Jae/fixprefixdb (#199)

* Fix PrefixDB Iterator
* PrefixDB Iterator/ReverseIterator fixes
* Bump version 0.8.2
* Update CHANGELOG.md about DebugDB
* Keep invalid source to be closed
* Use prefixBatch instead of memBatch

CHANGELOG.md

@@ -1,5 +1,16 @@
 # Changelog
 
+## 0.8.2 (April 12th, 2018)
+
+FEATURES:
+
+ - [db] DebugDB shows better colorized output
+
+BUG FIXES:
+
+ - [db] PrefixDB Iterator/ReverseIterator fixes
+ - [db] DebugDB fixes
+
 ## 0.8.1 (April 5th, 2018)
 
 FEATURES:

common/errors.go

@@ -178,7 +178,7 @@ func (err *cmnError) Format(s fmt.State, verb rune) {
 		if s.Flag('#') {
 			s.Write([]byte("--= Error =--\n"))
 			// Write msg.
-			s.Write([]byte(fmt.Sprintf("Message: %#s\n", err.msg)))
+			s.Write([]byte(fmt.Sprintf("Message: %s\n", err.msg)))
 			// Write cause.
 			s.Write([]byte(fmt.Sprintf("Cause: %#v\n", err.cause)))
 			// Write type.

common/os_test.go

@@ -23,11 +23,11 @@ func TestWriteFileAtomic(t *testing.T) {
 	}
 	defer os.Remove(f.Name())
 
-	if err := ioutil.WriteFile(f.Name(), old, 0664); err != nil {
+	if err = ioutil.WriteFile(f.Name(), old, 0664); err != nil {
 		t.Fatal(err)
 	}
 
-	if err := WriteFileAtomic(f.Name(), data, perm); err != nil {
+	if err = WriteFileAtomic(f.Name(), data, perm); err != nil {
 		t.Fatal(err)
 	}
 

db/common_test.go

@@ -33,6 +33,12 @@ func checkNextPanics(t *testing.T, itr Iterator) {
 	assert.Panics(t, func() { itr.Next() }, "checkNextPanics expected panic but didn't")
 }
 
+func checkDomain(t *testing.T, itr Iterator, start, end []byte) {
+	ds, de := itr.Domain()
+	assert.Equal(t, start, ds, "checkDomain domain start incorrect")
+	assert.Equal(t, end, de, "checkDomain domain end incorrect")
+}
+
 func checkItem(t *testing.T, itr Iterator, key []byte, value []byte) {
 	k, v := itr.Key(), itr.Value()
 	assert.Exactly(t, key, k)

db/debug_db.go

@@ -3,8 +3,14 @@ package db
 import (
 	"fmt"
 	"sync"
+
+	cmn "github.com/tendermint/tmlibs/common"
 )
 
+func _fmt(f string, az ...interface{}) string {
+	return fmt.Sprintf(f, az...)
+}
+
 //----------------------------------------
 // debugDB
 
@@ -26,78 +32,84 @@ func (ddb debugDB) Mutex() *sync.Mutex { return nil }
 
 // Implements DB.
 func (ddb debugDB) Get(key []byte) (value []byte) {
-	defer fmt.Printf("%v.Get(%X) %X\n", ddb.label, key, value)
+	defer func() {
+		fmt.Printf("%v.Get(%v) %v\n", ddb.label, cmn.Cyan(_fmt("%X", key)), cmn.Blue(_fmt("%X", value)))
+	}()
 	value = ddb.db.Get(key)
 	return
 }
 
 // Implements DB.
 func (ddb debugDB) Has(key []byte) (has bool) {
-	defer fmt.Printf("%v.Has(%X) %v\n", ddb.label, key, has)
+	defer func() {
+		fmt.Printf("%v.Has(%v) %v\n", ddb.label, cmn.Cyan(_fmt("%X", key)), has)
+	}()
 	return ddb.db.Has(key)
 }
 
 // Implements DB.
 func (ddb debugDB) Set(key []byte, value []byte) {
-	fmt.Printf("%v.Set(%X, %X)\n", ddb.label, key, value)
+	fmt.Printf("%v.Set(%v, %v)\n", ddb.label, cmn.Cyan(_fmt("%X", key)), cmn.Yellow(_fmt("%X", value)))
 	ddb.db.Set(key, value)
 }
 
 // Implements DB.
 func (ddb debugDB) SetSync(key []byte, value []byte) {
-	fmt.Printf("%v.SetSync(%X, %X)\n", ddb.label, key, value)
+	fmt.Printf("%v.SetSync(%v, %v)\n", ddb.label, cmn.Cyan(_fmt("%X", key)), cmn.Yellow(_fmt("%X", value)))
 	ddb.db.SetSync(key, value)
 }
 
 // Implements atomicSetDeleter.
 func (ddb debugDB) SetNoLock(key []byte, value []byte) {
-	fmt.Printf("%v.SetNoLock(%X, %X)\n", ddb.label, key, value)
-	ddb.db.Set(key, value)
+	fmt.Printf("%v.SetNoLock(%v, %v)\n", ddb.label, cmn.Cyan(_fmt("%X", key)), cmn.Yellow(_fmt("%X", value)))
+	ddb.db.(atomicSetDeleter).SetNoLock(key, value)
 }
 
 // Implements atomicSetDeleter.
 func (ddb debugDB) SetNoLockSync(key []byte, value []byte) {
-	fmt.Printf("%v.SetNoLockSync(%X, %X)\n", ddb.label, key, value)
-	ddb.db.SetSync(key, value)
+	fmt.Printf("%v.SetNoLockSync(%v, %v)\n", ddb.label, cmn.Cyan(_fmt("%X", key)), cmn.Yellow(_fmt("%X", value)))
+	ddb.db.(atomicSetDeleter).SetNoLockSync(key, value)
 }
 
 // Implements DB.
 func (ddb debugDB) Delete(key []byte) {
-	fmt.Printf("%v.Delete(%X)\n", ddb.label, key)
+	fmt.Printf("%v.Delete(%v)\n", ddb.label, cmn.Red(_fmt("%X", key)))
 	ddb.db.Delete(key)
 }
 
 // Implements DB.
 func (ddb debugDB) DeleteSync(key []byte) {
-	fmt.Printf("%v.DeleteSync(%X)\n", ddb.label, key)
+	fmt.Printf("%v.DeleteSync(%v)\n", ddb.label, cmn.Red(_fmt("%X", key)))
 	ddb.db.DeleteSync(key)
 }
 
 // Implements atomicSetDeleter.
 func (ddb debugDB) DeleteNoLock(key []byte) {
-	fmt.Printf("%v.DeleteNoLock(%X)\n", ddb.label, key)
-	ddb.db.Delete(key)
+	fmt.Printf("%v.DeleteNoLock(%v)\n", ddb.label, cmn.Red(_fmt("%X", key)))
+	ddb.db.(atomicSetDeleter).DeleteNoLock(key)
 }
 
 // Implements atomicSetDeleter.
 func (ddb debugDB) DeleteNoLockSync(key []byte) {
-	fmt.Printf("%v.DeleteNoLockSync(%X)\n", ddb.label, key)
-	ddb.db.DeleteSync(key)
+	fmt.Printf("%v.DeleteNoLockSync(%v)\n", ddb.label, cmn.Red(_fmt("%X", key)))
+	ddb.db.(atomicSetDeleter).DeleteNoLockSync(key)
 }
 
 // Implements DB.
 func (ddb debugDB) Iterator(start, end []byte) Iterator {
-	fmt.Printf("%v.Iterator(%X, %X)\n", ddb.label, start, end)
+	fmt.Printf("%v.Iterator(%v, %v)\n", ddb.label, cmn.Cyan(_fmt("%X", start)), cmn.Blue(_fmt("%X", end)))
 	return NewDebugIterator(ddb.label, ddb.db.Iterator(start, end))
 }
 
 // Implements DB.
 func (ddb debugDB) ReverseIterator(start, end []byte) Iterator {
-	fmt.Printf("%v.ReverseIterator(%X, %X)\n", ddb.label, start, end)
+	fmt.Printf("%v.ReverseIterator(%v, %v)\n", ddb.label, cmn.Cyan(_fmt("%X", start)), cmn.Blue(_fmt("%X", end)))
 	return NewDebugIterator(ddb.label, ddb.db.ReverseIterator(start, end))
 }
 
 // Implements DB.
+// Panics if the underlying db is not an
+// atomicSetDeleter.
 func (ddb debugDB) NewBatch() Batch {
 	fmt.Printf("%v.NewBatch()\n", ddb.label)
 	return NewDebugBatch(ddb.label, ddb.db.NewBatch())
@@ -137,14 +149,18 @@ func NewDebugIterator(label string, itr Iterator) debugIterator {
 
 // Implements Iterator.
 func (ditr debugIterator) Domain() (start []byte, end []byte) {
-	defer fmt.Printf("%v.itr.Domain() (%X,%X)\n", ditr.label, start, end)
+	defer func() {
+		fmt.Printf("%v.itr.Domain() (%X,%X)\n", ditr.label, start, end)
+	}()
 	start, end = ditr.itr.Domain()
 	return
 }
 
 // Implements Iterator.
 func (ditr debugIterator) Valid() (ok bool) {
-	defer fmt.Printf("%v.itr.Valid() %v\n", ditr.label, ok)
+	defer func() {
+		fmt.Printf("%v.itr.Valid() %v\n", ditr.label, ok)
+	}()
 	ok = ditr.itr.Valid()
 	return
 }
@@ -157,14 +173,14 @@ func (ditr debugIterator) Next() {
 
 // Implements Iterator.
 func (ditr debugIterator) Key() (key []byte) {
-	fmt.Printf("%v.itr.Key() %X\n", ditr.label, key)
+	fmt.Printf("%v.itr.Key() %v\n", ditr.label, cmn.Cyan(_fmt("%X", key)))
 	key = ditr.itr.Key()
 	return
 }
 
 // Implements Iterator.
 func (ditr debugIterator) Value() (value []byte) {
-	fmt.Printf("%v.itr.Value() %X\n", ditr.label, value)
+	fmt.Printf("%v.itr.Value() %v\n", ditr.label, cmn.Blue(_fmt("%X", value)))
 	value = ditr.itr.Value()
 	return
 }
@@ -193,13 +209,13 @@ func NewDebugBatch(label string, bch Batch) debugBatch {
 
 // Implements Batch.
 func (dbch debugBatch) Set(key, value []byte) {
-	fmt.Printf("%v.batch.Set(%X, %X)\n", dbch.label, key, value)
+	fmt.Printf("%v.batch.Set(%v, %v)\n", dbch.label, cmn.Cyan(_fmt("%X", key)), cmn.Yellow(_fmt("%X", value)))
 	dbch.bch.Set(key, value)
 }
 
 // Implements Batch.
 func (dbch debugBatch) Delete(key []byte) {
-	fmt.Printf("%v.batch.Delete(%X)\n", dbch.label, key)
+	fmt.Printf("%v.batch.Delete(%v)\n", dbch.label, cmn.Red(_fmt("%X", key)))
 	dbch.bch.Delete(key)
 }
 

db/mem_batch.go

@@ -1,6 +1,8 @@
 package db
 
-import "sync"
+import (
+	"sync"
+)
 
 type atomicSetDeleter interface {
 	Mutex() *sync.Mutex
@@ -66,6 +68,5 @@ func (mBatch *memBatch) write(doSync bool) {
 		case opTypeDelete:
 			mBatch.db.DeleteNoLock(op.key)
 		}
-
 	}
 }

db/mem_db.go

@@ -37,7 +37,8 @@ func (db *MemDB) Get(key []byte) []byte {
 	defer db.mtx.Unlock()
 	key = nonNilBytes(key)
 
-	return db.db[string(key)]
+	value := db.db[string(key)]
+	return value
 }
 
 // Implements DB.
@@ -162,7 +163,7 @@ func (db *MemDB) ReverseIterator(start, end []byte) Iterator {
 	db.mtx.Lock()
 	defer db.mtx.Unlock()
 
-	keys := db.getSortedKeys(end, start, true)
+	keys := db.getSortedKeys(start, end, true)
 	return newMemDBIterator(db, keys, start, end)
 }
 
@@ -236,7 +237,8 @@ func (itr *memDBIterator) assertIsValid() {
 func (db *MemDB) getSortedKeys(start, end []byte, reverse bool) []string {
 	keys := []string{}
 	for key := range db.db {
-		if IsKeyInDomain([]byte(key), start, end, false) {
+		inDomain := IsKeyInDomain([]byte(key), start, end, reverse)
+		if inDomain {
 			keys = append(keys, key)
 		}
 	}
@@ -244,7 +246,9 @@ func (db *MemDB) getSortedKeys(start, end []byte, reverse bool) []string {
 	if reverse {
 		nkeys := len(keys)
 		for i := 0; i < nkeys/2; i++ {
+			temp := keys[i]
 			keys[i] = keys[nkeys-i-1]
+			keys[nkeys-i-1] = temp
 		}
 	}
 	return keys

db/prefix_db.go

@@ -24,7 +24,8 @@ func IteratePrefix(db DB, prefix []byte) Iterator {
 TODO: Make test, maybe rename.
 // Like IteratePrefix but the iterator strips the prefix from the keys.
 func IteratePrefixStripped(db DB, prefix []byte) Iterator {
-	return newUnprefixIterator(prefix, IteratePrefix(db, prefix))
+	start, end := ...
+	return newPrefixIterator(prefix, start, end, IteratePrefix(db, prefix))
 }
 */
 
@@ -55,7 +56,9 @@ func (pdb *prefixDB) Get(key []byte) []byte {
 	pdb.mtx.Lock()
 	defer pdb.mtx.Unlock()
 
-	return pdb.db.Get(pdb.prefixed(key))
+	pkey := pdb.prefixed(key)
+	value := pdb.db.Get(pkey)
+	return value
 }
 
 // Implements DB.
@@ -71,7 +74,8 @@ func (pdb *prefixDB) Set(key []byte, value []byte) {
 	pdb.mtx.Lock()
 	defer pdb.mtx.Unlock()
 
-	pdb.db.Set(pdb.prefixed(key), value)
+	pkey := pdb.prefixed(key)
+	pdb.db.Set(pkey, value)
 }
 
 // Implements DB.
@@ -82,16 +86,6 @@ func (pdb *prefixDB) SetSync(key []byte, value []byte) {
 	pdb.db.SetSync(pdb.prefixed(key), value)
 }
 
-// Implements atomicSetDeleter.
-func (pdb *prefixDB) SetNoLock(key []byte, value []byte) {
-	pdb.db.Set(pdb.prefixed(key), value)
-}
-
-// Implements atomicSetDeleter.
-func (pdb *prefixDB) SetNoLockSync(key []byte, value []byte) {
-	pdb.db.SetSync(pdb.prefixed(key), value)
-}
-
 // Implements DB.
 func (pdb *prefixDB) Delete(key []byte) {
 	pdb.mtx.Lock()
@@ -108,28 +102,22 @@ func (pdb *prefixDB) DeleteSync(key []byte) {
 	pdb.db.DeleteSync(pdb.prefixed(key))
 }
 
-// Implements atomicSetDeleter.
-func (pdb *prefixDB) DeleteNoLock(key []byte) {
-	pdb.db.Delete(pdb.prefixed(key))
-}
-
-// Implements atomicSetDeleter.
-func (pdb *prefixDB) DeleteNoLockSync(key []byte) {
-	pdb.db.DeleteSync(pdb.prefixed(key))
-}
-
 // Implements DB.
 func (pdb *prefixDB) Iterator(start, end []byte) Iterator {
 	pdb.mtx.Lock()
 	defer pdb.mtx.Unlock()
 
-	pstart := append(pdb.prefix, start...)
-	pend := []byte(nil)
-	if end != nil {
-		pend = append(pdb.prefix, end...)
+	var pstart, pend []byte
+	pstart = append(cp(pdb.prefix), start...)
+	if end == nil {
+		pend = cpIncr(pdb.prefix)
+	} else {
+		pend = append(cp(pdb.prefix), end...)
 	}
-	return newUnprefixIterator(
+	return newPrefixIterator(
 		pdb.prefix,
+		start,
+		end,
 		pdb.db.Iterator(
 			pstart,
 			pend,
@@ -142,31 +130,68 @@ func (pdb *prefixDB) ReverseIterator(start, end []byte) Iterator {
 	pdb.mtx.Lock()
 	defer pdb.mtx.Unlock()
 
-	pstart := []byte(nil)
-	if start != nil {
-		pstart = append(pdb.prefix, start...)
+	var pstart, pend []byte
+	if start == nil {
+		// This may cause the underlying iterator to start with
+		// an item which doesn't start with prefix.  We will skip
+		// that item later in this function. See 'skipOne'.
+		pstart = cpIncr(pdb.prefix)
+	} else {
+		pstart = append(cp(pdb.prefix), start...)
 	}
-	pend := []byte(nil)
-	if end != nil {
-		pend = append(pdb.prefix, end...)
+	if end == nil {
+		// This may cause the underlying iterator to end with an
+		// item which doesn't start with prefix.  The
+		// prefixIterator will terminate iteration
+		// automatically upon detecting this.
+		pend = cpDecr(pdb.prefix)
+	} else {
+		pend = append(cp(pdb.prefix), end...)
 	}
-	return newUnprefixIterator(
+	ritr := pdb.db.ReverseIterator(pstart, pend)
+	if start == nil {
+		skipOne(ritr, cpIncr(pdb.prefix))
+	}
+	return newPrefixIterator(
 		pdb.prefix,
-		pdb.db.ReverseIterator(
-			pstart,
-			pend,
-		),
+		start,
+		end,
+		ritr,
 	)
 }
 
 // Implements DB.
+// Panics if the underlying DB is not an
+// atomicSetDeleter.
 func (pdb *prefixDB) NewBatch() Batch {
 	pdb.mtx.Lock()
 	defer pdb.mtx.Unlock()
 
-	return &memBatch{pdb, nil}
+	return newPrefixBatch(pdb.prefix, pdb.db.NewBatch())
 }
 
+/* NOTE: Uncomment to use memBatch instead of prefixBatch
+// Implements atomicSetDeleter.
+func (pdb *prefixDB) SetNoLock(key []byte, value []byte) {
+	pdb.db.(atomicSetDeleter).SetNoLock(pdb.prefixed(key), value)
+}
+
+// Implements atomicSetDeleter.
+func (pdb *prefixDB) SetNoLockSync(key []byte, value []byte) {
+	pdb.db.(atomicSetDeleter).SetNoLockSync(pdb.prefixed(key), value)
+}
+
+// Implements atomicSetDeleter.
+func (pdb *prefixDB) DeleteNoLock(key []byte) {
+	pdb.db.(atomicSetDeleter).DeleteNoLock(pdb.prefixed(key))
+}
+
+// Implements atomicSetDeleter.
+func (pdb *prefixDB) DeleteNoLockSync(key []byte) {
+	pdb.db.(atomicSetDeleter).DeleteNoLockSync(pdb.prefixed(key))
+}
+*/
+
 // Implements DB.
 func (pdb *prefixDB) Close() {
 	pdb.mtx.Lock()
@@ -201,52 +226,109 @@ func (pdb *prefixDB) Stats() map[string]string {
 }
 
 func (pdb *prefixDB) prefixed(key []byte) []byte {
-	return append(pdb.prefix, key...)
+	return append(cp(pdb.prefix), key...)
 }
 
 //----------------------------------------
+// prefixBatch
 
-// Strips prefix while iterating from Iterator.
-type unprefixIterator struct {
+type prefixBatch struct {
 	prefix []byte
-	source Iterator
+	source Batch
 }
 
-func newUnprefixIterator(prefix []byte, source Iterator) unprefixIterator {
-	return unprefixIterator{
+func newPrefixBatch(prefix []byte, source Batch) prefixBatch {
+	return prefixBatch{
 		prefix: prefix,
 		source: source,
 	}
 }
 
-func (itr unprefixIterator) Domain() (start []byte, end []byte) {
-	start, end = itr.source.Domain()
-	if len(start) > 0 {
-		start = stripPrefix(start, itr.prefix)
+func (pb prefixBatch) Set(key, value []byte) {
+	pkey := append(cp(pb.prefix), key...)
+	pb.source.Set(pkey, value)
 }
-	if len(end) > 0 {
-		end = stripPrefix(end, itr.prefix)
+
+func (pb prefixBatch) Delete(key []byte) {
+	pkey := append(cp(pb.prefix), key...)
+	pb.source.Delete(pkey)
 }
+
+func (pb prefixBatch) Write() {
+	pb.source.Write()
+}
+
+func (pb prefixBatch) WriteSync() {
+	pb.source.WriteSync()
+}
+
+//----------------------------------------
+// prefixIterator
+
+// Strips prefix while iterating from Iterator.
+type prefixIterator struct {
+	prefix []byte
+	start  []byte
+	end    []byte
+	source Iterator
+	valid  bool
+}
+
+func newPrefixIterator(prefix, start, end []byte, source Iterator) prefixIterator {
+	if !source.Valid() || !bytes.HasPrefix(source.Key(), prefix) {
+		return prefixIterator{
+			prefix: prefix,
+			start:  start,
+			end:    end,
+			source: source,
+			valid:  false,
+		}
+	} else {
+		return prefixIterator{
+			prefix: prefix,
+			start:  start,
+			end:    end,
+			source: source,
+			valid:  true,
+		}
+	}
+}
+
+func (itr prefixIterator) Domain() (start []byte, end []byte) {
+	return itr.start, itr.end
+}
+
+func (itr prefixIterator) Valid() bool {
+	return itr.valid && itr.source.Valid()
+}
+
+func (itr prefixIterator) Next() {
+	if !itr.valid {
+		panic("prefixIterator invalid, cannot call Next()")
+	}
+	itr.source.Next()
+	if !itr.source.Valid() || !bytes.HasPrefix(itr.source.Key(), itr.prefix) {
+		itr.source.Close()
+		itr.valid = false
 		return
 	}
-
-func (itr unprefixIterator) Valid() bool {
-	return itr.source.Valid()
 }
 
-func (itr unprefixIterator) Next() {
-	itr.source.Next()
+func (itr prefixIterator) Key() (key []byte) {
+	if !itr.valid {
+		panic("prefixIterator invalid, cannot call Key()")
 	}
-
-func (itr unprefixIterator) Key() (key []byte) {
 	return stripPrefix(itr.source.Key(), itr.prefix)
 }
 
-func (itr unprefixIterator) Value() (value []byte) {
+func (itr prefixIterator) Value() (value []byte) {
+	if !itr.valid {
+		panic("prefixIterator invalid, cannot call Value()")
+	}
 	return itr.source.Value()
 }
 
-func (itr unprefixIterator) Close() {
+func (itr prefixIterator) Close() {
 	itr.source.Close()
 }
 
@@ -261,3 +343,13 @@ func stripPrefix(key []byte, prefix []byte) (stripped []byte) {
 	}
 	return key[len(prefix):]
 }
+
+// If the first iterator item is skipKey, then
+// skip it.
+func skipOne(itr Iterator, skipKey []byte) {
+	if itr.Valid() {
+		if bytes.Equal(itr.Key(), skipKey) {
+			itr.Next()
+		}
+	}
+}

db/prefix_db_test.go

@@ -2,7 +2,7 @@ package db
 
 import "testing"
 
-func TestIteratePrefix(t *testing.T) {
+func mockDBWithStuff() DB {
 	db := NewMemDB()
 	// Under "key" prefix
 	db.Set(bz("key"), bz("value"))
@@ -14,10 +14,13 @@ func TestIteratePrefix(t *testing.T) {
 	db.Set(bz("k"), bz("val"))
 	db.Set(bz("ke"), bz("valu"))
 	db.Set(bz("kee"), bz("valuu"))
-	xitr := db.Iterator(nil, nil)
-	xitr.Key()
+	return db
+}
 
+func TestPrefixDBSimple(t *testing.T) {
+	db := mockDBWithStuff()
 	pdb := NewPrefixDB(db, bz("key"))
+
 	checkValue(t, pdb, bz("key"), nil)
 	checkValue(t, pdb, bz(""), bz("value"))
 	checkValue(t, pdb, bz("key1"), nil)
@@ -30,9 +33,14 @@ func TestIteratePrefix(t *testing.T) {
 	checkValue(t, pdb, bz("k"), nil)
 	checkValue(t, pdb, bz("ke"), nil)
 	checkValue(t, pdb, bz("kee"), nil)
+}
+
+func TestPrefixDBIterator1(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
 
 	itr := pdb.Iterator(nil, nil)
-	itr.Key()
+	checkDomain(t, itr, nil, nil)
 	checkItem(t, itr, bz(""), bz("value"))
 	checkNext(t, itr, true)
 	checkItem(t, itr, bz("1"), bz("value1"))
@@ -40,5 +48,100 @@ func TestIteratePrefix(t *testing.T) {
 	checkItem(t, itr, bz("2"), bz("value2"))
 	checkNext(t, itr, true)
 	checkItem(t, itr, bz("3"), bz("value3"))
+	checkNext(t, itr, false)
+	checkInvalid(t, itr)
+	itr.Close()
+}
+
+func TestPrefixDBIterator2(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
+
+	itr := pdb.Iterator(nil, bz(""))
+	checkDomain(t, itr, nil, bz(""))
+	checkInvalid(t, itr)
+	itr.Close()
+}
+
+func TestPrefixDBIterator3(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
+
+	itr := pdb.Iterator(bz(""), nil)
+	checkDomain(t, itr, bz(""), nil)
+	checkItem(t, itr, bz(""), bz("value"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz("1"), bz("value1"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz("2"), bz("value2"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz("3"), bz("value3"))
+	checkNext(t, itr, false)
+	checkInvalid(t, itr)
+	itr.Close()
+}
+
+func TestPrefixDBIterator4(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
+
+	itr := pdb.Iterator(bz(""), bz(""))
+	checkDomain(t, itr, bz(""), bz(""))
+	checkInvalid(t, itr)
+	itr.Close()
+}
+
+func TestPrefixDBReverseIterator1(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
+
+	itr := pdb.ReverseIterator(nil, nil)
+	checkDomain(t, itr, nil, nil)
+	checkItem(t, itr, bz("3"), bz("value3"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz("2"), bz("value2"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz("1"), bz("value1"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz(""), bz("value"))
+	checkNext(t, itr, false)
+	checkInvalid(t, itr)
+	itr.Close()
+}
+
+func TestPrefixDBReverseIterator2(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
+
+	itr := pdb.ReverseIterator(nil, bz(""))
+	checkDomain(t, itr, nil, bz(""))
+	checkItem(t, itr, bz("3"), bz("value3"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz("2"), bz("value2"))
+	checkNext(t, itr, true)
+	checkItem(t, itr, bz("1"), bz("value1"))
+	checkNext(t, itr, false)
+	checkInvalid(t, itr)
+	itr.Close()
+}
+
+func TestPrefixDBReverseIterator3(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
+
+	itr := pdb.ReverseIterator(bz(""), nil)
+	checkDomain(t, itr, bz(""), nil)
+	checkItem(t, itr, bz(""), bz("value"))
+	checkNext(t, itr, false)
+	checkInvalid(t, itr)
+	itr.Close()
+}
+
+func TestPrefixDBReverseIterator4(t *testing.T) {
+	db := mockDBWithStuff()
+	pdb := NewPrefixDB(db, bz("key"))
+
+	itr := pdb.ReverseIterator(bz(""), bz(""))
+	checkInvalid(t, itr)
 	itr.Close()
 }

db/util.go

@@ -33,6 +33,29 @@ func cpIncr(bz []byte) (ret []byte) {
 	return nil
 }
 
+// Returns a slice of the same length (big endian)
+// except decremented by one.
+// Returns nil on underflow (e.g. if bz bytes are all 0x00)
+// CONTRACT: len(bz) > 0
+func cpDecr(bz []byte) (ret []byte) {
+	if len(bz) == 0 {
+		panic("cpDecr expects non-zero bz length")
+	}
+	ret = cp(bz)
+	for i := len(bz) - 1; i >= 0; i-- {
+		if ret[i] > byte(0x00) {
+			ret[i]--
+			return
+		}
+		ret[i] = byte(0xFF)
+		if i == 0 {
+			// Underflow
+			return nil
+		}
+	}
+	return nil
+}
+
 // See DB interface documentation for more information.
 func IsKeyInDomain(key, start, end []byte, isReverse bool) bool {
 	if !isReverse {
@@ -43,7 +66,7 @@ func IsKeyInDomain(key, start, end []byte, isReverse bool) bool {
 			return false
 		}
 		return true
-	}
+	} else {
 		if start != nil && bytes.Compare(start, key) < 0 {
 			return false
 		}
@@ -52,3 +75,4 @@ func IsKeyInDomain(key, start, end []byte, isReverse bool) bool {
 		}
 		return true
 	}
+}

version/version.go

@@ -1,3 +1,3 @@
 package version
 
-const Version = "0.8.1"
+const Version = "0.8.2"