Add dependencies/vendor (whatsapp)

vendor/go.mau.fi/whatsmeow/binary/unpack.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2021 Tulir Asokan
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package binary
+
+import (
+	"bytes"
+	"compress/zlib"
+	"fmt"
+	"io"
+)
+
+// Unpack unpacks the given decrypted data from the WhatsApp web API.
+//
+// It checks the first byte to decide whether to uncompress the data with zlib or just return as-is
+// (without the first byte). There's currently no corresponding Pack function because Marshal
+// already returns the data with a leading zero (i.e. not compressed).
+func Unpack(data []byte) ([]byte, error) {
+	dataType, data := data[0], data[1:]
+	if 2&dataType > 0 {
+		if decompressor, err := zlib.NewReader(bytes.NewReader(data)); err != nil {
+			return nil, fmt.Errorf("failed to create zlib reader: %w", err)
+		} else if data, err = io.ReadAll(decompressor); err != nil {
+			return nil, err
+		}
+	}
+	return data, nil
+}