don't fetch message size unless necessary

when syncing flags but not re-newing non-fetched messages, there is no
need to query the message size for all messages, as the old ones are
queried only for their flags.

src/driver.h

@@ -74,7 +74,8 @@ typedef struct message {
 #define OPEN_OLD        (1<<0)
 #define OPEN_NEW        (1<<1)
 #define OPEN_FLAGS      (1<<2)
-#define OPEN_SIZE       (1<<3)
+#define OPEN_OLD_SIZE   (1<<3)
+#define OPEN_NEW_SIZE   (1<<4)
 #define OPEN_EXPUNGE    (1<<5)
 #define OPEN_SETFLAGS   (1<<6)
 #define OPEN_APPEND     (1<<7)
@@ -205,9 +206,11 @@ struct driver {
 	/* Load the message attributes needed to perform the requested operations.
 	 * Consider only messages with UIDs between minuid and maxuid (inclusive)
 	 * and those named in the excs array (smaller than minuid).
-	 * The driver takes ownership of the excs array. Messages below newuid do not need
-	 * to have the TUID populated even if OPEN_FIND is set. */
-	void (*load_box)( store_t *ctx, int minuid, int maxuid, int newuid, int_array_t excs,
+	 * The driver takes ownership of the excs array.
+	 * Messages starting with newuid need to have the TUID populated when OPEN_FIND is set.
+	 * Messages up to seenuid need to have the size populated when OPEN_OLD_SIZE is set;
+	 * likewise messages above seenuid when OPEN_NEW_SIZE is set. */
+	void (*load_box)( store_t *ctx, int minuid, int maxuid, int newuid, int seenuid, int_array_t excs,
 	                  void (*cb)( int sts, void *aux ), void *aux );
 
 	/* Fetch the contents and flags of the given message from the current mailbox. */

src/drv_imap.c

@@ -2352,7 +2352,7 @@ imap_set_range( imap_range_t *ranges, int *nranges, int low_flags, int high_flag
 static void imap_submit_load( imap_store_t *, const char *, int, struct imap_cmd_refcounted_state * );
 
 static void
-imap_load_box( store_t *gctx, int minuid, int maxuid, int newuid, int_array_t excs,
+imap_load_box( store_t *gctx, int minuid, int maxuid, int newuid, int seenuid, int_array_t excs,
                void (*cb)( int sts, void *aux ), void *aux )
 {
 	imap_store_t *ctx = (imap_store_t *)gctx;
@@ -2380,11 +2380,14 @@ imap_load_box( store_t *gctx, int minuid, int maxuid, int newuid, int_array_t ex
 		if (maxuid == INT_MAX)
 			maxuid = ctx->gen.uidnext ? ctx->gen.uidnext - 1 : 0x7fffffff;
 		if (maxuid >= minuid) {
-			imap_range_t ranges[2];
+			imap_range_t ranges[3];
 			ranges[0].first = minuid;
 			ranges[0].last = maxuid;
-			ranges[0].flags = shifted_bit( ctx->gen.opts, OPEN_SIZE, WantSize);
+			ranges[0].flags = 0;
 			int nranges = 1;
+			if (ctx->gen.opts & (OPEN_OLD_SIZE | OPEN_NEW_SIZE))
+				imap_set_range( ranges, &nranges, shifted_bit( ctx->gen.opts, OPEN_OLD_SIZE, WantSize),
+				                                  shifted_bit( ctx->gen.opts, OPEN_NEW_SIZE, WantSize), seenuid );
 			if (ctx->gen.opts & OPEN_FIND)
 				imap_set_range( ranges, &nranges, 0, WantTuids, newuid - 1 );
 			for (int r = 0; r < nranges; r++) {

src/drv_maildir.c

@@ -70,7 +70,7 @@ typedef struct maildir_message {
 typedef struct maildir_store {
 	store_t gen;
 	int uvfd, uvok, nuid, is_inbox, fresh[3];
-	int minuid, maxuid, newuid;
+	int minuid, maxuid, newuid, seenuid;
 	int_array_t excs;
 	char *trash;
 #ifdef USE_DB
@@ -1048,7 +1048,7 @@ maildir_scan( maildir_store_t *ctx, msg_t_array_alloc_t *msglist )
 				free( entry->base );
 				entry->base = nfstrndup( buf + bl + 4, fnl );
 			}
-			int want_size = (ctx->gen.opts & OPEN_SIZE);
+			int want_size = (uid > ctx->seenuid) ? (ctx->gen.opts & OPEN_NEW_SIZE) : (ctx->gen.opts & OPEN_OLD_SIZE);
 			int want_tuid = ((ctx->gen.opts & OPEN_FIND) && uid >= ctx->newuid);
 			if (!want_size && !want_tuid)
 				continue;
@@ -1280,7 +1280,7 @@ maildir_prepare_load_box( store_t *gctx, int opts )
 }
 
 static void
-maildir_load_box( store_t *gctx, int minuid, int maxuid, int newuid, int_array_t excs,
+maildir_load_box( store_t *gctx, int minuid, int maxuid, int newuid, int seenuid, int_array_t excs,
                   void (*cb)( int sts, void *aux ), void *aux )
 {
 	maildir_store_t *ctx = (maildir_store_t *)gctx;
@@ -1291,6 +1291,7 @@ maildir_load_box( store_t *gctx, int minuid, int maxuid, int newuid, int_array_t
 	ctx->minuid = minuid;
 	ctx->maxuid = maxuid;
 	ctx->newuid = newuid;
+	ctx->seenuid = seenuid;
 	ARRAY_SQUEEZE( &excs );
 	ctx->excs = excs;
 

src/sync.c

@@ -1208,8 +1208,12 @@ box_opened2( sync_vars_t *svars, int t )
 				opts[1-t] |= OPEN_NEW;
 			if (chan->ops[t] & OP_EXPUNGE)
 				opts[1-t] |= OPEN_FLAGS;
-			if (chan->stores[t]->max_size != INT_MAX)
-				opts[1-t] |= OPEN_SIZE;
+			if (chan->stores[t]->max_size != INT_MAX) {
+				if (chan->ops[t] & OP_RENEW)
+					opts[1-t] |= OPEN_OLD_SIZE;
+				if (chan->ops[t] & OP_NEW)
+					opts[1-t] |= OPEN_NEW_SIZE;
+			}
 		}
 		if (chan->ops[t] & OP_EXPUNGE) {
 			opts[t] |= OPEN_EXPUNGE;
@@ -1298,28 +1302,46 @@ box_opened2( sync_vars_t *svars, int t )
 	sync_deref( svars );
 }
 
+static int
+get_seenuid( sync_vars_t *svars, int t )
+{
+	int seenuid = 0;
+	for (sync_rec_t *srec = svars->srecs; srec; srec = srec->next)
+		if (!(srec->status & S_DEAD) && seenuid < srec->uid[t])
+			seenuid = srec->uid[t];
+	return seenuid;
+}
+
 static void box_loaded( int sts, void *aux );
 
 static void
 load_box( sync_vars_t *svars, int t, int minwuid, int_array_t mexcs )
 {
-	sync_rec_t *srec;
-	int maxwuid;
+	int maxwuid, seenuid;
 
 	if (svars->ctx[t]->opts & OPEN_NEW) {
 		if (minwuid > svars->maxuid[t] + 1)
 			minwuid = svars->maxuid[t] + 1;
 		maxwuid = INT_MAX;
+		if (svars->ctx[t]->opts & OPEN_OLD_SIZE)
+			seenuid = get_seenuid( svars, t );
+		else
+			seenuid = 0;
 	} else if (svars->ctx[t]->opts & OPEN_OLD) {
-		maxwuid = 0;
-		for (srec = svars->srecs; srec; srec = srec->next)
-			if (!(srec->status & S_DEAD) && srec->uid[t] > maxwuid)
-				maxwuid = srec->uid[t];
+		maxwuid = seenuid = get_seenuid( svars, t );
 	} else
-		maxwuid = 0;
+		maxwuid = seenuid = 0;
+	if (seenuid < svars->maxuid[t]) {
+		/* We cannot rely on the maxuid, as uni-directional syncing does not update it.
+		 * But if it is there, use it to avoid a possible gap in the fetched range. */
+		seenuid = svars->maxuid[t];
+	}
 	info( "Loading %s...\n", str_ms[t] );
-	debug( maxwuid == INT_MAX ? "loading %s [%d,inf]\n" : "loading %s [%d,%d]\n", str_ms[t], minwuid, maxwuid );
-	svars->drv[t]->load_box( svars->ctx[t], minwuid, maxwuid, svars->newuid[t], mexcs, box_loaded, AUX );
+	if (maxwuid == INT_MAX)
+		debug( "loading %s [%d,inf] (new >= %d, seen <= %d)\n", str_ms[t], minwuid, svars->newuid[t], seenuid );
+	else
+		debug( "loading %s [%d,%d] (new >= %d, seen <= %d)\n", str_ms[t], minwuid, maxwuid, svars->newuid[t], seenuid );
+	svars->drv[t]->load_box( svars->ctx[t], minwuid, maxwuid, svars->newuid[t], seenuid, mexcs, box_loaded, AUX );
 }
 
 typedef struct {
@@ -1384,7 +1406,7 @@ box_loaded( int sts, void *aux )
 		uid = tmsg->uid;
 		if (DFlags & DEBUG_SYNC) {
 			make_flags( tmsg->flags, fbuf );
-			printf( svars->ctx[t]->opts & OPEN_SIZE ? "  message %5d, %-4s, %6lu: " : "  message %5d, %-4s: ", uid, fbuf, tmsg->size );
+			printf( tmsg->size ? "  message %5d, %-4s, %6lu: " : "  message %5d, %-4s: ", uid, fbuf, tmsg->size );
 		}
 		idx = (uint)((uint)uid * 1103515245U) % hashsz;
 		while (srecmap[idx].uid) {