ripple-binary-codec/src/types/hash.ts

XRP Ledger binary codec

import { Comparable } from './serialized-type'
import { BinaryParser } from '../serdes/binary-parser'
import { hexToBytes } from '@xrplf/isomorphic/utils'
import { compare } from '../utils'

/**
 * Base class defining how to encode and decode hashes
 */
class Hash extends Comparable<Hash | string> {
  static readonly width: number

  constructor(bytes: Uint8Array) {
    super(bytes)
    if (this.bytes.length !== (this.constructor as typeof Hash).width) {
      throw new Error(`Invalid Hash length ${this.bytes.byteLength}`)
    }
  }

  /**
   * Construct a Hash object from an existing Hash object or a hex-string
   *
   * @param value A hash object or hex-string of a hash
   */
  static from<T extends Hash | string>(value: T): Hash {
    if (value instanceof this) {
      return value
    }

    if (typeof value === 'string') {
      return new this(hexToBytes(value))
    }

    throw new Error('Cannot construct Hash from given value')
  }

  /**
   * Read a Hash object from a BinaryParser
   *
   * @param parser BinaryParser to read the hash from
   * @param hint length of the bytes to read, optional
   */
  static fromParser(parser: BinaryParser, hint?: number): Hash {
    return new this(parser.read(hint ?? this.width))
  }

  /**
   * Overloaded operator for comparing two hash objects
   *
   * @param other The Hash to compare this to
   */
  compareTo(other: Hash): number {
    return compare(
      this.bytes,
      (this.constructor as typeof Hash).from(other).bytes,
    )
  }

  /**
   * @returns the hex-string representation of this Hash
   */
  toString(): string {
    return this.toHex()
  }

  /**
   * Returns four bits at the specified depth within a hash
   *
   * @param depth The depth of the four bits
   * @returns The number represented by the four bits
   */
  nibblet(depth: number): number {
    const byteIx = depth > 0 ? (depth / 2) | 0 : 0
    let b = this.bytes[byteIx]
    if (depth % 2 === 0) {
      b = (b & 0xf0) >>> 4
    } else {
      b = b & 0x0f
    }
    return b
  }
}

export { Hash }