source_map.js

// This file is a modified version of:
// https://cs.chromium.org/chromium/src/v8/tools/SourceMap.js?rcl=dd10454c1d
// from the V8 codebase. Logic specific to WebInspector is removed and linting
// is made to match the Node.js style guide.

// Copyright 2013 the V8 project 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.

// This is a copy from blink dev tools, see:
// http://src.chromium.org/viewvc/blink/trunk/Source/devtools/front_end/SourceMap.js
// revision: 153407

/*
 * Copyright (C) 2012 Google Inc. 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.
 */

'use strict';

const {
  ArrayIsArray,
  ArrayPrototypePush,
  ArrayPrototypeSlice,
  ArrayPrototypeSort,
  ObjectPrototypeHasOwnProperty,
  StringPrototypeCharAt,
} = primordials;

const { validateObject } = require('internal/validators');

let base64Map;

const VLQ_BASE_SHIFT = 5;
const VLQ_BASE_MASK = (1 << 5) - 1;
const VLQ_CONTINUATION_MASK = 1 << 5;

class StringCharIterator {
  /**
   * @constructor
   * @param {string} string
   */
  constructor(string) {
    this._string = string;
    this._position = 0;
  }

  /**
   * @return {string}
   */
  next() {
    return StringPrototypeCharAt(this._string, this._position++);
  }

  /**
   * @return {string}
   */
  peek() {
    return StringPrototypeCharAt(this._string, this._position);
  }

  /**
   * @return {boolean}
   */
  hasNext() {
    return this._position < this._string.length;
  }
}

/**
 * Implements Source Map V3 model.
 * See https://github.com/google/closure-compiler/wiki/Source-Maps
 * for format description.
 */
class SourceMap {
  #payload;
  #mappings = [];
  #sources = {};
  #sourceContentByURL = {};
  #lineLengths = undefined;

  /**
   * @constructor
   * @param {SourceMapV3} payload
   */
  constructor(payload, { lineLengths } = { __proto__: null }) {
    if (!base64Map) {
      const base64Digits =
             'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
      base64Map = {};
      for (let i = 0; i < base64Digits.length; ++i)
        base64Map[base64Digits[i]] = i;
    }
    this.#payload = cloneSourceMapV3(payload);
    this.#parseMappingPayload();
    if (ArrayIsArray(lineLengths) && lineLengths.length) {
      this.#lineLengths = lineLengths;
    }
  }

  /**
   * @return {object} raw source map v3 payload.
   */
  get payload() {
    return cloneSourceMapV3(this.#payload);
  }

  /**
   * @return {number[] | undefined} line lengths of generated source code
   */
  get lineLengths() {
    if (this.#lineLengths) {
      return ArrayPrototypeSlice(this.#lineLengths);
    }
    return undefined;
  }

  #parseMappingPayload = () => {
    if (this.#payload.sections) {
      this.#parseSections(this.#payload.sections);
    } else {
      this.#parseMap(this.#payload, 0, 0);
    }
    ArrayPrototypeSort(this.#mappings, compareSourceMapEntry);
  };

  /**
   * @param {Array.<SourceMapV3.Section>} sections
   */
  #parseSections = (sections) => {
    for (let i = 0; i < sections.length; ++i) {
      const section = sections[i];
      this.#parseMap(section.map, section.offset.line, section.offset.column);
    }
  };

  /**
   * @param {number} lineOffset 0-indexed line offset in compiled resource
   * @param {number} columnOffset 0-indexed column offset in compiled resource
   * @return {object} representing start of range if found, or empty object
   */
  findEntry(lineOffset, columnOffset) {
    let first = 0;
    let count = this.#mappings.length;
    while (count > 1) {
      const step = count >> 1;
      const middle = first + step;
      const mapping = this.#mappings[middle];
      if (lineOffset < mapping[0] ||
          (lineOffset === mapping[0] && columnOffset < mapping[1])) {
        count = step;
      } else {
        first = middle;
        count -= step;
      }
    }
    const entry = this.#mappings[first];
    if (!first && entry && (lineOffset < entry[0] ||
        (lineOffset === entry[0] && columnOffset < entry[1]))) {
      return {};
    } else if (!entry) {
      return {};
    }
    return {
      generatedLine: entry[0],
      generatedColumn: entry[1],
      originalSource: entry[2],
      originalLine: entry[3],
      originalColumn: entry[4],
      name: entry[5],
    };
  }

  /**
   * @param {number} lineNumber 1-indexed line number in compiled resource call site
   * @param {number} columnNumber 1-indexed column number in compiled resource call site
   * @return {object} representing origin call site if found, or empty object
   */
  findOrigin(lineNumber, columnNumber) {
    const range = this.findEntry(lineNumber - 1, columnNumber - 1);
    if (
      range.originalSource === undefined ||
      range.originalLine === undefined ||
      range.originalColumn === undefined ||
      range.generatedLine === undefined ||
      range.generatedColumn === undefined
    ) {
      return {};
    }
    const lineOffset = lineNumber - range.generatedLine;
    const columnOffset = columnNumber - range.generatedColumn;
    return {
      name: range.name,
      fileName: range.originalSource,
      lineNumber: range.originalLine + lineOffset,
      columnNumber: range.originalColumn + columnOffset,
    };
  }

  /**
   * @override
   */
  #parseMap(map, lineNumber, columnNumber) {
    let sourceIndex = 0;
    let sourceLineNumber = 0;
    let sourceColumnNumber = 0;
    let nameIndex = 0;

    const sources = [];
    const originalToCanonicalURLMap = {};
    for (let i = 0; i < map.sources.length; ++i) {
      const url = map.sources[i];
      originalToCanonicalURLMap[url] = url;
      ArrayPrototypePush(sources, url);
      this.#sources[url] = true;

      if (map.sourcesContent && map.sourcesContent[i])
        this.#sourceContentByURL[url] = map.sourcesContent[i];
    }

    const stringCharIterator = new StringCharIterator(map.mappings);
    let sourceURL = sources[sourceIndex];
    while (true) {
      if (stringCharIterator.peek() === ',')
        stringCharIterator.next();
      else {
        while (stringCharIterator.peek() === ';') {
          lineNumber += 1;
          columnNumber = 0;
          stringCharIterator.next();
        }
        if (!stringCharIterator.hasNext())
          break;
      }

      columnNumber += decodeVLQ(stringCharIterator);
      if (isSeparator(stringCharIterator.peek())) {
        ArrayPrototypePush(this.#mappings, [lineNumber, columnNumber]);
        continue;
      }

      const sourceIndexDelta = decodeVLQ(stringCharIterator);
      if (sourceIndexDelta) {
        sourceIndex += sourceIndexDelta;
        sourceURL = sources[sourceIndex];
      }
      sourceLineNumber += decodeVLQ(stringCharIterator);
      sourceColumnNumber += decodeVLQ(stringCharIterator);

      let name;
      if (!isSeparator(stringCharIterator.peek())) {
        nameIndex += decodeVLQ(stringCharIterator);
        name = map.names?.[nameIndex];
      }

      ArrayPrototypePush(
        this.#mappings,
        [lineNumber, columnNumber, sourceURL, sourceLineNumber,
         sourceColumnNumber, name],
      );
    }
  }
}

/**
 * @param {string} char
 * @return {boolean}
 */
function isSeparator(char) {
  return char === ',' || char === ';';
}

/**
 * @param {SourceMap.StringCharIterator} stringCharIterator
 * @return {number}
 */
function decodeVLQ(stringCharIterator) {
  // Read unsigned value.
  let result = 0;
  let shift = 0;
  let digit;
  do {
    digit = base64Map[stringCharIterator.next()];
    result += (digit & VLQ_BASE_MASK) << shift;
    shift += VLQ_BASE_SHIFT;
  } while (digit & VLQ_CONTINUATION_MASK);

  // Fix the sign.
  const negative = result & 1;
  // Use unsigned right shift, so that the 32nd bit is properly shifted to the
  // 31st, and the 32nd becomes unset.
  result >>>= 1;
  if (!negative) {
    return result;
  }

  // We need to OR here to ensure the 32nd bit (the sign bit in an Int32) is
  // always set for negative numbers. If `result` were 1, (meaning `negate` is
  // true and all other bits were zeros), `result` would now be 0. But -0
  // doesn't flip the 32nd bit as intended. All other numbers will successfully
  // set the 32nd bit without issue, so doing this is a noop for them.
  return -result | (1 << 31);
}

/**
 * @param {SourceMapV3} payload
 * @return {SourceMapV3}
 */
function cloneSourceMapV3(payload) {
  validateObject(payload, 'payload');
  payload = { ...payload };
  for (const key in payload) {
    if (ObjectPrototypeHasOwnProperty(payload, key) &&
        ArrayIsArray(payload[key])) {
      payload[key] = ArrayPrototypeSlice(payload[key]);
    }
  }
  return payload;
}

/**
 * @param {Array} entry1 source map entry [lineNumber, columnNumber, sourceURL,
 *  sourceLineNumber, sourceColumnNumber]
 * @param {Array} entry2 source map entry.
 * @return {number}
 */
function compareSourceMapEntry(entry1, entry2) {
  const { 0: lineNumber1, 1: columnNumber1 } = entry1;
  const { 0: lineNumber2, 1: columnNumber2 } = entry2;
  if (lineNumber1 !== lineNumber2) {
    return lineNumber1 - lineNumber2;
  }
  return columnNumber1 - columnNumber2;
}

module.exports = {
  SourceMap,
};