lib-mail: Add message_detail_address_parse

Parses e.g. username+foo@domain into
username@domain with detail foo, when
delimiter is set to +

src/lib-mail/message-address.c

@@ -527,3 +527,33 @@ bool message_header_is_address(const char *hdr_name)
 	}
 	return FALSE;
 }
+
+void message_detail_address_parse(const char *delimiters, const char *address,
+				  const char **username_r, char *delim_r,
+				  const char **detail_r)
+{
+	const char *p, *domain;
+	size_t idx;
+
+	*username_r = address;
+	*detail_r = "";
+	*delim_r = '\0';
+
+	domain = strchr(address, '@');
+	/* first character that matches the recipient_delimiter */
+	idx = strcspn(address, delimiters);
+	p = address[idx] != '\0' ? address + idx : NULL;
+
+	if (p != NULL && (domain == NULL || p < domain)) {
+		*delim_r = *p;
+		/* user+detail@domain */
+		*username_r = t_strdup_until(*username_r, p);
+		if (domain == NULL)
+			*detail_r = p+1;
+		else {
+			*detail_r = t_strdup_until(p+1, domain);
+			*username_r = t_strconcat(*username_r, domain, NULL);
+		}
+	}
+}
+

src/lib-mail/message-address.h

@@ -33,4 +33,10 @@ void message_address_write(string_t *str, const struct message_address *addr);
 /* Returns TRUE if header is known to be an address */
 bool message_header_is_address(const char *hdr_name);
 
+/* Parse address+detail@domain into address@domain and detail
+   using given delimiters. Returns used delimiter. */
+void message_detail_address_parse(const char *delimiters, const char *address,
+				  const char **username_r, char *delim_r,
+				  const char **detail_r);
+
 #endif