317 lines
7.2 KiB
Go
317 lines
7.2 KiB
Go
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// 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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"bytes"
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"encoding/binary"
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"fmt"
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"strconv"
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)
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func init() {
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registerDecoder(versionV1, func(data []byte) decoder {
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return newDecoderV1(data)
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})
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}
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type decoderV1 struct {
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data []byte
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root uint64
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len uint64
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}
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func newDecoderV1(data []byte) *decoderV1 {
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return &decoderV1{
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data: data,
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}
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}
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func (d *decoderV1) getRoot() int {
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if len(d.data) < footerSizeV1 {
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return noneAddr
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}
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footer := d.data[len(d.data)-footerSizeV1:]
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root := binary.LittleEndian.Uint64(footer[8:])
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return int(root)
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}
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func (d *decoderV1) getLen() int {
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if len(d.data) < footerSizeV1 {
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return 0
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}
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footer := d.data[len(d.data)-footerSizeV1:]
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dlen := binary.LittleEndian.Uint64(footer)
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return int(dlen)
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}
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func (d *decoderV1) stateAt(addr int, prealloc fstState) (fstState, error) {
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state, ok := prealloc.(*fstStateV1)
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if ok && state != nil {
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*state = fstStateV1{} // clear the struct
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} else {
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state = &fstStateV1{}
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}
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err := state.at(d.data, addr)
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if err != nil {
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return nil, err
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}
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return state, nil
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}
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type fstStateV1 struct {
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data []byte
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top int
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bottom int
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numTrans int
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// single trans only
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singleTransChar byte
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singleTransNext bool
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singleTransAddr uint64
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singleTransOut uint64
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// shared
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transSize int
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outSize int
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// multiple trans only
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final bool
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transTop int
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transBottom int
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destTop int
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destBottom int
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outTop int
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outBottom int
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outFinal int
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}
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func (f *fstStateV1) isEncodedSingle() bool {
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if f.data[f.top]>>7 > 0 {
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return true
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}
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return false
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}
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func (f *fstStateV1) at(data []byte, addr int) error {
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f.data = data
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if addr == emptyAddr {
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return f.atZero()
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} else if addr == noneAddr {
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return f.atNone()
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}
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if addr > len(data) || addr < 16 {
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return fmt.Errorf("invalid address %d/%d", addr, len(data))
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}
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f.top = addr
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f.bottom = addr
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if f.isEncodedSingle() {
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return f.atSingle(data, addr)
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}
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return f.atMulti(data, addr)
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}
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func (f *fstStateV1) atZero() error {
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f.top = 0
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f.bottom = 1
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f.numTrans = 0
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f.final = true
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f.outFinal = 0
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return nil
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}
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func (f *fstStateV1) atNone() error {
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f.top = 0
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f.bottom = 1
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f.numTrans = 0
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f.final = false
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f.outFinal = 0
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return nil
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}
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func (f *fstStateV1) atSingle(data []byte, addr int) error {
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// handle single transition case
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f.numTrans = 1
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f.singleTransNext = data[f.top]&transitionNext > 0
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f.singleTransChar = data[f.top] & maxCommon
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if f.singleTransChar == 0 {
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f.bottom-- // extra byte for uncommon
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f.singleTransChar = data[f.bottom]
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} else {
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f.singleTransChar = decodeCommon(f.singleTransChar)
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}
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if f.singleTransNext {
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// now we know the bottom, can compute next addr
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f.singleTransAddr = uint64(f.bottom - 1)
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f.singleTransOut = 0
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} else {
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f.bottom-- // extra byte with pack sizes
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f.transSize, f.outSize = decodePackSize(data[f.bottom])
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f.bottom -= f.transSize // exactly one trans
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f.singleTransAddr = readPackedUint(data[f.bottom : f.bottom+f.transSize])
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if f.outSize > 0 {
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f.bottom -= f.outSize // exactly one out (could be length 0 though)
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f.singleTransOut = readPackedUint(data[f.bottom : f.bottom+f.outSize])
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} else {
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f.singleTransOut = 0
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}
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// need to wait till we know bottom
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if f.singleTransAddr != 0 {
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f.singleTransAddr = uint64(f.bottom) - f.singleTransAddr
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}
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}
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return nil
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}
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func (f *fstStateV1) atMulti(data []byte, addr int) error {
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// handle multiple transitions case
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f.final = data[f.top]&stateFinal > 0
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f.numTrans = int(data[f.top] & maxNumTrans)
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if f.numTrans == 0 {
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f.bottom-- // extra byte for number of trans
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f.numTrans = int(data[f.bottom])
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if f.numTrans == 1 {
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// can't really be 1 here, this is special case that means 256
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f.numTrans = 256
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}
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}
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f.bottom-- // extra byte with pack sizes
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f.transSize, f.outSize = decodePackSize(data[f.bottom])
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f.transTop = f.bottom
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f.bottom -= f.numTrans // one byte for each transition
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f.transBottom = f.bottom
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f.destTop = f.bottom
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f.bottom -= f.numTrans * f.transSize
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f.destBottom = f.bottom
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if f.outSize > 0 {
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f.outTop = f.bottom
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f.bottom -= f.numTrans * f.outSize
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f.outBottom = f.bottom
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if f.final {
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f.bottom -= f.outSize
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f.outFinal = f.bottom
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}
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}
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return nil
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}
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func (f *fstStateV1) Address() int {
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return f.top
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}
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func (f *fstStateV1) Final() bool {
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return f.final
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}
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func (f *fstStateV1) FinalOutput() uint64 {
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if f.numTrans > 0 && f.final && f.outSize > 0 {
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return readPackedUint(f.data[f.outFinal : f.outFinal+f.outSize])
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}
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return 0
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}
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func (f *fstStateV1) NumTransitions() int {
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return f.numTrans
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}
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func (f *fstStateV1) TransitionAt(i int) byte {
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if f.isEncodedSingle() {
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return f.singleTransChar
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}
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transitionKeys := f.data[f.transBottom:f.transTop]
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return transitionKeys[f.numTrans-i-1]
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}
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func (f *fstStateV1) TransitionFor(b byte) (int, int, uint64) {
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if f.isEncodedSingle() {
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if f.singleTransChar == b {
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return 0, int(f.singleTransAddr), f.singleTransOut
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}
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return -1, noneAddr, 0
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}
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transitionKeys := f.data[f.transBottom:f.transTop]
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pos := bytes.IndexByte(transitionKeys, b)
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if pos < 0 {
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return -1, noneAddr, 0
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}
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transDests := f.data[f.destBottom:f.destTop]
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dest := int(readPackedUint(transDests[pos*f.transSize : pos*f.transSize+f.transSize]))
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if dest > 0 {
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// convert delta
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dest = f.bottom - dest
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}
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transVals := f.data[f.outBottom:f.outTop]
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var out uint64
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if f.outSize > 0 {
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out = readPackedUint(transVals[pos*f.outSize : pos*f.outSize+f.outSize])
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}
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return f.numTrans - pos - 1, dest, out
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}
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func (f *fstStateV1) String() string {
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rv := ""
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rv += fmt.Sprintf("State: %d (%#x)", f.top, f.top)
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if f.final {
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rv += " final"
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fout := f.FinalOutput()
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if fout != 0 {
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rv += fmt.Sprintf(" (%d)", fout)
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}
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}
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rv += "\n"
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rv += fmt.Sprintf("Data: % x\n", f.data[f.bottom:f.top+1])
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for i := 0; i < f.numTrans; i++ {
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transChar := f.TransitionAt(i)
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_, transDest, transOut := f.TransitionFor(transChar)
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rv += fmt.Sprintf(" - %d (%#x) '%s' ---> %d (%#x) with output: %d", transChar, transChar, string(transChar), transDest, transDest, transOut)
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rv += "\n"
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}
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if f.numTrans == 0 {
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rv += "\n"
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}
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return rv
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}
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func (f *fstStateV1) DotString(num int) string {
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rv := ""
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label := fmt.Sprintf("%d", num)
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final := ""
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if f.final {
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final = ",peripheries=2"
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}
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rv += fmt.Sprintf(" %d [label=\"%s\"%s];\n", f.top, label, final)
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for i := 0; i < f.numTrans; i++ {
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transChar := f.TransitionAt(i)
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_, transDest, transOut := f.TransitionFor(transChar)
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out := ""
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if transOut != 0 {
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out = fmt.Sprintf("/%d", transOut)
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}
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rv += fmt.Sprintf(" %d -> %d [label=\"%s%s\"];\n", f.top, transDest, escapeInput(transChar), out)
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}
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return rv
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}
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func escapeInput(b byte) string {
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x := strconv.AppendQuoteRune(nil, rune(b))
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return string(x[1:(len(x) - 1)])
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}
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