add metastore, switching sequence to use it

metastore is for storing metadata. This will be used later when moving
to distributed master mode.

go/metastore/backing_test.go

@@ -0,0 +1,30 @@
+package metastore
+
+import (
+	"testing"
+)
+
+func TestMemoryBacking(t *testing.T) {
+	ms := &MetaStore{NewMetaStoreMemoryBacking()}
+	verifySetGet(t, ms)
+}
+
+func TestFileBacking(t *testing.T) {
+	ms := &MetaStore{NewMetaStoreFileBacking()}
+	verifySetGet(t, ms)
+}
+
+func verifySetGet(t *testing.T, ms *MetaStore) {
+	data := uint64(234234)
+	ms.SetUint64(data, "/tmp", "sequence")
+	if !ms.Has("/tmp", "sequence") {
+		t.Errorf("Failed to set data")
+	}
+	if val, err := ms.GetUint64("/tmp", "sequence"); err == nil {
+		if val != data {
+			t.Errorf("Set %d, but read back %d", data, val)
+		}
+	} else {
+		t.Errorf("Failed to get back data:%s", err)
+	}
+}

go/metastore/file_backing.go

@@ -0,0 +1,34 @@
+package metastore
+
+import (
+	"io/ioutil"
+	"os"
+	"path"
+)
+
+// store data on disk, enough for most cases
+
+type MetaStoreFileBacking struct {
+}
+
+func NewMetaStoreFileBacking() MetaStoreFileBacking {
+	mms := MetaStoreFileBacking{}
+	return mms
+}
+
+func (mms MetaStoreFileBacking) Set(val []byte, elem ...string) error {
+	return ioutil.WriteFile(path.Join(elem...), val, 0644)
+}
+
+func (mms MetaStoreFileBacking) Get(elem ...string) (val []byte, err error) {
+	return ioutil.ReadFile(path.Join(elem...))
+}
+
+func (mms MetaStoreFileBacking) Has(elem ...string) (ok bool) {
+	seqFile, se := os.OpenFile(path.Join(elem...), os.O_RDONLY, 0644)
+	if se != nil {
+		return false
+	}
+	defer seqFile.Close()
+	return true
+}

go/metastore/memory_backing.go

@@ -0,0 +1,37 @@
+package metastore
+
+import (
+	"fmt"
+	"path"
+)
+
+//this is for testing only
+
+type MetaStoreMemoryBacking struct {
+	m map[string][]byte
+}
+
+func NewMetaStoreMemoryBacking() MetaStoreMemoryBacking {
+	mms := MetaStoreMemoryBacking{}
+	mms.m = make(map[string][]byte)
+	return mms
+}
+
+func (mms MetaStoreMemoryBacking) Set(val []byte, elem ...string) error {
+	mms.m[path.Join(elem...)] = val
+	return nil
+}
+
+func (mms MetaStoreMemoryBacking) Get(elem ...string) (val []byte, err error) {
+	var ok bool
+	val, ok = mms.m[path.Join(elem...)]
+	if !ok {
+		return nil, fmt.Errorf("Missing value for %s", path.Join(elem...))
+	}
+	return
+}
+
+func (mms MetaStoreMemoryBacking) Has(elem ...string) (ok bool) {
+	_, ok = mms.m[path.Join(elem...)]
+	return
+}

go/metastore/metastore.go

@@ -0,0 +1,35 @@
+package metastore
+
+import (
+	"code.google.com/p/weed-fs/go/util"
+	"errors"
+	"path"
+)
+
+type MetaStoreBacking interface {
+	Get(elem ...string) ([]byte, error)
+	Set(val []byte, elem ...string) error
+  Has(elem ...string) bool
+}
+
+type MetaStore struct {
+	MetaStoreBacking
+}
+
+func (m *MetaStore) SetUint64(val uint64, elem ...string) error {
+	b := make([]byte, 8)
+	util.Uint64toBytes(b, val)
+	return m.Set(b, elem...)
+}
+
+func (m *MetaStore) GetUint64(elem ...string) (val uint64, err error) {
+	if b, e := m.Get(elem...); e == nil && len(b) == 8 {
+		val = util.BytesToUint64(b)
+	} else {
+		if e != nil {
+			return 0, e
+		}
+		err = errors.New("Not found value for " + path.Join(elem...))
+	}
+	return
+}