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+/*
+Package bitset implements bitsets, a mapping
+between non-negative integers and boolean values. It should be more
+efficient than map[uint] bool.
+
+It provides methods for setting, clearing, flipping, and testing
+individual integers.
+
+But it also provides set intersection, union, difference,
+complement, and symmetric operations, as well as tests to
+check whether any, all, or no bits are set, and querying a
+bitset's current length and number of positive bits.
+
+BitSets are expanded to the size of the largest set bit; the
+memory allocation is approximately Max bits, where Max is
+the largest set bit. BitSets are never shrunk. On creation,
+a hint can be given for the number of bits that will be used.
+
+Many of the methods, including Set,Clear, and Flip, return
+a BitSet pointer, which allows for chaining.
+
+Example use:
+
+ import "bitset"
+ var b BitSet
+ b.Set(10).Set(11)
+ if b.Test(1000) {
+ b.Clear(1000)
+ }
+ if B.Intersection(bitset.New(100).Set(10)).Count() > 1 {
+ fmt.Println("Intersection works.")
+ }
+
+As an alternative to BitSets, one should check out the 'big' package,
+which provides a (less set-theoretical) view of bitsets.
+
+*/
+package bitset
+
+import (
+ "bufio"
+ "bytes"
+ "encoding/base64"
+ "encoding/binary"
+ "encoding/json"
+ "errors"
+ "fmt"
+ "io"
+ "strconv"
+)
+
+// the wordSize of a bit set
+const wordSize = uint(64)
+
+// log2WordSize is lg(wordSize)
+const log2WordSize = uint(6)
+
+// allBits has every bit set
+const allBits uint64 = 0xffffffffffffffff
+
+// default binary BigEndian
+var binaryOrder binary.ByteOrder = binary.BigEndian
+
+// default json encoding base64.URLEncoding
+var base64Encoding = base64.URLEncoding
+
+// Base64StdEncoding Marshal/Unmarshal BitSet with base64.StdEncoding(Default: base64.URLEncoding)
+func Base64StdEncoding() { base64Encoding = base64.StdEncoding }
+
+// LittleEndian Marshal/Unmarshal Binary as Little Endian(Default: binary.BigEndian)
+func LittleEndian() { binaryOrder = binary.LittleEndian }
+
+// A BitSet is a set of bits. The zero value of a BitSet is an empty set of length 0.
+type BitSet struct {
+ length uint
+ set []uint64
+}
+
+// Error is used to distinguish errors (panics) generated in this package.
+type Error string
+
+// safeSet will fixup b.set to be non-nil and return the field value
+func (b *BitSet) safeSet() []uint64 {
+ if b.set == nil {
+ b.set = make([]uint64, wordsNeeded(0))
+ }
+ return b.set
+}
+
+// From is a constructor used to create a BitSet from an array of integers
+func From(buf []uint64) *BitSet {
+ return &BitSet{uint(len(buf)) * 64, buf}
+}
+
+// Bytes returns the bitset as array of integers
+func (b *BitSet) Bytes() []uint64 {
+ return b.set
+}
+
+// wordsNeeded calculates the number of words needed for i bits
+func wordsNeeded(i uint) int {
+ if i > (Cap() - wordSize + 1) {
+ return int(Cap() >> log2WordSize)
+ }
+ return int((i + (wordSize - 1)) >> log2WordSize)
+}
+
+// New creates a new BitSet with a hint that length bits will be required
+func New(length uint) (bset *BitSet) {
+ defer func() {
+ if r := recover(); r != nil {
+ bset = &BitSet{
+ 0,
+ make([]uint64, 0),
+ }
+ }
+ }()
+
+ bset = &BitSet{
+ length,
+ make([]uint64, wordsNeeded(length)),
+ }
+
+ return bset
+}
+
+// Cap returns the total possible capacity, or number of bits
+func Cap() uint {
+ return ^uint(0)
+}
+
+// Len returns the number of bits in the BitSet.
+// Note the difference to method Count, see example.
+func (b *BitSet) Len() uint {
+ return b.length
+}
+
+// extendSetMaybe adds additional words to incorporate new bits if needed
+func (b *BitSet) extendSetMaybe(i uint) {
+ if i >= b.length { // if we need more bits, make 'em
+ if i >= Cap() {
+ panic("You are exceeding the capacity")
+ }
+ nsize := wordsNeeded(i + 1)
+ if b.set == nil {
+ b.set = make([]uint64, nsize)
+ } else if cap(b.set) >= nsize {
+ b.set = b.set[:nsize] // fast resize
+ } else if len(b.set) < nsize {
+ newset := make([]uint64, nsize, 2*nsize) // increase capacity 2x
+ copy(newset, b.set)
+ b.set = newset
+ }
+ b.length = i + 1
+ }
+}
+
+// Test whether bit i is set.
+func (b *BitSet) Test(i uint) bool {
+ if i >= b.length {
+ return false
+ }
+ return b.set[i>>log2WordSize]&(1<<(i&(wordSize-1))) != 0
+}
+
+// Set bit i to 1, the capacity of the bitset is automatically
+// increased accordingly.
+// If i>= Cap(), this function will panic.
+// Warning: using a very large value for 'i'
+// may lead to a memory shortage and a panic: the caller is responsible
+// for providing sensible parameters in line with their memory capacity.
+func (b *BitSet) Set(i uint) *BitSet {
+ b.extendSetMaybe(i)
+ b.set[i>>log2WordSize] |= 1 << (i & (wordSize - 1))
+ return b
+}
+
+// Clear bit i to 0
+func (b *BitSet) Clear(i uint) *BitSet {
+ if i >= b.length {
+ return b
+ }
+ b.set[i>>log2WordSize] &^= 1 << (i & (wordSize - 1))
+ return b
+}
+
+// SetTo sets bit i to value.
+// If i>= Cap(), this function will panic.
+// Warning: using a very large value for 'i'
+// may lead to a memory shortage and a panic: the caller is responsible
+// for providing sensible parameters in line with their memory capacity.
+func (b *BitSet) SetTo(i uint, value bool) *BitSet {
+ if value {
+ return b.Set(i)
+ }
+ return b.Clear(i)
+}
+
+// Flip bit at i.
+// If i>= Cap(), this function will panic.
+// Warning: using a very large value for 'i'
+// may lead to a memory shortage and a panic: the caller is responsible
+// for providing sensible parameters in line with their memory capacity.
+func (b *BitSet) Flip(i uint) *BitSet {
+ if i >= b.length {
+ return b.Set(i)
+ }
+ b.set[i>>log2WordSize] ^= 1 << (i & (wordSize - 1))
+ return b
+}
+
+// FlipRange bit in [start, end).
+// If end>= Cap(), this function will panic.
+// Warning: using a very large value for 'end'
+// may lead to a memory shortage and a panic: the caller is responsible
+// for providing sensible parameters in line with their memory capacity.
+func (b *BitSet) FlipRange(start, end uint) *BitSet {
+ if start >= end {
+ return b
+ }
+
+ b.extendSetMaybe(end - 1)
+ var startWord uint = start >> log2WordSize
+ var endWord uint = end >> log2WordSize
+ b.set[startWord] ^= ^(^uint64(0) << (start & (wordSize - 1)))
+ for i := startWord; i < endWord; i++ {
+ b.set[i] = ^b.set[i]
+ }
+ b.set[endWord] ^= ^uint64(0) >> (-end & (wordSize - 1))
+ return b
+}
+
+// Shrink shrinks BitSet so that the provided value is the last possible
+// set value. It clears all bits > the provided index and reduces the size
+// and length of the set.
+//
+// Note that the parameter value is not the new length in bits: it is the
+// maximal value that can be stored in the bitset after the function call.
+// The new length in bits is the parameter value + 1. Thus it is not possible
+// to use this function to set the length to 0, the minimal value of the length
+// after this function call is 1.
+//
+// A new slice is allocated to store the new bits, so you may see an increase in
+// memory usage until the GC runs. Normally this should not be a problem, but if you
+// have an extremely large BitSet its important to understand that the old BitSet will
+// remain in memory until the GC frees it.
+func (b *BitSet) Shrink(lastbitindex uint) *BitSet {
+ length := lastbitindex + 1
+ idx := wordsNeeded(length)
+ if idx > len(b.set) {
+ return b
+ }
+ shrunk := make([]uint64, idx)
+ copy(shrunk, b.set[:idx])
+ b.set = shrunk
+ b.length = length
+ b.set[idx-1] &= (allBits >> (uint64(64) - uint64(length&(wordSize-1))))
+ return b
+}
+
+// Compact shrinks BitSet to so that we preserve all set bits, while minimizing
+// memory usage. Compact calls Shrink.
+func (b *BitSet) Compact() *BitSet {
+ idx := len(b.set) - 1
+ for ; idx >= 0 && b.set[idx] == 0; idx-- {
+ }
+ newlength := uint((idx + 1) << log2WordSize)
+ if newlength >= b.length {
+ return b // nothing to do
+ }
+ if newlength > 0 {
+ return b.Shrink(newlength - 1)
+ }
+ // We preserve one word
+ return b.Shrink(63)
+}
+
+// InsertAt takes an index which indicates where a bit should be
+// inserted. Then it shifts all the bits in the set to the left by 1, starting
+// from the given index position, and sets the index position to 0.
+//
+// Depending on the size of your BitSet, and where you are inserting the new entry,
+// this method could be extremely slow and in some cases might cause the entire BitSet
+// to be recopied.
+func (b *BitSet) InsertAt(idx uint) *BitSet {
+ insertAtElement := (idx >> log2WordSize)
+
+ // if length of set is a multiple of wordSize we need to allocate more space first
+ if b.isLenExactMultiple() {
+ b.set = append(b.set, uint64(0))
+ }
+
+ var i uint
+ for i = uint(len(b.set) - 1); i > insertAtElement; i-- {
+ // all elements above the position where we want to insert can simply by shifted
+ b.set[i] <<= 1
+
+ // we take the most significant bit of the previous element and set it as
+ // the least significant bit of the current element
+ b.set[i] |= (b.set[i-1] & 0x8000000000000000) >> 63
+ }
+
+ // generate a mask to extract the data that we need to shift left
+ // within the element where we insert a bit
+ dataMask := ^(uint64(1)<<uint64(idx&(wordSize-1)) - 1)
+
+ // extract that data that we'll shift
+ data := b.set[i] & dataMask
+
+ // set the positions of the data mask to 0 in the element where we insert
+ b.set[i] &= ^dataMask
+
+ // shift data mask to the left and insert its data to the slice element
+ b.set[i] |= data << 1
+
+ // add 1 to length of BitSet
+ b.length++
+
+ return b
+}
+
+// String creates a string representation of the Bitmap
+func (b *BitSet) String() string {
+ // follows code from https://github.com/RoaringBitmap/roaring
+ var buffer bytes.Buffer
+ start := []byte("{")
+ buffer.Write(start)
+ counter := 0
+ i, e := b.NextSet(0)
+ for e {
+ counter = counter + 1
+ // to avoid exhausting the memory
+ if counter > 0x40000 {
+ buffer.WriteString("...")
+ break
+ }
+ buffer.WriteString(strconv.FormatInt(int64(i), 10))
+ i, e = b.NextSet(i + 1)
+ if e {
+ buffer.WriteString(",")
+ }
+ }
+ buffer.WriteString("}")
+ return buffer.String()
+}
+
+// DeleteAt deletes the bit at the given index position from
+// within the bitset
+// All the bits residing on the left of the deleted bit get
+// shifted right by 1
+// The running time of this operation may potentially be
+// relatively slow, O(length)
+func (b *BitSet) DeleteAt(i uint) *BitSet {
+ // the index of the slice element where we'll delete a bit
+ deleteAtElement := i >> log2WordSize
+
+ // generate a mask for the data that needs to be shifted right
+ // within that slice element that gets modified
+ dataMask := ^((uint64(1) << (i & (wordSize - 1))) - 1)
+
+ // extract the data that we'll shift right from the slice element
+ data := b.set[deleteAtElement] & dataMask
+
+ // set the masked area to 0 while leaving the rest as it is
+ b.set[deleteAtElement] &= ^dataMask
+
+ // shift the previously extracted data to the right and then
+ // set it in the previously masked area
+ b.set[deleteAtElement] |= (data >> 1) & dataMask
+
+ // loop over all the consecutive slice elements to copy each
+ // lowest bit into the highest position of the previous element,
+ // then shift the entire content to the right by 1
+ for i := int(deleteAtElement) + 1; i < len(b.set); i++ {
+ b.set[i-1] |= (b.set[i] & 1) << 63
+ b.set[i] >>= 1
+ }
+
+ b.length = b.length - 1
+
+ return b
+}
+
+// NextSet returns the next bit set from the specified index,
+// including possibly the current index
+// along with an error code (true = valid, false = no set bit found)
+// for i,e := v.NextSet(0); e; i,e = v.NextSet(i + 1) {...}
+//
+// Users concerned with performance may want to use NextSetMany to
+// retrieve several values at once.
+func (b *BitSet) NextSet(i uint) (uint, bool) {
+ x := int(i >> log2WordSize)
+ if x >= len(b.set) {
+ return 0, false
+ }
+ w := b.set[x]
+ w = w >> (i & (wordSize - 1))
+ if w != 0 {
+ return i + trailingZeroes64(w), true
+ }
+ x = x + 1
+ for x < len(b.set) {
+ if b.set[x] != 0 {
+ return uint(x)*wordSize + trailingZeroes64(b.set[x]), true
+ }
+ x = x + 1
+
+ }
+ return 0, false
+}
+
+// NextSetMany returns many next bit sets from the specified index,
+// including possibly the current index and up to cap(buffer).
+// If the returned slice has len zero, then no more set bits were found
+//
+// buffer := make([]uint, 256) // this should be reused
+// j := uint(0)
+// j, buffer = bitmap.NextSetMany(j, buffer)
+// for ; len(buffer) > 0; j, buffer = bitmap.NextSetMany(j,buffer) {
+// for k := range buffer {
+// do something with buffer[k]
+// }
+// j += 1
+// }
+//
+//
+// It is possible to retrieve all set bits as follow:
+//
+// indices := make([]uint, bitmap.Count())
+// bitmap.NextSetMany(0, indices)
+//
+// However if bitmap.Count() is large, it might be preferable to
+// use several calls to NextSetMany, for performance reasons.
+func (b *BitSet) NextSetMany(i uint, buffer []uint) (uint, []uint) {
+ myanswer := buffer
+ capacity := cap(buffer)
+ x := int(i >> log2WordSize)
+ if x >= len(b.set) || capacity == 0 {
+ return 0, myanswer[:0]
+ }
+ skip := i & (wordSize - 1)
+ word := b.set[x] >> skip
+ myanswer = myanswer[:capacity]
+ size := int(0)
+ for word != 0 {
+ r := trailingZeroes64(word)
+ t := word & ((^word) + 1)
+ myanswer[size] = r + i
+ size++
+ if size == capacity {
+ goto End
+ }
+ word = word ^ t
+ }
+ x++
+ for idx, word := range b.set[x:] {
+ for word != 0 {
+ r := trailingZeroes64(word)
+ t := word & ((^word) + 1)
+ myanswer[size] = r + (uint(x+idx) << 6)
+ size++
+ if size == capacity {
+ goto End
+ }
+ word = word ^ t
+ }
+ }
+End:
+ if size > 0 {
+ return myanswer[size-1], myanswer[:size]
+ }
+ return 0, myanswer[:0]
+}
+
+// NextClear returns the next clear bit from the specified index,
+// including possibly the current index
+// along with an error code (true = valid, false = no bit found i.e. all bits are set)
+func (b *BitSet) NextClear(i uint) (uint, bool) {
+ x := int(i >> log2WordSize)
+ if x >= len(b.set) {
+ return 0, false
+ }
+ w := b.set[x]
+ w = w >> (i & (wordSize - 1))
+ wA := allBits >> (i & (wordSize - 1))
+ index := i + trailingZeroes64(^w)
+ if w != wA && index < b.length {
+ return index, true
+ }
+ x++
+ for x < len(b.set) {
+ index = uint(x)*wordSize + trailingZeroes64(^b.set[x])
+ if b.set[x] != allBits && index < b.length {
+ return index, true
+ }
+ x++
+ }
+ return 0, false
+}
+
+// ClearAll clears the entire BitSet
+func (b *BitSet) ClearAll() *BitSet {
+ if b != nil && b.set != nil {
+ for i := range b.set {
+ b.set[i] = 0
+ }
+ }
+ return b
+}
+
+// wordCount returns the number of words used in a bit set
+func (b *BitSet) wordCount() int {
+ return len(b.set)
+}
+
+// Clone this BitSet
+func (b *BitSet) Clone() *BitSet {
+ c := New(b.length)
+ if b.set != nil { // Clone should not modify current object
+ copy(c.set, b.set)
+ }
+ return c
+}
+
+// Copy into a destination BitSet
+// Returning the size of the destination BitSet
+// like array copy
+func (b *BitSet) Copy(c *BitSet) (count uint) {
+ if c == nil {
+ return
+ }
+ if b.set != nil { // Copy should not modify current object
+ copy(c.set, b.set)
+ }
+ count = c.length
+ if b.length < c.length {
+ count = b.length
+ }
+ return
+}
+
+// Count (number of set bits).
+// Also known as "popcount" or "population count".
+func (b *BitSet) Count() uint {
+ if b != nil && b.set != nil {
+ return uint(popcntSlice(b.set))
+ }
+ return 0
+}
+
+// Equal tests the equivalence of two BitSets.
+// False if they are of different sizes, otherwise true
+// only if all the same bits are set
+func (b *BitSet) Equal(c *BitSet) bool {
+ if c == nil || b == nil {
+ return c == b
+ }
+ if b.length != c.length {
+ return false
+ }
+ if b.length == 0 { // if they have both length == 0, then could have nil set
+ return true
+ }
+ // testing for equality shoud not transform the bitset (no call to safeSet)
+
+ for p, v := range b.set {
+ if c.set[p] != v {
+ return false
+ }
+ }
+ return true
+}
+
+func panicIfNull(b *BitSet) {
+ if b == nil {
+ panic(Error("BitSet must not be null"))
+ }
+}
+
+// Difference of base set and other set
+// This is the BitSet equivalent of &^ (and not)
+func (b *BitSet) Difference(compare *BitSet) (result *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ result = b.Clone() // clone b (in case b is bigger than compare)
+ l := int(compare.wordCount())
+ if l > int(b.wordCount()) {
+ l = int(b.wordCount())
+ }
+ for i := 0; i < l; i++ {
+ result.set[i] = b.set[i] &^ compare.set[i]
+ }
+ return
+}
+
+// DifferenceCardinality computes the cardinality of the differnce
+func (b *BitSet) DifferenceCardinality(compare *BitSet) uint {
+ panicIfNull(b)
+ panicIfNull(compare)
+ l := int(compare.wordCount())
+ if l > int(b.wordCount()) {
+ l = int(b.wordCount())
+ }
+ cnt := uint64(0)
+ cnt += popcntMaskSlice(b.set[:l], compare.set[:l])
+ cnt += popcntSlice(b.set[l:])
+ return uint(cnt)
+}
+
+// InPlaceDifference computes the difference of base set and other set
+// This is the BitSet equivalent of &^ (and not)
+func (b *BitSet) InPlaceDifference(compare *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ l := int(compare.wordCount())
+ if l > int(b.wordCount()) {
+ l = int(b.wordCount())
+ }
+ for i := 0; i < l; i++ {
+ b.set[i] &^= compare.set[i]
+ }
+}
+
+// Convenience function: return two bitsets ordered by
+// increasing length. Note: neither can be nil
+func sortByLength(a *BitSet, b *BitSet) (ap *BitSet, bp *BitSet) {
+ if a.length <= b.length {
+ ap, bp = a, b
+ } else {
+ ap, bp = b, a
+ }
+ return
+}
+
+// Intersection of base set and other set
+// This is the BitSet equivalent of & (and)
+func (b *BitSet) Intersection(compare *BitSet) (result *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ b, compare = sortByLength(b, compare)
+ result = New(b.length)
+ for i, word := range b.set {
+ result.set[i] = word & compare.set[i]
+ }
+ return
+}
+
+// IntersectionCardinality computes the cardinality of the union
+func (b *BitSet) IntersectionCardinality(compare *BitSet) uint {
+ panicIfNull(b)
+ panicIfNull(compare)
+ b, compare = sortByLength(b, compare)
+ cnt := popcntAndSlice(b.set, compare.set)
+ return uint(cnt)
+}
+
+// InPlaceIntersection destructively computes the intersection of
+// base set and the compare set.
+// This is the BitSet equivalent of & (and)
+func (b *BitSet) InPlaceIntersection(compare *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ l := int(compare.wordCount())
+ if l > int(b.wordCount()) {
+ l = int(b.wordCount())
+ }
+ for i := 0; i < l; i++ {
+ b.set[i] &= compare.set[i]
+ }
+ for i := l; i < len(b.set); i++ {
+ b.set[i] = 0
+ }
+ if compare.length > 0 {
+ b.extendSetMaybe(compare.length - 1)
+ }
+}
+
+// Union of base set and other set
+// This is the BitSet equivalent of | (or)
+func (b *BitSet) Union(compare *BitSet) (result *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ b, compare = sortByLength(b, compare)
+ result = compare.Clone()
+ for i, word := range b.set {
+ result.set[i] = word | compare.set[i]
+ }
+ return
+}
+
+// UnionCardinality computes the cardinality of the uniton of the base set
+// and the compare set.
+func (b *BitSet) UnionCardinality(compare *BitSet) uint {
+ panicIfNull(b)
+ panicIfNull(compare)
+ b, compare = sortByLength(b, compare)
+ cnt := popcntOrSlice(b.set, compare.set)
+ if len(compare.set) > len(b.set) {
+ cnt += popcntSlice(compare.set[len(b.set):])
+ }
+ return uint(cnt)
+}
+
+// InPlaceUnion creates the destructive union of base set and compare set.
+// This is the BitSet equivalent of | (or).
+func (b *BitSet) InPlaceUnion(compare *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ l := int(compare.wordCount())
+ if l > int(b.wordCount()) {
+ l = int(b.wordCount())
+ }
+ if compare.length > 0 {
+ b.extendSetMaybe(compare.length - 1)
+ }
+ for i := 0; i < l; i++ {
+ b.set[i] |= compare.set[i]
+ }
+ if len(compare.set) > l {
+ for i := l; i < len(compare.set); i++ {
+ b.set[i] = compare.set[i]
+ }
+ }
+}
+
+// SymmetricDifference of base set and other set
+// This is the BitSet equivalent of ^ (xor)
+func (b *BitSet) SymmetricDifference(compare *BitSet) (result *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ b, compare = sortByLength(b, compare)
+ // compare is bigger, so clone it
+ result = compare.Clone()
+ for i, word := range b.set {
+ result.set[i] = word ^ compare.set[i]
+ }
+ return
+}
+
+// SymmetricDifferenceCardinality computes the cardinality of the symmetric difference
+func (b *BitSet) SymmetricDifferenceCardinality(compare *BitSet) uint {
+ panicIfNull(b)
+ panicIfNull(compare)
+ b, compare = sortByLength(b, compare)
+ cnt := popcntXorSlice(b.set, compare.set)
+ if len(compare.set) > len(b.set) {
+ cnt += popcntSlice(compare.set[len(b.set):])
+ }
+ return uint(cnt)
+}
+
+// InPlaceSymmetricDifference creates the destructive SymmetricDifference of base set and other set
+// This is the BitSet equivalent of ^ (xor)
+func (b *BitSet) InPlaceSymmetricDifference(compare *BitSet) {
+ panicIfNull(b)
+ panicIfNull(compare)
+ l := int(compare.wordCount())
+ if l > int(b.wordCount()) {
+ l = int(b.wordCount())
+ }
+ if compare.length > 0 {
+ b.extendSetMaybe(compare.length - 1)
+ }
+ for i := 0; i < l; i++ {
+ b.set[i] ^= compare.set[i]
+ }
+ if len(compare.set) > l {
+ for i := l; i < len(compare.set); i++ {
+ b.set[i] = compare.set[i]
+ }
+ }
+}
+
+// Is the length an exact multiple of word sizes?
+func (b *BitSet) isLenExactMultiple() bool {
+ return b.length%wordSize == 0
+}
+
+// Clean last word by setting unused bits to 0
+func (b *BitSet) cleanLastWord() {
+ if !b.isLenExactMultiple() {
+ b.set[len(b.set)-1] &= allBits >> (wordSize - b.length%wordSize)
+ }
+}
+
+// Complement computes the (local) complement of a biset (up to length bits)
+func (b *BitSet) Complement() (result *BitSet) {
+ panicIfNull(b)
+ result = New(b.length)
+ for i, word := range b.set {
+ result.set[i] = ^word
+ }
+ result.cleanLastWord()
+ return
+}
+
+// All returns true if all bits are set, false otherwise. Returns true for
+// empty sets.
+func (b *BitSet) All() bool {
+ panicIfNull(b)
+ return b.Count() == b.length
+}
+
+// None returns true if no bit is set, false otherwise. Returns true for
+// empty sets.
+func (b *BitSet) None() bool {
+ panicIfNull(b)
+ if b != nil && b.set != nil {
+ for _, word := range b.set {
+ if word > 0 {
+ return false
+ }
+ }
+ return true
+ }
+ return true
+}
+
+// Any returns true if any bit is set, false otherwise
+func (b *BitSet) Any() bool {
+ panicIfNull(b)
+ return !b.None()
+}
+
+// IsSuperSet returns true if this is a superset of the other set
+func (b *BitSet) IsSuperSet(other *BitSet) bool {
+ for i, e := other.NextSet(0); e; i, e = other.NextSet(i + 1) {
+ if !b.Test(i) {
+ return false
+ }
+ }
+ return true
+}
+
+// IsStrictSuperSet returns true if this is a strict superset of the other set
+func (b *BitSet) IsStrictSuperSet(other *BitSet) bool {
+ return b.Count() > other.Count() && b.IsSuperSet(other)
+}
+
+// DumpAsBits dumps a bit set as a string of bits
+func (b *BitSet) DumpAsBits() string {
+ if b.set == nil {
+ return "."
+ }
+ buffer := bytes.NewBufferString("")
+ i := len(b.set) - 1
+ for ; i >= 0; i-- {
+ fmt.Fprintf(buffer, "%064b.", b.set[i])
+ }
+ return buffer.String()
+}
+
+// BinaryStorageSize returns the binary storage requirements
+func (b *BitSet) BinaryStorageSize() int {
+ return binary.Size(uint64(0)) + binary.Size(b.set)
+}
+
+// WriteTo writes a BitSet to a stream
+func (b *BitSet) WriteTo(stream io.Writer) (int64, error) {
+ length := uint64(b.length)
+
+ // Write length
+ err := binary.Write(stream, binaryOrder, length)
+ if err != nil {
+ return 0, err
+ }
+
+ // Write set
+ err = binary.Write(stream, binaryOrder, b.set)
+ return int64(b.BinaryStorageSize()), err
+}
+
+// ReadFrom reads a BitSet from a stream written using WriteTo
+func (b *BitSet) ReadFrom(stream io.Reader) (int64, error) {
+ var length uint64
+
+ // Read length first
+ err := binary.Read(stream, binaryOrder, &length)
+ if err != nil {
+ return 0, err
+ }
+ newset := New(uint(length))
+
+ if uint64(newset.length) != length {
+ return 0, errors.New("unmarshalling error: type mismatch")
+ }
+
+ // Read remaining bytes as set
+ err = binary.Read(stream, binaryOrder, newset.set)
+ if err != nil {
+ return 0, err
+ }
+
+ *b = *newset
+ return int64(b.BinaryStorageSize()), nil
+}
+
+// MarshalBinary encodes a BitSet into a binary form and returns the result.
+func (b *BitSet) MarshalBinary() ([]byte, error) {
+ var buf bytes.Buffer
+ writer := bufio.NewWriter(&buf)
+
+ _, err := b.WriteTo(writer)
+ if err != nil {
+ return []byte{}, err
+ }
+
+ err = writer.Flush()
+
+ return buf.Bytes(), err
+}
+
+// UnmarshalBinary decodes the binary form generated by MarshalBinary.
+func (b *BitSet) UnmarshalBinary(data []byte) error {
+ buf := bytes.NewReader(data)
+ reader := bufio.NewReader(buf)
+
+ _, err := b.ReadFrom(reader)
+
+ return err
+}
+
+// MarshalJSON marshals a BitSet as a JSON structure
+func (b *BitSet) MarshalJSON() ([]byte, error) {
+ buffer := bytes.NewBuffer(make([]byte, 0, b.BinaryStorageSize()))
+ _, err := b.WriteTo(buffer)
+ if err != nil {
+ return nil, err
+ }
+
+ // URLEncode all bytes
+ return json.Marshal(base64Encoding.EncodeToString(buffer.Bytes()))
+}
+
+// UnmarshalJSON unmarshals a BitSet from JSON created using MarshalJSON
+func (b *BitSet) UnmarshalJSON(data []byte) error {
+ // Unmarshal as string
+ var s string
+ err := json.Unmarshal(data, &s)
+ if err != nil {
+ return err
+ }
+
+ // URLDecode string
+ buf, err := base64Encoding.DecodeString(s)
+ if err != nil {
+ return err
+ }
+
+ _, err = b.ReadFrom(bytes.NewReader(buf))
+ return err
+}