encode/number: add number decoding for base36

CMakeLists.txt

@@ -247,6 +247,7 @@ list (
     cpuid_x86.hpp
     debug.cpp
     debug.hpp
+    encode/number.hpp
     encode/base.cpp
     encode/base.hpp
     endian.cpp
@@ -531,6 +532,7 @@ if (TESTS)
         colour
         comparator
         coord
+        encode/number
         encode/base
         endian
         exe

encode/number.hpp

@@ -0,0 +1,34 @@
+/*
+ * 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/.
+ *
+ * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include "../view.hpp"
+
+///////////////////////////////////////////////////////////////////////////////
+namespace cruft::encode {
+    template <typename ValueT>
+    ValueT
+    decode36 (cruft::view<char const*> &src)
+    {
+        ValueT accum = 0;
+        for (auto const i: src) {
+            accum *= 36;
+
+            switch (i) {
+            case '0'...'9': accum += i - '0';      continue;
+            case 'a'...'z': accum += i - 'a' + 10; continue;
+            case 'A'...'Z': accum += i - 'A' + 10; continue;
+            default:
+                throw std::invalid_argument ("invalid character");
+            }
+        }
+
+        return accum;
+    }
+}

test/encode/number.cpp

@@ -0,0 +1,28 @@
+#include "encode/number.hpp"
+#include "tap.hpp"
+
+
+int main ()
+{
+    static struct {
+        char const *str;
+        unsigned value;
+    } const TESTS[] = {
+        {      "0",        0 },
+        {      "a",       10 },
+        {      "A",       10 },
+        {     "10",       36 },
+        {     "11",       37 },
+        {   "bfi0",   533304 },
+        { "15bfi0", 69397560 },
+    };
+
+    cruft::TAP::logger tap;
+
+    for (auto const &t: TESTS) {
+        cruft::view src (t.str);
+        tap.expect_eq (cruft::encode::decode36<unsigned> (src), t.value, "base36 decode '%!'", t.str);
+    }
+
+    return tap.status ();
+}