layout.ts

import { PublicKey } from "@solana/web3.js"
import BN from "bn.js"
import * as BL from "@solana/buffer-layout"

/**
 * Layout for a public key
 * @export
 * @param {string} [property]
 * @returns {PubkeyField}
 */
export function pubkey(property?: string): PubkeyField {
  return new PubkeyField(property)
}

/**
 * Layout for a public key
 * @export
 * @class PubkeyField
 * @extends {BL.Layout}
 */
export class PubkeyField extends BL.Layout<PublicKey> {
  /**
   * Creates an instance of PubkeyField.
   * @param {string} [property]
   * @memberof PubkeyField
   */
  constructor(property?: string) {
    super(32, property)
  }

  /**
   * TODO:
   * @param {Uint8Array} b
   * @param {number} [offset]
   * @returns {PublicKey}
   * @memberof PubkeyField
   */
  decode(b: Uint8Array, offset?: number): PublicKey {
    const start = offset ?? 0
    const data = b.slice(start, start + this.span)
    return new PublicKey(data)
  }

  /**
   * TODO:
   * @param {PublicKey} src
   * @param {Uint8Array} b
   * @param {number} [offset]
   * @returns {number}
   * @memberof PubkeyField
   */
  encode(src: PublicKey, b: Uint8Array, offset?: number): number {
    const start = offset ?? 0
    b.set(src.toBytes(), start)
    return this.span
  }
}

/**
 * Layout for an arbitrary sized unsigned int
 * @export
 * @class NumberField
 * @extends {BL.Layout}
 */
export class NumberField extends BL.Layout<BN> {
  /**
   * Creates an instance of NumberField which decodes to a BN.
   * @param span The number of bytes in the number
   * @param property Field name within in a struct
   */
  constructor(span: number, property?: string) {
    super(span, property)
  }

  /**
   * TODO:
   * @param {Uint8Array} b
   * @param {number} [offset]
   * @returns {BN}
   * @memberof NumberField
   */
  decode(b: Uint8Array, offset?: number): BN {
    const start = offset ?? 0
    const data = b.slice(start, start + this.span)
    return new BN(data, undefined, "le")
  }

  /**
   * TODO:
   * @param {BN} src
   * @param {Uint8Array} b
   * @param {number} [offset]
   * @returns {number}
   * @memberof NumberField
   */
  encode(src: BN, b: Uint8Array, offset?: number): number {
    const start = offset ?? 0
    b.set(src.toArray("le"), start)
    return this.span
  }
}

/**
 * Returns an unsigned number field that is 64 bits wide
 * @param property
 * @returns
 */
export function u64(property?: string): NumberField {
  return new NumberField(8, property)
}

/**
 * Returns an unsigned number field that is 128 bts wide
 * @export
 * @param {string} [property]
 * @returns {NumberField}
 */
export function number128Field(property?: string): NumberField {
  return new NumberField(16, property)
}

/**
 * Returns an unsigned number field that is 192 bits wide
 * @export
 * @param {string} [property]
 * @returns {NumberField}
 */
export function number192Field(property?: string): NumberField {
  return new NumberField(24, property)
}

/**
 * Layout for an arbitrary sized signed int
 * @export
 * @class SignedNumberField
 * @extends {BL.Layout}
 */
export class SignedNumberField extends BL.Layout<BN> {
  /**
   * Creates an instance of SignedNumberField.
   * @param {number} span
   * @param {string} [property]
   * @memberof SignedNumberField
   */
  constructor(span: number, property?: string) {
    super(span, property)
  }

  /**
   * TODO:
   * @param {Uint8Array} b
   * @param {number} [offset]
   * @returns {BN}
   * @memberof SignedNumberField
   */
  decode(b: Uint8Array, offset?: number): BN {
    const start = offset == undefined ? 0 : offset
    const data = b.slice(start, start + this.span)
    return new BN(data, undefined, "le").fromTwos(this.span * 8)
  }

  /**
   * TODO:
   * @param {BN} src
   * @param {Uint8Array} b
   * @param {number} [offset]
   * @returns {number}
   * @memberof SignedNumberField
   */
  encode(src: BN, b: Uint8Array, offset?: number): number {
    const start = offset == undefined ? 0 : offset
    b.set(src.toTwos(this.span * 8).toArray("le"), start)

    return this.span
  }
}

/**
 * Returns a signed number field that is 8 bytes wide
 * @export
 * @param {string} [property]
 * @returns {SignedNumberField}
 */
export function i64Field(property?: string): SignedNumberField {
  return new SignedNumberField(8, property)
}