chore: import upstream snapshot with attribution

src/butil/base64url.h

@@ -0,0 +1,54 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_BASE64URL_H_
+#define BASE_BASE64URL_H_
+
+#include <string>
+
+#include "butil/base_export.h"
+#include "butil/strings/string_piece.h"
+
+namespace butil {
+
+enum class Base64UrlEncodePolicy {
+    // Include the trailing padding in the output, when necessary.
+    INCLUDE_PADDING,
+
+    // Remove the trailing padding from the output.
+    OMIT_PADDING
+};
+
+// Encodes the |input| string in base64url, defined in RFC 4648:
+// https://tools.ietf.org/html/rfc4648#section-5
+//
+// The |policy| defines whether padding should be included or omitted from the
+// encoded |*output|. |input| and |*output| may reference the same storage.
+BUTIL_EXPORT void Base64UrlEncode(const StringPiece& input,
+                                 Base64UrlEncodePolicy policy,
+                                 std::string* output);
+
+enum class Base64UrlDecodePolicy {
+    // Require inputs to contain trailing padding if non-aligned.
+    REQUIRE_PADDING,
+
+    // Accept inputs regardless of whether they have the correct padding.
+    IGNORE_PADDING,
+
+    // Reject inputs if they contain any trailing padding.
+    DISALLOW_PADDING
+};
+
+// Decodes the |input| string in base64url, defined in RFC 4648:
+// https://tools.ietf.org/html/rfc4648#section-5
+//
+// The |policy| defines whether padding will be required, ignored or disallowed
+// altogether. |input| and |*output| may reference the same storage.
+BUTIL_EXPORT bool Base64UrlDecode(const StringPiece& input,
+                                 Base64UrlDecodePolicy policy,
+                                 std::string* output) WARN_UNUSED_RESULT;
+
+}  // namespace butil
+
+#endif  // BASE_BASE64URL_H_