1// Copyright (c) 2017 Couchbase, Inc. 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14 15package vellum 16 17// Transducer represents the general contract of a byte-based finite transducer 18type Transducer interface { 19 20 // all transducers are also automatons 21 Automaton 22 23 // IsMatchWithValue returns true if and only if the state is a match 24 // additionally it returns a states final value (if any) 25 IsMatchWithVal(int) (bool, uint64) 26 27 // Accept returns the next state given the input to the specified state 28 // additionally it returns the value associated with the transition 29 AcceptWithVal(int, byte) (int, uint64) 30} 31 32// TransducerGet implements an generic Get() method which works 33// on any implementation of Transducer 34// The caller MUST check the boolean return value for a match. 35// Zero is a valid value regardless of match status, 36// and if it is NOT a match, the value collected so far is returned. 37func TransducerGet(t Transducer, k []byte) (bool, uint64) { 38 var total uint64 39 i := 0 40 curr := t.Start() 41 for t.CanMatch(curr) && i < len(k) { 42 var transVal uint64 43 curr, transVal = t.AcceptWithVal(curr, k[i]) 44 if curr == noneAddr { 45 break 46 } 47 total += transVal 48 i++ 49 } 50 if i != len(k) { 51 return false, total 52 } 53 match, finalVal := t.IsMatchWithVal(curr) 54 return match, total + finalVal 55} 56