big number implementation, for future use in permissions bitfields (#…

…1176)

include/dpp/bignum.h

@@ -0,0 +1,101 @@
+/************************************************************************************
+ *
+ * D++, A Lightweight C++ library for Discord
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2021 Craig Edwards and D++ contributors
+ * (https://github.com/brainboxdotcc/DPP/graphs/contributors)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ ************************************************************************************/
+
+#pragma once
+#include <dpp/export.h>
+#include <dpp/snowflake.h>
+#include <memory>
+
+namespace dpp {
+
+/**
+ * @brief This contains the OpenSSL structs. It is not public,
+ * so that the public interface doesn't depend on OpenSSL directly.
+ */
+struct openssl_bignum;
+
+/**
+* @brief An arbitrary length integer number.
+ * Officially, the Discord documentation says that permission values can be any arbitrary
+ * number of digits. At time of writing there are only 50 bits of permissions, but this is
+ * set to grow larger and potentially past 64 bits. They will continue to send this data
+ * as a huge single integer at that point, because this is obviously sensible. /s
+ *
+ * @note dpp::bignumber uses OpenSSL BN_* under the hood, as we include openssl anyway
+ * for HTTPS.
+*/
+class DPP_EXPORT bignumber {
+	/**
+	 * @brief Internal opaque struct to contain OpenSSL things
+	 */
+	std::shared_ptr<openssl_bignum> ssl_bn{nullptr};
+public:
+	/**
+	 * @brief Construct a new bignumber object
+	 */
+	bignumber() = default;
+
+	/**
+	 * @brief Parse a std::string of an arbitrary length number into
+	 * a bignumber.
+	 * @param number_string string representation of a number. The
+	 * number must be an integer, and can be positive or negative.
+	 * @note Prefixing number_string with 0x will parse it as hexadecimal.
+	 * This is not case sensitive.
+	 */
+	bignumber(const std::string& number_string);
+
+	/**
+	 * @brief Build a bignumber from a vector of 64 bit values.
+	 * The values are accepted in "reverse order", so the first vector
+	 * entry at index 0 is the leftmost 64 bits of the bignum.
+	 * The vector can be any arbitrary length.
+	 * @param bits Vector of 64 bit values which represent the number
+	 */
+	bignumber(std::vector<uint64_t> bits);
+
+	/**
+	 * @brief Default destructor
+	 */
+	~bignumber() = default;
+
+	/**
+	 * @brief Get the string representation of the bignumber.
+	 * @param hex If false (the default) the number is returned in
+	 * decimal, else if this parameter is true, it will be returned
+	 * as hex (without leading '0x')
+	 * @return String representation of bignumber
+	 */
+	[[nodiscard]] std::string get_number(bool hex = false) const;
+
+	/**
+	 * @brief Get the array of 64 bit values that represents the
+	 * bignumber. This is what we should use to store bignumbers
+	 * in memory, not this bignumber class itself, as the bignumber
+	 * class instantiates OpenSSL structs and takes significantly
+	 * more ram than just a vector.
+	 * @return Vector of 64 bit values representing the bignumber
+	 */
+	[[nodiscard]] std::vector<uint64_t> get_binary() const;
+};
+
+} // namespace dpp

include/dpp/dpp.h

@@ -74,3 +74,4 @@
 #include <dpp/discordevents.h>
 #include <dpp/timed_listener.h>
 #include <dpp/collector.h>
+#include <dpp/bignum.h>

src/dpp/bignum.cpp

@@ -0,0 +1,102 @@
+/************************************************************************************
+ *
+ * D++, A Lightweight C++ library for Discord
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2021 Craig Edwards and D++ contributors
+ * (https://github.com/brainboxdotcc/DPP/graphs/contributors)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ ************************************************************************************/
+
+#include <dpp/bignum.h>
+#include <dpp/stringops.h>
+#include <openssl/bn.h>
+#include <cmath>
+
+namespace dpp {
+
+struct openssl_bignum {
+	/**
+	 * @brief OpenSSL BIGNUM pointer
+	 */
+	BIGNUM* bn{nullptr};
+
+	/**
+	 * @brief Construct BIGNUM using RAII
+	 */
+	openssl_bignum() : bn(BN_new()) {
+	}
+
+	/**
+	 * @brief Destruct BIGNUM using RAII
+	 */
+	~openssl_bignum() {
+		BN_free(bn);
+	}
+};
+
+bignumber::bignumber(const std::string& number_string) : ssl_bn(std::make_shared<openssl_bignum>()) {
+	if (dpp::lowercase(number_string.substr(0, 2)) == "0x") {
+		BN_hex2bn(&ssl_bn->bn, number_string.substr(2, number_string.length() - 2).c_str());
+	} else {
+		BN_dec2bn(&ssl_bn->bn, number_string.c_str());
+	}
+}
+
+/**
+ * Flip (reverse) bytes in a uint64_t
+ * @param bytes 64 bit value
+ * @return flipped 64 bit value
+ */
+inline uint64_t flip_bytes(uint64_t bytes) {
+	return ((((bytes) & 0xff00000000000000ull) >> 56)
+	       | (((bytes) & 0x00ff000000000000ull) >> 40)
+	       | (((bytes) & 0x0000ff0000000000ull) >> 24)
+	       | (((bytes) & 0x000000ff00000000ull) >> 8)
+	       | (((bytes) & 0x00000000ff000000ull) << 8)
+	       | (((bytes) & 0x0000000000ff0000ull) << 24)
+	       | (((bytes) & 0x000000000000ff00ull) << 40)
+	       | (((bytes) & 0x00000000000000ffull) << 56));
+}
+
+bignumber::bignumber(std::vector<uint64_t> bits): ssl_bn(std::make_shared<openssl_bignum>()) {
+	std::reverse(bits.begin(), bits.end());
+	for (auto& chunk : bits) {
+		chunk = flip_bytes(chunk);
+	}
+	BN_bin2bn(reinterpret_cast<unsigned char*>(bits.data()), bits.size() * sizeof(uint64_t), ssl_bn->bn);
+}
+
+std::string bignumber::get_number(bool hex) const {
+	char* number_str = hex ? BN_bn2hex(ssl_bn->bn) : BN_bn2dec(ssl_bn->bn);
+	std::string returned{number_str};
+	OPENSSL_free(number_str);
+	return returned;
+}
+
+std::vector<uint64_t> bignumber::get_binary() const {
+	std::size_t size = BN_num_bytes(ssl_bn->bn);
+	auto size_64_bit = static_cast<std::size_t>(ceil(static_cast<double>(size) / sizeof(uint64_t)));
+	std::vector<uint64_t> returned;
+	returned.resize(size_64_bit);
+	BN_bn2binpad(ssl_bn->bn, reinterpret_cast<unsigned char*>(returned.data()), returned.size() * sizeof(uint64_t));
+	std::reverse(returned.begin(), returned.end());
+	for (auto& chunk : returned) {
+		chunk = flip_bytes(chunk);
+	}
+	return returned;
+}
+
+}

src/dpp/cluster/channel.cpp

@@ -21,8 +21,6 @@
 #include <dpp/channel.h>
 #include <dpp/restrequest.h>
 
-#include <utility>
-
 namespace dpp {
 
 void cluster::channel_create(const class channel &c, command_completion_event_t callback) {

src/unittest/test.cpp

@@ -96,6 +96,21 @@ Markdown lol ||spoiler|| ~~strikethrough~~ `small *code* block`\n";
 	u3.id = 777;
 	set_test(COMPARISON, u1 == u2 && u1 != u3);
 
+	set_test(BIGNUM, false);
+	std::string big_in{"1234567890123456789012345678901234567890"};
+	dpp::bignumber big(big_in);
+	std::string returned = big.get_number();
+	set_test(BIGNUM, big_in == returned);
+
+	set_test(BIGNUM2, false);
+	std::vector<uint64_t> vec{0xff00ff00ff00ff00, 0x1122334455667788};
+	dpp::bignumber big2(vec);
+	returned = big2.get_number(true);
+	set_test(BIGNUM2, dpp::lowercase(returned) == "1122334455667788ff00ff00ff00ff00");
+
+	set_test(BIGNUM3, false);
+	std::vector<uint64_t> ret_bin = big2.get_binary();
+	set_test(BIGNUM3, ret_bin.size() == 2 && ret_bin[0] == 0xff00ff00ff00ff00 && ret_bin[1] == 0x1122334455667788);
 
 	set_test(ERRORS, false);
 

src/unittest/test.h

@@ -83,6 +83,9 @@ struct test_t {
 
 /* Current list of unit tests */
 DPP_TEST(SNOWFLAKE, "dpp::snowflake class", tf_offline);
+DPP_TEST(BIGNUM, "dpp::bignumber decimal to raw buffer", tf_offline);
+DPP_TEST(BIGNUM2, "dpp::bignumber raw buffer to hex", tf_offline);
+DPP_TEST(BIGNUM3, "dpp::bignumber to_binary()", tf_offline);
 DPP_TEST(JSON_INTERFACE, "dpp::json_interface class", tf_offline);
 DPP_TEST(CLUSTER, "Instantiate DPP cluster", tf_offline);
 DPP_TEST(BOTSTART, "cluster::start method", tf_online);