xo-vmdk-to-vhd/dist/vmdk-read-table.js

JS lib reading and writing .vmdk and .ova files

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = readVmdkGrainTable;
exports.readCapacityAndGrainTable = readCapacityAndGrainTable;
var _util = require("./util");
const SECTOR_SIZE = 512;
const HEADER_SIZE = 512;
const FOOTER_POSITION = -1024;
const DISK_CAPACITY_OFFSET = 12;
const GRAIN_SIZE_OFFSET = 20;
const NUM_GTE_PER_GT_OFFSET = 44;
const GRAIN_ADDRESS_OFFSET = 56;
const MANTISSA_BITS_IN_DOUBLE = 53;
const getLongLong = (buffer, offset, name) => {
  if (buffer.byteLength < offset + 8) {
    throw new Error(`buffer ${name} is too short, expecting ${offset + 8} minimum, got ${buffer.byteLength}`);
  }
  const dataView = new DataView(buffer);
  const highBits = dataView.getUint32(offset + 4, true);
  if (highBits >= Math.pow(2, MANTISSA_BITS_IN_DOUBLE - 32)) {
    throw new Error('Unsupported file, high order bits are too high in field ' + name);
  }
  const res = dataView.getUint32(offset, true);
  return res + highBits * Math.pow(2, 32);
};
async function readVmdkGrainTable(fileAccessor) {
  return (await readCapacityAndGrainTable(fileAccessor)).tablePromise;
}
async function grabTables(grainDirectoryEntries, grainDir, grainTablePhysicalSize, fileAccessor) {
  const cachedGrainTables = [];
  for (let i = 0; i < grainDirectoryEntries; i++) {
    const grainTableAddr = grainDir[i] * SECTOR_SIZE;
    if (grainTableAddr !== 0) {
      cachedGrainTables[i] = new Uint32Array(await fileAccessor(grainTableAddr, grainTableAddr + grainTablePhysicalSize));
    }
  }
  return cachedGrainTables;
}
async function readCapacityAndGrainTable(fileAccessor) {
  let headerBuffer = await fileAccessor(0, HEADER_SIZE);
  let grainAddrBuffer = headerBuffer.slice(GRAIN_ADDRESS_OFFSET, GRAIN_ADDRESS_OFFSET + 8);
  if (new Int8Array(grainAddrBuffer).every(val => val === -1)) {
    headerBuffer = await fileAccessor(FOOTER_POSITION, FOOTER_POSITION + HEADER_SIZE);
    grainAddrBuffer = headerBuffer.slice(GRAIN_ADDRESS_OFFSET, GRAIN_ADDRESS_OFFSET + 8);
  }
  const grainDirPosBytes = getLongLong(grainAddrBuffer, 0, 'grain directory address') * SECTOR_SIZE;
  const capacity = getLongLong(headerBuffer, DISK_CAPACITY_OFFSET, 'capacity') * SECTOR_SIZE;
  async function readTable() {
    const grainSizeByte = getLongLong(headerBuffer, GRAIN_SIZE_OFFSET, 'grain size') * SECTOR_SIZE;
    const grainCount = Math.ceil(capacity / grainSizeByte);
    const numGTEsPerGT = new DataView(headerBuffer).getUint32(NUM_GTE_PER_GT_OFFSET, true);
    const grainTablePhysicalSize = numGTEsPerGT * 4;
    const grainDirectoryEntries = Math.ceil(grainCount / numGTEsPerGT);
    const grainDirectoryPhysicalSize = grainDirectoryEntries * 4;
    const grainDir = new Uint32Array(await fileAccessor(grainDirPosBytes, grainDirPosBytes + grainDirectoryPhysicalSize));
    const cachedGrainTables = await grabTables(grainDirectoryEntries, grainDir, grainTablePhysicalSize, fileAccessor);
    const extractedGrainTable = [];
    for (let i = 0; i < grainCount; i++) {
      const directoryEntry = Math.floor(i / numGTEsPerGT);
      const grainTable = cachedGrainTables[directoryEntry];
      if (grainTable !== undefined) {
        const grainAddr = grainTable[i % numGTEsPerGT];
        if (grainAddr !== 0) {
          extractedGrainTable.push([i, grainAddr]);
        }
      }
    }
    extractedGrainTable.sort(([_i1, grainAddress1], [_i2, grainAddress2]) => grainAddress1 - grainAddress2);
    const byteLength = 4 * extractedGrainTable.length;
    const grainLogicalAddressList = new DataView(new ArrayBuffer(byteLength));
    const grainFileOffsetList = new DataView(new ArrayBuffer(byteLength));
    extractedGrainTable.forEach(([index, grainAddress], i) => {
      grainLogicalAddressList.setUint32(i * 4, index, true);
      grainFileOffsetList.setUint32(i * 4, grainAddress, true);
    });
    return {
      grainLogicalAddressList: grainLogicalAddressList.buffer,
      grainFileOffsetList: grainFileOffsetList.buffer
    };
  }
  return {
    tablePromise: (0, _util.suppressUnhandledRejection)(readTable()),
    capacityBytes: capacity
  };
}
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