From ff14b83b1ecdbf180aec84b34f72a562771d8b0b Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Mon, 18 Aug 2014 18:01:34 +0200
Subject: [PATCH] Made encode/decode api more symmetric. Added some unit test
 for the encoders/decoders.

---
 common/coords.go      | 56 +++++++++++++++++++++----------------------
 common/coords_test.go | 47 ++++++++++++++++++++++++++++++++++--
 sqlite.go             | 13 +++++++---
 3 files changed, 83 insertions(+), 33 deletions(-)

diff --git a/common/coords.go b/common/coords.go
index 6bbc0af..da10333 100644
--- a/common/coords.go
+++ b/common/coords.go
@@ -9,40 +9,40 @@ import (
 	"strconv"
 )
 
-type (
-	KeyTransformer func(int64) int64
-	KeyEncoder     func(int64) []byte
-	KeyDecoder     func([]byte) int64
-	KeySplitter    func(int64) (int16, int16, int16)
-	KeyJoiner      func(int16, int16, int16) int64
-)
-
-// Constructs a database key out of byte slice.
-func DecodePosFromBytes(key []byte) (pos int64, err error) {
-	return strconv.ParseInt(string(key), 10, 64)
-}
-
-// Encode a block pos to byte slice.
-func EncodePosToBytes(key int64) []byte {
-	return []byte(strconv.FormatInt(key, 10))
-}
-
-func EncodeAsBigEndian(key int64) (enc []byte) {
-	enc = make([]byte, 8)
-	binary.BigEndian.PutUint64(enc, uint64(key))
-	return
-}
-
-func DecodeFromBigEndian(key []byte) int64 {
-	return int64(binary.BigEndian.Uint64(key))
-}
-
 const (
 	numBitsPerComponent = 12
 	maxPositive         = 2048
 	modulo              = 4096
 )
 
+type (
+	KeyTransformer func(int64) int64
+	KeyEncoder     func(int64) ([]byte, error)
+	KeyDecoder     func([]byte) (int64, error)
+	KeySplitter    func(int64) (int16, int16, int16)
+	KeyJoiner      func(int16, int16, int16) int64
+)
+
+// Constructs a database key out of byte slice.
+func DecodeStringFromBytes(key []byte) (pos int64, err error) {
+	return strconv.ParseInt(string(key), 10, 64)
+}
+
+// Encode a block pos to byte slice.
+func EncodeStringToBytes(key int64) ([]byte, error) {
+	return []byte(strconv.FormatInt(key, 10)), nil
+}
+
+func EncodeToBigEndian(key int64) (enc []byte, err error) {
+	enc = make([]byte, 8)
+	binary.BigEndian.PutUint64(enc, uint64(key))
+	return
+}
+
+func DecodeFromBigEndian(key []byte) (int64, error) {
+	return int64(binary.BigEndian.Uint64(key)), nil
+}
+
 func XYZToInterleaved(x, y, z int16) (result int64) {
 	const end = 1 << (numBitsPerComponent + 1)
 	setmask := int64(1)
diff --git a/common/coords_test.go b/common/coords_test.go
index 169206f..84e32c9 100644
--- a/common/coords_test.go
+++ b/common/coords_test.go
@@ -2,11 +2,10 @@ package common
 
 import "testing"
 
-//var data = []int16{-2}
 var data = []int16{
 	-2045, -1850, -1811, -1629, -1104,
 	-967, -725, -646, -329, -212,
-	-150, 88, 524, 527, 549,
+	-150, -1, 0, 1, 88, 524, 527, 549,
 	1783, 1817, 1826, 2028, 2032}
 
 func allData(f func(int16, int16, int16)) {
@@ -19,6 +18,50 @@ func allData(f func(int16, int16, int16)) {
 	}
 }
 
+func checkEncodeDecode(
+	desc string,
+	join KeyJoiner,
+	encode KeyEncoder, decode KeyDecoder,
+	x, y, z int16, t *testing.T) {
+
+	k1 := join(x, y, z)
+	var err error
+	var b []byte
+	if b, err = encode(k1); err != nil {
+		t.Errorf("%s: Failed to encode (%d, %d, %d) %s\n",
+			desc, x, y, z, err)
+		return
+	}
+	var k2 int64
+	if k2, err = decode(b); err != nil {
+		t.Errorf("%s: Failed to decode (%d, %d, %d) %s\n",
+			desc, x, y, z, err)
+		return
+	}
+
+	if k1 != k2 {
+		t.Errorf("%s: Expected %d got %d for (%d, %d, %d) %b\n",
+			desc, k1, k2, x, y, z)
+	}
+}
+
+func TestEncodeDecode(t *testing.T) {
+	allData(func(x, y, z int16) {
+		checkEncodeDecode(
+			"Big endian",
+			XYZToInterleaved,
+			EncodeToBigEndian, DecodeFromBigEndian,
+			x, y, z, t)
+	})
+	allData(func(x, y, z int16) {
+		checkEncodeDecode(
+			"String",
+			XYZToInterleaved,
+			EncodeStringToBytes, DecodeStringFromBytes,
+			x, y, z, t)
+	})
+}
+
 func checkJoinSplit(
 	desc string,
 	join KeyJoiner, split KeySplitter,
diff --git a/sqlite.go b/sqlite.go
index 4f4cc6d..4d9a0ea 100644
--- a/sqlite.go
+++ b/sqlite.go
@@ -139,7 +139,7 @@ func (ss *SqliteSession) txStmt(stmt *sql.Stmt) *sql.Stmt {
 
 func (ss *SqliteSession) Fetch(hash, key []byte) (data []byte, err error) {
 	var pos int64
-	if pos, err = common.DecodePosFromBytes(key); err != nil {
+	if pos, err = common.DecodeStringFromBytes(key); err != nil {
 		return
 	}
 
@@ -161,7 +161,7 @@ func (ss *SqliteSession) InTransaction() bool {
 
 func (ss *SqliteSession) Store(hash, key, value []byte) (exists bool, err error) {
 	var pos int64
-	if pos, err = common.DecodePosFromBytes(key); err != nil {
+	if pos, err = common.DecodeStringFromBytes(key); err != nil {
 		return
 	}
 
@@ -241,13 +241,20 @@ func (ss *SqliteSession) AllKeys(hash []byte) (keys chan []byte, n int, err erro
 		defer globalLock.RUnlock()
 		defer rows.Close()
 		defer close(keys)
+		var err error
 		for rows.Next() {
 			var key int64
 			if err := rows.Scan(&key); err != nil {
 				log.Printf("WARN: %s", err)
 				break
 			}
-			keys <- common.EncodePosToBytes(key)
+			var encoded []byte
+			if encoded, err = common.EncodeStringToBytes(key); err != nil {
+				log.Printf("Cannot encode key: %d %s\n", key, err)
+				break
+			}
+
+			keys <- encoded
 		}
 	}()