Add a benchmark to test runtime performance.

Numbers are comparable to the gaspardpetit/base64 benchmark,
in which the runtime duration of encoding or decoding runs is
averaged out over many iterations (1 million or up to 0.5s,
whichever one is shorter). Code is all new.

Run test/benchmark_cppcodec without arguments to get numbers
for encoding to strings, decoding to strings and decoding to
vector<uint8_t> for base64_rfc4648.

This should be enough to test the performance fix for Windows
from #35. We can add command line options later, such as
selecting the codec or the set of decoded buffer sizes.

Author: jpetso

test/CMakeLists.txt

@@ -16,3 +16,5 @@ endif()
 
 add_executable(test_cppcodec test_cppcodec.cpp)
 add_test(cppcodec test_cppcodec)
+
+add_executable(benchmark_cppcodec benchmark_cppcodec.cpp)

test/benchmark_cppcodec.cpp

@@ -0,0 +1,148 @@
+/**
+ *  Copyright (C) 2018 Jakob Petsovits
+ *  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.
+ */
+
+#include <cppcodec/hex_lower.hpp>
+#include <cppcodec/base32_rfc4648.hpp>
+#include <cppcodec/base64_rfc4648.hpp>
+
+#include <chrono>
+#include <iostream>
+#include <iomanip>
+#include <random>
+#include <stdint.h>
+#include <string>
+#include <vector>
+
+const size_t max_iterations = 1000000; // 1m iterations ought to be enough for anybody
+const size_t iteration_max_ms = 500; // half a second
+
+uint8_t random_uint8()
+{
+    static std::random_device rd;
+    static std::mt19937 pseudo_random(rd());
+    static std::uniform_int_distribution<int> dist(0, 255);
+    return static_cast<uint8_t>(dist(pseudo_random));
+}
+
+template <typename Codec>
+void benchmark(std::ostream& stream, const std::vector<size_t>& decoded_sizes)
+{
+    using clock = std::chrono::high_resolution_clock;
+
+    // Measure decoding into both uint8_t and string.
+    std::vector<double> time_encoding_str(decoded_sizes.size());
+    std::vector<double> time_decoding_vec_u8(decoded_sizes.size());
+    std::vector<double> time_decoding_str(decoded_sizes.size());
+    std::vector<std::vector<uint8_t>> decoded_vec_u8(decoded_sizes.size());
+    std::vector<std::string> decoded_str(decoded_sizes.size());
+    std::vector<std::string> encoded_str(decoded_sizes.size());
+
+    for (size_t i = 0; i < decoded_sizes.size(); ++i) {
+        decoded_vec_u8[i].resize(decoded_sizes[i]);
+        for (size_t j = 0; j < decoded_sizes[i]; ++j) {
+            decoded_vec_u8[i][j] = random_uint8();
+        }
+    }
+
+    auto flags = stream.flags();
+    auto precision = stream.precision();
+    stream << std::fixed << std::setprecision(4)
+            << "Encoding:\n";
+
+    for (size_t i = 0; i < decoded_sizes.size(); ++i) {
+        encoded_str[i] = std::string();
+        clock::time_point start = clock::now();
+        clock::time_point end = start + std::chrono::milliseconds(iteration_max_ms);
+        size_t j = 0;
+        for (; j < max_iterations; ++j) {
+            if (clock::now() > end) {
+                break;
+            }
+            encoded_str[i] = Codec::encode(decoded_vec_u8[i]);
+        }
+        time_encoding_str[i] = std::chrono::duration_cast<std::chrono::microseconds>(
+                clock::now() - start).count() / static_cast<double>(j);
+
+        stream << (i == 0 ? "" : "\t") << decoded_sizes[i] << ": "
+                << time_encoding_str[i] << std::flush;
+    }
+
+    stream << "\n" << "Decoding to string:\n";
+
+    for (size_t i = 0; i < decoded_sizes.size(); ++i) {
+        decoded_str[i] = std::string();
+        clock::time_point start = clock::now();
+        clock::time_point end = start + std::chrono::milliseconds(iteration_max_ms);
+        size_t j = 0;
+        for (; j < max_iterations; ++j) {
+            if (clock::now() > end) {
+                break;
+            }
+#ifdef _MSC_VER
+            decoded_str[i] = Codec::decode<std::string>(encoded_str[i]);
+#else
+            decoded_str[i] =
+                    Codec::template decode<std::string>(encoded_str[i]);
+#endif
+        }
+        time_decoding_str[i] = std::chrono::duration_cast<std::chrono::microseconds>(
+                clock::now() - start).count() / static_cast<double>(j);
+
+        stream << (i == 0 ? "" : "\t") << decoded_sizes[i] << ": "
+                << time_decoding_str[i] << std::flush;
+    }
+
+    stream << "\n" << "Decoding to vector<uint8_t>:\n";
+
+    for (size_t i = 0; i < decoded_sizes.size(); ++i) {
+        decoded_vec_u8[i] = std::vector<uint8_t>();
+        clock::time_point start = clock::now();
+        clock::time_point end = start + std::chrono::milliseconds(iteration_max_ms);
+        size_t j = 0;
+        for (; j < max_iterations; ++j) {
+            if (clock::now() > end) {
+                break;
+            }
+            decoded_vec_u8[i] = Codec::decode(encoded_str[i]);
+        }
+        time_decoding_vec_u8[i] = std::chrono::duration_cast<std::chrono::microseconds>(
+                clock::now() - start).count() / static_cast<double>(j);
+
+        stream << (i == 0 ? "" : "\t") << decoded_sizes[i] << ": "
+                << time_decoding_vec_u8[i] << std::flush;
+    }
+
+    stream << std::setprecision(precision) << "\n";
+    stream.flags(flags);
+}
+
+int main(int argc, char *argv[])
+{
+    std::vector<size_t> decoded_sizes = {
+        1, 4, 8, 16, 32, 64, 128, 256, 2048, 4096, 32768
+    };
+
+    std::cout << "base64_rfc4648: [decoded size: microseconds]\n";
+    benchmark<cppcodec::base64_rfc4648>(std::cout, decoded_sizes);
+    return 0;
+}