Put the FormatToStream function in its own compilation unit as it might

be useful for other things to.

pglablib/FormatToStream.cpp

@@ -0,0 +1,29 @@
+#include "FormatToStream.h"
+#include <QRegularExpression>
+#include <QTextStream>
+
+void FormatToStream(QTextStream &stream, QString format, std::function<void(QTextStream &, QString)> field_callback)
+{
+	// Use static to optimize only once
+	static QRegularExpression cached_find_var_re("(?:[^\\\\]|^)(\\/%([a-zA-Z0-9_-]+)%\\/)", QRegularExpression::OptimizeOnFirstUsageOption);
+
+	int from = 0;
+	QRegularExpressionMatch match;
+	while (format.indexOf(cached_find_var_re, from, &match) >= 0) {
+		if (from > 0) {
+			// Because the regex has to check for backslash in front we have the from position
+			// one position before where we actually should continue for the second match and later ie when from > 0
+			// Therefor increase from by 1 to make the substring (midRef) calculation work
+			++from;
+		}
+		// copy code before the var to the stream
+		stream << format.midRef(from, match.capturedStart(1) - from);
+		field_callback(stream, match.captured(2));
+		from = match.capturedEnd()-1; // -1 because it wants to match one character before or start of line to make sure there is no backslash
+	}
+	if (from > 0) {
+		// same reason as at the start of the loop
+		++from;
+	}
+	stream << format.midRef(from);
+}