TextEncoder.encodeInto()

20214

TextEncoder.encodeInto() Uint8Array UTF-8 encode() WASM

encodeInto(string, uint8Array)

string
uint8Array: Uint8Array UTF-8

read: UTF-8 UTF-16 uint8Array string.length
written: Uint8Array UTF-8

encoder.encodeInto() TypedArray.prototype.subarray()

const encoder = new TextEncoder();

function encodeIntoAtPosition(string, u8array, position) {
  return encoder.encodeInto(
    string,
    position ? u8array.subarray(position | 0) : u8array,
  );
}

const u8array = new Uint8Array(8);
encodeIntoAtPosition("hello", u8array, 2);
console.log(u8array.join()); // 0,0,104,101,108,108,111,0

JavaScript s UTF-8 s.length s.length * 3 WASM s.length * 3 s.length * 3 3 s.length * 2 s.length * 2 + 5

roundUpToBucketSize(s.length) s.length * 3 t roundUpToBucketSize(s.length) + t >= s.length * 3 s.length * 3 roundUpToBucketSize(s.length) read s.length written + (s.length - read) * 3 s read written

roundUpToBucketSize() Wasm 2 roundUpToBucketSize() 2 2 Wasm roundUpToBucketSize()

2 3 2 3 0 WASM Rust 0 C++ C++ std::string C

0

U+0000encodeInto() 0x00 encodeInto() C 0x00

Wasm C 0x00 JavaScript U+0000 Wasm

const encoder = new TextEncoder();

function encodeIntoWithSentinel(string, u8array, position) {
  const stats = encoder.encodeInto(
    string,
    position ? u8array.subarray(position | 0) : u8array,
  );
  if (stats.written < u8array.length) u8array[stats.written] = 0; // append null if room
  return stats;
}

html

<p class="source">This is a sample paragraph.</p>
<p class="result"></p>

const sourcePara = document.querySelector(".source");
const resultPara = document.querySelector(".result");
const string = sourcePara.textContent;

const textEncoder = new TextEncoder();
const utf8 = new Uint8Array(string.length);

const encodedResults = textEncoder.encodeInto(string, utf8);
resultPara.textContent +=
  `Bytes read: ${encodedResults.read}` +
  ` | Bytes written: ${encodedResults.written}` +
  ` | Encoded result: ${utf8}`;


Encoding # ref-for-dom-textencoder-encodeinto

MDN

202431 MDN

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