From 567c44e2ec5fba3e9219a89ba2dfbbc3dca801ad Mon Sep 17 00:00:00 2001
From: Kleis Auke Wolthuizen <github@kleisauke.nl>
Date: Fri, 18 Nov 2022 12:55:55 +0100
Subject: [PATCH] jxlload: simplify rewinding (#3170)

This partially reverts commit e88db2ce.
---
 libvips/foreign/jxlload.c | 54 +++++++++++++++++++--------------------
 1 file changed, 26 insertions(+), 28 deletions(-)

diff --git a/libvips/foreign/jxlload.c b/libvips/foreign/jxlload.c
index 343c2402..72b06537 100644
--- a/libvips/foreign/jxlload.c
+++ b/libvips/foreign/jxlload.c
@@ -158,6 +158,14 @@ vips_foreign_load_jxl_build( VipsObject *object )
 
 	jxl->runner = JxlThreadParallelRunnerCreate( NULL, 
 		vips_concurrency_get() );
+	jxl->decoder = JxlDecoderCreate( NULL );
+
+	if( JxlDecoderSetParallelRunner( jxl->decoder, 
+		JxlThreadParallelRunner, jxl->runner ) ) {
+		vips_foreign_load_jxl_error( jxl, 
+			"JxlDecoderSetParallelRunner" );
+		return( -1 );
+	}
 
 	if( VIPS_OBJECT_CLASS( vips_foreign_load_jxl_parent_class )->
 		build( object ) )
@@ -493,24 +501,19 @@ vips_foreign_load_jxl_header( VipsForeignLoad *load )
 	printf( "vips_foreign_load_jxl_header:\n" );
 #endif /*DEBUG*/
 
-        /* Build the decoder we will use for the header.
-         */
-	jxl->decoder = JxlDecoderCreate( NULL );
-	if( JxlDecoderSubscribeEvents( jxl->decoder, 
-		JXL_DEC_COLOR_ENCODING |
-		JXL_DEC_BASIC_INFO ) ) { 
-		vips_foreign_load_jxl_error( jxl, "JxlDecoderSubscribeEvents" );
+	if( vips_source_rewind( jxl->source ) )
 		return( -1 );
-	}
-	if( JxlDecoderSetParallelRunner( jxl->decoder, 
-		JxlThreadParallelRunner, jxl->runner ) ) {
-		vips_foreign_load_jxl_error( jxl, 
-			"JxlDecoderSetParallelRunner" );
+
+	JxlDecoderRewind( jxl->decoder );
+	if( JxlDecoderSubscribeEvents( jxl->decoder,
+		JXL_DEC_COLOR_ENCODING |
+		JXL_DEC_BASIC_INFO ) ) {
+		vips_foreign_load_jxl_error( jxl,
+			"JxlDecoderSubscribeEvents" );
 		return( -1 );
 	}
 
-	if( vips_source_rewind( jxl->source ) ||
-                vips_foreign_load_jxl_fill_input( jxl, 0 ) )
+	if( vips_foreign_load_jxl_fill_input( jxl, 0 ) )
 		return( -1 );
 	JxlDecoderSetInput( jxl->decoder, 
 		jxl->input_buffer, jxl->bytes_in_buffer );
@@ -620,26 +623,21 @@ vips_foreign_load_jxl_load( VipsForeignLoad *load )
 	if( vips_foreign_load_jxl_set_header( jxl, t[0] ) ) 
 		return( -1 );
 
-	/* We have to make a new decoder ... we can't be certain the header
-         * decoder left the input in the correct place.
-         */
-	VIPS_FREEF( JxlDecoderDestroy, jxl->decoder );
+	/* We have to rewind ... we can't be certain the header
+	 * decoder left the input in the correct place.
+	 */
+	if( vips_source_rewind( jxl->source ) )
+		return( -1 );
 
-	jxl->decoder = JxlDecoderCreate( NULL );
+	JxlDecoderRewind( jxl->decoder );
 	if( JxlDecoderSubscribeEvents( jxl->decoder, 
 		JXL_DEC_FULL_IMAGE ) ) {
-		vips_foreign_load_jxl_error( jxl, "JxlDecoderSubscribeEvents" );
-		return( -1 );
-	}
-	if( JxlDecoderSetParallelRunner( jxl->decoder, 
-		JxlThreadParallelRunner, jxl->runner ) ) {
-		vips_foreign_load_jxl_error( jxl, 
-			"JxlDecoderSetParallelRunner" );
+		vips_foreign_load_jxl_error( jxl,
+			"JxlDecoderSubscribeEvents" );
 		return( -1 );
 	}
 
-	if( vips_source_rewind( jxl->source ) ||
-                vips_foreign_load_jxl_fill_input( jxl, 0 ) )
+	if( vips_foreign_load_jxl_fill_input( jxl, 0 ) )
 		return( -1 );
 	JxlDecoderSetInput( jxl->decoder, 
 		jxl->input_buffer, jxl->bytes_in_buffer );