SongFilter: new filter "modified-since"

NEWS

@@ -7,6 +7,7 @@ ver 0.19 (not yet released)
   - "idle" with unrecognized event name fails
   - "list" on album artist falls back to the artist tag
   - "list" and "count" allow grouping
+  - new "search"/"find" filter "modified-since"
 * database
   - proxy: forward "idle" events
   - proxy: forward the "update" command

doc/protocol.xml

@@ -1553,7 +1553,7 @@ OK
             <para>
               Finds songs in the db that are exactly
               <varname>WHAT</varname>.  <varname>TYPE</varname> can
-              be any tag supported by MPD, or one of the three special
+              be any tag supported by MPD, or one of the special
               parameters:
             </para>
 
@@ -1578,6 +1578,14 @@ OK
                   music directory)
                 </para>
               </listitem>
+
+              <listitem>
+                <para>
+                  <parameter>modified-since</parameter> compares the
+                  file's time stamp with the given value (ISO 8601 or
+                  UNIX time stamp)
+                </para>
+              </listitem>
             </itemizedlist>
 
             <para>

src/SongFilter.cxx

@@ -48,6 +48,9 @@ locate_parse_type(const char *str)
 	if (strcmp(str, "base") == 0)
 		return LOCATE_TAG_BASE_TYPE;
 
+	if (strcmp(str, "modified-since") == 0)
+		return LOCATE_TAG_MODIFIED_SINCE;
+
 	return tag_name_parse_i(str);
 }
 
@@ -66,6 +69,11 @@ SongFilter::Item::Item(unsigned _tag, const char *_value, bool _fold_case)
 {
 }
 
+SongFilter::Item::Item(unsigned _tag, time_t _time)
+	:tag(_tag), time(_time)
+{
+}
+
 bool
 SongFilter::Item::StringMatch(const char *s) const
 {
@@ -128,6 +136,9 @@ SongFilter::Item::Match(const DetachedSong &song) const
 	if (tag == LOCATE_TAG_BASE_TYPE)
 		return uri_is_child_or_same(value.c_str(), song.GetURI());
 
+	if (tag == LOCATE_TAG_MODIFIED_SINCE)
+		return song.GetLastModified() >= time;
+
 	if (tag == LOCATE_TAG_FILE_TYPE)
 		return StringMatch(song.GetURI());
 
@@ -142,6 +153,9 @@ SongFilter::Item::Match(const LightSong &song) const
 		return uri_is_child_or_same(value.c_str(), uri.c_str());
 	}
 
+	if (tag == LOCATE_TAG_MODIFIED_SINCE)
+		return song.mtime >= time;
+
 	if (tag == LOCATE_TAG_FILE_TYPE) {
 		const auto uri = song.GetURI();
 		return StringMatch(uri.c_str());
@@ -160,6 +174,58 @@ SongFilter::~SongFilter()
 	/* this destructor exists here just so it won't get inlined */
 }
 
+#if !defined(__GLIBC__) && !defined(WIN32)
+
+/**
+ * Determine the time zone offset in a portable way.
+ */
+gcc_const
+static time_t
+GetTimeZoneOffset()
+{
+	time_t t = 1234567890;
+	struct tm tm;
+	tm.tm_isdst = 0;
+	gmtime_r(&t, &tm);
+	return t - mktime(&tm);
+}
+
+#endif
+
+gcc_pure
+static time_t
+ParseTimeStamp(const char *s)
+{
+	assert(s != nullptr);
+
+	char *endptr;
+	unsigned long long value = strtoull(s, &endptr, 10);
+	if (*endptr == 0 && endptr > s)
+		/* it's an integral UNIX time stamp */
+		return (time_t)value;
+
+#ifdef WIN32
+	/* TODO: emulate strptime()? */
+	return 0;
+#else
+	/* try ISO 8601 */
+
+	struct tm tm;
+	const char *end = strptime(s, "%FT%TZ", &tm);
+	if (end == nullptr || *end != 0)
+		return 0;
+
+#ifdef __GLIBC__
+	/* timegm() is a GNU extension */
+	return timegm(&tm);
+#else
+	tm.tm_isdst = 0;
+	return mktime(&tm) + GetTimeZoneOffset();
+#endif /* !__GLIBC__ */
+
+#endif /* !WIN32 */
+}
+
 bool
 SongFilter::Parse(const char *tag_string, const char *value, bool fold_case)
 {
@@ -175,6 +241,15 @@ SongFilter::Parse(const char *tag_string, const char *value, bool fold_case)
 		fold_case = false;
 	}
 
+	if (tag == LOCATE_TAG_MODIFIED_SINCE) {
+		time_t t = ParseTimeStamp(value);
+		if (t == 0)
+			return false;
+
+		items.push_back(Item(tag, t));
+		return true;
+	}
+
 	items.push_back(Item(tag, value, fold_case));
 	return true;
 }

src/SongFilter.hxx

@@ -26,11 +26,13 @@
 #include <string>
 
 #include <stdint.h>
+#include <time.h>
 
 /**
  * Limit the search to files within the given directory.
  */
 #define LOCATE_TAG_BASE_TYPE (TAG_NUM_OF_ITEM_TYPES + 1)
+#define LOCATE_TAG_MODIFIED_SINCE (TAG_NUM_OF_ITEM_TYPES + 2)
 
 #define LOCATE_TAG_FILE_TYPE	TAG_NUM_OF_ITEM_TYPES+10
 #define LOCATE_TAG_ANY_TYPE     TAG_NUM_OF_ITEM_TYPES+20
@@ -51,9 +53,15 @@ public:
 
 		std::string value;
 
+		/**
+		 * For #LOCATE_TAG_MODIFIED_SINCE
+		 */
+		time_t time;
+
 	public:
 		gcc_nonnull(3)
 		Item(unsigned tag, const char *value, bool fold_case=false);
+		Item(unsigned tag, time_t time);
 
 		Item(const Item &other) = delete;
 		Item(Item &&) = default;