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export function utf8Count(str: string): number {  const strLength = str.length;
  let byteLength = 0;  let pos = 0;  while (pos < strLength) {    let value = str.charCodeAt(pos++);
    if ((value & 0xffffff80) === 0) {      // 1-byte      byteLength++;      continue;    } else if ((value & 0xfffff800) === 0) {      // 2-bytes      byteLength += 2;    } else {      // handle surrogate pair      if (value >= 0xd800 && value <= 0xdbff) {        // high surrogate        if (pos < strLength) {          const extra = str.charCodeAt(pos);          if ((extra & 0xfc00) === 0xdc00) {            ++pos;            value = ((value & 0x3ff) << 10) + (extra & 0x3ff) + 0x10000;          }        }      }
      if ((value & 0xffff0000) === 0) {        // 3-byte        byteLength += 3;      } else {        // 4-byte        byteLength += 4;      }    }  }  return byteLength;}
export function utf8EncodeJs(str: string, output: Uint8Array, outputOffset: number): void {  const strLength = str.length;  let offset = outputOffset;  let pos = 0;  while (pos < strLength) {    let value = str.charCodeAt(pos++);
    if ((value & 0xffffff80) === 0) {      // 1-byte      output[offset++] = value;      continue;    } else if ((value & 0xfffff800) === 0) {      // 2-bytes      output[offset++] = ((value >> 6) & 0x1f) | 0xc0;    } else {      // handle surrogate pair      if (value >= 0xd800 && value <= 0xdbff) {        // high surrogate        if (pos < strLength) {          const extra = str.charCodeAt(pos);          if ((extra & 0xfc00) === 0xdc00) {            ++pos;            value = ((value & 0x3ff) << 10) + (extra & 0x3ff) + 0x10000;          }        }      }
      if ((value & 0xffff0000) === 0) {        // 3-byte        output[offset++] = ((value >> 12) & 0x0f) | 0xe0;        output[offset++] = ((value >> 6) & 0x3f) | 0x80;      } else {        // 4-byte        output[offset++] = ((value >> 18) & 0x07) | 0xf0;        output[offset++] = ((value >> 12) & 0x3f) | 0x80;        output[offset++] = ((value >> 6) & 0x3f) | 0x80;      }    }
    output[offset++] = (value & 0x3f) | 0x80;  }}
// TextEncoder and TextDecoder are standardized in whatwg encoding:// https://encoding.spec.whatwg.org/// and available in all the modern browsers:// https://caniuse.com/textencoder// They are available in Node.js since v12 LTS as well:// https://nodejs.org/api/globals.html#textencoder
const sharedTextEncoder = new TextEncoder();
// This threshold should be determined by benchmarking, which might vary in engines and input data.// Run `npx ts-node benchmark/encode-string.ts` for details.const TEXT_ENCODER_THRESHOLD = 50;
export function utf8EncodeTE(str: string, output: Uint8Array, outputOffset: number): void {  sharedTextEncoder.encodeInto(str, output.subarray(outputOffset));}
export function utf8Encode(str: string, output: Uint8Array, outputOffset: number): void {  if (str.length > TEXT_ENCODER_THRESHOLD) {    utf8EncodeTE(str, output, outputOffset);  } else {    utf8EncodeJs(str, output, outputOffset);  }}
const CHUNK_SIZE = 0x1_000;
export function utf8DecodeJs(bytes: Uint8Array, inputOffset: number, byteLength: number): string {  let offset = inputOffset;  const end = offset + byteLength;
  const units: Array<number> = [];  let result = "";  while (offset < end) {    const byte1 = bytes[offset++]!;    if ((byte1 & 0x80) === 0) {      // 1 byte      units.push(byte1);    } else if ((byte1 & 0xe0) === 0xc0) {      // 2 bytes      const byte2 = bytes[offset++]! & 0x3f;      units.push(((byte1 & 0x1f) << 6) | byte2);    } else if ((byte1 & 0xf0) === 0xe0) {      // 3 bytes      const byte2 = bytes[offset++]! & 0x3f;      const byte3 = bytes[offset++]! & 0x3f;      units.push(((byte1 & 0x1f) << 12) | (byte2 << 6) | byte3);    } else if ((byte1 & 0xf8) === 0xf0) {      // 4 bytes      const byte2 = bytes[offset++]! & 0x3f;      const byte3 = bytes[offset++]! & 0x3f;      const byte4 = bytes[offset++]! & 0x3f;      let unit = ((byte1 & 0x07) << 0x12) | (byte2 << 0x0c) | (byte3 << 0x06) | byte4;      if (unit > 0xffff) {        unit -= 0x10000;        units.push(((unit >>> 10) & 0x3ff) | 0xd800);        unit = 0xdc00 | (unit & 0x3ff);      }      units.push(unit);    } else {      units.push(byte1);    }
    if (units.length >= CHUNK_SIZE) {      result += String.fromCharCode(...units);      units.length = 0;    }  }
  if (units.length > 0) {    result += String.fromCharCode(...units);  }
  return result;}
const sharedTextDecoder = new TextDecoder();
// This threshold should be determined by benchmarking, which might vary in engines and input data.// Run `npx ts-node benchmark/decode-string.ts` for details.const TEXT_DECODER_THRESHOLD = 200;
export function utf8DecodeTD(bytes: Uint8Array, inputOffset: number, byteLength: number): string {  const stringBytes = bytes.subarray(inputOffset, inputOffset + byteLength);  return sharedTextDecoder.decode(stringBytes);}
export function utf8Decode(bytes: Uint8Array, inputOffset: number, byteLength: number): string {  if (byteLength > TEXT_DECODER_THRESHOLD) {    return utf8DecodeTD(bytes, inputOffset, byteLength);  } else {    return utf8DecodeJs(bytes, inputOffset, byteLength);  }}