Function _fill

lib/buffer.js:1124–1195

(buf, value, offset, end, encoding)

};

function _fill(buf, value, offset, end, encoding) {
  if (typeof value === 'string') {
    if (offset === undefined || typeof offset === 'string') {
      encoding = offset;
      offset = 0;
      end = buf.length;
    } else if (typeof end === 'string') {
      encoding = end;
      end = buf.length;
    }

    const normalizedEncoding = normalizeEncoding(encoding);
    if (normalizedEncoding === undefined) {
      validateString(encoding, 'encoding');
      throw new ERR_UNKNOWN_ENCODING(encoding);
    }

    if (value.length === 0) {
      // If value === '' default to zero.
      value = 0;
    } else if (value.length === 1) {
      // Fast path: If `value` fits into a single byte, use that numeric value.
      // ASCII shares this branch with utf8 since code < 128 covers the full
      // ASCII range; anything outside falls through to C++ bindingFill.
      if (normalizedEncoding === 'utf8' || normalizedEncoding === 'ascii') {
        const code = StringPrototypeCharCodeAt(value, 0);
        if (code < 128) {
          value = code;
        }
      } else if (normalizedEncoding === 'latin1') {
        value = StringPrototypeCharCodeAt(value, 0);
      }
    }
  } else {
    encoding = undefined;
  }

  if (offset === undefined) {
    offset = 0;
    end = buf.length;
  } else {
    validateOffset(offset, 'offset');
    // Invalid ranges are not set to a default, so can range check early.
    if (end === undefined) {
      end = buf.length;
    } else {
      validateOffset(end, 'end', 0, buf.length);
    }
    if (offset >= end)
      return buf;
  }


  if (typeof value === 'number') {
    // OOB check
    const byteLen = TypedArrayPrototypeGetByteLength(buf);
    const fillLength = end - offset;
    if (offset > end || fillLength + offset > byteLen)