Replace multiple stream callbacks with SerdEvent

This makes plumbing easier since everything goes through the same "stream" and
only one callback is required to handling everything.  It's also more easily
extensible in case more event types need to be added in the future.

1 files changed, 99 insertions, 0 deletions

diff --git a/include/serd/event.h b/include/serd/event.h
new file mode 100644
index 00000000..0c6437f6
--- /dev/null
+++ b/include/serd/event.h
@@ -0,0 +1,99 @@
+// Copyright 2011-2022 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#ifndef SERD_EVENT_H
+#define SERD_EVENT_H
+
+#include "serd/attributes.h"
+#include "serd/node.h"
+#include "serd/statement.h"
+#include "serd/status.h"
+
+SERD_BEGIN_DECLS
+
+/**
+   @defgroup serd_event Events
+   @ingroup serd_streaming
+   @{
+*/
+
+/// Type of a SerdEvent
+typedef enum {
+  SERD_BASE      = 1, ///< Base URI changed
+  SERD_PREFIX    = 2, ///< New URI prefix
+  SERD_STATEMENT = 3, ///< Statement
+  SERD_END       = 4, ///< End of anonymous node
+} SerdEventType;
+
+/**
+   Event for base URI changes.
+
+   Emitted whenever the base URI changes.
+*/
+typedef struct {
+  SerdEventType                type; ///< #SERD_BASE
+  const SerdNode* SERD_NONNULL uri;  ///< Base URI
+} SerdBaseEvent;
+
+/**
+   Event for namespace definitions.
+
+   Emitted whenever a prefix is defined.
+*/
+typedef struct {
+  SerdEventType                type; ///< #SERD_PREFIX
+  const SerdNode* SERD_NONNULL name; ///< Prefix name
+  const SerdNode* SERD_NONNULL uri;  ///< Namespace URI
+} SerdPrefixEvent;
+
+/**
+   Event for statements.
+
+   Emitted for every statement.
+*/
+typedef struct {
+  SerdEventType                     type;      ///< #SERD_STATEMENT
+  SerdStatementFlags                flags;     ///< Flags for pretty-printing
+  const SerdStatement* SERD_NONNULL statement; ///< Statement
+} SerdStatementEvent;
+
+/**
+   Event for the end of anonymous node descriptions.
+
+   This is emitted to indicate that the given anonymous node will no longer be
+   described.  This is used by the writer which may, for example, need to
+   write a delimiter.
+*/
+typedef struct {
+  SerdEventType                type; ///< #SERD_END
+  const SerdNode* SERD_NONNULL node; ///< Anonymous node that is finished
+} SerdEndEvent;
+
+/**
+   An event in a data stream.
+
+   Streams of data are represented as a series of events.  Events represent
+   everything that can occur in an RDF document, and are used to plumb together
+   different components.  For example, when parsing a document, a reader emits
+   a stream of events which can be sent to a writer to rewrite a document, or
+   to an inserter to build a model in memory.
+*/
+typedef union {
+  SerdEventType      type;      ///< Event type (always set)
+  SerdBaseEvent      base;      ///< Base URI changed
+  SerdPrefixEvent    prefix;    ///< New namespace prefix
+  SerdStatementEvent statement; ///< Statement
+  SerdEndEvent       end;       ///< End of anonymous node
+} SerdEvent;
+
+/// Function for handling events
+typedef SerdStatus (*SerdEventFunc)(void* SERD_NULLABLE           handle,
+                                    const SerdEvent* SERD_NONNULL event);
+
+/**
+   @}
+*/
+
+SERD_END_DECLS
+
+#endif // SERD_EVENT_H