sori.studio/server/utils/zip-writer.js

import { deflateRawSync } from 'node:zlib'

const crcTable = Array.from({ length: 256 }, (_, index) => {
  let value = index

  for (let bit = 0; bit < 8; bit += 1) {
    value = value & 1 ? 0xedb88320 ^ (value >>> 1) : value >>> 1
  }

  return value >>> 0
})

/**
 * CRC32 값을 계산한다.
 * @param {Buffer} input - 원본 데이터
 * @returns {number} CRC32
 */
const calculateCrc32 = (input) => {
  let crc = 0xffffffff

  for (const byte of input) {
    crc = crcTable[(crc ^ byte) & 0xff] ^ (crc >>> 8)
  }

  return (crc ^ 0xffffffff) >>> 0
}

/**
 * ZIP DOS 날짜/시간 값을 만든다.
 * @param {Date} date - 기준 날짜
 * @returns {{ dosDate: number, dosTime: number }} DOS 날짜/시간
 */
const createDosDateTime = (date) => {
  const year = Math.max(date.getFullYear(), 1980)

  return {
    dosTime: (date.getHours() << 11) | (date.getMinutes() << 5) | Math.floor(date.getSeconds() / 2),
    dosDate: ((year - 1980) << 9) | ((date.getMonth() + 1) << 5) | date.getDate()
  }
}

/**
 * ZIP 엔트리 경로를 정리한다.
 * @param {string} pathValue - 엔트리 경로
 * @returns {string} 정리된 경로
 */
const normalizeZipPath = (pathValue) => String(pathValue || '')
  .replace(/\\/g, '/')
  .replace(/^\/+/g, '')
  .replace(/\.\.+/g, '.')

/**
 * ZIP 로컬 파일 헤더를 만든다.
 * @param {Object} entry - 엔트리 정보
 * @returns {Buffer} 로컬 파일 헤더
 */
const createLocalFileHeader = (entry) => {
  const header = Buffer.alloc(30)
  header.writeUInt32LE(0x04034b50, 0)
  header.writeUInt16LE(20, 4)
  header.writeUInt16LE(0x0800, 6)
  header.writeUInt16LE(8, 8)
  header.writeUInt16LE(entry.dosTime, 10)
  header.writeUInt16LE(entry.dosDate, 12)
  header.writeUInt32LE(entry.crc32, 14)
  header.writeUInt32LE(entry.compressedSize, 18)
  header.writeUInt32LE(entry.uncompressedSize, 22)
  header.writeUInt16LE(entry.name.length, 26)
  header.writeUInt16LE(0, 28)

  return Buffer.concat([header, entry.name])
}

/**
 * ZIP 중앙 디렉터리 헤더를 만든다.
 * @param {Object} entry - 엔트리 정보
 * @returns {Buffer} 중앙 디렉터리 헤더
 */
const createCentralDirectoryHeader = (entry) => {
  const header = Buffer.alloc(46)
  header.writeUInt32LE(0x02014b50, 0)
  header.writeUInt16LE(20, 4)
  header.writeUInt16LE(20, 6)
  header.writeUInt16LE(0x0800, 8)
  header.writeUInt16LE(8, 10)
  header.writeUInt16LE(entry.dosTime, 12)
  header.writeUInt16LE(entry.dosDate, 14)
  header.writeUInt32LE(entry.crc32, 16)
  header.writeUInt32LE(entry.compressedSize, 20)
  header.writeUInt32LE(entry.uncompressedSize, 24)
  header.writeUInt16LE(entry.name.length, 28)
  header.writeUInt16LE(0, 30)
  header.writeUInt16LE(0, 32)
  header.writeUInt16LE(0, 34)
  header.writeUInt16LE(0, 36)
  header.writeUInt32LE(0, 38)
  header.writeUInt32LE(entry.offset, 42)

  return Buffer.concat([header, entry.name])
}

/**
 * ZIP 종료 레코드를 만든다.
 * @param {number} entryCount - 엔트리 개수
 * @param {number} centralDirectorySize - 중앙 디렉터리 크기
 * @param {number} centralDirectoryOffset - 중앙 디렉터리 시작 위치
 * @returns {Buffer} 종료 레코드
 */
const createEndOfCentralDirectory = (entryCount, centralDirectorySize, centralDirectoryOffset) => {
  const endRecord = Buffer.alloc(22)
  endRecord.writeUInt32LE(0x06054b50, 0)
  endRecord.writeUInt16LE(0, 4)
  endRecord.writeUInt16LE(0, 6)
  endRecord.writeUInt16LE(entryCount, 8)
  endRecord.writeUInt16LE(entryCount, 10)
  endRecord.writeUInt32LE(centralDirectorySize, 12)
  endRecord.writeUInt32LE(centralDirectoryOffset, 16)
  endRecord.writeUInt16LE(0, 20)

  return endRecord
}

/**
 * 메모리에서 ZIP 파일 버퍼를 만든다.
 * @param {Array<{ path: string, data: Buffer | string }>} files - ZIP 파일 목록
 * @returns {Buffer} ZIP 버퍼
 */
export const createZipBuffer = (files) => {
  const localFileParts = []
  const centralDirectoryParts = []
  const entries = []
  let offset = 0

  for (const file of files) {
    const normalizedPath = normalizeZipPath(file.path)
    if (!normalizedPath) {
      continue
    }

    const rawData = Buffer.isBuffer(file.data) ? file.data : Buffer.from(String(file.data), 'utf8')
    const compressedData = deflateRawSync(rawData)
    const { dosDate, dosTime } = createDosDateTime(new Date())
    const entry = {
      name: Buffer.from(normalizedPath, 'utf8'),
      crc32: calculateCrc32(rawData),
      compressedSize: compressedData.length,
      uncompressedSize: rawData.length,
      dosDate,
      dosTime,
      offset
    }
    const localHeader = createLocalFileHeader(entry)

    localFileParts.push(localHeader, compressedData)
    offset += localHeader.length + compressedData.length
    entries.push(entry)
  }

  for (const entry of entries) {
    centralDirectoryParts.push(createCentralDirectoryHeader(entry))
  }

  const centralDirectory = Buffer.concat(centralDirectoryParts)
  const endRecord = createEndOfCentralDirectory(entries.length, centralDirectory.length, offset)

  return Buffer.concat([...localFileParts, centralDirectory, endRecord])
}