use expat for xml read

we were using libxml for xml load, use expat instead, we get it for free
with glib

ChangeLog

@@ -34,6 +34,8 @@
 - vips_region_shrink() knows about alpha, helps dzsave and tiffsave
 - vips_sequential() no longer stalls ahead threads, instead we constrain sinks
   more tightly ... this makes seq more versatile and more reliable
+- use expat, not libxml, for XML load ... removes a required dependency, since
+  we get expat as part of glib
 
 8/12/16 started 8.4.5
 - allow libgsf-1.14.26 to help centos, thanks tdiprima

libvips/include/vips/header.h

@@ -77,14 +77,6 @@ extern "C" {
  */
 #define VIPS_META_ICC_NAME "icc-profile-data"
 
-/**
- * VIPS_META_XML:
- *
- * The original XML that was used to code the metadata after reading a VIPS
- * format file.
- */
-#define VIPS_META_XML "xml-header"
-
 /**
  * VIPS_META_IMAGEDESCRIPTION:
  *

libvips/iofuncs/vips.c

@@ -17,6 +17,8 @@
  * 	  image.c ... this file now just does read / write to disc
  * 28/3/11
  * 	- moved to vips_ namespace
+ * 25/2/17
+ * 	- use expat for xml read
  */
 
 /*
@@ -435,9 +437,9 @@ vips__read_extension_block( VipsImage *im, int *size )
 
 	psize = image_pixel_length( im );
 	g_assert( im->file_length > 0 );
-	if( im->file_length - psize > 10 * 1024 * 1024 ) {
+	if( im->file_length - psize > 100 * 1024 * 1024 ) {
 		vips_error( "VipsImage",
-			"%s", _( "more than a 10 megabytes of XML? "
+			"%s", _( "more than 100 megabytes of XML? "
 			"sufferin' succotash!" ) );
 		return( NULL );
 	}
@@ -457,74 +459,108 @@ vips__read_extension_block( VipsImage *im, int *size )
 	return( buf );
 }
 
-/* Read everything after the pixels into memory.
+static int
-
+parser_read_fd( XML_Parser parser, int fd )
-	FIXME ... why can't we use xmlParserInputBufferCreateFd and parse
-	directly from the fd rather than having to read the stupid thing into 
-	memory
-
-	the libxml API docs are impossible to decipher
-
- */
-static xmlDoc *
-read_xml( VipsImage *im )
 {
-	void *buf;
+	const int chunk_size = 1024; 
-	int size;
-	xmlDoc *doc;
-	xmlNode *node;
 
-	if( !(buf = vips__read_extension_block( im, &size )) )
+	ssize_t bytes_read;
-		return( NULL );
+
-	if( !(doc = xmlParseMemory( buf, size )) ) {
+	do {
-		vips_free( buf );
+		void *buf;
-		return( NULL );
+
-	}
+		if( !(buf = XML_GetBuffer( parser, chunk_size )) ) {
-	vips_free( buf );
+			vips_error( "VipsImage", 
-	if( !(node = xmlDocGetRootElement( doc )) ||
+				"%s", _( "unable to allocate read buffer" ) );
-		!node->nsDef ||
+			return( -1 );
-		!vips_isprefix( NAMESPACE, (char *) node->nsDef->href ) ) {
+		}
-		vips_error( "VipsImage", 
+		bytes_read = read( fd, buf, chunk_size );
-			"%s", _( "incorrect namespace in XML" ) );
+		if( bytes_read == (ssize_t) -1 ) {
-		xmlFreeDoc( doc );
+			vips_error( "VipsImage", 
-		return( NULL );
+				"%s", _( "read error while fetching XML" ) );
-	}
+			return( -1 );
+		}
+
+		if( !XML_ParseBuffer( parser, bytes_read, bytes_read == 0 ) ) {
+			vips_error( "VipsImage", 
+				"%s", _( "XML parse error" ) );
+			return( -1 );
+		}
+	} while( bytes_read > 0 );
+
+	return( 0 );
+}
+
+#define MAX_PARSE_ATTR (256)
+
+/* What we track during expat parse.
+ */
+typedef struct _VipsExpatParse {
+	VipsImage *image;
+
+	/* TRUE for in header section.
+	 */
+	gboolean header;
+
+	/* For the current node, the type and name.
+	 */
+	XML_Char type[MAX_PARSE_ATTR];
+	XML_Char name[MAX_PARSE_ATTR];
+
+	/* Accumulate data here.
+	 */
+	char *data;
+	size_t current_size;
+
+	gboolean error;
+} VipsExpatParse;
+
+static void
+parser_element_start_handler( void *user_data, 
+	const XML_Char *name, const XML_Char **atts )
+{
+	VipsExpatParse *vep = (VipsExpatParse *) user_data;
+	const XML_Char **p;
 
 #ifdef DEBUG
-	printf( "read_xml: namespace == %s\n", node->nsDef->href );
+	printf( "parser_element_start: %s\n", name );
+	for( p = atts; *p; p += 2 ) 
+		printf( "%s = %s\n", p[0], p[1] );
 #endif /*DEBUG*/
 
-	return( doc );
+	if( strcmp( name, "field" ) == 0 ) { 
+		for( p = atts; *p; p += 2 ) {
+			if( strcmp( p[0], "name" ) == 0 )
+				vips_strncpy( vep->name, p[1], MAX_PARSE_ATTR ); 
+			if( strcmp( p[0], "type" ) == 0 )
+				vips_strncpy( vep->type, p[1], MAX_PARSE_ATTR ); 
+		}
+
+		vep->current_size = 0;
+	} 
+	else if( strcmp( name, "header" ) == 0 )  
+		vep->header = TRUE;
+	else if( strcmp( name, "meta" ) == 0 )  
+		vep->header = FALSE;
+	else if( strcmp( name, "root" ) == 0 ) {
+		for( p = atts; *p; p += 2 ) 
+			if( strcmp( p[0], "xmlns" ) == 0 &&
+				!vips_isprefix( NAMESPACE, p[1] ) ) {
+				vips_error( "VipsImage", "%s", 
+					_( "incorrect namespace in XML" ) );
+				vep->error = TRUE;
+			}
+	}
 }
 
-/* Find the first child node with a name.
+static void
- */
+parser_append( VipsExpatParse *vep, const XML_Char *data, int len )
-static xmlNode *
-get_node( xmlNode *base, const char *name )
 {
-	xmlNode *i;
+	size_t new_size = vep->current_size + len;
 
-	for( i = base->children; i; i = i->next )
+	vep->data = g_realloc( vep->data, new_size );
-		if( strcmp( (char *) i->name, name ) == 0 )
+	memcpy( vep->data + vep->current_size, data, len );
-			return( i );
+	vep->current_size = new_size;
-
-	return( NULL );
-}
-
-/* Read a string property to a buffer. TRUE for success.
- */
-static int
-get_sprop( xmlNode *xnode, const char *name, char *buf, int sz )
-{
-        char *value = (char *) xmlGetProp( xnode, (xmlChar *) name );
-
-        if( !value )
-                return( 0 );
-
-        vips_strncpy( buf, value, sz );
-        VIPS_FREEF( xmlFree, value );
-
-        return( 1 );
 }
 
 /* Chop history into lines, add each one as a refstring.
@@ -556,119 +592,76 @@ set_history( VipsImage *im, char *history )
 	im->history_list = g_slist_reverse( history_list );
 }
 
-/* Load header fields.
- */
 static int
-rebuild_header_builtin( VipsImage *im, xmlNode *i )
+set_meta( VipsImage *image, GType gtype, const char *name, const char *data )
 {
-	char name[256];
+	GValue save_value = { 0 };
+	GValue value = { 0 };
 
-	if( get_sprop( i, "name", name, 256 ) ) {
+	g_value_init( &save_value, VIPS_TYPE_SAVE_STRING );
-		if( strcmp( name, "Hist" ) == 0 ) {
+	vips_value_set_save_string( &save_value, data );
-			char *history;
 
-			/* Have to take (another) copy, since we need to free
+	g_value_init( &value, gtype );
-			 * with xmlFree().
+	if( !g_value_transform( &save_value, &value ) ) {
+		g_value_unset( &save_value );
+		vips_error( "VipsImage", "%s", 
+			_( "error transforming from save format" ) );
+		return( -1 ); 
+	}
+
+	vips_image_set( image, name, &value );
+	g_value_unset( &save_value );
+	g_value_unset( &value );
+
+	return( 0 );
+}
+
+static void
+parser_element_end_handler( void *user_data, const XML_Char *name )
+{
+	VipsExpatParse *vep = (VipsExpatParse *) user_data;
+
+#ifdef DEBUG
+	printf( "parser_element_end_handler: %s\n", name ); 
+#endif /*DEBUG*/
+
+	if( strcmp( name, "field" ) == 0 ) {
+		parser_append( vep, "", 1 );
+
+#ifdef DEBUG
+		printf( "parser_element_end_handler: %zd bytes\n", 
+			vep->current_size ); 
+#endif /*DEBUG*/
+
+		if( vep->header ) {
+			if( strcmp( name, "Hist" ) == 0 ) 
+				set_history( vep->image, vep->data );
+		}
+		else {
+			GType gtype = g_type_from_name( vep->type );
+
+			/* Can we convert from VIPS_SAVE_STRING to type?
 			 */
-			history = (char *) xmlNodeGetContent( i );
+			if( gtype && 
-			set_history( im, history );
+				g_value_type_transformable( 
-			xmlFree( history );
+					VIPS_TYPE_SAVE_STRING, gtype ) &&
+				set_meta( vep->image, 
+					gtype, vep->name, vep->data ) ) 
+				vep->error = TRUE;
 		}
 	}
-
-	return( 0 );
 }
 
-/* Load meta fields.
+static void
- */
+parser_data_handler( void *user_data, const XML_Char *data, int len )
-static int
-rebuild_header_meta( VipsImage *im, xmlNode *i )
 {
-	char name[256];
+	VipsExpatParse *vep = (VipsExpatParse *) user_data;
-	char type[256];
 
-	if( get_sprop( i, "name", name, 256 ) &&
+#ifdef DEBUG
-		get_sprop( i, "type", type, 256 ) ) {
+	printf( "parser_data_handler: %d bytes\n", len ); 
-		GType gtype = g_type_from_name( type );
+#endif /*DEBUG*/
 
-		/* Can we convert from VIPS_SAVE_STRING to type?
+	parser_append( vep, data, len );
-		 */
-		if( gtype && 
-			g_value_type_transformable( 
-				VIPS_TYPE_SAVE_STRING, gtype ) ) {
-			char *content;
-			GValue save_value = { 0 };
-			GValue value = { 0 };
-
-			content = (char *) xmlNodeGetContent( i );
-			g_value_init( &save_value, VIPS_TYPE_SAVE_STRING );
-			vips_value_set_save_string( &save_value, content );
-			xmlFree( content );
-
-			g_value_init( &value, gtype );
-			if( !g_value_transform( &save_value, &value ) ) {
-				g_value_unset( &save_value );
-				vips_error( "VipsImage", 
-					"%s", _( "error transforming from "
-					"save format" ) );
-				return( -1 );
-			}
-			vips_image_set( im, name, &value );
-			g_value_unset( &save_value );
-			g_value_unset( &value );
-		}
-	}
-
-	return( 0 );
-}
-
-static xmlDoc *
-get_xml( VipsImage *im )
-{
-	if( vips_image_get_typeof( im, VIPS_META_XML ) ) {
-		xmlDoc *doc;
-
-		if( vips_image_get_area( im, VIPS_META_XML, (void *) &doc ) )
-			return( NULL );
-
-		return( doc );
-	}
-
-	return( NULL );
-}
-
-/* Rebuild header fields that depend on stuff saved in xml.
- */
-static int
-rebuild_header( VipsImage *im )
-{
-	xmlDoc *doc;
-
-	if( (doc = get_xml( im )) ) {
-		xmlNode *root;
-		xmlNode *block;
-
-		if( !(root = xmlDocGetRootElement( doc )) )
-			return( -1 );
-		if( (block = get_node( root, "header" )) ) {
-			xmlNode *i;
-
-			for( i = block->children; i; i = i->next )
-				if( strcmp( (char *) i->name, "field" ) == 0 ) 
-					if( rebuild_header_builtin( im, i ) )
-						return( -1 );
-		}
-		if( (block = get_node( root, "meta" )) ) {
-			xmlNode *i;
-
-			for( i = block->children; i; i = i->next )
-				if( strcmp( (char *) i->name, "field" ) == 0 ) 
-					if( rebuild_header_meta( im, i ) )
-						return( -1 );
-		}
-	}
-
-	return( 0 );
 }
 
 /* Called at the end of vips open ... get any XML after the pixel data
@@ -677,24 +670,35 @@ rebuild_header( VipsImage *im )
 static int 
 readhist( VipsImage *im )
 {
-	/* Junk any old xml meta.
+	XML_Parser parser;
-	 */
+	VipsExpatParse vep;
-	if( vips_image_get_typeof( im, VIPS_META_XML ) ) 
-		vips_image_set_area( im, VIPS_META_XML, NULL, NULL );
 
-	if( vips__has_extension_block( im ) ) {
+	if( vips__seek( im->fd, image_pixel_length( im ) ) ) 
-		xmlDoc *doc;
-
-		if( !(doc = read_xml( im )) )
-			return( -1 );
-		vips_image_set_area( im, VIPS_META_XML, 
-			(VipsCallbackFn) xmlFreeDoc, doc );
-	}
-
-	if( rebuild_header( im ) )
 		return( -1 );
 
-	return( 0 );
+	parser = XML_ParserCreate( "UTF-8" );
+
+	vep.image = im;
+	vep.data = NULL;
+	vep.current_size = 0;
+	vep.error = FALSE;
+	XML_SetUserData( parser, &vep );
+
+	XML_SetElementHandler( parser, 
+		parser_element_start_handler, parser_element_end_handler );
+	XML_SetCharacterDataHandler( parser, parser_data_handler ); 
+
+	if( parser_read_fd( parser, im->fd ) ||
+		vep.error ) { 
+		g_free( vep.data );
+		XML_ParserFree( parser );
+		return( -1 );
+	}
+
+	g_free( vep.data );
+	XML_ParserFree( parser );
+
+	return( 0 ); 
 }
 
 #define MAX_STRSIZE (32768)     /* Max size of text for stack strings */