@webbuf/rw

npm install @webbuf/rw

import { BufWriter, BufReader } from "@webbuf/rw";
import { zigZagEncode, zigZagDecode } from "@webbuf/numbers";
import {
  U8,
  U16BE,
  U32BE,
  U64BE,
  U16LE,
  U32LE,
  U64LE,
  U128LE,
  U256LE,
} from "@webbuf/numbers";
import { FixedBuf } from "@webbuf/fixedbuf";

const writer = new BufWriter();

// Separate codecs: SLEB128 is not ZigZag followed by ULEB128.
const variable = new BufWriter()
  .writeULEB128(300n)
  .writeSLEB128(-1n)
  .writeULEB128(zigZagEncode(-1n));
if (variable.toBuf().toHex() !== "ac027f01") throw new Error("Wrong bytes");
const variableReader = new BufReader(variable.toBuf());
if (variableReader.readULEB128() !== 300n)
  throw new Error("Wrong unsigned value");
if (variableReader.readSLEB128() !== -1n) throw new Error("Wrong signed value");
if (zigZagDecode(variableReader.readULEB128()) !== -1n)
  throw new Error("Wrong ZigZag value");

// Write numbers
writer.writeU8(U8.fromN(255));
writer.writeU16BE(U16BE.fromN(1000));
writer.writeU32BE(U32BE.fromN(123456));
writer.writeU64BE(U64BE.fromBn(0x123456789abcdef0n));

// Write fixed buffers
const hash = FixedBuf.fromRandom<32>(32);
writer.write(hash.buf);

// Write variable-length data
writer.writeVarIntU64BE(U64BE.fromBn(1000n));

// Fixed-width little-endian fields (not varints)
writer.writeU16LE(U16LE.fromN(1000));
writer.writeU32LE(U32LE.fromN(123456));
writer.writeU64LE(U64LE.fromBn(0x123456789abcdef0n));
writer.writeU128LE(U128LE.fromBn(1n << 100n));
writer.writeU256LE(U256LE.fromBn(1n << 200n));

// Get result
const buf = writer.toBuf();