Add string formatting function with named params.

In addition to the formatting function, a matching Escape type is added.

include/znc/ZNCString.h

@@ -27,6 +27,7 @@ using std::pair;
 #define _SQL(s) CString("'" + CString(s).Escape_n(CString::ESQL) + "'")
 #define _URL(s) CString(s).Escape_n(CString::EURL)
 #define _HTML(s) CString(s).Escape_n(CString::EHTML)
+#define _NAMEDFMT(s) CString(s).Escape_n(CString::ENAMEDFMT)
 
 class CString;
 class MCString;
@@ -68,7 +69,8 @@ public:
 		EASCII,
 		EURL,
 		EHTML,
-		ESQL
+		ESQL,
+		ENAMEDFMT
 	} EEscape;
 
 	explicit CString(bool b) : string(b ? "true" : "false") {}
@@ -282,6 +284,16 @@ public:
 					   const CString& sLeft = "", const CString& sRight = "", bool bTrimQuotes = true,
 					   bool bTrimWhiteSpace = false) const;
 
+	/** Build a string from a format string, replacing values from a map.
+	 * The format specification can contain simple named parameters that match
+	 * keys in the given map. For example in the string "a {b} c", the key "b"
+	 * is looked up in the map, and inserted for "{b}".
+	 * @param sFormat The format specification.
+	 * @param msValues A map of named parameters to their values.
+	 * @return The string with named parameters replaced.
+	 */
+	static CString NamedFormat(const CString& sFormat, const MCString& msValues);
+
 	/** Produces a random string.
 	 * @param uLength The length of the resulting string.
 	 * @return A random string.

src/ZNCString.cpp

@@ -171,6 +171,8 @@ CString::EEscape CString::ToEscape(const CString& sEsc) {
 		return EURL;
 	} else if (sEsc.Equals("SQL")) {
 		return ESQL;
+	} else if (sEsc.Equals("NAMEDFMT")) {
+		return ENAMEDFMT;
 	}
 
 	return EASCII;
@@ -276,6 +278,16 @@ CString CString::Escape_n(EEscape eFrom, EEscape eTo) const {
 					}
 				}
 
+				break;
+			case ENAMEDFMT:
+				if (*p != '\\' || iLength < (a +1)) {
+					ch = *p;
+				} else {
+					a++;
+					p++;
+					ch = *p;
+				}
+
 				break;
 		}
 
@@ -316,6 +328,13 @@ CString CString::Escape_n(EEscape eFrom, EEscape eTo) const {
 				} else if (ch == '\\') { sRet += '\\'; sRet += '\\';
 				} else { sRet += ch; }
 
+				break;
+			case ENAMEDFMT:
+				if (ch == '\\') { sRet += '\\'; sRet += '\\';
+				} else if (ch == '{') { sRet += '\\'; sRet += '{';
+				} else if (ch == '}') { sRet += '\\'; sRet += '}';
+				} else { sRet += ch; }
+
 				break;
 		}
 	}
@@ -639,6 +658,51 @@ unsigned int CString::Split(const CString& sDelim, SCString& ssRet, bool bAllowE
 	return ssRet.size();
 }
 
+CString CString::NamedFormat(const CString& sFormat, const MCString& msValues) {
+	CString sRet;
+
+	CString sKey;
+	bool bEscape = false;
+	bool bParam = false;
+	const char* p = sFormat.c_str();
+
+	while (*p) {
+		if (!bParam) {
+			if (bEscape) {
+				sRet += *p;
+				bEscape = false;
+			} else if (*p == '\\') {
+				bEscape = true;
+			} else if (*p == '{') {
+				bParam = true;
+				sKey.clear();
+			} else {
+				sRet += *p;
+			}
+
+		} else {
+			if (bEscape) {
+				sKey += *p;
+				bEscape = false;
+			} else if (*p == '\\') {
+				bEscape = true;
+			} else if (*p == '}') {
+				bParam = false;
+				MCString::const_iterator it = msValues.find(sKey);
+				if (it != msValues.end()) {
+					sRet += (*it).second;
+				}
+			} else {
+				sKey += *p;
+			}
+		}
+
+		p++;
+	}
+
+	return sRet;
+}
+
 CString CString::RandomString(unsigned int uLength) {
 	const char chars[] = "abcdefghijklmnopqrstuvwxyz"
 		"ABCDEFGHIJKLMNOPQRSTUVWXYZ"