Move to exception handling rather than error passing throughout.

This frees us from passing errors back everywhere, and hence enables us
to pass results back as return values.

Rather than having to explicitly check for errors everywhere and bubble
them, we now allow exception handling to do the work for us; the
downside to this is that we no longer emit as much debugging information
as we did before (though this could be put back in). For now, the
debugging information we have lost has been retained in comments
with 'RJW:' at the start.

This code needs fuller testing, but is being committed as a work in
progress.

1 files changed, 46 insertions, 34 deletions

diff --git a/xps/xps_zip.c b/xps/xps_zip.c
index 954a8a00..f02bf33e 100644
--- a/xps/xps_zip.c
+++ b/xps/xps_zip.c
@@ -389,66 +389,72 @@ xps_read_part(xps_document *doc, char *partname)
 	return xps_read_zip_part(doc, partname);
 }
 
-static int
-xps_open_directory(fz_context *fctx, xps_document **ctxp, char *directory)
+static xps_document *
+xps_open_directory(fz_context *ctx, char *directory)
 {
 	xps_document *doc;
-	int code;
 
-	doc = fz_malloc(fctx, sizeof(xps_document));
+	doc = fz_malloc(ctx, sizeof(xps_document));
 	memset(doc, 0, sizeof *doc);
 
-	doc->directory = fz_strdup(fctx, directory);
-	doc->ctx = fctx;
+	doc->directory = fz_strdup(ctx, directory);
+	doc->ctx = ctx;
 
-	code = xps_read_page_list(doc);
-	if (code)
+	fz_try(ctx)
+	{
+		xps_read_page_list(doc);
+	}
+	fz_catch(ctx)
 	{
 		xps_free_context(doc);
-		return fz_error_note(code, "cannot read page list");
+		fz_throw(ctx, "cannot read page list");
 	}
 
-	*ctxp = doc;
-	return fz_okay;
+	return doc;
 }
 
-int
-xps_open_stream(xps_document **ctxp, fz_stream *file)
+xps_document *
+xps_open_stream(fz_stream *file)
 {
 	xps_document *doc;
-	int code;
+	fz_context *ctx = file->ctx;
 
-	doc = fz_malloc(file->ctx, sizeof(xps_document));
+	doc = fz_malloc(ctx, sizeof(xps_document));
 	memset(doc, 0, sizeof *doc);
 
-	doc->ctx = file->ctx;
+	doc->ctx = ctx;
 	doc->file = fz_keep_stream(file);
 
-	code = xps_find_and_read_zip_dir(doc);
-	if (code < 0)
+	fz_try(ctx)
+	{
+		xps_find_and_read_zip_dir(doc);
+	}
+	fz_catch(ctx)
 	{
 		xps_free_context(doc);
-		return fz_error_note(code, "cannot read zip central directory");
+		fz_throw(ctx, "cannot read zip central directory");
 	}
 
-	code = xps_read_page_list(doc);
-	if (code)
+	fz_try(ctx)
+	{
+		xps_read_page_list(doc);
+	}
+	fz_catch(ctx)
 	{
 		xps_free_context(doc);
-		return fz_error_note(code, "cannot read page list");
+		fz_throw(ctx, "cannot read page list");
 	}
 
-	*ctxp = doc;
-	return fz_okay;
+	return doc;
 }
 
-int
-xps_open_file(fz_context *doc, xps_document **ctxp, char *filename)
+xps_document *
+xps_open_file(fz_context *ctx, char *filename)
 {
 	char buf[2048];
 	fz_stream *file;
 	char *p;
-	int code;
+	xps_document *doc;
 
 	if (strstr(filename, "/_rels/.rels") || strstr(filename, "\\_rels\\.rels"))
 	{
@@ -457,18 +463,24 @@ xps_open_file(fz_context *doc, xps_document **ctxp, char *filename)
 		if (!p)
 			p = strstr(buf, "\\_rels\\.rels");
 		*p = 0;
-		return xps_open_directory(doc, ctxp, buf);
+		return xps_open_directory(ctx, buf);
 	}
 
-	file = fz_open_file(doc, filename);
+	file = fz_open_file(ctx, filename);
 	if (!file)
-		return fz_error_make("cannot open file '%s': %s", filename, strerror(errno));
+		fz_throw(ctx, "cannot open file '%s': %s", filename, strerror(errno));
 
-	code = xps_open_stream(ctxp, file);
+	fz_try(ctx)
+	{
+		doc = xps_open_stream(file);
+	}
+	fz_catch(ctx)
+	{
+		fz_close(file);
+		fz_throw(ctx, "cannot load document '%s'", filename);
+	}
 	fz_close(file);
-	if (code)
-		return fz_error_note(code, "cannot load document '%s'", filename);
-	return fz_okay;
+	return doc;
 }
 
 void