xz: Check for filter chain compatibility for --flush-timeout.

This avoids LZMA_PROG_ERROR from lzma_code() with filter chains
that don't support LZMA_SYNC_FLUSH.

1 files changed, 21 insertions, 9 deletions

diff --git a/src/xz/coder.c b/src/xz/coder.c
index 9accecad..947b4721 100644
--- a/src/xz/coder.c
+++ b/src/xz/coder.c
@@ -195,15 +195,27 @@ coder_set_compression_settings(void)
 	// Print the selected filter chain.
 	message_filters_show(V_DEBUG, filters);
 
-	// Disable encoder threads when --flush-timeout is used because
-	// the threaded encoder doesn't support LZMA_SYNC_FLUSH.
-	// FIXME: When LZMA_SYNC_FLUSH is supported, this should be changed.
-	if (opt_mode == MODE_COMPRESS && opt_flush_timeout != 0
-			&& hardware_threads_get() > 1) {
-		message(V_WARNING, _("Switching to single-threaded mode "
-				"due to --flush-timeout=%" PRIu64),
-				opt_flush_timeout);
-		hardware_threads_set(1);
+	// The --flush-timeout option requires LZMA_SYNC_FLUSH support
+	// from the filter chain. Currently threaded encoder doesn't support
+	// LZMA_SYNC_FLUSH so single-threaded mode must be used.
+	if (opt_mode == MODE_COMPRESS && opt_flush_timeout != 0) {
+		for (size_t i = 0; i < filters_count; ++i) {
+			switch (filters[i].id) {
+			case LZMA_FILTER_LZMA2:
+			case LZMA_FILTER_DELTA:
+				break;
+
+			default:
+				message_fatal(_("The filter chain is "
+					"incompatible with --flush-timeout"));
+			}
+		}
+
+		if (hardware_threads_get() > 1) {
+			message(V_WARNING, _("Switching to single-threaded "
+					"mode due to --flush-timeout"));
+			hardware_threads_set(1);
+		}
 	}
 
 	// Get the memory usage. Note that if --format=raw was used,