1 files changed, 38 insertions, 0 deletions
diff --git a/include/base64_url.hpp b/include/base64_url.hpp
new file mode 100644
index 0000000..271940e
--- /dev/null
+++ b/include/base64_url.hpp
@@ -0,0 +1,38 @@
+#pragma once
+
+#include <cppcodec/base64_rfc4648.hpp>
+
+static constexpr const char base64_url_alphabet[] = {
+    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
+    'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
+    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_'
+};
+
+class base64_url_impl
+{
+public:
+    template <typename Codec> using codec_impl = cppcodec::detail::stream_codec<Codec, base64_url_impl>;
+
+    static CPPCODEC_ALWAYS_INLINE constexpr size_t alphabet_size() {
+        static_assert(sizeof(base64_url_alphabet) == 64, "base64 alphabet must have 64 values");
+        return sizeof(base64_url_alphabet);
+    }
+    static CPPCODEC_ALWAYS_INLINE constexpr char symbol(cppcodec::detail::alphabet_index_t idx)
+    {
+        return base64_url_alphabet[idx];
+    }
+    static CPPCODEC_ALWAYS_INLINE constexpr char normalized_symbol(char c) { return c; }
+
+    static CPPCODEC_ALWAYS_INLINE constexpr bool generates_padding() { return true; }
+    static CPPCODEC_ALWAYS_INLINE constexpr bool requires_padding() { return true; }
+    static CPPCODEC_ALWAYS_INLINE constexpr char padding_symbol() { return '='; }
+    static CPPCODEC_ALWAYS_INLINE constexpr bool is_padding_symbol(char c) { return c == '='; }
+    static CPPCODEC_ALWAYS_INLINE constexpr bool is_eof_symbol(char c) { return c == '\0'; }
+
+    // RFC4648 does not specify any whitespace being allowed in base64 encodings.
+    static CPPCODEC_ALWAYS_INLINE constexpr bool should_ignore(char) { return false; }
+};
+
+using base64_url = cppcodec::detail::codec<cppcodec::detail::base64<base64_url_impl>>;
+\ No newline at end of file