navio-blsct/src/managedObj.ts

TypeScript bindings for the `libblsct` library used by the [Navio](https://nav.io/) blockchain to construct confidential transactions based on the BLS12-381 curve.

import {
  BlsctRetVal,
  freeObj,
} from './blsct'
import util from 'util'

export type FinalizerInfo = {
  cls: string,
  obj: any,
  isBorrow: boolean,
}

const finalizer = new FinalizationRegistry(
  (fi: FinalizerInfo) => {
    if (fi.obj && !fi.isBorrow) {
      freeObj(fi.obj)
      fi.obj = undefined
    }
  }
)

export abstract class ManagedObj {
  protected obj: any
  protected objSize: number
  protected fi: FinalizerInfo

  constructor(
    obj: any,
  ) {
    this.fi = {
      obj,
      cls: this.constructor.name,
      isBorrow: false,
    }
    if (obj !== undefined) {
      finalizer.register(this, this.fi, this)
    }
    this.obj = obj
    this.objSize = 0
  }

  abstract value(): any
  
  size(): number {
    return this.objSize
  }

  move(): any {
    if (this.obj === undefined) {
      throw new Error('Obj has already been moved')
    }
    const obj = this.obj
    this.obj = undefined

    // both fi.obj and unregister can suppress freeing memory
    // using both just in case either of them fails
    this.fi.obj = undefined
    finalizer.unregister(this)

    return obj  
  }

  static fromObj<T extends ManagedObj>(
    this: new (obj: any, objSize?: number) => T, 
    obj: any
  ): T {
    return new this(obj)
  }

  static fromObjAndSize<T extends ManagedObj>(
    this: new (obj: any) => T, 
    obj: any,
    objSize: number,
  ): T {
    const x = new this(obj)
    x.objSize = objSize
    return x
  }

  toString(): string {
    return `${this.constructor.name}(${this.serialize()})`
  }

  [util.inspect.custom](): string {
    return this.toString()
  }

  serialize(): string {
    return 'NOT IMPLEMENTED'
  }

  protected static _deserialize<T extends ManagedObj>(
    this: new (obj: any) => T,
    hex: string,
    deserializer: (hex: string) => BlsctRetVal
  ): T {
    if (hex.length % 2 !== 0) {
      hex = `0${hex}`
    }
    const rv = deserializer(hex)
    if (rv.result !== 0) {
      freeObj(rv)
      throw new Error(`Deserialization failed. Error code = ${rv.result}`)
    }
    const x = new this(rv.value)
    x.objSize = rv.value_size
    freeObj(rv)
    return x
  }
}