@regrapes/access-db-parser/src/parsing-primitives.ts

A pure javascript Microsoft AccessDB files (.mdb, .accdb) parser

import { TextDecoder } from 'util'

import { Parser } from 'binary-parser'

import type { Version } from './types'

const originalArray = Parser.prototype.array

Parser.prototype.array = function (this: any, varName: any, options: any) {
  if (options.length === 0) {
    return this.setNextParser('array', varName, options)
  }
  return originalArray.call(this, varName, options)
}

export const ACCESSHEADER = new Parser()
  .seek(4)
  .string('jetString', {
    zeroTerminated: true,
  })
  .uint32le('jetVersion')
  .seek(126)

export const MEMO = new Parser().uint32le('memoLength').uint32le('recordPointer').uint32le('memoUnknown').saveOffset('memoEnd')

const VERSION_3_FLAGS = new Parser()
  .bit1('hyperlink')
  .bit1('autoGUID')
  .bit1('unk1')
  .bit1('replication')
  .bit1('unk2')
  .bit1('autonumber')
  .bit1('canBeNull')
  .bit1('fixedLength')

const VERSION_4_FLAGS = new Parser()
  .bit1('hyperlink')
  .bit1('autoGUID')
  .bit1('unk1')
  .bit1('replication')
  .bit1('unk2')
  .bit1('autonumber')
  .bit1('canBeNull')
  .bit1('fixedLength')
  .bit1('unk3')
  .bit1('unk4')
  .bit1('unk5')
  .bit1('modernPackageType')
  .bit1('unk6')
  .bit1('unk7')
  .bit1('unk8')
  .bit1('compressedUnicode')

export const TDEF_HEADER = new Parser()
  .seek(2)
  .uint16le('peekVersion')
  .seek(-2)
  .uint16le('tdefVer')
  .uint32le('nextPagePtr')
  .saveOffset('headerEnd')

export const parseTableHead = (buffer: Buffer, version: Version = 3) =>
  new Parser()
    .nest('TDEF_header', { type: TDEF_HEADER })
    .uint32le('tableDefinitionLength')
    // Conditional
    .uint32le('ver4Unknown')
    .seek(version > 3 ? 0 : -4)
    .uint32le('numberOfRows')
    .uint32le('autonumber')
    // Conditional
    .uint32le('autonumberIncrement')
    .seek(version > 3 ? 0 : -4)
    // Conditional
    .uint32le('complexAutonumber')
    .seek(version > 3 ? 0 : -4)
    // Conditional
    .uint32le('ver4Unknown1')
    .seek(version > 3 ? 0 : -4)
    // Conditional
    .uint32le('ver4Unknown2')
    .seek(version > 3 ? 0 : -4)
    .uint8('tableTypeFlags')
    .uint16le('nextColumnID')
    .uint16le('variableColumns')
    .uint16le('columnCount')
    .uint32le('indexCount')
    .uint32le('realIndexCount')
    .uint32le('rowPageMap')
    .uint32le('freeSpacePageMap')
    .saveOffset('tDefHeaderEnd')
    .parse(buffer)

export const parseTableData = (buffer: Buffer, realIndexCount: number, columnCount: number, version: Version = 3) => {
  const REAL_INDEX = new Parser()
    .uint32le('unk1')
    .uint32le('indexRowCount')
    .seek(version > 3 ? 0 : -4)
    // Conditional
    .uint32le('ver4AlwaysZero')
  const VARIOUS_TEXT_V3 = new Parser().uint16le('LCID').uint16le('codePage').uint16le('variousText3Unknown')
  const VARIOUS_TEXT_V4 = new Parser().uint16le('collation').uint8('variousText4Unknown').uint8('collationVersionNumber')
  const VARIOUS_TEXT = version === 3 ? VARIOUS_TEXT_V3 : VARIOUS_TEXT_V4
  const VARIOUS_DEC_V3 = new Parser()
    .uint16le('variousDec3Unknown')
    .uint8('maxNumberOfDigits')
    .uint8('numberOfDecimal')
    .uint16le('variousDec3Unknown2')
  const VARIOUS_DEC_V4 = new Parser().uint8('maxNumOfDigits').uint8('numOfDecimalDigits').uint16le('variousDec4Unknown')
  const VARIOUS_DEC = version === 3 ? VARIOUS_DEC_V3 : VARIOUS_DEC_V4
  const COLUMN = new Parser()
    .uint8('type')
    // Conditional
    .uint32le('ver4Unknown3')
    .seek(version > 3 ? 0 : -4)
    .uint16le('columnID')
    .uint16le('variableColumnNumber')
    .uint16le('columnIndex')
    .choice('various', {
      tag: 'type',
      choices: {
        1: VARIOUS_DEC,
        2: VARIOUS_DEC,
        3: VARIOUS_DEC,
        4: VARIOUS_DEC,
        5: VARIOUS_DEC,
        6: VARIOUS_DEC,
        7: VARIOUS_DEC,
        8: VARIOUS_DEC,
        9: VARIOUS_TEXT,
        10: VARIOUS_TEXT,
        11: VARIOUS_TEXT,
        12: VARIOUS_TEXT,
      },
      defaultChoice: new Parser().seek(version === 3 ? 6 : 4),
    })
    .choice('columnFlags', {
      // eslint-disable-next-line no-new-func
      tag: new Function(`return ${version === 3 ? 1 : 0}`) as any,
      choices: {
        1: VERSION_3_FLAGS,
        0: VERSION_4_FLAGS,
      },
    })
    // Conditional
    .uint32le('ver4Unknown4')
    .seek(version > 3 ? 0 : -4)
    .uint16le('fixedOffset')
    .uint16le('length')
  const COLUMN_NAMES_V3 = new Parser().uint8('colNamesLen').string('colNameStr', {
    length: 'colNamesLen',
    encoding: 'utf8',
    stripNull: true,
  })
  const COLUMN_NAMES_V4 = new Parser().uint16le('colNamesLen').buffer('colNameStr', {
    length: 'colNamesLen',
  })
  // .string("colNameStr", {
  // 	length: "colNamesLen",
  // 	encoding: "utf16",
  // 	stripNull: true,
  // });
  const COLUMN_NAMES: typeof COLUMN_NAMES_V3 = version === 3 ? COLUMN_NAMES_V3 : (COLUMN_NAMES_V4 as any)
  const res = new Parser()
    .array('readIndex', {
      length: realIndexCount,
      type: REAL_INDEX,
    })
    .array('column', {
      length: columnCount,
      type: COLUMN,
    })
    .array('columnNames', {
      length: columnCount,
      type: COLUMN_NAMES,
    })
    .parse(buffer)

  if (version !== 3) {
    for (const columnName of res.columnNames) {
      const buffer = columnName.colNameStr as unknown as Buffer
      columnName.colNameStr = new TextDecoder('utf-16le').decode(buffer)
    }
  }
  return res
}

export const parseDataPageHeader = (buffer: Buffer, version: Version = 3) =>
  new Parser()
    .seek(2)
    .uint16le('dataFreeSpace')
    .uint32le('owner')
    .seek(version > 3 ? 0 : -4)
    // Conditional
    .uint32le('ver4UnknownData')
    .uint16le('recordCount')
    .array('recordOffsets', {
      length: 'recordCount',
      type: 'uint16le',
    })
    .parse(buffer)

export const parseRelativeObjectMetadataStruct = (buffer: Buffer, variableJumpTablesCNT = 0, version: Version = 3) => {
  if (version === 3) {
    return new Parser()
      .uint8('variableLengthFieldCount')
      .array('variableLengthJumpTable', {
        length: variableJumpTablesCNT,
        type: 'uint8',
      })
      .array('variableLengthFieldOffsets', {
        length() {
          return this.variableLengthFieldCount
        },
        type: 'uint8',
      })
      .uint8('varLenCount')
      .saveOffset('relativeMetadataEnd')
      .parse(buffer)
  } else {
    const part1 = new Parser()
      .uint16le('variableLengthFieldCount')
      .array('variableLengthJumpTable', {
        length: variableJumpTablesCNT,
        type: 'uint8',
      })
      .saveOffset('part2StartOffset')
      .parse(buffer)
    const part2 = new Parser()
      .array('variableLengthFieldOffsets', {
        length: (part1.variableLengthFieldCount & 0xff) >>> 0,
        type: 'uint16le',
      })
      .uint16le('varLenCount')
      .saveOffset('relativeMetadataEnd')
      .parse(buffer.slice(part1.part2StartOffset))
    const result = { ...part1, ...part2 }
    return result
  }
}

export type PropType<TObj, TProp extends keyof TObj> = TObj[TProp]
export type Column = PropType<ReturnType<typeof parseTableData>, 'column'>[0] & {
  colNameStr: string
}
export type TableHeader = ReturnType<typeof parseTableHead>