112 lines
3.3 KiB
Go
112 lines
3.3 KiB
Go
// 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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/*
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Package vellum is a library for building, serializing and executing an FST (finite
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state transducer).
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There are two distinct phases, building an FST and using it.
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When building an FST, you insert keys ([]byte) and their associated value
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(uint64). Insert operations MUST be done in lexicographic order. While
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building the FST, data is streamed to an underlying Writer. At the conclusion
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of building, you MUST call Close() on the builder.
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After completion of the build phase, you can either Open() the FST if you
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serialized it to disk. Alternatively, if you already have the bytes in
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memory, you can use Load(). By default, Open() will use mmap to avoid loading
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the entire file into memory.
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Once the FST is ready, you can use the Contains() method to see if a keys is
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in the FST. You can use the Get() method to see if a key is in the FST and
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retrieve it's associated value. And, you can use the Iterator method to
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enumerate key/value pairs within a specified range.
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*/
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package vellum
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import (
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"errors"
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"io"
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)
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// ErrOutOfOrder is returned when values are not inserted in
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// lexicographic order.
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var ErrOutOfOrder = errors.New("values not inserted in lexicographic order")
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// ErrIteratorDone is returned by Iterator/Next/Seek methods when the
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// Current() value pointed to by the iterator is greater than the last
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// key in this FST, or outside the configured startKeyInclusive/endKeyExclusive
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// range of the Iterator.
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var ErrIteratorDone = errors.New("iterator-done")
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// BuilderOpts is a structure to let advanced users customize the behavior
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// of the builder and some aspects of the generated FST.
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type BuilderOpts struct {
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Encoder int
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RegistryTableSize int
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RegistryMRUSize int
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}
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// New returns a new Builder which will stream out the
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// underlying representation to the provided Writer as the set is built.
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func New(w io.Writer, opts *BuilderOpts) (*Builder, error) {
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return newBuilder(w, opts)
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}
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// Open loads the FST stored in the provided path
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func Open(path string) (*FST, error) {
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return open(path)
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}
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// Load will return the FST represented by the provided byte slice.
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func Load(data []byte) (*FST, error) {
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return new(data, nil)
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}
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// Merge will iterate through the provided Iterators, merge duplicate keys
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// with the provided MergeFunc, and build a new FST to the provided Writer.
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func Merge(w io.Writer, opts *BuilderOpts, itrs []Iterator, f MergeFunc) error {
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builder, err := New(w, opts)
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if err != nil {
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return err
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}
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itr, err := NewMergeIterator(itrs, f)
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for err == nil {
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k, v := itr.Current()
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err = builder.Insert(k, v)
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if err != nil {
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return err
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}
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err = itr.Next()
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}
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if err != nil && err != ErrIteratorDone {
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return err
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}
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err = itr.Close()
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if err != nil {
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return err
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}
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err = builder.Close()
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if err != nil {
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return err
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}
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return nil
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}
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