"use strict";
var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");
var _classCallCheck2 = _interopRequireDefault(require("@babel/runtime/helpers/classCallCheck"));
var _createClass2 = _interopRequireDefault(require("@babel/runtime/helpers/createClass"));
var BITS_PER_BYTE = 8;
var abs = Math.abs,
ceil = Math.ceil,
floor = Math.floor,
log2 = Math.log2;
var gcd = function gcd(a, b) {
var la = a;
var lb = b;
while (lb !== 0) {
var _ref = [lb, la % lb];
la = _ref[0];
lb = _ref[1];
}
return abs(la);
};
var lcm = function lcm(a, b) {
return a / gcd(a, b) * b;
};
var genNdxFn = function genNdxFn(bitsPerChar) {
// If BITS_PER_BYTEs is a multiple of bitsPerChar, we can slice off an integer number
// of chars per byte.
if (lcm(bitsPerChar, BITS_PER_BYTE) === BITS_PER_BYTE) {
return function (chunk, slice, bytes) {
var lShift = bitsPerChar;
var rShift = BITS_PER_BYTE - bitsPerChar;
return (bytes[chunk] << lShift * slice & 0xff) >> rShift;
};
} // Otherwise, while slicing off bits per char, we can possibly straddle two
// of bytes, so a more work is involved
var slicesPerChunk = lcm(bitsPerChar, BITS_PER_BYTE) / BITS_PER_BYTE;
return function (chunk, slice, bytes) {
var bNum = chunk * slicesPerChunk;
var offset = slice * bitsPerChar / BITS_PER_BYTE;
var lOffset = floor(offset);
var rOffset = ceil(offset);
var rShift = BITS_PER_BYTE - bitsPerChar;
var lShift = slice * bitsPerChar % BITS_PER_BYTE;
var ndx = (bytes[bNum + lOffset] << lShift & 0xff) >> rShift;
var r1Bits = (rOffset + 1) * BITS_PER_BYTE;
var s1Bits = (slice + 1) * bitsPerChar;
var rShiftIt = (r1Bits - s1Bits) % BITS_PER_BYTE;
if (rShift < rShiftIt) {
ndx += bytes[bNum + rOffset] >> rShiftIt;
}
return ndx;
};
};
var CharSet = /*#__PURE__*/function () {
function CharSet(chars) {
(0, _classCallCheck2["default"])(this, CharSet);
if (!(typeof chars === 'string' || chars instanceof String)) {
throw new Error('Invalid chars: Must be string');
}
var length = chars.length;
if (![2, 4, 8, 16, 32, 64].includes(length)) {
throw new Error('Invalid char count: must be one of 2,4,8,16,32,64');
} // Ensure no repeated characters
for (var i = 0; i < length; i += 1) {
var c = chars.charAt(i);
for (var j = i + 1; j < length; j += 1) {
if (c === chars.charAt(j)) {
throw new Error('Characters not unique');
}
}
}
this.chars = chars;
this.bitsPerChar = floor(log2(length));
this.length = length;
this.ndxFn = genNdxFn(this.bitsPerChar);
this.charsPerChunk = lcm(this.bitsPerChar, BITS_PER_BYTE) / this.bitsPerChar;
}
(0, _createClass2["default"])(CharSet, [{
key: "bytesNeeded",
value: function bytesNeeded(bitLen) {
var count = ceil(bitLen / this.bitsPerChar);
return ceil(count * this.bitsPerChar / BITS_PER_BYTE);
}
}]);
return CharSet;
}();
module.exports = {
CharSet: CharSet
};