What is the equivalent of Nodejs Buffer in Swift

I have a small snippet of code in nodejs, it is a utility class for encoding Kafka request data, and I will like to write the equivalent in Swift, what is the equivalent of the buffer class from nodejs in swift.

const INT8_SIZE = 1
const INT16_SIZE = 2
const INT32_SIZE = 4
const INT64_SIZE = 8


class Encoder {
  constructor(length = 16) {
    this.buffer = Buffer.alloc(length)
    this.offset = 0;
  }
  writeInt8(value) {
    this.increaseBufferSize(INT8_SIZE)
    this.buffer.writeInt8(value, this.offset)
    this.offset += INT8_SIZE

    return this;
  }

  writeInt16(value) {
    this.increaseBufferSize(INT16_SIZE)
    this.buffer.writeInt16BE(value, this.offset)
    this.offset += INT16_SIZE

    return this;
  }

  writeInt32(value) {
    this.increaseBufferSize(INT32_SIZE)
    this.buffer.writeInt32BE(value, this.offset)
    this.offset += INT32_SIZE

    return this;
  }

  writeInt64(value) {
    this.increaseBufferSize(INT64_SIZE)
    this.buffer.writeBigInt64BE(value, this.offset)
    this.offset += INT64_SIZE

    return this;
  }

  writeString(value) {
    if (value === null) {
      this.writeInt16(-1)
      return this
    }

    const byteLength = Buffer.byteLength(value)
    this.increaseBufferSize(INT16_SIZE + byteLength)
    this.writeInt16(byteLength)
    this.buffer.write(value, this.offset, 'utf8')
    this.offset += byteLength

    return this
  }
}