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device/cppcodec/base32_crockford.hpp

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+/**
+ *  Copyright (C) 2015 Topology LP
+ *  All rights reserved.
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining a copy
+ *  of this software and associated documentation files (the "Software"), to
+ *  deal in the Software without restriction, including without limitation the
+ *  rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ *  sell copies of the Software, and to permit persons to whom the Software is
+ *  furnished to do so, subject to the following conditions:
+ *
+ *  The above copyright notice and this permission notice shall be included in
+ *  all copies or substantial portions of the Software.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ *  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ *  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ *  IN THE SOFTWARE.
+ */
+
+#ifndef CPPCODEC_BASE32_CROCKFORD
+#define CPPCODEC_BASE32_CROCKFORD
+
+#include "detail/codec.hpp"
+#include "detail/base32.hpp"
+
+namespace cppcodec {
+
+namespace detail {
+
+static constexpr const char base32_crockford_alphabet[] = {
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', // at index 10
+    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',           // 18 - no I
+    'J', 'K',                                         // 20 - no L
+    'M', 'N',                                         // 22 - no O
+    'P', 'Q', 'R', 'S', 'T',                          // 27 - no U
+    'V', 'W', 'X', 'Y', 'Z'                           // 32
+};
+
+class base32_crockford_base
+{
+public:
+    static CPPCODEC_ALWAYS_INLINE constexpr size_t alphabet_size() {
+        static_assert(sizeof(base32_crockford_alphabet) == 32, "base32 alphabet must have 32 values");
+        return sizeof(base32_crockford_alphabet);
+    }
+    static CPPCODEC_ALWAYS_INLINE constexpr char symbol(alphabet_index_t idx)
+    {
+        return base32_crockford_alphabet[idx];
+    }
+    static CPPCODEC_ALWAYS_INLINE constexpr char normalized_symbol(char c)
+    {
+        // Hex decoding is always case-insensitive (even in RFC 4648), the question
+        // is only for encoding whether to use upper-case or lower-case letters.
+        return (c == 'O' || c == 'o') ? '0'
+            : (c == 'I' || c == 'i' || c == 'L' || c == 'l') ? '1'
+            : (c >= 'a' && c <= 'z') ? (c - 'a' + 'A')
+            : c;
+    }
+
+    static CPPCODEC_ALWAYS_INLINE constexpr bool generates_padding() { return false; }
+    static CPPCODEC_ALWAYS_INLINE constexpr bool requires_padding() { return false; }
+    static CPPCODEC_ALWAYS_INLINE constexpr bool is_padding_symbol(char) { return false; }
+    static CPPCODEC_ALWAYS_INLINE constexpr bool is_eof_symbol(char c) { return c == '\0'; }
+
+    static CPPCODEC_ALWAYS_INLINE constexpr bool should_ignore(char c) {
+        return c == '-'; // "Hyphens (-) can be inserted into strings [for readability]."
+    }
+};
+
+// base32_crockford is a concatenative iterative (i.e. streaming) interpretation of Crockford base32.
+// It interprets the statement "zero-extend the number to make its bit-length a multiple of 5"
+// to mean zero-extending it on the right.
+// (The other possible interpretation is base32_crockford_num, a place-based single number encoding system.
+// See http://merrigrove.blogspot.ca/2014/04/what-heck-is-base64-encoding-really.html for more info.)
+class base32_crockford : public base32_crockford_base
+{
+public:
+    template <typename Codec> using codec_impl = stream_codec<Codec, base32_crockford>;
+};
+
+} // namespace detail
+
+using base32_crockford = detail::codec<detail::base32<detail::base32_crockford>>;
+
+} // namespace cppcodec
+
+#endif // CPPCODEC_BASE32_CROCKFORD