Codechange: switch StringBuilder to use std::string as backend

src/strings.cpp

@@ -303,11 +303,10 @@ std::string GetString(StringID string)
  */
 std::string GetStringWithArgs(StringID string, StringParameters *args)
 {
-	char buffer[DRAW_STRING_BUFFER];
-	char *state = buffer;
-	StringBuilder builder(&state, lastof(buffer));
+	std::string result;
+	StringBuilder builder(result);
 	GetStringWithArgs(builder, string, args);
-	return std::string(buffer, builder.GetEnd());
+	return result;
 }
 
 /**
@@ -838,9 +837,8 @@ static void FormatString(StringBuilder &builder, const char *str_arg, StringPara
 		 * the parameters. So, we need to gather the type information via the
 		 * dry run first, before we can continue formatting the string.
 		 */
-		char buffer[DRAW_STRING_BUFFER];
-		char *state = buffer;
-		StringBuilder dry_run_builder(&state, lastof(buffer));
+		std::string buffer;
+		StringBuilder dry_run_builder(buffer);
 		if (UsingNewGRFTextStack()) {
 			/* Values from the NewGRF text stack are only copied to the normal
 			 * argv array at the time they are encountered. That means that if
@@ -1004,21 +1002,17 @@ static void FormatString(StringBuilder &builder, const char *str_arg, StringPara
 					char *p = input + Utf8Encode(input, args->GetTypeAtOffset(offset));
 					*p = '\0';
 
-					/* The gender is stored at the start of the formatted string.
-					 * So to determine the gender after formatting we only need
-					 * enough space for the gender index token, one character
-					 * for the actual gender and one character for '\0'. */
-					char buf[MAX_CHAR_LENGTH + 1 + 1];
-					char *state = buf;
+					/* The gender is stored at the start of the formatted string. */
 					bool old_sgd = _scan_for_gender_data;
 					_scan_for_gender_data = true;
-					StringBuilder tmp_builder(&state, lastof(buf));
+					std::string buffer;
+					StringBuilder tmp_builder(buffer);
 					StringParameters tmp_params(args->GetPointerToOffset(offset), args->num_param - offset, nullptr);
 					FormatString(tmp_builder, input, &tmp_params);
 					_scan_for_gender_data = old_sgd;
 
 					/* And determine the string. */
-					const char *s = buf;
+					const char *s = buffer.c_str();
 					WChar c = Utf8Consume(&s);
 					/* Does this string have a gender, if so, set it */
 					if (c == SCC_GENDER_INDEX) gender = (byte)s[0];

src/strings_internal.h

@@ -20,9 +20,7 @@
  * extra functions to ease the migration from char buffers to std::string.
  */
 class StringBuilder {
-	char **current; ///< The current location to add strings.
-	char *start;   ///< The begin of the string.
-	const char *last; ///< The last element of the buffer.
+	std::string *string;
 
 public:
 	/* Required type for this to be an output_iterator; mimics std::back_insert_iterator. */
@@ -37,7 +35,7 @@ public:
 	 * @param start The start location to write to.
 	 * @param last  The last location to write to.
 	 */
-	StringBuilder(char **start, const char *last) : current(start), start(*start), last(last) {}
+	StringBuilder(std::string &string) : string(&string) {}
 
 	/* Required operators for this to be an output_iterator; mimics std::back_insert_iterator, which has no-ops. */
 	StringBuilder &operator++() { return *this; }
@@ -63,7 +61,7 @@ public:
 	 */
 	StringBuilder &operator+=(const char value)
 	{
-		if (*this->current != this->last) *(*this->current)++ = value;
+		this->string->push_back(value);
 		return *this;
 	}
 
@@ -72,54 +70,31 @@ public:
 	 * @param str The string to add.
 	 * @return Reference to this inserter.
 	 */
-	StringBuilder &operator+=(const char *str)
+	StringBuilder &operator+=(std::string_view str)
 	{
-		*this->current = strecpy(*this->current, str, this->last);
+		*this->string += str;
 		return *this;
 	}
 
-	/**
-	 * Operator to append the given string to the output buffer.
-	 * @param str The string to add.
-	 * @return Reference to this inserter.
-	 */
-	StringBuilder &operator+=(const std::string &str)
-	{
-		return this->operator+=(str.c_str());
-	}
-
 	/**
 	 * Encode the given Utf8 character into the output buffer.
 	 * @param c The character to encode.
-	 * @return true iff there was enough space and the character got added.
 	 */
 	bool Utf8Encode(WChar c)
 	{
-		if (this->Remaining() < Utf8CharLen(c)) return false;
-
-		(*this->current) += ::Utf8Encode(*this->current, c);
+		auto iterator = std::back_inserter(*this->string);
+		::Utf8Encode(iterator, c);
 		return true;
 	}
 
 	/**
 	 * Remove the given amount of characters from the back of the string.
 	 * @param amount The amount of characters to remove.
+	 * @return true iff there was enough space and the character got added.
 	 */
 	void RemoveElementsFromBack(size_t amount)
 	{
-		*this->current = std::max(this->start, *this->current - amount);
-	}
-
-	/**
-	 * Get the pointer to the this->last written element in the buffer.
-	 * This call does '\0' terminate the string, whereas other calls do not
-	 * (necessarily) do this.
-	 * @return The this->current end of the string.
-	 */
-	char *GetEnd()
-	{
-		**this->current = '\0';
-		return *this->current;
+		this->string->erase(this->string->size() - std::min(amount, this->string->size()));
 	}
 
 	/**
@@ -128,7 +103,7 @@ public:
 	 */
 	ptrdiff_t Remaining()
 	{
-		return (ptrdiff_t)(this->last - *this->current);
+		return 42; // Just something big-ish, as there's always space (until allocation fails)
 	}
 
 	/**
@@ -137,7 +112,7 @@ public:
 	 */
 	size_t CurrentIndex()
 	{
-		return *this->current - this->start;
+		return this->string->size();
 	}
 
 	/**
@@ -146,7 +121,7 @@ public:
 	 */
 	char &operator[](size_t index)
 	{
-		return this->start[index];
+		return (*this->string)[index];
 	}
 };
 

src/townname.cpp

@@ -65,11 +65,10 @@ static void GetTownName(StringBuilder &builder, const TownNameParams *par, uint3
  */
 std::string GetTownName(const TownNameParams *par, uint32 townnameparts)
 {
-	char buffer[DRAW_STRING_BUFFER];
-	char *state = buffer;
-	StringBuilder builder(&state, lastof(buffer));
+	std::string result;
+	StringBuilder builder(result);
 	GetTownName(builder, par, townnameparts);
-	return std::string(buffer, builder.GetEnd());
+	return result;
 }
 
 /**
@@ -1024,19 +1023,6 @@ void GenerateTownNameString(StringBuilder &builder, size_t lang, uint32 seed)
 {
 	assert(lang < lengthof(_town_name_generators));
 
-	/* Some generators need at least 9 bytes in buffer.  English generators need 5 for
-	 * string replacing, others use constructions like strlen(buf)-3 and so on.
-	 * Finnish generator needs to fit all strings from _name_finnish_1.
-	 * Czech generator needs to fit almost whole town name...
-	 * These would break. Using another temporary buffer results in ~40% slower code,
-	 * so use it only when really needed. */
 	const TownNameGeneratorParams *par = &_town_name_generators[lang];
-	if (builder.Remaining() >= par->min) return par->proc(builder, seed);
-
-	std::string buffer(par->min + 1, '\0');
-	char *state = buffer.data();
-	StringBuilder buffer_builder(&state, buffer.data() + par->min);
-	par->proc(buffer_builder, seed);
-
-	builder += buffer;
+	return par->proc(builder, seed);
 }