetchSql); err != nil {
+		db.Close()
+		return
+	}
+
+	sbp = &SQLiteBlockProducer{
+		db:       db,
+		rows:     rows,
+		splitter: splitter}
+
+	return
+}
+
+func (sbp *SQLiteBlockProducer) Next() (block Block, err error) {
+	if sbp.rows == nil {
+		err = NoMoreBlocksErr
+		return
+	}
+	if sbp.rows.Next() {
+		var key int64
+		if err = sbp.rows.Scan(&key, &block.Data); err == nil {
+			block.Coord = sbp.splitter(key)
+		}
+	} else {
+		sbp.rows.Close()
+		sbp.rows = nil
+		err = NoMoreBlocksErr
+	}
+	return
+}
+
+func (sbp *SQLiteBlockProducer) Close() error {
+	if sbp.rows != nil {
+		sbp.rows.Close()
+	}
+	return sbp.db.Close()
+}