Implement `--seed` argumentHEADmaster

Enables users to customize the seed used for the pseudorandom number generator.

4 files changed, 46 insertions, 32 deletions

diff --git a/README.md b/README.md
index 9b6ab36..214e2b8 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,8 @@ i.e. `echo "$the_paragraph_above" | justify --length 40 --offset 2` results in:
 	  leading   spaces  may  be  defined using
 	  `--offset`.
 
+The seed used to pseudorandomly distribute missing spaces may be customized via the `--seed` argument.
+
 ## Requirements
 
 * CMake
diff --git a/justify.cc b/justify.cc
index c417dfd..9115d83 100644
--- a/justify.cc
+++ b/justify.cc
@@ -23,6 +23,11 @@ boost::optional<boost::program_options::variables_map> input(
 			boost::program_options::value<int>(),
 			"Number of spaces to be prepended on each line"
 		)
+		(
+			"seed",
+			boost::program_options::value<std::uint32_t>(),
+			"Seed for pseudorandomly distributing missing spaces"
+		)
 	;
 
 	boost::program_options::variables_map variables;
@@ -51,8 +56,9 @@ bool process(const boost::program_options::variables_map& variables) {
 	std::cout.sync_with_stdio(false);
 	std::cin.sync_with_stdio(false);
 
-	std::uint8_t line_length = 60;
-	std::uint8_t line_offset = 0;
+	std::uint8_t  line_length = 60;
+	std::uint8_t  line_offset = 0;
+	std::uint32_t seed        = 3473018784;
 
 	if ( variables.count("length") ) {
 		const int user_length = variables["length"].as<int>();
@@ -78,7 +84,11 @@ bool process(const boost::program_options::variables_map& variables) {
 		}
 	}
 
-	justify::LineAccumulator acc{line_length, line_offset};
+	if ( variables.count("seed") ) {
+		seed = variables["seed"].as<std::uint32_t>();
+	}
+
+	justify::LineAccumulator acc{line_length, line_offset, seed};
 	std::string              token;
 
 	while ( std::cin.good() ) {
diff --git a/src/line_accumulator.cc b/src/line_accumulator.cc
index 9ce389b..a203fac 100644
--- a/src/line_accumulator.cc
+++ b/src/line_accumulator.cc
@@ -6,23 +6,17 @@
 
 namespace {
 
-static std::mt19937 generator;
-
 std::uint8_t getRandomIndex(
-	const int          seed,
+	std::mt19937&      generator,
 	const std::uint8_t n
 ) {
-	generator.seed(seed);
-
 	return std::uniform_int_distribution<std::uint8_t>{0, n}(generator);
 }
 
 std::vector<std::uint8_t> getRandomIndizes(
-	const int          seed,
-	const std::uint8_t n
+	std::mt19937&       generator,
+	const std::uint8_t  n
 ) {
-	generator.seed(seed);
-
 	std::vector<std::uint8_t> indizes(n);
 	std::iota(indizes.begin(), indizes.end(), 0);
 	std::shuffle(
@@ -55,11 +49,13 @@ std::size_t getCharacterLength(const std::string& token) {
 namespace justify {
 
 LineAccumulator::LineAccumulator(
-	const std::uint8_t max_length,
-	const std::uint8_t offset
+	const std::uint8_t  max_length,
+	const std::uint8_t  offset,
+	const std::uint32_t seed
 ):
 	max_length_{max_length},
 	offset_{offset},
+	generator_{seed},
 	length_{0},
 	tokens_{} { }
 
@@ -67,14 +63,6 @@ LineAccumulator::~LineAccumulator() {
 	this->discharge(false);
 }
 
-std::uint8_t LineAccumulator::getMissing() const {
-	if ( this->length_ < this->max_length_ ) {
-		return this->max_length_ - this->length_;
-	} else {
-		return 0;
-	}
-}
-
 void LineAccumulator::operator()(const std::string& token) {
 	const std::size_t tokenLength = getCharacterLength(token);
 
@@ -91,10 +79,15 @@ void LineAccumulator::operator()(const std::string& token) {
 	}
 }
 
-void LineAccumulator::justify() {
-	const int seed = this->tokens_.size()
-	               + this->getMissing();
+std::uint8_t LineAccumulator::getMissing() const {
+	if ( this->length_ < this->max_length_ ) {
+		return this->max_length_ - this->length_;
+	} else {
+		return 0;
+	}
+}
 
+void LineAccumulator::justify() {
 	switch ( this->tokens_.size() ) {
 		// There is no sensible block justification of null or any single token
 		case 0:
@@ -137,14 +130,18 @@ void LineAccumulator::justify() {
 		}
 		// randomly distribute missing spaces
 		case 1: {
-			this->tokens_[
-				getRandomIndex(seed, this->tokens_.size() - 2)
-			].second += 1;
+			this->tokens_[getRandomIndex(
+				this->generator_,
+				this->tokens_.size() - 2
+			)].second += 1;
 
 			break;
 		}
 		default: {
-			const auto indizes = getRandomIndizes(seed, this->tokens_.size() - 2);
+			const auto indizes = getRandomIndizes(
+				this->generator_,
+				this->tokens_.size() - 2
+			);
 
 			std::for_each(
 				indizes.begin(),
diff --git a/src/line_accumulator.h b/src/line_accumulator.h
index 69b4c74..db75c8c 100644
--- a/src/line_accumulator.h
+++ b/src/line_accumulator.h
@@ -9,23 +9,28 @@ namespace justify {
 
 class LineAccumulator {
 	public:
-		LineAccumulator(const std::uint8_t max_length, const std::uint8_t offset);
+		LineAccumulator(
+			const std::uint8_t  max_length,
+			const std::uint8_t  offset,
+			const std::uint32_t seed
+		);
 		~LineAccumulator();
 
-		std::uint8_t getMissing() const;
-
 		void operator()(const std::string& token);
 
 	private:
 		const std::uint8_t max_length_;
 		const std::uint8_t offset_;
 
+		std::mt19937 generator_;
 		std::uint8_t length_;
 
 		std::vector<
 			std::pair<std::string, std::uint8_t>
 		> tokens_;
 
+		std::uint8_t getMissing() const;
+
 		void justify();
 		void discharge(const bool full);