front_end/core/common/WasmDisassembly.ts

// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as Platform from '../platform/platform.js';

/**
 * Metadata to map between bytecode #offsets and line numbers in the
 * disassembly for WebAssembly modules.
 */

interface FunctionBodyOffset {
  start: number;
  end: number;
}
export class WasmDisassembly {
  readonly #offsets: number[];
  #functionBodyOffsets: FunctionBodyOffset[];

  constructor(offsets: number[], functionBodyOffsets: FunctionBodyOffset[]) {
    this.#offsets = offsets;
    this.#functionBodyOffsets = functionBodyOffsets;
  }

  get lineNumbers(): number {
    return this.#offsets.length;
  }

  bytecodeOffsetToLineNumber(bytecodeOffset: number): number {
    return Platform.ArrayUtilities.upperBound(
               this.#offsets, bytecodeOffset, Platform.ArrayUtilities.DEFAULT_COMPARATOR) -
        1;
  }

  lineNumberToBytecodeOffset(lineNumber: number): number {
    return this.#offsets[lineNumber];
  }

  /**
   * returns an iterable enumerating all the non-breakable line numbers in the disassembly
   */
  * nonBreakableLineNumbers(): Iterable<number> {
    let lineNumber = 0;
    let functionIndex = 0;
    while (lineNumber < this.lineNumbers) {
      if (functionIndex < this.#functionBodyOffsets.length) {
        const offset = this.lineNumberToBytecodeOffset(lineNumber);
        if (offset >= this.#functionBodyOffsets[functionIndex].start) {
          lineNumber = this.bytecodeOffsetToLineNumber(this.#functionBodyOffsets[functionIndex++].end) + 1;
          continue;
        }
      }
      yield lineNumber++;
    }
  }
}