Method decode

lib/internal/encoding.js:481–560

(input = empty, options = kEmptyObject)

  }

  decode(input = empty, options = kEmptyObject) {
    validateDecoder(this);
    validateObject(options, 'options', kValidateObjectAllowObjectsAndNull);

    if (this[kSingleByte]) return this[kSingleByte](parseInput(input));

    const stream = options?.stream;
    if (this[kUTF8FastPath]) {
      const chunk = this[kChunk];
      const ignoreBom = this[kIgnoreBOM] || this[kBOMSeen];
      if (!stream) {
        this[kBOMSeen] = false;
        if (!chunk) return decodeUTF8(input, ignoreBom, this[kFatal]);
      }

      let u = parseInput(input);
      if (u.length === 0 && stream) return ''; // no state change
      let prefix;
      if (chunk) {
        const merged = mergePrefixUtf8(u, this[kChunk]);
        if (u.length < 3) {
          u = merged; // Might be unfinished, but fully consumed old u
        } else {
          prefix = merged; // Stops at complete chunk
          const add = prefix.length - this[kChunk].length;
          if (add > 0) u = u.subarray(add);
        }

        this[kChunk] = null;
      }

      if (stream) {
        const trail = unfinishedBytesUtf8(u, u.length);
        if (trail > 0) {
          this[kChunk] = new FastBuffer(u.subarray(-trail)); // copy
          if (!prefix && trail === u.length) return ''; // No further state change
          u = u.subarray(0, -trail);
        }
      }

      try {
        const res = (prefix ? decodeUTF8(prefix, ignoreBom, this[kFatal]) : '') +
                    decodeUTF8(u, ignoreBom || prefix, this[kFatal]);

        // "BOM seen" is set on the current decode call only if it did not error,
        // in "serialize I/O queue" after decoding
        // We don't get here if we had no complete data to process,
        // and we don't want BOM processing after that if streaming
        if (stream) this[kBOMSeen] = true;

        return res;
      } catch (e) {
        this[kChunk] = null; // Reset unfinished chunk on errors
        // The correct way per spec seems to be not destroying the decoder state (aka BOM here) in stream mode
        throw e;
      }
    }