refactor(all): using namespace considered harmful

* project-wide refactor to accomodate removal of "using namespace xyz"
  to stop polluting top-level namespace with "std" as recommended by the
  Google C++ style guide.
* use a pre-commit hook to enforce this

ref:
https://google.github.io/styleguide/cppguide.html#Namespaces

.pre-commit-config.yaml

@@ -20,6 +20,10 @@ repos:
         files: \.(cpp|cc|cxx,h)$
         types: [file, c++]
         types_or: [file, c++, header]
+  - repo: https://github.com/gringolito/cpp-pre-commit-hooks
+    rev: 3481ddf0fb
+    hooks:
+    - id: check-using-namespace-directive
   - repo: local
     hooks:
       - id: make-test

generator.cpp

@@ -17,8 +17,6 @@
 namespace fortuna {
 namespace generator {
 
-using namespace std;
-
 struct Generator::G_state{
 	int64_t k;
 	unsigned __int128 ctr;
@@ -40,17 +38,17 @@ auto Generator::get_state() -> G_state {
 	return G_state{};
 }
 
-auto Generator::reseed(const string& s) -> void {
+auto Generator::reseed(const std::string& s) -> void {
 	G_state G = get_state();
-	string to_be_hashed = std::to_string(G.k) + s;
+	std::string to_be_hashed = std::to_string(G.k) + s;
 	// TODO(me): wrap do_sha in a try-catch
-	string a = do_sha(to_be_hashed);
+	std::string a = do_sha(to_be_hashed);
 	// str, size, base
 	G.k = stol(a,nullptr,10);
 	G.ctr++;
 }
 
-auto Generator::do_sha(const string& k_n_s) -> string {
+auto Generator::do_sha(const std::string& k_n_s) -> std::string {
 	/* do sha256 */
 	using std::cout;
 	using std::endl;
@@ -58,7 +56,7 @@ auto Generator::do_sha(const string& k_n_s) -> string {
 	using CryptoPP::HashFilter;
 	using CryptoPP::StringSink;
 
-	string digest;
+	std::string digest;
 
 	CryptoPP::SHA256 sha2_256;
 	CryptoPP::SHA3_256 sha3_256;
@@ -88,7 +86,7 @@ auto Generator::do_sha(const string& k_n_s) -> string {
 	return "42";
 }
 
-auto Generator::do_crypto(int64_t k, unsigned __int128 ctr) -> string {
+auto Generator::do_crypto(int64_t k, unsigned __int128 ctr) -> std::string {
 	/* this function calls the block cipher
 	 * returns a string of k*(16 bytes);
 	 * do whatever atm */
@@ -97,10 +95,10 @@ auto Generator::do_crypto(int64_t k, unsigned __int128 ctr) -> string {
 	return "";
 }
 
-auto Generator::generate_blocks(unsigned int k_blocks) -> string {
+auto Generator::generate_blocks(unsigned int k_blocks) -> std::string {
 	G_state G = get_state();
 	assert (G.ctr!=0);
-	string r = "";
+	std::string r = "";
 	for (int i = 0; i < k_blocks; ++i) {
 		r += do_crypto(G.k, G.ctr);
 		G.ctr++;
@@ -108,20 +106,20 @@ auto Generator::generate_blocks(unsigned int k_blocks) -> string {
 	return r;
 }
 
-auto Generator::generate_random_data(uint n) -> string {
+auto Generator::generate_random_data(uint n) -> std::string {
 	G_state G = get_state();
-	string r = "";
+	std::string r = "";
 	if (n < 0){
 		/* this should not be possible */
 		printf("[*] error: n cannot be < 0\n");
-		throw invalid_argument("n cannot be < 0");
+		throw std::invalid_argument("n cannot be < 0");
 	} else if (n > pow(2,20)){
 		printf("[*] error: n cannot be > 2^20\n");
-		throw invalid_argument("n cannot be > 2^20");
+		throw std::invalid_argument("n cannot be > 2^20");
 	}
 	/* do magic to compute r
 	 * r ← first-n-bytes(GenerateBlocks(G, ceil(n/16) )) */
-	string rr = generate_blocks(ceil(n/16));
+	std::string rr = generate_blocks(ceil(n/16));
 	r = rr.substr(0,n);
 
 	/* re-key */

generator.h

@@ -6,26 +6,24 @@
 namespace fortuna {
 namespace generator {
 
-using namespace std;
-
 class Generator {
 public:
 	void initialize_generator();
-	auto generate_blocks(unsigned int k_blocks) -> string;
+	auto generate_blocks(unsigned int k_blocks) -> std::string;
 
 private:
 	struct G_state;
 
-	auto reseed(const string& s) -> void;
+	auto reseed(const std::string& s) -> void;
 
-	auto do_sha(const string& k_n_s) -> string;
+	auto do_sha(const std::string& k_n_s) -> std::string;
 
-	auto do_crypto(int64_t k, unsigned __int128 ctr) -> string;
+	auto do_crypto(int64_t k, unsigned __int128 ctr) -> std::string;
 
 	/* n is the number of random bytes to generate */
-	auto generate_random_data(uint n) -> string;
+	auto generate_random_data(uint n) -> std::string;
 
-	auto strtolowerpls(string &s) -> string;
+	auto strtolowerpls(std::string &s) -> std::string;
 
 protected:
 	auto get_state() -> Generator::G_state;