add nocache flag, use for sequential file ops

stop it caching sequential file read (eg. sequential tiff read), since
you can only read sequentially once

ChangeLog

@@ -4,6 +4,7 @@
 - much faster vips_argument_map()
 - make jpeg pyramids work with tiff4
 - tiff loader always offers THINSTRIP (thanks Diuming)
+- add "nocache" operation flag, set for sequential load (thanks Diuming)
 
 19/4/12 started 7.28.5
 - ifthenelse blend mode was broken

libvips/foreign/foreign.c

@@ -698,6 +698,10 @@ vips_foreign_load_temp( VipsForeignLoad *load )
 		printf( "vips_foreign_load_temp: partial sequential temp\n" );
 #endif /*DEBUG*/
 
+		/* You can't reuse sequential operations.
+		 */
+		vips_operation_set_nocache( VIPS_OPERATION( load ), TRUE );
+
 		return( vips_image_new() );
 	}
 

libvips/include/vips/operation.h

@@ -66,6 +66,12 @@ typedef struct _VipsOperation {
 	guint hash;
 	gboolean found_hash;
 
+	/* Set this before the end of _build() to stop this operation from 
+	 * being cached. Some things, like sequential read from a TIFF file, 
+	 * can't be reused.
+	 */
+	gboolean nocache;
+
 } VipsOperation;
 
 typedef struct _VipsOperationClass {
@@ -89,6 +95,7 @@ void vips_call_options( GOptionGroup *group, VipsOperation *operation );
 int vips_call_argv( VipsOperation *operation, int argc, char **argv );
 
 void vips_cache_drop_all( void );
+void vips_operation_set_nocache( VipsOperation *operation, gboolean nocache );
 int vips_cache_operation_buildp( VipsOperation **operation );
 VipsOperation *vips_cache_operation_build( VipsOperation *operation );
 void vips_cache_set_max( int max );

libvips/iofuncs/cache.c

@@ -621,7 +621,7 @@ vips_cache_operation_buildp( VipsOperation **operation )
 
 #ifdef VIPS_DEBUG
 	printf( "vips_cache_operation_build: " );
-	vips_object_print_summary_stdout( VIPS_OBJECT( *operation ) );
+	vips_object_print_dump( VIPS_OBJECT( *operation ) );
 #endif /*VIPS_DEBUG*/
 
 	vips_cache_init();
@@ -643,15 +643,22 @@ vips_cache_operation_buildp( VipsOperation **operation )
 	}
 	else {
 		if( vips__cache_trace ) {
-			printf( "vips cache: miss %p\n  ", *operation );
+			if( (*operation)->nocache ) 
+				printf( "vips cache: uncacheable %p\n  ", 
+					*operation );
+			else
+				printf( "vips cache: miss %p\n  ", *operation );
 			vips_object_print_summary( VIPS_OBJECT( *operation ) );
 		}
 
 		if( vips_object_build( VIPS_OBJECT( *operation ) ) )
 			return( -1 );
 
-		vips_cache_ref( *operation );
-		g_hash_table_insert( vips_cache_table, *operation, *operation );
+		if( !(*operation)->nocache ) {
+			vips_cache_ref( *operation );
+			g_hash_table_insert( vips_cache_table, 
+				*operation, *operation );
+		}
 	}
 
 	return( 0 );

libvips/iofuncs/operation.c

@@ -946,3 +946,23 @@ vips_call_argv( VipsOperation *operation, int argc, char **argv )
 	return( 0 );
 }
 
+/**
+ * vips_operation_set_nocache: 
+ * @operation: operation to set
+ * @nocache: TRUE means don't cache this operation
+ *
+ * Set this before the end of _build() to stop this operation being cached.
+ * Some operations, like sequential read from a TIFF file, for example, cannot
+ * be reused.
+ */
+void 
+vips_operation_set_nocache( VipsOperation *operation, gboolean nocache )
+{
+#ifdef VIPS_DEBUG
+	printf( "vips_operation_set_nocache: " );
+	vips_object_print_name( VIPS_OBJECT( operation ) );
+	printf( " %d\n", nocache );
+#endif /*VIPS_DEBUG*/
+
+	operation->nocache = nocache;
+}