db: Simplify exists check, fix IsKeyInDomain signature, Iterator Close

+ *FSDB.HasKey now uses common.FileExists to test for file existence
+ IsKeyInDomain takes key as a []byte slice instead of as a string
to avoid extraneous []byte<-->string conversions for start and end
+ Iterator.Close() instead of Iterator.Release()
+ withDB helper to encapsulate DB creation, deferred cleanups
so that for loops can use opened DBs and discard them ASAP

Addressing accepted changes from review with @jaekwon

db/backend_test.go

@@ -45,33 +45,37 @@ func TestBackendsGetSetDelete(t *testing.T) {
 	}
 }
 
+func withDB(t *testing.T, creator dbCreator, fn func(DB)) {
+	name := cmn.Fmt("test_%x", cmn.RandStr(12))
+	db, err := creator(name, "")
+	defer cleanupDBDir("", name)
+	assert.Nil(t, err)
+	fn(db)
+	db.Close()
+}
+
 func TestBackendsNilKeys(t *testing.T) {
 	// test all backends
 	for dbType, creator := range backends {
-		name := cmn.Fmt("test_%x", cmn.RandStr(12))
-		db, err := creator(name, "")
-		defer cleanupDBDir("", name)
-		assert.Nil(t, err)
-
-		panicMsg := "expecting %s.%s to panic"
-		assert.Panics(t, func() { db.Get(nil) }, panicMsg, dbType, "get")
-		assert.Panics(t, func() { db.Has(nil) }, panicMsg, dbType, "has")
-		assert.Panics(t, func() { db.Set(nil, []byte("abc")) }, panicMsg, dbType, "set")
-		assert.Panics(t, func() { db.SetSync(nil, []byte("abc")) }, panicMsg, dbType, "setsync")
-		assert.Panics(t, func() { db.Delete(nil) }, panicMsg, dbType, "delete")
-		assert.Panics(t, func() { db.DeleteSync(nil) }, panicMsg, dbType, "deletesync")
-
-		db.Close()
+		withDB(t, creator, func(db DB) {
+			panicMsg := "expecting %s.%s to panic"
+			assert.Panics(t, func() { db.Get(nil) }, panicMsg, dbType, "get")
+			assert.Panics(t, func() { db.Has(nil) }, panicMsg, dbType, "has")
+			assert.Panics(t, func() { db.Set(nil, []byte("abc")) }, panicMsg, dbType, "set")
+			assert.Panics(t, func() { db.SetSync(nil, []byte("abc")) }, panicMsg, dbType, "setsync")
+			assert.Panics(t, func() { db.Delete(nil) }, panicMsg, dbType, "delete")
+			assert.Panics(t, func() { db.DeleteSync(nil) }, panicMsg, dbType, "deletesync")
+		})
 	}
 }
 
 func TestGoLevelDBBackendStr(t *testing.T) {
-	name := cmn.Fmt("test_%x", cmn.RandStr(12))
-	db := NewDB(name, LevelDBBackendStr, "")
-	defer cleanupDBDir("", name)
-
-	if _, ok := backends[CLevelDBBackendStr]; !ok {
-		_, ok := db.(*GoLevelDB)
-		assert.True(t, ok)
-	}
+        name := cmn.Fmt("test_%x", cmn.RandStr(12))
+        db := NewDB(name, LevelDBBackendStr, "")
+        defer cleanupDBDir("", name)
+ 
+        if _, ok := backends[CLevelDBBackendStr]; !ok {
+                _, ok := db.(*GoLevelDB)
+                assert.True(t, ok)
+        }
 }

db/c_level_db.go

@@ -109,7 +109,7 @@ func (db *CLevelDB) Close() {
 
 func (db *CLevelDB) Print() {
 	itr := db.Iterator(BeginningKey(), EndingKey())
-	defer itr.Release()
+	defer itr.Close()
 	for ; itr.Valid(); itr.Next() {
 		key := itr.Key()
 		value := itr.Value()
@@ -231,7 +231,7 @@ func (c *cLevelDBIterator) checkEndKey() []byte {
 	return key
 }
 
-func (c *cLevelDBIterator) Release() {
+func (c *cLevelDBIterator) Close() {
 	c.itr.Close()
 }
 

db/fsdb.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 
 	"github.com/pkg/errors"
+	cmn "github.com/tendermint/tmlibs/common"
 )
 
 const (
@@ -64,13 +65,7 @@ func (db *FSDB) Has(key []byte) bool {
 	panicNilKey(key)
 
 	path := db.nameToPath(key)
-	_, err := read(path)
-	if os.IsNotExist(err) {
-		return false
-	} else if err != nil {
-		panic(errors.Wrapf(err, "Getting key %s (0x%X)", string(key), key))
-	}
-	return true
+	return cmn.FileExists(path)
 }
 
 func (db *FSDB) Set(key []byte, value []byte) {
@@ -246,7 +241,7 @@ func list(dirPath string, start, end []byte) ([]string, error) {
 		if err != nil {
 			return nil, fmt.Errorf("Failed to unescape %s while listing", name)
 		}
-		if IsKeyInDomain(n, start, end) {
+		if IsKeyInDomain([]byte(n), start, end) {
 			paths = append(paths, n)
 		}
 	}

db/go_level_db.go

@@ -263,10 +263,6 @@ func (it *goLevelDBIterator) Close() {
 	it.source.Release()
 }
 
-func (it *goLevelDBIterator) Release() {
-	it.source.Release()
-}
-
 func (it *goLevelDBIterator) assertNoError() {
 	if err := it.source.Error(); err != nil {
 		panic(err)

db/mem_db.go

@@ -157,7 +157,7 @@ func (db *MemDB) ReverseIterator(start, end []byte) Iterator {
 func (db *MemDB) getSortedKeys(start, end []byte) []string {
 	keys := []string{}
 	for key, _ := range db.db {
-		if IsKeyInDomain(key, start, end) {
+		if IsKeyInDomain([]byte(key), start, end) {
 			keys = append(keys, key)
 		}
 	}
@@ -222,5 +222,3 @@ func (it *memDBIterator) Close() {
 	it.db = nil
 	it.keys = nil
 }
-
-func (it *memDBIterator) Release() {}

db/types.go

@@ -68,7 +68,7 @@ func EndingKey() []byte {
 	Usage:
 
 	var itr Iterator = ...
-	defer itr.Release()
+	defer itr.Close()
 
 	for ; itr.Valid(); itr.Next() {
 		k, v := itr.Key(); itr.Value()
@@ -108,7 +108,7 @@ type Iterator interface {
 	Value() []byte
 
 	// Release deallocates the given Iterator.
-	Release()
+	Close()
 }
 
 // For testing convenience.

db/util.go

@@ -2,7 +2,6 @@ package db
 
 import (
 	"bytes"
-	"strings"
 )
 
 func IteratePrefix(db DB, prefix []byte) Iterator {
@@ -39,8 +38,8 @@ func cpIncr(bz []byte) (ret []byte) {
 	return EndingKey()
 }
 
-func IsKeyInDomain(key string, start, end []byte) bool {
-	leftCondition := bytes.Equal(start, BeginningKey()) || strings.Compare(key, string(start)) >= 0
-	rightCondition := bytes.Equal(end, EndingKey()) || strings.Compare(key, string(end)) < 0
+func IsKeyInDomain(key, start, end []byte) bool {
+	leftCondition := bytes.Equal(start, BeginningKey()) || bytes.Compare(key, start) >= 0
+	rightCondition := bytes.Equal(end, EndingKey()) || bytes.Compare(key, end) < 0
 	return leftCondition && rightCondition
 }