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Merge branch 'sock_encoding' into atree_encode

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hppeng 2022-06-30 05:40:21 -07:00
parent ffc0d4b9b4 c7054ce25a
commit 7e40d6a926
1 changed files with 263 additions and 23 deletions
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244
js/utils.js
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@ -74,6 +74,8 @@ function log(b, n) {
// https://stackoverflow.com/a/27696695
// Modified for fixed precision
// Base64.fromInt(-2147483648); // gives "200000"
// Base64.toInt("200000"); // gives -2147483648
Base64 = (function () {
var digitsStr =
// 0 8 16 24 32 40 48 56 63
@ -125,8 +127,246 @@ Base64 = (function () {
};
})();
// Base64.fromInt(-2147483648); // gives "200000"
// Base64.toInt("200000"); // gives -2147483648
/** A class used to represent an arbitrary length bit vector. Very useful for encoding and decoding.
*
*/
class BitVector {
/** Constructs an arbitrary-length bit vector.
* @class
* @param {String | Number} data - The data to append.
* @param {Number} length - A set length for the data. Ignored if data is a string.
*
* The structure of the Uint32Array should be [[last, ..., first], ..., [last, ..., first], [empty space, last, ..., first]]
*/
constructor(data, length) {
let bit_vec = [];
if (typeof data === "string") {
let int = 0;
let bv_idx = 0;
length = data.length * 6;
for (let i = 0; i < data.length; i++) {
let char = Base64.toInt(data[i]);
let pre_pos = bv_idx % 32;
int |= (char << bv_idx);
bv_idx += 6;
let post_pos = bv_idx % 32;
if (post_pos < pre_pos) { //we have to have filled up the integer
bit_vec.push(int);
int = (char >>> (6 - post_pos));
}
if (i == data.length - 1 && post_pos != 0) {
bit_vec.push(int);
}
}
} else if (typeof data === "number") {
if (typeof length === "undefined")
if (length < 0) {
throw new RangeError("BitVector must have nonnegative length.");
}
//convert to int just in case
data = Math.round(data);
//range of numbers that won't fit in a uint32
if (data > 2**32 - 1 || data < -(2 ** 32 - 1)) {
throw new RangeError("Numerical data has to fit within a 32-bit integer range to instantiate a BitVector.");
}
bit_vec.push(data);
} else {
throw new TypeError("BitVector must be instantiated with a Number or a B64 String");
}
this.length = length;
this.bits = new Uint32Array(bit_vec);
}
/** Return value of bit at index idx.
*
* @param {Number} idx - The index to read
*
* @returns The bit value at position idx
*/
read_bit(idx) {
if (idx < 0 || idx >= this.length) {
throw new RangeError("Cannot read bit outside the range of the BitVector.");
}
return ((this.bits[Math.floor(idx / 32)] & (1 << (idx % 32))) == 0 ? 0 : 1);
}
/** Returns an integer value (if possible) made from the range of bits [start, end). Undefined behavior if the range to read is too big.
*
* @param {Number} start - The index to start slicing from. Inclusive.
* @param {Number} end - The index to end slicing at. Exclusive.
*
* @returns An integer representation of the sliced bits.
*/
slice(start, end) {
//TO NOTE: JS shifting is ALWAYS in mod 32. a << b will do a << (b mod 32) implicitly.
if (end < start) {
throw new RangeError("Cannot slice a range where the end is before the start.");
} else if (end == start) {
return 0;
} else if (end - start > 32) {
//requesting a slice of longer than 32 bits (safe integer "length")
throw new RangeError("Cannot slice a range of longer than 32 bits (unsafe to store in an integer).");
}
let res = 0;
if (Math.floor((end - 1) / 32) == Math.floor(start / 32)) {
//the range is within 1 uint32 section - do some relatively fast bit twiddling
res = (this.bits[Math.floor(start / 32)] & ~((((~0) << ((end - 1))) << 1) | ~((~0) << (start)))) >>> (start % 32);
} else {
//the number of bits in the uint32s
let start_pos = (start % 32);
let int_idx = Math.floor(start/32);
res = (this.bits[int_idx] & ((~0) << (start))) >>> (start_pos);
res |= (this.bits[int_idx + 1] & ~((~0) << (end))) << (32 - start_pos);
}
return res;
// General code - slow
// for (let i = start; i < end; i++) {
// res |= (get_bit(i) << (i - start));
// }
}
/** Assign bit at index idx to 1.
*
* @param {Number} idx - The index to set.
*/
set_bit(idx) {
if (idx < 0 || idx >= this.length) {
throw new RangeError("Cannot set bit outside the range of the BitVector.");
}
this.bits[Math.floor(idx / 32)] |= (1 << idx % 32);
}
/** Assign bit at index idx to 0.
*
* @param {Number} idx - The index to clear.
*/
clear_bit(idx) {
if (idx < 0 || idx >= this.length) {
throw new RangeError("Cannot clear bit outside the range of the BitVector.");
}
this.bits[Math.floor(idx / 32)] &= ~(1 << idx % 32);
}
/** Creates a string version of the bit vector in B64. Does not keep the order of elements a sensible human readable format.
*
* @returns A b64 string representation of the BitVector.
*/
toB64() {
if (this.length == 0) {
return "";
}
let b64_str = "";
let i = 0;
while (i < this.length) {
b64_str += Base64.fromIntV(this.slice(i, i + 6), 1);
i += 6;
}
return b64_str;
}
/** Returns a BitVector in bitstring format. Probably only useful for dev debugging.
*
* @returns A bit string representation of the BitVector. Goes from higher-indexed bits to lower-indexed bits. (n ... 0)
*/
toString() {
let ret_str = "";
for (let i = 0; i < this.length; i++) {
ret_str = (this.read_bit(i) == 0 ? "0": "1") + ret_str;
}
return ret_str;
}
/** Returns a BitVector in bitstring format. Probably only useful for dev debugging.
*
* @returns A bit string representation of the BitVector. Goes from lower-indexed bits to higher-indexed bits. (0 ... n)
*/
toStringR() {
let ret_str = "";
for (let i = 0; i < this.length; i++) {
ret_str += (this.read_bit(i) == 0 ? "0": "1");
}
return ret_str;
}
/** Appends data to the BitVector.
*
* @param {Number | String} data - The data to append.
* @param {Number} length - The length, in bits, of the new data. This is ignored if data is a string.
*/
append(data, length) {
if (length < 0) {
throw new RangeError("BitVector length must increase by a nonnegative number.");
}
let bit_vec = [];
for (const uint of this.bits) {
bit_vec.push(uint);
}
if (typeof data === "string") {
let int = bit_vec[bit_vec.length - 1];
let bv_idx = this.length;
length = data.length * 6;
let updated_curr = false;
for (let i = 0; i < data.length; i++) {
let char = Base64.toInt(data[i]);
let pre_pos = bv_idx % 32;
int |= (char << bv_idx);
bv_idx += 6;
let post_pos = bv_idx % 32;
if (post_pos < pre_pos) { //we have to have filled up the integer
if (bit_vec.length == this.bits.length && !updated_curr) {
bit_vec[bit_vec.length - 1] = int;
updated_curr = true;
} else {
bit_vec.push(int);
}
int = (char >>> (6 - post_pos));
}
if (i == data.length - 1) {
if (bit_vec.length == this.bits.length && !updated_curr) {
bit_vec[bit_vec.length - 1] = int;
} else if (post_pos != 0) {
bit_vec.push(int);
}
}
}
} else if (typeof data === "number") {
//convert to int just in case
let int = Math.round(data);
//range of numbers that "could" fit in a uint32 -> [0, 2^32) U [-2^31, 2^31)
if (data > 2**32 - 1 || data < -(2 ** 31)) {
throw new RangeError("Numerical data has to fit within a 32-bit integer range to instantiate a BitVector.");
}
//could be split between multiple new ints
//reminder that shifts implicitly mod 32
bit_vec[bit_vec.length - 1] |= ((int & ~((~0) << length)) << (this.length));
if (((this.length - 1) % 32 + 1) + length > 32) {
bit_vec.push(int >>> (32 - this.length));
}
} else {
throw new TypeError("BitVector must be appended with a Number or a B64 String");
}
this.bits = new Uint32Array(bit_vec);
this.length += length;
}
};
/*
Turns a raw stat and a % stat into a final stat on the basis that - raw and >= 100% becomes 0 and + raw and <=-100% becomes negative.