+++ /dev/null
-// Copyright 2014 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package intsets provides Sparse, a compact and fast representation
-// for sparse sets of int values.
-//
-// The time complexity of the operations Len, Insert, Remove and Has
-// is in O(n) but in practice those methods are faster and more
-// space-efficient than equivalent operations on sets based on the Go
-// map type. The IsEmpty, Min, Max, Clear and TakeMin operations
-// require constant time.
-//
-package intsets // import "golang.org/x/tools/container/intsets"
-
-// TODO(adonovan):
-// - Add InsertAll(...int), RemoveAll(...int)
-// - Add 'bool changed' results for {Intersection,Difference}With too.
-//
-// TODO(adonovan): implement Dense, a dense bit vector with a similar API.
-// The space usage would be proportional to Max(), not Len(), and the
-// implementation would be based upon big.Int.
-//
-// TODO(adonovan): opt: make UnionWith and Difference faster.
-// These are the hot-spots for go/pointer.
-
-import (
- "bytes"
- "fmt"
-)
-
-// A Sparse is a set of int values.
-// Sparse operations (even queries) are not concurrency-safe.
-//
-// The zero value for Sparse is a valid empty set.
-//
-// Sparse sets must be copied using the Copy method, not by assigning
-// a Sparse value.
-//
-type Sparse struct {
- // An uninitialized Sparse represents an empty set.
- // An empty set may also be represented by
- // root.next == root.prev == &root.
- //
- // The root is always the block with the smallest offset.
- // It can be empty, but only if it is the only block; in that case, offset is
- // MaxInt (which is not a valid offset).
- root block
-}
-
-type word uintptr
-
-const (
- _m = ^word(0)
- bitsPerWord = 8 << (_m>>8&1 + _m>>16&1 + _m>>32&1)
- bitsPerBlock = 256 // optimal value for go/pointer solver performance
- wordsPerBlock = bitsPerBlock / bitsPerWord
-)
-
-// Limit values of implementation-specific int type.
-const (
- MaxInt = int(^uint(0) >> 1)
- MinInt = -MaxInt - 1
-)
-
-// -- block ------------------------------------------------------------
-
-// A set is represented as a circular doubly-linked list of blocks,
-// each containing an offset and a bit array of fixed size
-// bitsPerBlock; the blocks are ordered by increasing offset.
-//
-// The set contains an element x iff the block whose offset is x - (x
-// mod bitsPerBlock) has the bit (x mod bitsPerBlock) set, where mod
-// is the Euclidean remainder.
-//
-// A block may only be empty transiently.
-//
-type block struct {
- offset int // offset mod bitsPerBlock == 0
- bits [wordsPerBlock]word // contains at least one set bit
- next, prev *block // doubly-linked list of blocks
-}
-
-// wordMask returns the word index (in block.bits)
-// and single-bit mask for the block's ith bit.
-func wordMask(i uint) (w uint, mask word) {
- w = i / bitsPerWord
- mask = 1 << (i % bitsPerWord)
- return
-}
-
-// insert sets the block b's ith bit and
-// returns true if it was not already set.
-//
-func (b *block) insert(i uint) bool {
- w, mask := wordMask(i)
- if b.bits[w]&mask == 0 {
- b.bits[w] |= mask
- return true
- }
- return false
-}
-
-// remove clears the block's ith bit and
-// returns true if the bit was previously set.
-// NB: may leave the block empty.
-//
-func (b *block) remove(i uint) bool {
- w, mask := wordMask(i)
- if b.bits[w]&mask != 0 {
- b.bits[w] &^= mask
- return true
- }
- return false
-}
-
-// has reports whether the block's ith bit is set.
-func (b *block) has(i uint) bool {
- w, mask := wordMask(i)
- return b.bits[w]&mask != 0
-}
-
-// empty reports whether b.len()==0, but more efficiently.
-func (b *block) empty() bool {
- for _, w := range b.bits {
- if w != 0 {
- return false
- }
- }
- return true
-}
-
-// len returns the number of set bits in block b.
-func (b *block) len() int {
- var l int
- for _, w := range b.bits {
- l += popcount(w)
- }
- return l
-}
-
-// max returns the maximum element of the block.
-// The block must not be empty.
-func (b *block) max() int {
- bi := b.offset + bitsPerBlock
- // Decrement bi by number of high zeros in last.bits.
- for i := len(b.bits) - 1; i >= 0; i-- {
- if w := b.bits[i]; w != 0 {
- return bi - nlz(w) - 1
- }
- bi -= bitsPerWord
- }
- panic("BUG: empty block")
-}
-
-// min returns the minimum element of the block,
-// and also removes it if take is set.
-// The block must not be initially empty.
-// NB: may leave the block empty.
-func (b *block) min(take bool) int {
- for i, w := range b.bits {
- if w != 0 {
- tz := ntz(w)
- if take {
- b.bits[i] = w &^ (1 << uint(tz))
- }
- return b.offset + int(i*bitsPerWord) + tz
- }
- }
- panic("BUG: empty block")
-}
-
-// lowerBound returns the smallest element of the block that is greater than or
-// equal to the element corresponding to the ith bit. If there is no such
-// element, the second return value is false.
-func (b *block) lowerBound(i uint) (int, bool) {
- w := i / bitsPerWord
- bit := i % bitsPerWord
-
- if val := b.bits[w] >> bit; val != 0 {
- return b.offset + int(i) + ntz(val), true
- }
-
- for w++; w < wordsPerBlock; w++ {
- if val := b.bits[w]; val != 0 {
- return b.offset + int(w*bitsPerWord) + ntz(val), true
- }
- }
-
- return 0, false
-}
-
-// forEach calls f for each element of block b.
-// f must not mutate b's enclosing Sparse.
-func (b *block) forEach(f func(int)) {
- for i, w := range b.bits {
- offset := b.offset + i*bitsPerWord
- for bi := 0; w != 0 && bi < bitsPerWord; bi++ {
- if w&1 != 0 {
- f(offset)
- }
- offset++
- w >>= 1
- }
- }
-}
-
-// offsetAndBitIndex returns the offset of the block that would
-// contain x and the bit index of x within that block.
-//
-func offsetAndBitIndex(x int) (int, uint) {
- mod := x % bitsPerBlock
- if mod < 0 {
- // Euclidean (non-negative) remainder
- mod += bitsPerBlock
- }
- return x - mod, uint(mod)
-}
-
-// -- Sparse --------------------------------------------------------------
-
-// none is a shared, empty, sentinel block that indicates the end of a block
-// list.
-var none block
-
-// Dummy type used to generate an implicit panic. This must be defined at the
-// package level; if it is defined inside a function, it prevents the inlining
-// of that function.
-type to_copy_a_sparse_you_must_call_its_Copy_method struct{}
-
-// init ensures s is properly initialized.
-func (s *Sparse) init() {
- root := &s.root
- if root.next == nil {
- root.offset = MaxInt
- root.next = root
- root.prev = root
- } else if root.next.prev != root {
- // Copying a Sparse x leads to pernicious corruption: the
- // new Sparse y shares the old linked list, but iteration
- // on y will never encounter &y.root so it goes into a
- // loop. Fail fast before this occurs.
- // We don't want to call panic here because it prevents the
- // inlining of this function.
- _ = (interface{}(nil)).(to_copy_a_sparse_you_must_call_its_Copy_method)
- }
-}
-
-func (s *Sparse) first() *block {
- s.init()
- if s.root.offset == MaxInt {
- return &none
- }
- return &s.root
-}
-
-// next returns the next block in the list, or end if b is the last block.
-func (s *Sparse) next(b *block) *block {
- if b.next == &s.root {
- return &none
- }
- return b.next
-}
-
-// prev returns the previous block in the list, or end if b is the first block.
-func (s *Sparse) prev(b *block) *block {
- if b.prev == &s.root {
- return &none
- }
- return b.prev
-}
-
-// IsEmpty reports whether the set s is empty.
-func (s *Sparse) IsEmpty() bool {
- return s.root.next == nil || s.root.offset == MaxInt
-}
-
-// Len returns the number of elements in the set s.
-func (s *Sparse) Len() int {
- var l int
- for b := s.first(); b != &none; b = s.next(b) {
- l += b.len()
- }
- return l
-}
-
-// Max returns the maximum element of the set s, or MinInt if s is empty.
-func (s *Sparse) Max() int {
- if s.IsEmpty() {
- return MinInt
- }
- return s.root.prev.max()
-}
-
-// Min returns the minimum element of the set s, or MaxInt if s is empty.
-func (s *Sparse) Min() int {
- if s.IsEmpty() {
- return MaxInt
- }
- return s.root.min(false)
-}
-
-// LowerBound returns the smallest element >= x, or MaxInt if there is no such
-// element.
-func (s *Sparse) LowerBound(x int) int {
- offset, i := offsetAndBitIndex(x)
- for b := s.first(); b != &none; b = s.next(b) {
- if b.offset > offset {
- return b.min(false)
- }
- if b.offset == offset {
- if y, ok := b.lowerBound(i); ok {
- return y
- }
- }
- }
- return MaxInt
-}
-
-// block returns the block that would contain offset,
-// or nil if s contains no such block.
-// Precondition: offset is a multiple of bitsPerBlock.
-func (s *Sparse) block(offset int) *block {
- for b := s.first(); b != &none && b.offset <= offset; b = s.next(b) {
- if b.offset == offset {
- return b
- }
- }
- return nil
-}
-
-// Insert adds x to the set s, and reports whether the set grew.
-func (s *Sparse) Insert(x int) bool {
- offset, i := offsetAndBitIndex(x)
-
- b := s.first()
- for ; b != &none && b.offset <= offset; b = s.next(b) {
- if b.offset == offset {
- return b.insert(i)
- }
- }
-
- // Insert new block before b.
- new := s.insertBlockBefore(b)
- new.offset = offset
- return new.insert(i)
-}
-
-// removeBlock removes a block and returns the block that followed it (or end if
-// it was the last block).
-func (s *Sparse) removeBlock(b *block) *block {
- if b != &s.root {
- b.prev.next = b.next
- b.next.prev = b.prev
- if b.next == &s.root {
- return &none
- }
- return b.next
- }
-
- first := s.root.next
- if first == &s.root {
- // This was the only block.
- s.Clear()
- return &none
- }
- s.root.offset = first.offset
- s.root.bits = first.bits
- if first.next == &s.root {
- // Single block remaining.
- s.root.next = &s.root
- s.root.prev = &s.root
- } else {
- s.root.next = first.next
- first.next.prev = &s.root
- }
- return &s.root
-}
-
-// Remove removes x from the set s, and reports whether the set shrank.
-func (s *Sparse) Remove(x int) bool {
- offset, i := offsetAndBitIndex(x)
- if b := s.block(offset); b != nil {
- if !b.remove(i) {
- return false
- }
- if b.empty() {
- s.removeBlock(b)
- }
- return true
- }
- return false
-}
-
-// Clear removes all elements from the set s.
-func (s *Sparse) Clear() {
- s.root = block{
- offset: MaxInt,
- next: &s.root,
- prev: &s.root,
- }
-}
-
-// If set s is non-empty, TakeMin sets *p to the minimum element of
-// the set s, removes that element from the set and returns true.
-// Otherwise, it returns false and *p is undefined.
-//
-// This method may be used for iteration over a worklist like so:
-//
-// var x int
-// for worklist.TakeMin(&x) { use(x) }
-//
-func (s *Sparse) TakeMin(p *int) bool {
- if s.IsEmpty() {
- return false
- }
- *p = s.root.min(true)
- if s.root.empty() {
- s.removeBlock(&s.root)
- }
- return true
-}
-
-// Has reports whether x is an element of the set s.
-func (s *Sparse) Has(x int) bool {
- offset, i := offsetAndBitIndex(x)
- if b := s.block(offset); b != nil {
- return b.has(i)
- }
- return false
-}
-
-// forEach applies function f to each element of the set s in order.
-//
-// f must not mutate s. Consequently, forEach is not safe to expose
-// to clients. In any case, using "range s.AppendTo()" allows more
-// natural control flow with continue/break/return.
-//
-func (s *Sparse) forEach(f func(int)) {
- for b := s.first(); b != &none; b = s.next(b) {
- b.forEach(f)
- }
-}
-
-// Copy sets s to the value of x.
-func (s *Sparse) Copy(x *Sparse) {
- if s == x {
- return
- }
-
- xb := x.first()
- sb := s.first()
- for xb != &none {
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- sb.offset = xb.offset
- sb.bits = xb.bits
- xb = x.next(xb)
- sb = s.next(sb)
- }
- s.discardTail(sb)
-}
-
-// insertBlockBefore returns a new block, inserting it before next.
-// If next is the root, the root is replaced. If next is end, the block is
-// inserted at the end.
-func (s *Sparse) insertBlockBefore(next *block) *block {
- if s.IsEmpty() {
- if next != &none {
- panic("BUG: passed block with empty set")
- }
- return &s.root
- }
-
- if next == &s.root {
- // Special case: we need to create a new block that will become the root
- // block.The old root block becomes the second block.
- second := s.root
- s.root = block{
- next: &second,
- }
- if second.next == &s.root {
- s.root.prev = &second
- } else {
- s.root.prev = second.prev
- second.next.prev = &second
- second.prev = &s.root
- }
- return &s.root
- }
- if next == &none {
- // Insert before root.
- next = &s.root
- }
- b := new(block)
- b.next = next
- b.prev = next.prev
- b.prev.next = b
- next.prev = b
- return b
-}
-
-// discardTail removes block b and all its successors from s.
-func (s *Sparse) discardTail(b *block) {
- if b != &none {
- if b == &s.root {
- s.Clear()
- } else {
- b.prev.next = &s.root
- s.root.prev = b.prev
- }
- }
-}
-
-// IntersectionWith sets s to the intersection s ∩ x.
-func (s *Sparse) IntersectionWith(x *Sparse) {
- if s == x {
- return
- }
-
- xb := x.first()
- sb := s.first()
- for xb != &none && sb != &none {
- switch {
- case xb.offset < sb.offset:
- xb = x.next(xb)
-
- case xb.offset > sb.offset:
- sb = s.removeBlock(sb)
-
- default:
- var sum word
- for i := range sb.bits {
- r := xb.bits[i] & sb.bits[i]
- sb.bits[i] = r
- sum |= r
- }
- if sum != 0 {
- sb = s.next(sb)
- } else {
- // sb will be overwritten or removed
- }
-
- xb = x.next(xb)
- }
- }
-
- s.discardTail(sb)
-}
-
-// Intersection sets s to the intersection x ∩ y.
-func (s *Sparse) Intersection(x, y *Sparse) {
- switch {
- case s == x:
- s.IntersectionWith(y)
- return
- case s == y:
- s.IntersectionWith(x)
- return
- case x == y:
- s.Copy(x)
- return
- }
-
- xb := x.first()
- yb := y.first()
- sb := s.first()
- for xb != &none && yb != &none {
- switch {
- case xb.offset < yb.offset:
- xb = x.next(xb)
- continue
- case xb.offset > yb.offset:
- yb = y.next(yb)
- continue
- }
-
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- sb.offset = xb.offset
-
- var sum word
- for i := range sb.bits {
- r := xb.bits[i] & yb.bits[i]
- sb.bits[i] = r
- sum |= r
- }
- if sum != 0 {
- sb = s.next(sb)
- } else {
- // sb will be overwritten or removed
- }
-
- xb = x.next(xb)
- yb = y.next(yb)
- }
-
- s.discardTail(sb)
-}
-
-// Intersects reports whether s ∩ x ≠ ∅.
-func (s *Sparse) Intersects(x *Sparse) bool {
- sb := s.first()
- xb := x.first()
- for sb != &none && xb != &none {
- switch {
- case xb.offset < sb.offset:
- xb = x.next(xb)
- case xb.offset > sb.offset:
- sb = s.next(sb)
- default:
- for i := range sb.bits {
- if sb.bits[i]&xb.bits[i] != 0 {
- return true
- }
- }
- sb = s.next(sb)
- xb = x.next(xb)
- }
- }
- return false
-}
-
-// UnionWith sets s to the union s ∪ x, and reports whether s grew.
-func (s *Sparse) UnionWith(x *Sparse) bool {
- if s == x {
- return false
- }
-
- var changed bool
- xb := x.first()
- sb := s.first()
- for xb != &none {
- if sb != &none && sb.offset == xb.offset {
- for i := range xb.bits {
- if sb.bits[i] != xb.bits[i] {
- sb.bits[i] |= xb.bits[i]
- changed = true
- }
- }
- xb = x.next(xb)
- } else if sb == &none || sb.offset > xb.offset {
- sb = s.insertBlockBefore(sb)
- sb.offset = xb.offset
- sb.bits = xb.bits
- changed = true
-
- xb = x.next(xb)
- }
- sb = s.next(sb)
- }
- return changed
-}
-
-// Union sets s to the union x ∪ y.
-func (s *Sparse) Union(x, y *Sparse) {
- switch {
- case x == y:
- s.Copy(x)
- return
- case s == x:
- s.UnionWith(y)
- return
- case s == y:
- s.UnionWith(x)
- return
- }
-
- xb := x.first()
- yb := y.first()
- sb := s.first()
- for xb != &none || yb != &none {
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- switch {
- case yb == &none || (xb != &none && xb.offset < yb.offset):
- sb.offset = xb.offset
- sb.bits = xb.bits
- xb = x.next(xb)
-
- case xb == &none || (yb != &none && yb.offset < xb.offset):
- sb.offset = yb.offset
- sb.bits = yb.bits
- yb = y.next(yb)
-
- default:
- sb.offset = xb.offset
- for i := range xb.bits {
- sb.bits[i] = xb.bits[i] | yb.bits[i]
- }
- xb = x.next(xb)
- yb = y.next(yb)
- }
- sb = s.next(sb)
- }
-
- s.discardTail(sb)
-}
-
-// DifferenceWith sets s to the difference s ∖ x.
-func (s *Sparse) DifferenceWith(x *Sparse) {
- if s == x {
- s.Clear()
- return
- }
-
- xb := x.first()
- sb := s.first()
- for xb != &none && sb != &none {
- switch {
- case xb.offset > sb.offset:
- sb = s.next(sb)
-
- case xb.offset < sb.offset:
- xb = x.next(xb)
-
- default:
- var sum word
- for i := range sb.bits {
- r := sb.bits[i] & ^xb.bits[i]
- sb.bits[i] = r
- sum |= r
- }
- if sum == 0 {
- sb = s.removeBlock(sb)
- } else {
- sb = s.next(sb)
- }
- xb = x.next(xb)
- }
- }
-}
-
-// Difference sets s to the difference x ∖ y.
-func (s *Sparse) Difference(x, y *Sparse) {
- switch {
- case x == y:
- s.Clear()
- return
- case s == x:
- s.DifferenceWith(y)
- return
- case s == y:
- var y2 Sparse
- y2.Copy(y)
- s.Difference(x, &y2)
- return
- }
-
- xb := x.first()
- yb := y.first()
- sb := s.first()
- for xb != &none && yb != &none {
- if xb.offset > yb.offset {
- // y has block, x has &none
- yb = y.next(yb)
- continue
- }
-
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- sb.offset = xb.offset
-
- switch {
- case xb.offset < yb.offset:
- // x has block, y has &none
- sb.bits = xb.bits
-
- sb = s.next(sb)
-
- default:
- // x and y have corresponding blocks
- var sum word
- for i := range sb.bits {
- r := xb.bits[i] & ^yb.bits[i]
- sb.bits[i] = r
- sum |= r
- }
- if sum != 0 {
- sb = s.next(sb)
- } else {
- // sb will be overwritten or removed
- }
-
- yb = y.next(yb)
- }
- xb = x.next(xb)
- }
-
- for xb != &none {
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- sb.offset = xb.offset
- sb.bits = xb.bits
- sb = s.next(sb)
-
- xb = x.next(xb)
- }
-
- s.discardTail(sb)
-}
-
-// SymmetricDifferenceWith sets s to the symmetric difference s ∆ x.
-func (s *Sparse) SymmetricDifferenceWith(x *Sparse) {
- if s == x {
- s.Clear()
- return
- }
-
- sb := s.first()
- xb := x.first()
- for xb != &none && sb != &none {
- switch {
- case sb.offset < xb.offset:
- sb = s.next(sb)
- case xb.offset < sb.offset:
- nb := s.insertBlockBefore(sb)
- nb.offset = xb.offset
- nb.bits = xb.bits
- xb = x.next(xb)
- default:
- var sum word
- for i := range sb.bits {
- r := sb.bits[i] ^ xb.bits[i]
- sb.bits[i] = r
- sum |= r
- }
- if sum == 0 {
- sb = s.removeBlock(sb)
- } else {
- sb = s.next(sb)
- }
- xb = x.next(xb)
- }
- }
-
- for xb != &none { // append the tail of x to s
- sb = s.insertBlockBefore(sb)
- sb.offset = xb.offset
- sb.bits = xb.bits
- sb = s.next(sb)
- xb = x.next(xb)
- }
-}
-
-// SymmetricDifference sets s to the symmetric difference x ∆ y.
-func (s *Sparse) SymmetricDifference(x, y *Sparse) {
- switch {
- case x == y:
- s.Clear()
- return
- case s == x:
- s.SymmetricDifferenceWith(y)
- return
- case s == y:
- s.SymmetricDifferenceWith(x)
- return
- }
-
- sb := s.first()
- xb := x.first()
- yb := y.first()
- for xb != &none && yb != &none {
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- switch {
- case yb.offset < xb.offset:
- sb.offset = yb.offset
- sb.bits = yb.bits
- sb = s.next(sb)
- yb = y.next(yb)
- case xb.offset < yb.offset:
- sb.offset = xb.offset
- sb.bits = xb.bits
- sb = s.next(sb)
- xb = x.next(xb)
- default:
- var sum word
- for i := range sb.bits {
- r := xb.bits[i] ^ yb.bits[i]
- sb.bits[i] = r
- sum |= r
- }
- if sum != 0 {
- sb.offset = xb.offset
- sb = s.next(sb)
- }
- xb = x.next(xb)
- yb = y.next(yb)
- }
- }
-
- for xb != &none { // append the tail of x to s
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- sb.offset = xb.offset
- sb.bits = xb.bits
- sb = s.next(sb)
- xb = x.next(xb)
- }
-
- for yb != &none { // append the tail of y to s
- if sb == &none {
- sb = s.insertBlockBefore(sb)
- }
- sb.offset = yb.offset
- sb.bits = yb.bits
- sb = s.next(sb)
- yb = y.next(yb)
- }
-
- s.discardTail(sb)
-}
-
-// SubsetOf reports whether s ∖ x = ∅.
-func (s *Sparse) SubsetOf(x *Sparse) bool {
- if s == x {
- return true
- }
-
- sb := s.first()
- xb := x.first()
- for sb != &none {
- switch {
- case xb == &none || xb.offset > sb.offset:
- return false
- case xb.offset < sb.offset:
- xb = x.next(xb)
- default:
- for i := range sb.bits {
- if sb.bits[i]&^xb.bits[i] != 0 {
- return false
- }
- }
- sb = s.next(sb)
- xb = x.next(xb)
- }
- }
- return true
-}
-
-// Equals reports whether the sets s and t have the same elements.
-func (s *Sparse) Equals(t *Sparse) bool {
- if s == t {
- return true
- }
- sb := s.first()
- tb := t.first()
- for {
- switch {
- case sb == &none && tb == &none:
- return true
- case sb == &none || tb == &none:
- return false
- case sb.offset != tb.offset:
- return false
- case sb.bits != tb.bits:
- return false
- }
-
- sb = s.next(sb)
- tb = t.next(tb)
- }
-}
-
-// String returns a human-readable description of the set s.
-func (s *Sparse) String() string {
- var buf bytes.Buffer
- buf.WriteByte('{')
- s.forEach(func(x int) {
- if buf.Len() > 1 {
- buf.WriteByte(' ')
- }
- fmt.Fprintf(&buf, "%d", x)
- })
- buf.WriteByte('}')
- return buf.String()
-}
-
-// BitString returns the set as a string of 1s and 0s denoting the sum
-// of the i'th powers of 2, for each i in s. A radix point, always
-// preceded by a digit, appears if the sum is non-integral.
-//
-// Examples:
-// {}.BitString() = "0"
-// {4,5}.BitString() = "110000"
-// {-3}.BitString() = "0.001"
-// {-3,0,4,5}.BitString() = "110001.001"
-//
-func (s *Sparse) BitString() string {
- if s.IsEmpty() {
- return "0"
- }
-
- min, max := s.Min(), s.Max()
- var nbytes int
- if max > 0 {
- nbytes = max
- }
- nbytes++ // zero bit
- radix := nbytes
- if min < 0 {
- nbytes += len(".") - min
- }
-
- b := make([]byte, nbytes)
- for i := range b {
- b[i] = '0'
- }
- if radix < nbytes {
- b[radix] = '.'
- }
- s.forEach(func(x int) {
- if x >= 0 {
- x += len(".")
- }
- b[radix-x] = '1'
- })
- return string(b)
-}
-
-// GoString returns a string showing the internal representation of
-// the set s.
-//
-func (s *Sparse) GoString() string {
- var buf bytes.Buffer
- for b := s.first(); b != &none; b = s.next(b) {
- fmt.Fprintf(&buf, "block %p {offset=%d next=%p prev=%p",
- b, b.offset, b.next, b.prev)
- for _, w := range b.bits {
- fmt.Fprintf(&buf, " 0%016x", w)
- }
- fmt.Fprintf(&buf, "}\n")
- }
- return buf.String()
-}
-
-// AppendTo returns the result of appending the elements of s to slice
-// in order.
-func (s *Sparse) AppendTo(slice []int) []int {
- s.forEach(func(x int) {
- slice = append(slice, x)
- })
- return slice
-}
-
-// -- Testing/debugging ------------------------------------------------
-
-// check returns an error if the representation invariants of s are violated.
-func (s *Sparse) check() error {
- s.init()
- if s.root.empty() {
- // An empty set must have only the root block with offset MaxInt.
- if s.root.next != &s.root {
- return fmt.Errorf("multiple blocks with empty root block")
- }
- if s.root.offset != MaxInt {
- return fmt.Errorf("empty set has offset %d, should be MaxInt", s.root.offset)
- }
- return nil
- }
- for b := s.first(); ; b = s.next(b) {
- if b.offset%bitsPerBlock != 0 {
- return fmt.Errorf("bad offset modulo: %d", b.offset)
- }
- if b.empty() {
- return fmt.Errorf("empty block")
- }
- if b.prev.next != b {
- return fmt.Errorf("bad prev.next link")
- }
- if b.next.prev != b {
- return fmt.Errorf("bad next.prev link")
- }
- if b.next == &s.root {
- break
- }
- if b.offset >= b.next.offset {
- return fmt.Errorf("bad offset order: b.offset=%d, b.next.offset=%d",
- b.offset, b.next.offset)
- }
- }
- return nil
-}
projects / dotfiles / .git / blobdiff