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55 lines
1.8 KiB
55 lines
1.8 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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// Transducer represents the general contract of a byte-based finite transducer
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type Transducer interface {
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// all transducers are also automatons
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Automaton
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// IsMatchWithValue returns true if and only if the state is a match
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// additionally it returns a states final value (if any)
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IsMatchWithVal(int) (bool, uint64)
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// Accept returns the next state given the input to the specified state
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// additionally it returns the value associated with the transition
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AcceptWithVal(int, byte) (int, uint64)
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}
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// TransducerGet implements an generic Get() method which works
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// on any implementation of Transducer
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// The caller MUST check the boolean return value for a match.
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// Zero is a valid value regardless of match status,
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// and if it is NOT a match, the value collected so far is returned.
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func TransducerGet(t Transducer, k []byte) (bool, uint64) {
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var total uint64
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i := 0
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curr := t.Start()
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for t.CanMatch(curr) && i < len(k) {
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var transVal uint64
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curr, transVal = t.AcceptWithVal(curr, k[i])
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if curr == noneAddr {
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break
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}
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total += transVal
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i++
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}
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if i != len(k) {
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return false, total
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}
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match, finalVal := t.IsMatchWithVal(curr)
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return match, total + finalVal
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}
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