package bits import ( "encoding/binary" "fmt" "regexp" "strings" "sync" tmmath "github.com/tendermint/tendermint/libs/math" tmrand "github.com/tendermint/tendermint/libs/rand" ) // BitArray is a thread-safe implementation of a bit array. type BitArray struct { mtx sync.Mutex Bits int `json:"bits"` // NOTE: persisted via reflect, must be exported Elems []uint64 `json:"elems"` // NOTE: persisted via reflect, must be exported } // NewBitArray returns a new bit array. // It returns nil if the number of bits is zero. func NewBitArray(bits int) *BitArray { if bits <= 0 { return nil } return &BitArray{ Bits: bits, Elems: make([]uint64, (bits+63)/64), } } // Size returns the number of bits in the bitarray func (bA *BitArray) Size() int { if bA == nil { return 0 } return bA.Bits } // GetIndex returns the bit at index i within the bit array. // The behavior is undefined if i >= bA.Bits func (bA *BitArray) GetIndex(i int) bool { if bA == nil { return false } bA.mtx.Lock() defer bA.mtx.Unlock() return bA.getIndex(i) } func (bA *BitArray) getIndex(i int) bool { if i >= bA.Bits { return false } return bA.Elems[i/64]&(uint64(1)< 0 } // SetIndex sets the bit at index i within the bit array. // The behavior is undefined if i >= bA.Bits func (bA *BitArray) SetIndex(i int, v bool) bool { if bA == nil { return false } bA.mtx.Lock() defer bA.mtx.Unlock() return bA.setIndex(i, v) } func (bA *BitArray) setIndex(i int, v bool) bool { if i >= bA.Bits { return false } if v { bA.Elems[i/64] |= (uint64(1) << uint(i%64)) } else { bA.Elems[i/64] &= ^(uint64(1) << uint(i%64)) } return true } // Copy returns a copy of the provided bit array. func (bA *BitArray) Copy() *BitArray { if bA == nil { return nil } bA.mtx.Lock() defer bA.mtx.Unlock() return bA.copy() } func (bA *BitArray) copy() *BitArray { c := make([]uint64, len(bA.Elems)) copy(c, bA.Elems) return &BitArray{ Bits: bA.Bits, Elems: c, } } func (bA *BitArray) copyBits(bits int) *BitArray { c := make([]uint64, (bits+63)/64) copy(c, bA.Elems) return &BitArray{ Bits: bits, Elems: c, } } // Or returns a bit array resulting from a bitwise OR of the two bit arrays. // If the two bit-arrys have different lengths, Or right-pads the smaller of the two bit-arrays with zeroes. // Thus the size of the return value is the maximum of the two provided bit arrays. func (bA *BitArray) Or(o *BitArray) *BitArray { if bA == nil && o == nil { return nil } if bA == nil && o != nil { return o.Copy() } if o == nil { return bA.Copy() } bA.mtx.Lock() o.mtx.Lock() c := bA.copyBits(tmmath.MaxInt(bA.Bits, o.Bits)) smaller := tmmath.MinInt(len(bA.Elems), len(o.Elems)) for i := 0; i < smaller; i++ { c.Elems[i] |= o.Elems[i] } bA.mtx.Unlock() o.mtx.Unlock() return c } // And returns a bit array resulting from a bitwise AND of the two bit arrays. // If the two bit-arrys have different lengths, this truncates the larger of the two bit-arrays from the right. // Thus the size of the return value is the minimum of the two provided bit arrays. func (bA *BitArray) And(o *BitArray) *BitArray { if bA == nil || o == nil { return nil } bA.mtx.Lock() o.mtx.Lock() defer func() { bA.mtx.Unlock() o.mtx.Unlock() }() return bA.and(o) } func (bA *BitArray) and(o *BitArray) *BitArray { c := bA.copyBits(tmmath.MinInt(bA.Bits, o.Bits)) for i := 0; i < len(c.Elems); i++ { c.Elems[i] &= o.Elems[i] } return c } // Not returns a bit array resulting from a bitwise Not of the provided bit array. func (bA *BitArray) Not() *BitArray { if bA == nil { return nil // Degenerate } bA.mtx.Lock() defer bA.mtx.Unlock() return bA.not() } func (bA *BitArray) not() *BitArray { c := bA.copy() for i := 0; i < len(c.Elems); i++ { c.Elems[i] = ^c.Elems[i] } return c } // Sub subtracts the two bit-arrays bitwise, without carrying the bits. // Note that carryless subtraction of a - b is (a and not b). // The output is the same as bA, regardless of o's size. // If bA is longer than o, o is right padded with zeroes func (bA *BitArray) Sub(o *BitArray) *BitArray { if bA == nil || o == nil { // TODO: Decide if we should do 1's complement here? return nil } bA.mtx.Lock() o.mtx.Lock() // output is the same size as bA c := bA.copyBits(bA.Bits) // Only iterate to the minimum size between the two. // If o is longer, those bits are ignored. // If bA is longer, then skipping those iterations is equivalent // to right padding with 0's smaller := tmmath.MinInt(len(bA.Elems), len(o.Elems)) for i := 0; i < smaller; i++ { // &^ is and not in golang c.Elems[i] &^= o.Elems[i] } bA.mtx.Unlock() o.mtx.Unlock() return c } // IsEmpty returns true iff all bits in the bit array are 0 func (bA *BitArray) IsEmpty() bool { if bA == nil { return true // should this be opposite? } bA.mtx.Lock() defer bA.mtx.Unlock() for _, e := range bA.Elems { if e > 0 { return false } } return true } // IsFull returns true iff all bits in the bit array are 1. func (bA *BitArray) IsFull() bool { if bA == nil { return true } bA.mtx.Lock() defer bA.mtx.Unlock() // Check all elements except the last for _, elem := range bA.Elems[:len(bA.Elems)-1] { if (^elem) != 0 { return false } } // Check that the last element has (lastElemBits) 1's lastElemBits := (bA.Bits+63)%64 + 1 lastElem := bA.Elems[len(bA.Elems)-1] return (lastElem+1)&((uint64(1)< 0 { trueIndices = append(trueIndices, curBit) } curBit++ } } // handle last element lastElem := bA.Elems[numElems-1] numFinalBits := bA.Bits - curBit for i := 0; i < numFinalBits; i++ { if (lastElem & (uint64(1) << uint64(i))) > 0 { trueIndices = append(trueIndices, curBit) } curBit++ } return trueIndices } // String returns a string representation of BitArray: BA{}, // where is a sequence of 'x' (1) and '_' (0). // The includes spaces and newlines to help people. // For a simple sequence of 'x' and '_' characters with no spaces or newlines, // see the MarshalJSON() method. // Example: "BA{_x_}" or "nil-BitArray" for nil. func (bA *BitArray) String() string { return bA.StringIndented("") } // StringIndented returns the same thing as String(), but applies the indent // at every 10th bit, and twice at every 50th bit. func (bA *BitArray) StringIndented(indent string) string { if bA == nil { return "nil-BitArray" } bA.mtx.Lock() defer bA.mtx.Unlock() return bA.stringIndented(indent) } func (bA *BitArray) stringIndented(indent string) string { lines := []string{} bits := "" for i := 0; i < bA.Bits; i++ { if bA.getIndex(i) { bits += "x" } else { bits += "_" } if i%100 == 99 { lines = append(lines, bits) bits = "" } if i%10 == 9 { bits += indent } if i%50 == 49 { bits += indent } } if len(bits) > 0 { lines = append(lines, bits) } return fmt.Sprintf("BA{%v:%v}", bA.Bits, strings.Join(lines, indent)) } // Bytes returns the byte representation of the bits within the bitarray. func (bA *BitArray) Bytes() []byte { bA.mtx.Lock() defer bA.mtx.Unlock() numBytes := (bA.Bits + 7) / 8 bytes := make([]byte, numBytes) for i := 0; i < len(bA.Elems); i++ { elemBytes := [8]byte{} binary.LittleEndian.PutUint64(elemBytes[:], bA.Elems[i]) copy(bytes[i*8:], elemBytes[:]) } return bytes } // Update sets the bA's bits to be that of the other bit array. // The copying begins from the begin of both bit arrays. func (bA *BitArray) Update(o *BitArray) { if bA == nil || o == nil { return } bA.mtx.Lock() o.mtx.Lock() defer func() { bA.mtx.Unlock() o.mtx.Unlock() }() copy(bA.Elems, o.Elems) } // MarshalJSON implements json.Marshaler interface by marshaling bit array // using a custom format: a string of '-' or 'x' where 'x' denotes the 1 bit. func (bA *BitArray) MarshalJSON() ([]byte, error) { if bA == nil { return []byte("null"), nil } bA.mtx.Lock() defer bA.mtx.Unlock() bits := `"` for i := 0; i < bA.Bits; i++ { if bA.getIndex(i) { bits += `x` } else { bits += `_` } } bits += `"` return []byte(bits), nil } var bitArrayJSONRegexp = regexp.MustCompile(`\A"([_x]*)"\z`) // UnmarshalJSON implements json.Unmarshaler interface by unmarshaling a custom // JSON description. func (bA *BitArray) UnmarshalJSON(bz []byte) error { b := string(bz) if b == "null" { // This is required e.g. for encoding/json when decoding // into a pointer with pre-allocated BitArray. bA.Bits = 0 bA.Elems = nil return nil } // Validate 'b'. match := bitArrayJSONRegexp.FindStringSubmatch(b) if match == nil { return fmt.Errorf("bitArray in JSON should be a string of format %q but got %s", bitArrayJSONRegexp.String(), b) } bits := match[1] // Construct new BitArray and copy over. numBits := len(bits) bA2 := NewBitArray(numBits) for i := 0; i < numBits; i++ { if bits[i] == 'x' { bA2.SetIndex(i, true) } } *bA = *bA2 //nolint:govet return nil }