homework/chat-server/node_modules/minizlib/index.js

'use strict'

const assert = require('assert')
const Buffer = require('buffer').Buffer
const realZlib = require('zlib')

const constants = exports.constants = require('./constants.js')
const Minipass = require('minipass')

const OriginalBufferConcat = Buffer.concat

const _superWrite = Symbol('_superWrite')
class ZlibError extends Error {
  constructor (err) {
    super('zlib: ' + err.message)
    this.code = err.code
    this.errno = err.errno
    /* istanbul ignore if */
    if (!this.code)
      this.code = 'ZLIB_ERROR'

    this.message = 'zlib: ' + err.message
    Error.captureStackTrace(this, this.constructor)
  }

  get name () {
    return 'ZlibError'
  }
}

// the Zlib class they all inherit from
// This thing manages the queue of requests, and returns
// true or false if there is anything in the queue when
// you call the .write() method.
const _opts = Symbol('opts')
const _flushFlag = Symbol('flushFlag')
const _finishFlushFlag = Symbol('finishFlushFlag')
const _fullFlushFlag = Symbol('fullFlushFlag')
const _handle = Symbol('handle')
const _onError = Symbol('onError')
const _sawError = Symbol('sawError')
const _level = Symbol('level')
const _strategy = Symbol('strategy')
const _ended = Symbol('ended')
const _defaultFullFlush = Symbol('_defaultFullFlush')

class ZlibBase extends Minipass {
  constructor (opts, mode) {
    if (!opts || typeof opts !== 'object')
      throw new TypeError('invalid options for ZlibBase constructor')

    super(opts)
    this[_ended] = false
    this[_opts] = opts

    this[_flushFlag] = opts.flush
    this[_finishFlushFlag] = opts.finishFlush
    // this will throw if any options are invalid for the class selected
    try {
      this[_handle] = new realZlib[mode](opts)
    } catch (er) {
      // make sure that all errors get decorated properly
      throw new ZlibError(er)
    }

    this[_onError] = (err) => {
      this[_sawError] = true
      // there is no way to cleanly recover.
      // continuing only obscures problems.
      this.close()
      this.emit('error', err)
    }

    this[_handle].on('error', er => this[_onError](new ZlibError(er)))
    this.once('end', () => this.close)
  }

  close () {
    if (this[_handle]) {
      this[_handle].close()
      this[_handle] = null
      this.emit('close')
    }
  }

  reset () {
    if (!this[_sawError]) {
      assert(this[_handle], 'zlib binding closed')
      return this[_handle].reset()
    }
  }

  flush (flushFlag) {
    if (this.ended)
      return

    if (typeof flushFlag !== 'number')
      flushFlag = this[_fullFlushFlag]
    this.write(Object.assign(Buffer.alloc(0), { [_flushFlag]: flushFlag }))
  }

  end (chunk, encoding, cb) {
    if (chunk)
      this.write(chunk, encoding)
    this.flush(this[_finishFlushFlag])
    this[_ended] = true
    return super.end(null, null, cb)
  }

  get ended () {
    return this[_ended]
  }

  write (chunk, encoding, cb) {
    // process the chunk using the sync process
    // then super.write() all the outputted chunks
    if (typeof encoding === 'function')
      cb = encoding, encoding = 'utf8'

    if (typeof chunk === 'string')
      chunk = Buffer.from(chunk, encoding)

    if (this[_sawError])
      return
    assert(this[_handle], 'zlib binding closed')

    // _processChunk tries to .close() the native handle after it's done, so we
    // intercept that by temporarily making it a no-op.
    const nativeHandle = this[_handle]._handle
    const originalNativeClose = nativeHandle.close
    nativeHandle.close = () => {}
    const originalClose = this[_handle].close
    this[_handle].close = () => {}
    // It also calls `Buffer.concat()` at the end, which may be convenient
    // for some, but which we are not interested in as it slows us down.
    Buffer.concat = (args) => args
    let result
    try {
      const flushFlag = typeof chunk[_flushFlag] === 'number'
        ? chunk[_flushFlag] : this[_flushFlag]
      result = this[_handle]._processChunk(chunk, flushFlag)
      // if we don't throw, reset it back how it was
      Buffer.concat = OriginalBufferConcat
    } catch (err) {
      // or if we do, put Buffer.concat() back before we emit error
      // Error events call into user code, which may call Buffer.concat()
      Buffer.concat = OriginalBufferConcat
      this[_onError](new ZlibError(err))
    } finally {
      if (this[_handle]) {
        // Core zlib resets `_handle` to null after attempting to close the
        // native handle. Our no-op handler prevented actual closure, but we
        // need to restore the `._handle` property.
        this[_handle]._handle = nativeHandle
        nativeHandle.close = originalNativeClose
        this[_handle].close = originalClose
        // `_processChunk()` adds an 'error' listener. If we don't remove it
        // after each call, these handlers start piling up.
        this[_handle].removeAllListeners('error')
      }
    }

    let writeReturn
    if (result) {
      if (Array.isArray(result) && result.length > 0) {
        // The first buffer is always `handle._outBuffer`, which would be
        // re-used for later invocations; so, we always have to copy that one.
        writeReturn = this[_superWrite](Buffer.from(result[0]))
        for (let i = 1; i < result.length; i++) {
          writeReturn = this[_superWrite](result[i])
        }
      } else {
        writeReturn = this[_superWrite](Buffer.from(result))
      }
    }

    if (cb)
      cb()
    return writeReturn
  }

  [_superWrite] (data) {
    return super.write(data)
  }
}

class Zlib extends ZlibBase {
  constructor (opts, mode) {
    opts = opts || {}

    opts.flush = opts.flush || constants.Z_NO_FLUSH
    opts.finishFlush = opts.finishFlush || constants.Z_FINISH
    super(opts, mode)

    this[_fullFlushFlag] = constants.Z_FULL_FLUSH
    this[_level] = opts.level
    this[_strategy] = opts.strategy
  }

  params (level, strategy) {
    if (this[_sawError])
      return

    if (!this[_handle])
      throw new Error('cannot switch params when binding is closed')

    // no way to test this without also not supporting params at all
    /* istanbul ignore if */
    if (!this[_handle].params)
      throw new Error('not supported in this implementation')

    if (this[_level] !== level || this[_strategy] !== strategy) {
      this.flush(constants.Z_SYNC_FLUSH)
      assert(this[_handle], 'zlib binding closed')
      // .params() calls .flush(), but the latter is always async in the
      // core zlib. We override .flush() temporarily to intercept that and
      // flush synchronously.
      const origFlush = this[_handle].flush
      this[_handle].flush = (flushFlag, cb) => {
        this.flush(flushFlag)
        cb()
      }
      try {
        this[_handle].params(level, strategy)
      } finally {
        this[_handle].flush = origFlush
      }
      /* istanbul ignore else */
      if (this[_handle]) {
        this[_level] = level
        this[_strategy] = strategy
      }
    }
  }
}

// minimal 2-byte header
class Deflate extends Zlib {
  constructor (opts) {
    super(opts, 'Deflate')
  }
}

class Inflate extends Zlib {
  constructor (opts) {
    super(opts, 'Inflate')
  }
}

// gzip - bigger header, same deflate compression
const _portable = Symbol('_portable')
class Gzip extends Zlib {
  constructor (opts) {
    super(opts, 'Gzip')
    this[_portable] = opts && !!opts.portable
  }

  [_superWrite] (data) {
    if (!this[_portable])
      return super[_superWrite](data)

    // we'll always get the header emitted in one first chunk
    // overwrite the OS indicator byte with 0xFF
    this[_portable] = false
    data[9] = 255
    return super[_superWrite](data)
  }
}

class Gunzip extends Zlib {
  constructor (opts) {
    super(opts, 'Gunzip')
  }
}

// raw - no header
class DeflateRaw extends Zlib {
  constructor (opts) {
    super(opts, 'DeflateRaw')
  }
}

class InflateRaw extends Zlib {
  constructor (opts) {
    super(opts, 'InflateRaw')
  }
}

// auto-detect header.
class Unzip extends Zlib {
  constructor (opts) {
    super(opts, 'Unzip')
  }
}

class Brotli extends ZlibBase {
  constructor (opts, mode) {
    opts = opts || {}

    opts.flush = opts.flush || constants.BROTLI_OPERATION_PROCESS
    opts.finishFlush = opts.finishFlush || constants.BROTLI_OPERATION_FINISH

    super(opts, mode)

    this[_fullFlushFlag] = constants.BROTLI_OPERATION_FLUSH
  }
}

class BrotliCompress extends Brotli {
  constructor (opts) {
    super(opts, 'BrotliCompress')
  }
}

class BrotliDecompress extends Brotli {
  constructor (opts) {
    super(opts, 'BrotliDecompress')
  }
}

exports.Deflate = Deflate
exports.Inflate = Inflate
exports.Gzip = Gzip
exports.Gunzip = Gunzip
exports.DeflateRaw = DeflateRaw
exports.InflateRaw = InflateRaw
exports.Unzip = Unzip
/* istanbul ignore else */
if (typeof realZlib.BrotliCompress === 'function') {
  exports.BrotliCompress = BrotliCompress
  exports.BrotliDecompress = BrotliDecompress
} else {
  exports.BrotliCompress = exports.BrotliDecompress = class {
    constructor () {
      throw new Error('Brotli is not supported in this version of Node.js')
    }
  }
}