Codechange: Use std::span/std::string_view for strecpy. (#12848)

This avoids needing to manually pass the last character of the destination buffer, and allows use of standard library functions.

src/strgen/strgen.cpp

@@ -108,11 +108,11 @@ void FileStringReader::HandlePragma(char *str)
 	if (!memcmp(str, "id ", 3)) {
 		this->data.next_string_id = std::strtoul(str + 3, nullptr, 0);
 	} else if (!memcmp(str, "name ", 5)) {
-		strecpy(_lang.name, str + 5, lastof(_lang.name));
+		strecpy(_lang.name, str + 5);
 	} else if (!memcmp(str, "ownname ", 8)) {
-		strecpy(_lang.own_name, str + 8, lastof(_lang.own_name));
+		strecpy(_lang.own_name, str + 8);
 	} else if (!memcmp(str, "isocode ", 8)) {
-		strecpy(_lang.isocode, str + 8, lastof(_lang.isocode));
+		strecpy(_lang.isocode, str + 8);
 	} else if (!memcmp(str, "textdir ", 8)) {
 		if (!memcmp(str + 8, "ltr", 3)) {
 			_lang.text_dir = TD_LTR;
@@ -123,13 +123,13 @@ void FileStringReader::HandlePragma(char *str)
 		}
 	} else if (!memcmp(str, "digitsep ", 9)) {
 		str += 9;
-		strecpy(_lang.digit_group_separator, strcmp(str, "{NBSP}") == 0 ? NBSP : str, lastof(_lang.digit_group_separator));
+		strecpy(_lang.digit_group_separator, strcmp(str, "{NBSP}") == 0 ? NBSP : str);
 	} else if (!memcmp(str, "digitsepcur ", 12)) {
 		str += 12;
-		strecpy(_lang.digit_group_separator_currency, strcmp(str, "{NBSP}") == 0 ? NBSP : str, lastof(_lang.digit_group_separator_currency));
+		strecpy(_lang.digit_group_separator_currency, strcmp(str, "{NBSP}") == 0 ? NBSP : str);
 	} else if (!memcmp(str, "decimalsep ", 11)) {
 		str += 11;
-		strecpy(_lang.digit_decimal_separator, strcmp(str, "{NBSP}") == 0 ? NBSP : str, lastof(_lang.digit_decimal_separator));
+		strecpy(_lang.digit_decimal_separator, strcmp(str, "{NBSP}") == 0 ? NBSP : str);
 	} else if (!memcmp(str, "winlangid ", 10)) {
 		const char *buf = str + 10;
 		long langid = std::strtol(buf, nullptr, 16);
@@ -153,7 +153,7 @@ void FileStringReader::HandlePragma(char *str)
 
 			if (s == nullptr) break;
 			if (_lang.num_genders >= MAX_NUM_GENDERS) FatalError("Too many genders, max {}", MAX_NUM_GENDERS);
-			strecpy(_lang.genders[_lang.num_genders], s, lastof(_lang.genders[_lang.num_genders]));
+			strecpy(_lang.genders[_lang.num_genders], s);
 			_lang.num_genders++;
 		}
 	} else if (!memcmp(str, "case ", 5)) {
@@ -165,7 +165,7 @@ void FileStringReader::HandlePragma(char *str)
 
 			if (s == nullptr) break;
 			if (_lang.num_cases >= MAX_NUM_CASES) FatalError("Too many cases, max {}", MAX_NUM_CASES);
-			strecpy(_lang.cases[_lang.num_cases], s, lastof(_lang.cases[_lang.num_cases]));
+			strecpy(_lang.cases[_lang.num_cases], s);
 			_lang.num_cases++;
 		}
 	} else {

src/strgen/strgen_base.cpp

@@ -756,9 +756,9 @@ void StringReader::ParseFile()
 
 	/* For each new file we parse, reset the genders, and language codes. */
 	MemSetT(&_lang, 0);
-	strecpy(_lang.digit_group_separator, ",", lastof(_lang.digit_group_separator));
+	strecpy(_lang.digit_group_separator, ",");
-	strecpy(_lang.digit_group_separator_currency, ",", lastof(_lang.digit_group_separator_currency));
+	strecpy(_lang.digit_group_separator_currency, ",");
-	strecpy(_lang.digit_decimal_separator, ".", lastof(_lang.digit_decimal_separator));
+	strecpy(_lang.digit_decimal_separator, ".");
 
 	_cur_line = 1;
 	while (this->data.next_string_id < this->data.max_strings) {

src/string.cpp

@@ -50,34 +50,27 @@
  * Copies characters from one buffer to another.
  *
  * Copies the source string to the destination buffer with respect of the
- * terminating null-character and the last pointer to the last element in
+ * terminating null-character and the size of the destination buffer.
- * the destination buffer. If the last pointer is set to nullptr no boundary
- * check is performed.
  *
- * @note usage: strecpy(dst, src, lastof(dst));
+ * @note usage: strecpy(dst, src);
- * @note lastof() applies only to fixed size arrays
  *
  * @param dst The destination buffer
  * @param src The buffer containing the string to copy
- * @param last The pointer to the last element of the destination buffer
- * @return The pointer to the terminating null-character in the destination buffer
  */
-char *strecpy(char *dst, const char *src, const char *last)
+void strecpy(std::span<char> dst, std::string_view src)
 {
-	assert(dst <= last);
+	/* Ensure source string fits with NUL terminator; dst must be at least 1 character longer than src. */
-	while (dst != last && *src != '\0') {
+	if (std::empty(dst) || std::size(src) >= std::size(dst) - 1U) {
-		*dst++ = *src++;
-	}
-	*dst = '\0';
-
-	if (dst == last && *src != '\0') {
 #if defined(STRGEN) || defined(SETTINGSGEN)
 		FatalError("String too long for destination buffer");
 #else /* STRGEN || SETTINGSGEN */
 		Debug(misc, 0, "String too long for destination buffer");
+		src = src.substr(0, std::size(dst) - 1U);
 #endif /* STRGEN || SETTINGSGEN */
 	}
-	return dst;
+
+	auto it = std::copy(std::begin(src), std::end(src), std::begin(dst));
+	*it = '\0';
 }
 
 /**

src/string_func.h

@@ -17,7 +17,7 @@
 #include "core/bitmath_func.hpp"
 #include "string_type.h"
 
-char *strecpy(char *dst, const char *src, const char *last) NOACCESS(3);
+void strecpy(std::span<char> dst, std::string_view src);
 
 std::string FormatArrayAsHex(std::span<const uint8_t> data);