@mysten/bcs/dist/esm/reader.js

BCS - Canonical Binary Serialization implementation for JavaScript

import { ulebDecode } from "./uleb.js";
class BcsReader {
  /**
   * @param {Uint8Array} data Data to use as a buffer.
   */
  constructor(data) {
    this.bytePosition = 0;
    this.dataView = new DataView(data.buffer, data.byteOffset, data.byteLength);
  }
  /**
   * Shift current cursor position by `bytes`.
   *
   * @param {Number} bytes Number of bytes to
   * @returns {this} Self for possible chaining.
   */
  shift(bytes) {
    this.bytePosition += bytes;
    return this;
  }
  /**
   * Read U8 value from the buffer and shift cursor by 1.
   * @returns
   */
  read8() {
    const value = this.dataView.getUint8(this.bytePosition);
    this.shift(1);
    return value;
  }
  /**
   * Read U16 value from the buffer and shift cursor by 2.
   * @returns
   */
  read16() {
    const value = this.dataView.getUint16(this.bytePosition, true);
    this.shift(2);
    return value;
  }
  /**
   * Read U32 value from the buffer and shift cursor by 4.
   * @returns
   */
  read32() {
    const value = this.dataView.getUint32(this.bytePosition, true);
    this.shift(4);
    return value;
  }
  /**
   * Read U64 value from the buffer and shift cursor by 8.
   * @returns
   */
  read64() {
    const value1 = this.read32();
    const value2 = this.read32();
    const result = value2.toString(16) + value1.toString(16).padStart(8, "0");
    return BigInt("0x" + result).toString(10);
  }
  /**
   * Read U128 value from the buffer and shift cursor by 16.
   */
  read128() {
    const value1 = BigInt(this.read64());
    const value2 = BigInt(this.read64());
    const result = value2.toString(16) + value1.toString(16).padStart(16, "0");
    return BigInt("0x" + result).toString(10);
  }
  /**
   * Read U128 value from the buffer and shift cursor by 32.
   * @returns
   */
  read256() {
    const value1 = BigInt(this.read128());
    const value2 = BigInt(this.read128());
    const result = value2.toString(16) + value1.toString(16).padStart(32, "0");
    return BigInt("0x" + result).toString(10);
  }
  /**
   * Read `num` number of bytes from the buffer and shift cursor by `num`.
   * @param num Number of bytes to read.
   */
  readBytes(num) {
    const start = this.bytePosition + this.dataView.byteOffset;
    const value = new Uint8Array(this.dataView.buffer, start, num);
    this.shift(num);
    return value;
  }
  /**
   * Read ULEB value - an integer of varying size. Used for enum indexes and
   * vector lengths.
   * @returns {Number} The ULEB value.
   */
  readULEB() {
    const start = this.bytePosition + this.dataView.byteOffset;
    const buffer = new Uint8Array(this.dataView.buffer, start);
    const { value, length } = ulebDecode(buffer);
    this.shift(length);
    return value;
  }
  /**
   * Read a BCS vector: read a length and then apply function `cb` X times
   * where X is the length of the vector, defined as ULEB in BCS bytes.
   * @param cb Callback to process elements of vector.
   * @returns {Array<Any>} Array of the resulting values, returned by callback.
   */
  readVec(cb) {
    const length = this.readULEB();
    const result = [];
    for (let i = 0; i < length; i++) {
      result.push(cb(this, i, length));
    }
    return result;
  }
}
export {
  BcsReader
};
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