song: use flex arrays to store song->url

Reduce the number of allocations we make, so there's less
pressure on the allocator and less overhead to keep track
of the allocations in.

src/directory.c

@@ -298,7 +298,7 @@ removeDeletedFromDirectory(char *path_max_tmp, Directory * directory)
 
 	for (i = sv->nr; --i >= 0; ) { /* cleaner deletes if we go backwards */
 		Song *song = sv->base[i];
-		if (!song || !song->url)
+		if (!song || !*song->url)
 			continue; /* does this happen?, perhaps assert() */
 
 		if (dirname)

src/song.c

@@ -28,6 +28,19 @@
 
 #include "os_compat.h"
 
+Song *
+song_alloc(const char *url, enum song_type type, struct _Directory *parent)
+{
+	size_t urllen = strlen(url);
+	Song *song = xmalloc(sizeof(Song) + urllen);
+
+	song->tag = NULL;
+	memcpy(song->url, url, urllen + 1);
+	song->type = type;
+	song->parentDir = parent;
+
+	return song;
+}
 
 Song *newSong(const char *url, enum song_type type, Directory * parentDir)
 {
@@ -38,11 +51,7 @@ Song *newSong(const char *url, enum song_type type, Directory * parentDir)
 		return NULL;
 	}
 
-	song = xmalloc(sizeof(*song));
-	song->tag = NULL;
-	song->url = xstrdup(url);
-	song->type = type;
-	song->parentDir = parentDir;
+	song = song_alloc(url, type, parentDir);
 
 	assert(type == SONG_TYPE_URL || parentDir);
 
@@ -75,7 +84,6 @@ void freeSong(Song * song)
 
 void freeJustSong(Song * song)
 {
-	free(song->url);
 	if (song->tag)
 		tag_free(song->tag);
 	free(song);
@@ -114,7 +122,7 @@ char *get_song_url(char *path_max_tmp, Song *song)
 	if (!song)
 		return NULL;
 
-	assert(song->url != NULL);
+	assert(*song->url);
 
 	if (!song->parentDir || !song->parentDir->path)
 		strcpy(path_max_tmp, song->url);

src/song.h

@@ -20,6 +20,7 @@
 #define SONG_H
 
 #include "os_compat.h"
+#include "gcc.h"
 
 #define SONG_BEGIN	"songList begin"
 #define SONG_END	"songList end"
@@ -35,12 +36,15 @@ enum song_type {
 struct client;
 
 typedef struct _Song {
-	char *url;
 	enum song_type type;
 	struct tag *tag;
 	struct _Directory *parentDir;
 	time_t mtime;
-} Song;
+	char url[1];
+} mpd_packed Song;
+
+Song *
+song_alloc(const char *url, enum song_type type, struct _Directory *parent);
 
 Song *newSong(const char *url, enum song_type type,
 	      struct _Directory *parentDir);

src/song_save.c

@@ -111,18 +111,14 @@ void readSongInfoIntoList(FILE *fp, struct songvec *sv,
 			if (song)
 				insertSongIntoList(sv, song);
 
-			song = xmalloc(sizeof(*song));
-			song->url = xstrdup(buffer + strlen(SONG_KEY));
-			song->type = SONG_TYPE_FILE;
-			song->parentDir = parentDir;
+			song = song_alloc(buffer + strlen(SONG_KEY),
+					  SONG_TYPE_FILE, parentDir);
 		} else if (*buffer == 0) {
 			/* ignore empty lines (starting with '\0') */
 		} else if (song == NULL) {
 			FATAL("Problems reading song info\n");
 		} else if (0 == strncmp(SONG_FILE, buffer, strlen(SONG_FILE))) {
-			/* we don't need this info anymore
-			   song->url = xstrdup(&(buffer[strlen(SONG_FILE)]));
-			 */
+			/* we don't need this info anymore */
 		} else if (matchesAnMpdTagItemKey(buffer, &itemType)) {
 			if (!song->tag) {
 				song->tag = tag_new();