From 0e7f2124c73988a1cdb1e227d35c0e4e775b6517 Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Fri, 1 Jan 2021 11:12:15 +0000
Subject: [PATCH] improve file testing

and add some checks that the load subclasses have been defined
correctly
---
 libvips/foreign/foreign.c | 65 +++++++++++++++++++++++++++------------
 1 file changed, 45 insertions(+), 20 deletions(-)

diff --git a/libvips/foreign/foreign.c b/libvips/foreign/foreign.c
index fb4df9c8..8ce247af 100644
--- a/libvips/foreign/foreign.c
+++ b/libvips/foreign/foreign.c
@@ -381,10 +381,13 @@ vips_foreign_init( VipsForeign *object )
 static void *
 file_add_class( VipsForeignClass *class, GSList **files )
 {
-	/* Append so we don't reverse the list of files. Sort will not reorder
-	 * items of equal priority. 
+	/* We exclude "rawload" as it has a different API.
 	 */
-	*files = g_slist_append( *files, class );
+	if( !vips_isprefix( "rawload", VIPS_OBJECT_CLASS( class )->nickname ) ) 
+		/* Append so we don't reverse the list of files. Sort will 
+		 * not reorder items of equal priority. 
+		 */
+		*files = g_slist_append( *files, class );
 
 	return( NULL );
 }
@@ -437,6 +440,7 @@ vips_foreign_map( const char *base, VipsSListMap2Fn fn, void *a, void *b )
 }
 #endif /*DEBUG*/
 	result = vips_slist_map2( files, fn, a, b );
+
 	g_slist_free( files );
 
 	return( result );
@@ -496,14 +500,21 @@ vips_foreign_find_load_sub( VipsForeignLoadClass *load_class,
 	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( load_class );
 	VipsForeignClass *class = VIPS_FOREIGN_CLASS( load_class );
 
+	/* Ignore the buffer and source loaders.
+	 */
+	if( vips_ispostfix( object_class->nickname, "_buffer" ) ||
+		vips_ispostfix( object_class->nickname, "_source" ) ) 
+		return( NULL );
+
 #ifdef DEBUG
 	printf( "vips_foreign_find_load_sub: %s\n", 
 		VIPS_OBJECT_CLASS( class )->nickname );
 #endif /*DEBUG*/
 
-	if( load_class->is_a &&
-		!vips_ispostfix( object_class->nickname, "_buffer" ) &&
-		!vips_ispostfix( object_class->nickname, "_source" ) ) {
+	/* Try to sniff the filetype from the first few bytes, if we can,
+	 * otherwise fall back to checking the filename suffix.
+	 */
+	if( load_class->is_a ) {
 		if( load_class->is_a( filename ) ) 
 			return( load_class );
 
@@ -511,14 +522,13 @@ vips_foreign_find_load_sub( VipsForeignLoadClass *load_class,
 		printf( "vips_foreign_find_load_sub: is_a failed\n" ); 
 #endif /*DEBUG*/
 	}
-	else if( class->suffs && 
-		vips_filename_suffix_match( filename, class->suffs ) )
-		return( load_class );
-	else {
-#ifdef DEBUG
-		printf( "vips_foreign_find_load_sub: suffix match failed\n" ); 
-#endif /*DEBUG*/
+	else if( class->suffs ) {
+		if( vips_filename_suffix_match( filename, class->suffs ) )
+			return( load_class );
 	}
+	else 
+		g_warning( "loader %s has no is_a method and no suffix list", 
+			object_class->nickname );
 
 	return( NULL );
 }
@@ -606,10 +616,18 @@ vips_foreign_find_load_buffer_sub( VipsForeignLoadClass *load_class,
 {
 	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( load_class );
 
-	if( load_class->is_a_buffer &&
-		vips_ispostfix( object_class->nickname, "_buffer" ) &&
-		load_class->is_a_buffer( *buf, *len ) ) 
-		return( load_class );
+	/* Skip non-buffer loaders.
+	 */
+	if( !vips_ispostfix( object_class->nickname, "_buffer" ) )
+		return( NULL );
+
+	if( load_class->is_a_buffer ) {
+		if( load_class->is_a_buffer( *buf, *len ) ) 
+			return( load_class );
+	}
+	else
+		g_warning( "loader %s has no is_a_buffer method", 
+			object_class->nickname );
 
 	return( NULL );
 }
@@ -656,9 +674,13 @@ vips_foreign_find_load_source_sub( void *item, void *a, void *b )
 	VipsForeignLoadClass *load_class = VIPS_FOREIGN_LOAD_CLASS( item );
 	VipsSource *source = VIPS_SOURCE( a );
 
-	if( load_class->is_a_source &&
-		vips_ispostfix( object_class->nickname, "_source" ) ) {
-		/* We may have done a read() rather than a sniff() in one of
+	/* Skip non-source loaders.
+	 */
+	if( !vips_ispostfix( object_class->nickname, "_source" ) )
+		return( NULL );
+
+	if( load_class->is_a_source ) {
+		/* We may have done a _read() rather than a _sniff() in one of
 		 * the is_a testers. Always rewind.
 		 */
 		(void) vips_source_rewind( source );
@@ -666,6 +688,9 @@ vips_foreign_find_load_source_sub( void *item, void *a, void *b )
 		if( load_class->is_a_source( source ) ) 
 			return( load_class );
 	}
+	else 
+		g_warning( "loader %s has no is_a_source method", 
+			object_class->nickname );
 
 	return( NULL );
 }