@deepkit/bson
Version:
Deepkit BSON parser
107 lines • 4.12 kB
JavaScript
;
/*
* Deepkit Framework
* Copyright (C) 2021 Deepkit UG, Marc J. Schmidt
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the MIT License.
*
* You should have received a copy of the MIT License along with this program.
*/
Object.defineProperty(exports, "__esModule", { value: true });
exports.utf8Slice = void 0;
/*!
* The buffer module from node.js, for the browser.
*
* @author Feross Aboukhadijeh <https://feross.org>
* @license MIT
*/
function utf8Slice(buf, start, end) {
end = Math.min(buf.length, end);
const res = [];
let i = start;
while (i < end) {
const firstByte = buf[i];
let codePoint = null;
let bytesPerSequence = (firstByte > 0xEF)
? 4
: (firstByte > 0xDF)
? 3
: (firstByte > 0xBF)
? 2
: 1;
if (i + bytesPerSequence <= end) {
let secondByte, thirdByte, fourthByte, tempCodePoint;
switch (bytesPerSequence) {
case 1:
if (firstByte < 0x80) {
codePoint = firstByte;
}
break;
case 2:
secondByte = buf[i + 1];
if ((secondByte & 0xC0) === 0x80) {
tempCodePoint = (firstByte & 0x1F) << 0x6 | (secondByte & 0x3F);
if (tempCodePoint > 0x7F) {
codePoint = tempCodePoint;
}
}
break;
case 3:
secondByte = buf[i + 1];
thirdByte = buf[i + 2];
if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80) {
tempCodePoint = (firstByte & 0xF) << 0xC | (secondByte & 0x3F) << 0x6 | (thirdByte & 0x3F);
if (tempCodePoint > 0x7FF && (tempCodePoint < 0xD800 || tempCodePoint > 0xDFFF)) {
codePoint = tempCodePoint;
}
}
break;
case 4:
secondByte = buf[i + 1];
thirdByte = buf[i + 2];
fourthByte = buf[i + 3];
if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80 && (fourthByte & 0xC0) === 0x80) {
tempCodePoint = (firstByte & 0xF) << 0x12 | (secondByte & 0x3F) << 0xC | (thirdByte & 0x3F) << 0x6 | (fourthByte & 0x3F);
if (tempCodePoint > 0xFFFF && tempCodePoint < 0x110000) {
codePoint = tempCodePoint;
}
}
}
}
if (codePoint === null) {
// we did not generate a valid codePoint so insert a
// replacement char (U+FFFD) and advance only 1 byte
codePoint = 0xFFFD;
bytesPerSequence = 1;
}
else if (codePoint > 0xFFFF) {
// encode to utf16 (surrogate pair dance)
codePoint -= 0x10000;
res.push(codePoint >>> 10 & 0x3FF | 0xD800);
codePoint = 0xDC00 | codePoint & 0x3FF;
}
res.push(codePoint);
i += bytesPerSequence;
}
return decodeCodePointsArray(res);
}
exports.utf8Slice = utf8Slice;
// Based on http://stackoverflow.com/a/22747272/680742, the browser with
// the lowest limit is Chrome, with 0x10000 args.
// We go 1 magnitude less, for safety
const MAX_ARGUMENTS_LENGTH = 0x1000;
function decodeCodePointsArray(codePoints) {
const len = codePoints.length;
if (len <= MAX_ARGUMENTS_LENGTH) {
return String.fromCharCode.apply(String, codePoints); // avoid extra slice()
}
// Decode in chunks to avoid "call stack size exceeded".
let res = '';
let i = 0;
while (i < len) {
res += String.fromCharCode.apply(String, codePoints.slice(i, i += MAX_ARGUMENTS_LENGTH));
}
return res;
}
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