With string_view, stripping whitespace can be done without allocs.

Common/Data/Format/IniFile.cpp

@@ -37,7 +37,8 @@ bool StringViewEqualCaseInsensitive(const std::string_view lhs, const std::strin
 }
 
 // This unescapes # signs.
-static bool ParseLineKey(const std::string &line, size_t &pos, std::string *keyOut) {
+// NOTE: These parse functions can make better use of the string_view - the pos argument should not be needed, for example.
+static bool ParseLineKey(std::string_view line, size_t &pos, std::string *keyOut) {
 	std::string key = "";
 
 	while (pos < line.size()) {
@@ -52,7 +53,8 @@ static bool ParseLineKey(const std::string &line, size_t &pos, std::string *keyO
 			}
 
 			// Escaped.
-			key += line.substr(pos, next - pos - 1) + "#";
+			key += line.substr(pos, next - pos - 1);
+			key.push_back('#');
 			pos = next + 1;
 		} else if (line[next] == '=') {
 			// Hurray, done.
@@ -68,11 +70,11 @@ static bool ParseLineKey(const std::string &line, size_t &pos, std::string *keyO
 	return true;
 }
 
-static bool ParseLineValue(const std::string &line, size_t &pos, std::string *valueOut) {
+static bool ParseLineValue(std::string_view line, size_t &pos, std::string *valueOut) {
 	std::string value = "";
 
-	std::string strippedLine = StripSpaces(line.substr(pos));
-	if (strippedLine[0] == '"' && strippedLine[strippedLine.size()-1] == '"') {
+	std::string_view strippedLine = StripSpaces(line.substr(pos));
+	if (strippedLine.size() >= 2 && strippedLine[0] == '"' && strippedLine[strippedLine.size() - 1] == '"') {
 		// Don't remove comment if is surrounded by " "
 		value += line.substr(pos);
 		pos = line.npos; // Won't enter the while below
@@ -92,7 +94,8 @@ static bool ParseLineValue(const std::string &line, size_t &pos, std::string *va
 			break;
 		} else {
 			// Escaped.
-			value += line.substr(pos, next - pos - 1) + "#";
+			value += line.substr(pos, next - pos - 1);
+			value.push_back('#');
 			pos = next + 1;
 		}
 	}
@@ -104,7 +107,7 @@ static bool ParseLineValue(const std::string &line, size_t &pos, std::string *va
 	return true;
 }
 
-static bool ParseLineComment(const std::string& line, size_t &pos, std::string *commentOut) {
+static bool ParseLineComment(std::string_view line, size_t &pos, std::string *commentOut) {
 	// Don't bother with anything if we don't need the comment data.
 	if (commentOut) {
 		// Include any whitespace/formatting in the comment.
@@ -125,8 +128,7 @@ static bool ParseLineComment(const std::string& line, size_t &pos, std::string *
 	return true;
 }
 
-// Ugh, this is ugly.
-static bool ParseLine(const std::string& line, std::string* keyOut, std::string* valueOut, std::string* commentOut)
+static bool ParseLine(std::string_view line, std::string* keyOut, std::string* valueOut, std::string* commentOut)
 {
 	// Rules:
 	// 1. A line starting with ; is commented out.
@@ -150,7 +152,7 @@ static bool ParseLine(const std::string& line, std::string* keyOut, std::string*
 	return true;
 }
 
-static std::string EscapeHash(const std::string &value) {
+static std::string EscapeHash(std::string_view value) {
 	std::string result = "";
 
 	for (size_t pos = 0; pos < value.size(); ) {
@@ -159,17 +161,22 @@ static std::string EscapeHash(const std::string &value) {
 			result += value.substr(pos);
 			pos = value.npos;
 		} else {
-			result += value.substr(pos, next - pos) + "\\#";
+			result += value.substr(pos, next - pos);
+			result += "\\#";
 			pos = next + 1;
 		}
 	}
 
 	return result;
 }
 
-void ParsedIniLine::ParseFrom(const std::string &line) {
-	// TODO: Skip whitespace.
-	if (line[0] == '#') {
+void ParsedIniLine::ParseFrom(std::string_view line) {
+	line = StripSpaces(line);
+	if (line.empty()) {
+		key.clear();
+		value.clear();
+		comment.clear();
+	} else if (line[0] == '#') {
 		key.clear();
 		value.clear();
 		comment = line;

Common/Data/Format/IniFile.h

@@ -33,7 +33,7 @@ class ParsedIniLine {
 	}
 
 	// Comments only come from "ParseFrom".
-	void ParseFrom(const std::string &line);
+	void ParseFrom(std::string_view line);
 	void Reconstruct(std::string *output) const;
 
 	// Having these as views allows a more efficient internal representation, like one joint string.

Common/StringUtils.cpp

@@ -239,18 +239,15 @@ std::string StringFromFormat(const char* format, ...)
 	return temp;
 }
 
-std::string StringFromInt(int value)
-{
+std::string StringFromInt(int value) {
 	char temp[16];
 	snprintf(temp, sizeof(temp), "%d", value);
 	return temp;
 }
 
 // Turns "  hej " into "hej". Also handles tabs.
-std::string StripSpaces(const std::string &str)
-{
+std::string StripSpaces(const std::string &str) {
 	const size_t s = str.find_first_not_of(" \t\r\n");
-
 	if (str.npos != s)
 		return str.substr(s, str.find_last_not_of(" \t\r\n") - s + 1);
 	else
@@ -268,6 +265,25 @@ std::string StripQuotes(const std::string& s)
 		return s;
 }
 
+// Turns "  hej " into "hej". Also handles tabs.
+std::string_view StripSpaces(std::string_view str) {
+	const size_t s = str.find_first_not_of(" \t\r\n");
+	if (str.npos != s)
+		return str.substr(s, str.find_last_not_of(" \t\r\n") - s + 1);
+	else
+		return "";
+}
+
+// "\"hello\"" is turned to "hello"
+// This one assumes that the string has already been space stripped in both
+// ends, as done by StripSpaces above, for example.
+std::string_view StripQuotes(std::string_view s) {
+	if (s.size() && '\"' == s[0] && '\"' == *s.rbegin())
+		return s.substr(1, s.size() - 2);
+	else
+		return s;
+}
+
 void SplitString(const std::string& str, const char delim, std::vector<std::string>& output)
 {
 	size_t next = 0;

Common/StringUtils.h

@@ -21,6 +21,7 @@
 #include <cstdint>
 #include <string>
 #include <cstring>
+#include <string_view>
 #include <vector>
 
 #ifdef _MSC_VER
@@ -83,6 +84,9 @@ std::string StringFromInt(int value);
 std::string StripSpaces(const std::string &s);
 std::string StripQuotes(const std::string &s);
 
+std::string_view StripSpaces(std::string_view s);
+std::string_view StripQuotes(std::string_view s);
+
 void SplitString(const std::string& str, const char delim, std::vector<std::string>& output);
 
 void GetQuotedStrings(const std::string& str, std::vector<std::string>& output);