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gitea/vendor/github.com/couchbase/vellum/decoder_v1.go

316 lines
7.2 KiB

// Copyright (c) 2017 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package vellum
import (
"bytes"
"encoding/binary"
"fmt"
"strconv"
)
func init() {
registerDecoder(versionV1, func(data []byte) decoder {
return newDecoderV1(data)
})
}
type decoderV1 struct {
data []byte
root uint64
len uint64
}
func newDecoderV1(data []byte) *decoderV1 {
return &decoderV1{
data: data,
}
}
func (d *decoderV1) getRoot() int {
if len(d.data) < footerSizeV1 {
return noneAddr
}
footer := d.data[len(d.data)-footerSizeV1:]
root := binary.LittleEndian.Uint64(footer[8:])
return int(root)
}
func (d *decoderV1) getLen() int {
if len(d.data) < footerSizeV1 {
return 0
}
footer := d.data[len(d.data)-footerSizeV1:]
dlen := binary.LittleEndian.Uint64(footer)
return int(dlen)
}
func (d *decoderV1) stateAt(addr int, prealloc fstState) (fstState, error) {
state, ok := prealloc.(*fstStateV1)
if ok && state != nil {
*state = fstStateV1{} // clear the struct
} else {
state = &fstStateV1{}
}
err := state.at(d.data, addr)
if err != nil {
return nil, err
}
return state, nil
}
type fstStateV1 struct {
data []byte
top int
bottom int
numTrans int
// single trans only
singleTransChar byte
singleTransNext bool
singleTransAddr uint64
singleTransOut uint64
// shared
transSize int
outSize int
// multiple trans only
final bool
transTop int
transBottom int
destTop int
destBottom int
outTop int
outBottom int
outFinal int
}
func (f *fstStateV1) isEncodedSingle() bool {
if f.data[f.top]>>7 > 0 {
return true
}
return false
}
func (f *fstStateV1) at(data []byte, addr int) error {
f.data = data
if addr == emptyAddr {
return f.atZero()
} else if addr == noneAddr {
return f.atNone()
}
if addr > len(data) || addr < 16 {
return fmt.Errorf("invalid address %d/%d", addr, len(data))
}
f.top = addr
f.bottom = addr
if f.isEncodedSingle() {
return f.atSingle(data, addr)
}
return f.atMulti(data, addr)
}
func (f *fstStateV1) atZero() error {
f.top = 0
f.bottom = 1
f.numTrans = 0
f.final = true
f.outFinal = 0
return nil
}
func (f *fstStateV1) atNone() error {
f.top = 0
f.bottom = 1
f.numTrans = 0
f.final = false
f.outFinal = 0
return nil
}
func (f *fstStateV1) atSingle(data []byte, addr int) error {
// handle single transition case
f.numTrans = 1
f.singleTransNext = data[f.top]&transitionNext > 0
f.singleTransChar = data[f.top] & maxCommon
if f.singleTransChar == 0 {
f.bottom-- // extra byte for uncommon
f.singleTransChar = data[f.bottom]
} else {
f.singleTransChar = decodeCommon(f.singleTransChar)
}
if f.singleTransNext {
// now we know the bottom, can compute next addr
f.singleTransAddr = uint64(f.bottom - 1)
f.singleTransOut = 0
} else {
f.bottom-- // extra byte with pack sizes
f.transSize, f.outSize = decodePackSize(data[f.bottom])
f.bottom -= f.transSize // exactly one trans
f.singleTransAddr = readPackedUint(data[f.bottom : f.bottom+f.transSize])
if f.outSize > 0 {
f.bottom -= f.outSize // exactly one out (could be length 0 though)
f.singleTransOut = readPackedUint(data[f.bottom : f.bottom+f.outSize])
} else {
f.singleTransOut = 0
}
// need to wait till we know bottom
if f.singleTransAddr != 0 {
f.singleTransAddr = uint64(f.bottom) - f.singleTransAddr
}
}
return nil
}
func (f *fstStateV1) atMulti(data []byte, addr int) error {
// handle multiple transitions case
f.final = data[f.top]&stateFinal > 0
f.numTrans = int(data[f.top] & maxNumTrans)
if f.numTrans == 0 {
f.bottom-- // extra byte for number of trans
f.numTrans = int(data[f.bottom])
if f.numTrans == 1 {
// can't really be 1 here, this is special case that means 256
f.numTrans = 256
}
}
f.bottom-- // extra byte with pack sizes
f.transSize, f.outSize = decodePackSize(data[f.bottom])
f.transTop = f.bottom
f.bottom -= f.numTrans // one byte for each transition
f.transBottom = f.bottom
f.destTop = f.bottom
f.bottom -= f.numTrans * f.transSize
f.destBottom = f.bottom
if f.outSize > 0 {
f.outTop = f.bottom
f.bottom -= f.numTrans * f.outSize
f.outBottom = f.bottom
if f.final {
f.bottom -= f.outSize
f.outFinal = f.bottom
}
}
return nil
}
func (f *fstStateV1) Address() int {
return f.top
}
func (f *fstStateV1) Final() bool {
return f.final
}
func (f *fstStateV1) FinalOutput() uint64 {
if f.numTrans > 0 && f.final && f.outSize > 0 {
return readPackedUint(f.data[f.outFinal : f.outFinal+f.outSize])
}
return 0
}
func (f *fstStateV1) NumTransitions() int {
return f.numTrans
}
func (f *fstStateV1) TransitionAt(i int) byte {
if f.isEncodedSingle() {
return f.singleTransChar
}
transitionKeys := f.data[f.transBottom:f.transTop]
return transitionKeys[f.numTrans-i-1]
}
func (f *fstStateV1) TransitionFor(b byte) (int, int, uint64) {
if f.isEncodedSingle() {
if f.singleTransChar == b {
return 0, int(f.singleTransAddr), f.singleTransOut
}
return -1, noneAddr, 0
}
transitionKeys := f.data[f.transBottom:f.transTop]
pos := bytes.IndexByte(transitionKeys, b)
if pos < 0 {
return -1, noneAddr, 0
}
transDests := f.data[f.destBottom:f.destTop]
dest := int(readPackedUint(transDests[pos*f.transSize : pos*f.transSize+f.transSize]))
if dest > 0 {
// convert delta
dest = f.bottom - dest
}
transVals := f.data[f.outBottom:f.outTop]
var out uint64
if f.outSize > 0 {
out = readPackedUint(transVals[pos*f.outSize : pos*f.outSize+f.outSize])
}
return f.numTrans - pos - 1, dest, out
}
func (f *fstStateV1) String() string {
rv := ""
rv += fmt.Sprintf("State: %d (%#x)", f.top, f.top)
if f.final {
rv += " final"
fout := f.FinalOutput()
if fout != 0 {
rv += fmt.Sprintf(" (%d)", fout)
}
}
rv += "\n"
rv += fmt.Sprintf("Data: % x\n", f.data[f.bottom:f.top+1])
for i := 0; i < f.numTrans; i++ {
transChar := f.TransitionAt(i)
_, transDest, transOut := f.TransitionFor(transChar)
rv += fmt.Sprintf(" - %d (%#x) '%s' ---> %d (%#x) with output: %d", transChar, transChar, string(transChar), transDest, transDest, transOut)
rv += "\n"
}
if f.numTrans == 0 {
rv += "\n"
}
return rv
}
func (f *fstStateV1) DotString(num int) string {
rv := ""
label := fmt.Sprintf("%d", num)
final := ""
if f.final {
final = ",peripheries=2"
}
rv += fmt.Sprintf(" %d [label=\"%s\"%s];\n", f.top, label, final)
for i := 0; i < f.numTrans; i++ {
transChar := f.TransitionAt(i)
_, transDest, transOut := f.TransitionFor(transChar)
out := ""
if transOut != 0 {
out = fmt.Sprintf("/%d", transOut)
}
rv += fmt.Sprintf(" %d -> %d [label=\"%s%s\"];\n", f.top, transDest, escapeInput(transChar), out)
}
return rv
}
func escapeInput(b byte) string {
x := strconv.AppendQuoteRune(nil, rune(b))
return string(x[1:(len(x) - 1)])
}