88 lines
2.3 KiB
Go
88 lines
2.3 KiB
Go
// 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 vellum
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"fmt"
|
|
"io"
|
|
)
|
|
|
|
const headerSize = 16
|
|
|
|
type encoderConstructor func(w io.Writer) encoder
|
|
type decoderConstructor func([]byte) decoder
|
|
|
|
var encoders = map[int]encoderConstructor{}
|
|
var decoders = map[int]decoderConstructor{}
|
|
|
|
type encoder interface {
|
|
start() error
|
|
encodeState(s *builderNode, addr int) (int, error)
|
|
finish(count, rootAddr int) error
|
|
reset(w io.Writer)
|
|
}
|
|
|
|
func loadEncoder(ver int, w io.Writer) (encoder, error) {
|
|
if cons, ok := encoders[ver]; ok {
|
|
return cons(w), nil
|
|
}
|
|
return nil, fmt.Errorf("no encoder for version %d registered", ver)
|
|
}
|
|
|
|
func registerEncoder(ver int, cons encoderConstructor) {
|
|
encoders[ver] = cons
|
|
}
|
|
|
|
type decoder interface {
|
|
getRoot() int
|
|
getLen() int
|
|
stateAt(addr int, prealloc fstState) (fstState, error)
|
|
}
|
|
|
|
func loadDecoder(ver int, data []byte) (decoder, error) {
|
|
if cons, ok := decoders[ver]; ok {
|
|
return cons(data), nil
|
|
}
|
|
return nil, fmt.Errorf("no decoder for version %d registered", ver)
|
|
}
|
|
|
|
func registerDecoder(ver int, cons decoderConstructor) {
|
|
decoders[ver] = cons
|
|
}
|
|
|
|
func decodeHeader(header []byte) (ver int, typ int, err error) {
|
|
if len(header) < headerSize {
|
|
err = fmt.Errorf("invalid header < 16 bytes")
|
|
return
|
|
}
|
|
ver = int(binary.LittleEndian.Uint64(header[0:8]))
|
|
typ = int(binary.LittleEndian.Uint64(header[8:16]))
|
|
return
|
|
}
|
|
|
|
// fstState represents a state inside the FTS runtime
|
|
// It is the main contract between the FST impl and the decoder
|
|
// The FST impl should work only with this interface, while only the decoder
|
|
// impl knows the physical representation.
|
|
type fstState interface {
|
|
Address() int
|
|
Final() bool
|
|
FinalOutput() uint64
|
|
NumTransitions() int
|
|
TransitionFor(b byte) (int, int, uint64)
|
|
TransitionAt(i int) byte
|
|
}
|