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BitArray.js
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BitArray.js
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export default class BitArray extends DataView {
#getter;
#setter;
#bytesPerIndex;
#shiftAmount;
// n >> 3 is Math.floor(n/8)
// n & 7 is n % 8
constructor(sizeOrBuffer, byteSize = 8) {
let len = 0;
let validValues = [8, 16, 32, 64];
if (validValues.indexOf(byteSize) == -1) {
throw new Error("Mode must be one of: " + validValues);
}
if (sizeOrBuffer instanceof ArrayBuffer) {
len = sizeOrBuffer.byteLength * byteSize;
super(sizeOrBuffer);
} else if (Number.isInteger(sizeOrBuffer)) {
if (sizeOrBuffer > 1.5e10) { throw new Error("BitArray size can not exceed 1.5e10"); }
len = sizeOrBuffer;
super(new ArrayBuffer(Math.ceil(len / byteSize) * byteSize)); // Must be multiples of the byteSize
} else {
throw new Error("A size or buffer must be provided when initalizing a BitArray");
}
this.#getter = byteSize != 64 ? this["getUint" + byteSize] : this.getBigUint64;
this.#setter = byteSize != 64 ? this["setUint" + byteSize] : this.setBigUint64;
this.#shiftAmount = validValues.indexOf(byteSize) + 3;
this.#bytesPerIndex = byteSize/8;
Object.defineProperty(this, "byteSize", {
configurable: false,
enumerable: false,
writable: false,
value: byteSize
});
Object.defineProperty(this, "indexes", {
configurable: false,
enumerable: false,
writable: false,
value: Math.ceil(len / byteSize)
});
Object.defineProperty(this, "length", {
configurable: false,
enumerable: false,
writable: false,
value: len
});
}
get popcount(){
let m1 = 0x55555555;
let m2 = 0x33333333;
let m4 = 0x0f0f0f0f;
let h01 = 0x01010101;
let pc = 0;
let x;
for (let i = 0; i < this.buffer.byteLength; i++){
x = this.getIndex(i);
x -= (x >> 1) & m1; //put count of each 2 bits into those 2 bits
x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits
x = (x + (x >> 4)) & m4; //put count of each 8 bits into those 8 bits
pc += (x * h01) >> 56;
}
return pc;
}
getIndex(i) {
let offset = i >> this.#shiftAmount * this.#bytesPerIndex;
return this.#getter(offset);
}
setIndex(i, v) {
let offset = i >> this.#shiftAmount * this.#bytesPerIndex;
this.#setter(offset, v);
}
at(i) {
// Fetches the value at the given index
if (i >= 0 && i < this.length) {
return this.getIndex(i) & (1 << (i & 7)) ? 1 : 0;
}
return 0;
}
set(i, bool = true) {
// Sets the value at the given index to the provided boolean
if (i >= 0 && i < this.length) {
this.setIndex(i, this.getIndex(i) | (bool << (i & 7)));
}
}
reset(i) {
// Sets the value at the given index to 0
if (i >= 0 && i < this.length) {
this.setIndex(i, this.getIndex(i) & ~(1 << (i & 7)));
}
}
fill() {
// Fills the array with 1s
let max = {
"8":255,
"16":65535,
"32":4294967295,
"64":18446744073709551615
};
for (let i = 0; i < this.length; i++) {
this.setIndex(i , max[this.byteSize]);
}
}
clear(){
// Fills the array with 0s
for (let i = 0; i < this.length; i++) {
this.setIndex(i, 0);
}
}
toggle(i) {
// Flips the value at the given index
if (i >= 0 && i < this.length) {
this.setIndex(i, this.getIndex(i) ^ (1 << (i & 7)));
}
}
slice(a = 0, b = this.length) {
return new BitArray(b - a, this.buffer.slice(a >> this.#shiftAmount, b >> this.#shiftAmount));
}
toString() {
let msg = [];
for (let i = 0; i < this.length; i++) {
msg.push(this.at(i));
}
return msg.join('');
}
and(bar, newArray = false) {
// And of this and bar. Example: 1100 & 1001 = 1000
let result = newArray ? new BitArray(this.length, this.byteSize) : this;
for (let i = 0; i < this.length; i++) {
if (i < bar.length) {
result.setIndex(i, this.getIndex(i) & bar.getIndex(i));
} else {
result.setIndex(i, 0);
}
}
return result;
}
or(bar, newArray = false) {
// Or of this and bar. Example: 1100 | 1001 = 1101
let result = newArray ? new BitArray(this.length, this.byteSize) : this;
for (let i = 0; i < this.length; i++) {
if (i < bar.length) {
result.setIndex(i, this.getIndex(i) | bar.getIndex(i));
} else {
result.setIndex(i, this.getIndex(i));
}
}
return result;
}
xor(bar, newArray = false) {
// Xor of this and bar. Example: 1100 ^ 1001 = 0101;
let result = newArray ? new BitArray(this.length, this.byteSize) : this;
for (let i = 0; i < result.length; i++) {
if (i < bar.length) {
result.setIndex(i, this.getIndex(i) ^ bar.getIndex(i));
} else {
result.setIndex(i, this.getIndex(i));
}
}
return result;
}
not(newArray = false) {
// Flips all the bits in this buffer. Example: 1100 = 0011
let result = newArray ? new BitArray(this.length, this.byteSize) : this;
for (let i = 0; i < this.length; i++) {
result.setIndex(i, ~(this.getIndex(i) >> 0));
}
return result;
}
clone() {
// Copies the values from this BitArray into a new BitArray
let result = new BitArray(this.length, this.byteSize);
for (let i = 0; i < this.indexes; i++) {
result.setIndex(i, this.getIndex(i));
}
return result;
}
}