add new fields command to zap cmd-line util

index/scorch/segment/zap/cmd/zap/cmd/fields.go

@@ -0,0 +1,70 @@
+//  Copyright (c) 2017 Couchbase, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 		http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/blevesearch/bleve/index/scorch/segment/zap"
+	"github.com/spf13/cobra"
+)
+
+// fieldsCmd represents the fields command
+var fieldsCmd = &cobra.Command{
+	Use:   "fields [path]",
+	Short: "fields prints the fields in the specified file",
+	Long:  `The fields command lets you print the fields in the specified file.`,
+	RunE: func(cmd *cobra.Command, args []string) error {
+
+		data := segment.Data()
+
+		crcOffset := len(data) - 4
+		verOffset := crcOffset - 4
+		chunkOffset := verOffset - 4
+		fieldsOffset := chunkOffset - 8
+		fieldsIndexOffset := binary.BigEndian.Uint64(data[fieldsOffset : fieldsOffset+8])
+		fieldsIndexEnd := uint64(len(data) - zap.FooterSize)
+
+		// iterate through fields index
+		var fieldID uint64
+		for fieldsIndexOffset+(8*fieldID) < fieldsIndexEnd {
+			addr := binary.BigEndian.Uint64(data[fieldsIndexOffset+(8*fieldID) : fieldsIndexOffset+(8*fieldID)+8])
+			var n uint64
+			indexedLoc, read := binary.Uvarint(data[addr:fieldsIndexEnd])
+			n += uint64(read)
+
+			var dictLoc uint64
+			dictLoc, read = binary.Uvarint(data[addr+n : fieldsIndexEnd])
+			n += uint64(read)
+
+			var nameLen uint64
+			nameLen, read = binary.Uvarint(data[addr+n : fieldsIndexEnd])
+			n += uint64(read)
+
+			name := string(data[addr+n : addr+n+nameLen])
+
+			fmt.Printf("field %d '%s' indexedLoc: %t starts at %d (%x)\n", fieldID, name, indexedLoc == 1, dictLoc, dictLoc)
+
+			fieldID++
+		}
+
+		return nil
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(fieldsCmd)
+}