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tahamajs/Other_Lessons / AP /TA_1 /AP-ECE-UT.github.io /node_modules /source-map /lib /base64-vlq.js
| /* -*- Mode: js; js-indent-level: 2; -*- */ | |
| /* | |
| * Copyright 2011 Mozilla Foundation and contributors | |
| * Licensed under the New BSD license. See LICENSE or: | |
| * http://opensource.org/licenses/BSD-3-Clause | |
| * | |
| * Based on the Base 64 VLQ implementation in Closure Compiler: | |
| * https://code.google.com/p/closure-compiler/source/browse/trunk/src/com/google/debugging/sourcemap/Base64VLQ.java | |
| * | |
| * Copyright 2011 The Closure Compiler Authors. All rights reserved. | |
| * Redistribution and use in source and binary forms, with or without | |
| * modification, are permitted provided that the following conditions are | |
| * met: | |
| * | |
| * * Redistributions of source code must retain the above copyright | |
| * notice, this list of conditions and the following disclaimer. | |
| * * Redistributions in binary form must reproduce the above | |
| * copyright notice, this list of conditions and the following | |
| * disclaimer in the documentation and/or other materials provided | |
| * with the distribution. | |
| * * Neither the name of Google Inc. nor the names of its | |
| * contributors may be used to endorse or promote products derived | |
| * from this software without specific prior written permission. | |
| * | |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| */ | |
| const base64 = require("./base64"); | |
| // A single base 64 digit can contain 6 bits of data. For the base 64 variable | |
| // length quantities we use in the source map spec, the first bit is the sign, | |
| // the next four bits are the actual value, and the 6th bit is the | |
| // continuation bit. The continuation bit tells us whether there are more | |
| // digits in this value following this digit. | |
| // | |
| // Continuation | |
| // | Sign | |
| // | | | |
| // V V | |
| // 101011 | |
| const VLQ_BASE_SHIFT = 5; | |
| // binary: 100000 | |
| const VLQ_BASE = 1 << VLQ_BASE_SHIFT; | |
| // binary: 011111 | |
| const VLQ_BASE_MASK = VLQ_BASE - 1; | |
| // binary: 100000 | |
| const VLQ_CONTINUATION_BIT = VLQ_BASE; | |
| /** | |
| * Converts from a two-complement value to a value where the sign bit is | |
| * placed in the least significant bit. For example, as decimals: | |
| * 1 becomes 2 (10 binary), -1 becomes 3 (11 binary) | |
| * 2 becomes 4 (100 binary), -2 becomes 5 (101 binary) | |
| */ | |
| function toVLQSigned(aValue) { | |
| return aValue < 0 | |
| ? ((-aValue) << 1) + 1 | |
| : (aValue << 1) + 0; | |
| } | |
| /** | |
| * Converts to a two-complement value from a value where the sign bit is | |
| * placed in the least significant bit. For example, as decimals: | |
| * 2 (10 binary) becomes 1, 3 (11 binary) becomes -1 | |
| * 4 (100 binary) becomes 2, 5 (101 binary) becomes -2 | |
| */ | |
| // eslint-disable-next-line no-unused-vars | |
| function fromVLQSigned(aValue) { | |
| const isNegative = (aValue & 1) === 1; | |
| const shifted = aValue >> 1; | |
| return isNegative | |
| ? -shifted | |
| : shifted; | |
| } | |
| /** | |
| * Returns the base 64 VLQ encoded value. | |
| */ | |
| exports.encode = function base64VLQ_encode(aValue) { | |
| let encoded = ""; | |
| let digit; | |
| let vlq = toVLQSigned(aValue); | |
| do { | |
| digit = vlq & VLQ_BASE_MASK; | |
| vlq >>>= VLQ_BASE_SHIFT; | |
| if (vlq > 0) { | |
| // There are still more digits in this value, so we must make sure the | |
| // continuation bit is marked. | |
| digit |= VLQ_CONTINUATION_BIT; | |
| } | |
| encoded += base64.encode(digit); | |
| } while (vlq > 0); | |
| return encoded; | |
| }; | |
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