@msgpack/msgpack/src/utils/int.ts

MessagePack for ECMA-262/JavaScript/TypeScript

// Integer Utility

export const UINT32_MAX = 0xffff_ffff;

// DataView extension to handle int64 / uint64,
// where the actual range is 53-bits integer (a.k.a. safe integer)

export function setUint64(view: DataView, offset: number, value: number): void {
  const high = value / 0x1_0000_0000;
  const low = value; // high bits are truncated by DataView
  view.setUint32(offset, high);
  view.setUint32(offset + 4, low);
}

export function setInt64(view: DataView, offset: number, value: number): void {
  const high = Math.floor(value / 0x1_0000_0000);
  const low = value; // high bits are truncated by DataView
  view.setUint32(offset, high);
  view.setUint32(offset + 4, low);
}

export function getInt64(view: DataView, offset: number): number {
  const high = view.getInt32(offset);
  const low = view.getUint32(offset + 4);
  return high * 0x1_0000_0000 + low;
}

export function getUint64(view: DataView, offset: number): number {
  const high = view.getUint32(offset);
  const low = view.getUint32(offset + 4);
  return high * 0x1_0000_0000 + low;
}