Платформа ЦРНП "Мирокод" для разработки проектов
https://git.mirocod.ru
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87 lines
2.3 KiB
87 lines
2.3 KiB
// Copyright (c) 2017 Couchbase, Inc. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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package vellum |
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import ( |
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"encoding/binary" |
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"fmt" |
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"io" |
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) |
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const headerSize = 16 |
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type encoderConstructor func(w io.Writer) encoder |
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type decoderConstructor func([]byte) decoder |
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var encoders = map[int]encoderConstructor{} |
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var decoders = map[int]decoderConstructor{} |
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type encoder interface { |
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start() error |
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encodeState(s *builderNode, addr int) (int, error) |
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finish(count, rootAddr int) error |
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reset(w io.Writer) |
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} |
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func loadEncoder(ver int, w io.Writer) (encoder, error) { |
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if cons, ok := encoders[ver]; ok { |
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return cons(w), nil |
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} |
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return nil, fmt.Errorf("no encoder for version %d registered", ver) |
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} |
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func registerEncoder(ver int, cons encoderConstructor) { |
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encoders[ver] = cons |
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} |
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type decoder interface { |
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getRoot() int |
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getLen() int |
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stateAt(addr int, prealloc fstState) (fstState, error) |
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} |
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func loadDecoder(ver int, data []byte) (decoder, error) { |
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if cons, ok := decoders[ver]; ok { |
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return cons(data), nil |
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} |
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return nil, fmt.Errorf("no decoder for version %d registered", ver) |
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} |
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func registerDecoder(ver int, cons decoderConstructor) { |
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decoders[ver] = cons |
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} |
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func decodeHeader(header []byte) (ver int, typ int, err error) { |
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if len(header) < headerSize { |
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err = fmt.Errorf("invalid header < 16 bytes") |
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return |
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} |
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ver = int(binary.LittleEndian.Uint64(header[0:8])) |
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typ = int(binary.LittleEndian.Uint64(header[8:16])) |
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return |
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} |
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// fstState represents a state inside the FTS runtime |
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// It is the main contract between the FST impl and the decoder |
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// The FST impl should work only with this interface, while only the decoder |
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// impl knows the physical representation. |
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type fstState interface { |
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Address() int |
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Final() bool |
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FinalOutput() uint64 |
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NumTransitions() int |
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TransitionFor(b byte) (int, int, uint64) |
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TransitionAt(i int) byte |
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}
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