CacheDB (#67)

* Add CacheDB & SimpleMap
* Generic memBatch; Fix cLevelDB tests
* CacheWrap() for CacheDB and MemDB
* Change Iterator to match LeviGo Iterator
* Fixes from review
* cacheWrapWriteMutex and some race fixes
* Use tmlibs/common
* NewCWWMutex is exposed.  DB can be CacheWrap'd
* Remove GetOK, not needed
* Fsdb (#72)
* Add FSDB
* Review fixes from Anton
* Review changes
* Fixes from review

db/common_test.go

@@ -0,0 +1,172 @@
+package db
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	cmn "github.com/tendermint/tmlibs/common"
+)
+
+func checkValid(t *testing.T, itr Iterator, expected bool) {
+	valid := itr.Valid()
+	assert.Equal(t, expected, valid)
+}
+
+func checkNext(t *testing.T, itr Iterator, expected bool) {
+	itr.Next()
+	valid := itr.Valid()
+	assert.Equal(t, expected, valid)
+}
+
+func checkNextPanics(t *testing.T, itr Iterator) {
+	assert.Panics(t, func() { itr.Next() }, "checkNextPanics expected panic but didn't")
+}
+
+func checkPrevPanics(t *testing.T, itr Iterator) {
+	assert.Panics(t, func() { itr.Prev() }, "checkPrevPanics expected panic but didn't")
+}
+
+func checkPrev(t *testing.T, itr Iterator, expected bool) {
+	itr.Prev()
+	valid := itr.Valid()
+	assert.Equal(t, expected, valid)
+}
+
+func checkItem(t *testing.T, itr Iterator, key []byte, value []byte) {
+	k, v := itr.Key(), itr.Value()
+	assert.Exactly(t, key, k)
+	assert.Exactly(t, value, v)
+}
+
+func checkInvalid(t *testing.T, itr Iterator) {
+	checkValid(t, itr, false)
+	checkKeyPanics(t, itr)
+	checkValuePanics(t, itr)
+	checkNextPanics(t, itr)
+	checkPrevPanics(t, itr)
+}
+
+func checkKeyPanics(t *testing.T, itr Iterator) {
+	assert.Panics(t, func() { itr.Key() }, "checkKeyPanics expected panic but didn't")
+}
+
+func checkValuePanics(t *testing.T, itr Iterator) {
+	assert.Panics(t, func() { itr.Key() }, "checkValuePanics expected panic but didn't")
+}
+
+func newTempDB(t *testing.T, backend string) (db DB) {
+	dir, dirname := cmn.Tempdir("test_go_iterator")
+	db = NewDB("testdb", backend, dirname)
+	dir.Close()
+	return db
+}
+
+func TestDBIteratorSingleKey(t *testing.T) {
+	for backend, _ := range backends {
+		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
+			db := newTempDB(t, backend)
+			db.SetSync(bz("1"), bz("value_1"))
+			itr := db.Iterator()
+
+			checkValid(t, itr, true)
+			checkNext(t, itr, false)
+			checkValid(t, itr, false)
+			checkNextPanics(t, itr)
+
+			// Once invalid...
+			checkInvalid(t, itr)
+		})
+	}
+}
+
+func TestDBIteratorTwoKeys(t *testing.T) {
+	for backend, _ := range backends {
+		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
+			db := newTempDB(t, backend)
+			db.SetSync(bz("1"), bz("value_1"))
+			db.SetSync(bz("2"), bz("value_1"))
+
+			{ // Fail by calling Next too much
+				itr := db.Iterator()
+				checkValid(t, itr, true)
+
+				for i := 0; i < 10; i++ {
+					checkNext(t, itr, true)
+					checkValid(t, itr, true)
+
+					checkPrev(t, itr, true)
+					checkValid(t, itr, true)
+				}
+
+				checkNext(t, itr, true)
+				checkValid(t, itr, true)
+
+				checkNext(t, itr, false)
+				checkValid(t, itr, false)
+
+				checkNextPanics(t, itr)
+
+				// Once invalid...
+				checkInvalid(t, itr)
+			}
+
+			{ // Fail by calling Prev too much
+				itr := db.Iterator()
+				checkValid(t, itr, true)
+
+				for i := 0; i < 10; i++ {
+					checkNext(t, itr, true)
+					checkValid(t, itr, true)
+
+					checkPrev(t, itr, true)
+					checkValid(t, itr, true)
+				}
+
+				checkPrev(t, itr, false)
+				checkValid(t, itr, false)
+
+				checkPrevPanics(t, itr)
+
+				// Once invalid...
+				checkInvalid(t, itr)
+			}
+		})
+	}
+}
+
+func TestDBIteratorEmpty(t *testing.T) {
+	for backend, _ := range backends {
+		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
+			db := newTempDB(t, backend)
+			itr := db.Iterator()
+
+			checkInvalid(t, itr)
+		})
+	}
+}
+
+func TestDBIteratorEmptySeek(t *testing.T) {
+	for backend, _ := range backends {
+		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
+			db := newTempDB(t, backend)
+			itr := db.Iterator()
+			itr.Seek(bz("1"))
+
+			checkInvalid(t, itr)
+		})
+	}
+}
+
+func TestDBIteratorBadSeek(t *testing.T) {
+	for backend, _ := range backends {
+		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
+			db := newTempDB(t, backend)
+			db.SetSync(bz("1"), bz("value_1"))
+			itr := db.Iterator()
+			itr.Seek(bz("2"))
+
+			checkInvalid(t, itr)
+		})
+	}
+}