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bits.go
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bits.go
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package rlepluslazy
import (
"errors"
"sort"
)
var ErrEndOfIterator = errors.New("end of iterator")
type it2b struct {
source RunIterator
curIdx uint64
run Run
}
func (it *it2b) HasNext() bool {
return it.run.Valid()
}
func (it *it2b) Next() (uint64, error) {
it.run.Len--
res := it.curIdx
it.curIdx++
return res, it.prep()
}
func (it *it2b) Nth(n uint64) (uint64, error) {
skip := n + 1
for it.run.Len < skip {
if !it.HasNext() {
return 0, ErrEndOfIterator
}
skip -= it.run.Len
it.curIdx += it.run.Len
it.run.Len = 0
if err := it.prep(); err != nil {
return 0, err
}
}
it.run.Len -= skip
it.curIdx += skip
res := it.curIdx - 1
return res, it.prep()
}
func (it *it2b) prep() error {
for !it.run.Valid() && it.source.HasNext() {
var err error
it.run, err = it.source.NextRun()
if err != nil {
return err
}
if !it.run.Val {
it.curIdx += it.run.Len
it.run.Len = 0
}
}
return nil
}
func BitsFromRuns(source RunIterator) (BitIterator, error) {
it := &it2b{source: source}
if err := it.prep(); err != nil {
return nil, err
}
return it, nil
}
type sliceIt struct {
s []uint64
}
func (it sliceIt) HasNext() bool {
return len(it.s) != 0
}
func (it *sliceIt) Next() (uint64, error) {
if len(it.s) == 0 {
return 0, ErrEndOfIterator
}
res := it.s[0]
it.s = it.s[1:]
return res, nil
}
func (it *sliceIt) Nth(n uint64) (uint64, error) {
if uint64(len(it.s)) <= n {
it.s = nil
return 0, ErrEndOfIterator
}
res := it.s[n]
it.s = it.s[n+1:]
return res, nil
}
func BitsFromSlice(slice []uint64) BitIterator {
sort.Slice(slice, func(i, j int) bool { return slice[i] < slice[j] })
return &sliceIt{slice}
}
type it2r struct {
source BitIterator
runIdx uint64
run [2]Run
}
func (it *it2r) HasNext() bool {
return it.run[0].Valid()
}
func (it *it2r) NextRun() (Run, error) {
res := it.run[0]
it.runIdx = it.runIdx + res.Len
it.run[0], it.run[1] = it.run[1], Run{}
return res, it.prep()
}
func (it *it2r) prep() error {
if !it.HasNext() {
return nil
}
if !it.run[0].Val {
it.run[1].Val = true
it.run[1].Len = 1
return nil
}
for it.source.HasNext() && !it.run[1].Valid() {
nB, err := it.source.Next()
if err != nil {
return err
}
//fmt.Printf("runIdx: %d, run[0].Len: %d, nB: %d\n", it.runIdx, it.run[0].Len, nB)
if it.runIdx+it.run[0].Len == nB {
it.run[0].Len++
} else {
it.run[1].Len = nB - it.runIdx - it.run[0].Len
it.run[1].Val = false
}
}
return nil
}
func (it *it2r) init() error {
if it.source.HasNext() {
nB, err := it.source.Next()
if err != nil {
return err
}
it.run[0].Len = nB
it.run[0].Val = false
it.run[1].Len = 1
it.run[1].Val = true
}
if !it.run[0].Valid() {
it.run[0], it.run[1] = it.run[1], Run{}
return it.prep()
}
return nil
}
func SliceFromRuns(source RunIterator) ([]uint64, error) {
rit, err := BitsFromRuns(source)
if err != nil {
return nil, err
}
res := make([]uint64, 0)
for rit.HasNext() {
bit, err := rit.Next()
if err != nil {
return nil, err
}
res = append(res, bit)
}
return res, nil
}
func RunsFromBits(source BitIterator) (RunIterator, error) {
it := &it2r{source: source}
if err := it.init(); err != nil {
return nil, err
}
return it, nil
}
func RunsFromSlice(slice []uint64) (RunIterator, error) {
return RunsFromBits(BitsFromSlice(slice))
}