Deprecate the versions of Base64Escape() and WebSafeBase64Escape()
that use an output parameter.

These versions are clearly inferior to the versions that return
a string.

This is a response to https://github.com/abseil/abseil-cpp/issues/2015

Fixes #2015

PiperOrigin-RevId: 870281461
Change-Id: I92f23d51d05a243dde88c997c1e8448819c5bc77

absl/strings/escaping.cc

diff --git a/absl/strings/escaping.cc b/absl/strings/escaping.cc
index 9f887b8..1171e8d 100644
--- a/absl/strings/escaping.cc
+++ b/absl/strings/escaping.cc
@@ -954,19 +954,6 @@
   return Base64UnescapeInternal(src.data(), src.size(), dest, kUnWebSafeBase64);
 }
 
-void Base64Escape(absl::string_view src, std::string* absl_nonnull dest) {
-  strings_internal::Base64EscapeInternal(
-      reinterpret_cast<const unsigned char*>(src.data()), src.size(), dest,
-      true, strings_internal::kBase64Chars);
-}
-
-void WebSafeBase64Escape(absl::string_view src,
-                         std::string* absl_nonnull dest) {
-  strings_internal::Base64EscapeInternal(
-      reinterpret_cast<const unsigned char*>(src.data()), src.size(), dest,
-      false, strings_internal::kWebSafeBase64Chars);
-}
-
 std::string Base64Escape(absl::string_view src) {
   std::string dest;
   strings_internal::Base64EscapeInternal(

absl/strings/escaping.h

diff --git a/absl/strings/escaping.h b/absl/strings/escaping.h
index 3aaf39c..aaacc28 100644
--- a/absl/strings/escaping.h
+++ b/absl/strings/escaping.h
@@ -126,16 +126,26 @@
 // Encodes a `src` string into a base64-encoded 'dest' string with padding
 // characters. This function conforms with RFC 4648 section 4 (base64) and RFC
 // 2045.
-void Base64Escape(absl::string_view src, std::string* absl_nonnull dest);
 std::string Base64Escape(absl::string_view src);
+[[deprecated(
+    "Use the string-returning version of "
+    "Base64Escape()")]] ABSL_REFACTOR_INLINE inline void
+Base64Escape(absl::string_view src, std::string* absl_nonnull dest) {
+  *dest = Base64Escape(src);
+}
 
 // WebSafeBase64Escape()
 //
 // Encodes a `src` string into a base64 string, like Base64Escape() does, but
 // outputs '-' instead of '+' and '_' instead of '/', and does not pad 'dest'.
 // This function conforms with RFC 4648 section 5 (base64url).
-void WebSafeBase64Escape(absl::string_view src, std::string* absl_nonnull dest);
 std::string WebSafeBase64Escape(absl::string_view src);
+[[deprecated(
+    "Use the string-returning version of "
+    "WebSafeBase64Escape()")]] ABSL_REFACTOR_INLINE inline void
+WebSafeBase64Escape(absl::string_view src, std::string* absl_nonnull dest) {
+  *dest = WebSafeBase64Escape(src);
+}
 
 // Base64Unescape()
 //