Merge pull request #767 from cosmos/sunny/IAVLsubspace

KVStore Subspaces

types/store.go

@@ -111,6 +111,14 @@ type KVStore interface {
 	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
 	ReverseIterator(start, end []byte) Iterator
 
+	// Iterator over all the keys with a certain prefix in ascending order.
+	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
+	SubspaceIterator(prefix []byte) Iterator
+
+	// Iterator over all the keys with a certain prefix in descending order.
+	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
+	ReverseSubspaceIterator(prefix []byte) Iterator
+
 	// TODO Not yet implemented.
 	// CreateSubKVStore(key *storeKey) (KVStore, error)
 
@@ -222,3 +230,29 @@ func (key *KVStoreKey) Name() string {
 func (key *KVStoreKey) String() string {
 	return fmt.Sprintf("KVStoreKey{%p, %s}", key, key.name)
 }
+
+// PrefixEndBytes returns the []byte that would end a
+// range query for all []byte with a certain prefix
+// Deals with last byte of prefix being FF without overflowing
+func PrefixEndBytes(prefix []byte) []byte {
+	if prefix == nil {
+		return nil
+	}
+
+	end := make([]byte, len(prefix))
+	copy(end, prefix)
+
+	for {
+		if end[len(end)-1] != byte(255) {
+			end[len(end)-1]++
+			break
+		} else {
+			end = end[:len(end)-1]
+			if len(end) == 0 {
+				end = nil
+				break
+			}
+		}
+	}
+	return end
+}

types/store_test.go

@@ -0,0 +1,29 @@
+package types
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPrefixEndBytes(t *testing.T) {
+	assert := assert.New(t)
+
+	var testCases = []struct {
+		prefix   []byte
+		expected []byte
+	}{
+		{[]byte{byte(55), byte(255), byte(255), byte(0)}, []byte{byte(55), byte(255), byte(255), byte(1)}},
+		{[]byte{byte(55), byte(255), byte(255), byte(15)}, []byte{byte(55), byte(255), byte(255), byte(16)}},
+		{[]byte{byte(55), byte(200), byte(255)}, []byte{byte(55), byte(201)}},
+		{[]byte{byte(55), byte(255), byte(255)}, []byte{byte(56)}},
+		{[]byte{byte(255), byte(255), byte(255)}, nil},
+		{[]byte{byte(255)}, nil},
+		{nil, nil},
+	}
+
+	for _, test := range testCases {
+		end := PrefixEndBytes(test.prefix)
+		assert.Equal(test.expected, end)
+	}
+}