Gawain: add method of stepping over data directly

This avoids using GWN_vertbuf_attr_set which needs to calculate the
offset and perform a memcpy every call.

Exposing the data directly allows us to avoid a memcpy in some cases
and means we can write to the vertex buffer's memory directly.

3 files changed, 52 insertions, 0 deletions

diff --git a/intern/gawain/gawain/common.h b/intern/gawain/gawain/common.h
index e21b241160d..e96a3b5c2a2 100644
--- a/intern/gawain/gawain/common.h
+++ b/intern/gawain/gawain/common.h
@@ -25,3 +25,10 @@
 #if TRUST_NO_ONE
   #include <assert.h>
 #endif
+
+/* GWN_INLINE */
+#if defined(_MSC_VER)
+#  define GWN_INLINE static __forceinline
+#else
+#  define GWN_INLINE static inline __attribute__((always_inline)) __attribute__((__unused__))
+#endif
\ No newline at end of file
diff --git a/intern/gawain/gawain/vertex_buffer.h b/intern/gawain/gawain/vertex_buffer.h
index 46f83f5c551..57179062df4 100644
--- a/intern/gawain/gawain/vertex_buffer.h
+++ b/intern/gawain/gawain/vertex_buffer.h
@@ -49,6 +49,31 @@ void GWN_vertbuf_attr_set(Gwn_VertBuf*, unsigned a_idx, unsigned v_idx, const vo
 void GWN_vertbuf_attr_fill(Gwn_VertBuf*, unsigned a_idx, const void* data); // tightly packed, non interleaved input data
 void GWN_vertbuf_attr_fill_stride(Gwn_VertBuf*, unsigned a_idx, unsigned stride, const void* data);
 
+// For low level access only
+typedef struct {
+	unsigned size;
+	unsigned stride;
+	GLubyte* data;
+	GLubyte* data_init;
+#if TRUST_NO_ONE
+	// Only for overflow check
+	GLubyte* _data_end;
+#endif
+} Gwn_VertBufRaw;
+
+GWN_INLINE void *GWN_vertbuf_raw_step(Gwn_VertBufRaw *a)
+	{
+	GLubyte* data = a->data;
+	a->data += a->stride;
+#if TRUST_NO_ONE
+	assert(data < a->_data_end);
+#endif
+	return (void *)data;
+	}
+
+void GWN_vertbuf_attr_get_raw_data(Gwn_VertBuf*, unsigned a_idx, Gwn_VertBufRaw *access);
+
+
 // TODO: decide whether to keep the functions below
 // doesn't immediate mode satisfy these needs?
 
diff --git a/intern/gawain/src/vertex_buffer.c b/intern/gawain/src/vertex_buffer.c
index 03691b0c21d..a9b481261f3 100644
--- a/intern/gawain/src/vertex_buffer.c
+++ b/intern/gawain/src/vertex_buffer.c
@@ -151,6 +151,26 @@ void GWN_vertbuf_attr_fill_stride(Gwn_VertBuf* verts, unsigned a_idx, unsigned s
 		}
 	}
 
+void GWN_vertbuf_attr_get_raw_data(Gwn_VertBuf* verts, unsigned a_idx, Gwn_VertBufRaw *access)
+	{
+	const Gwn_VertFormat* format = &verts->format;
+	const Gwn_VertAttr* a = format->attribs + a_idx;
+
+#if TRUST_NO_ONE
+	assert(a_idx < format->attrib_ct);
+	assert(verts->data != NULL); // data must be in main mem
+#endif
+
+	access->size = a->sz;
+	access->stride = format->stride;
+	access->data = (GLubyte*)verts->data + a->offset;
+	access->data_init = access->data;
+#if TRUST_NO_ONE
+	access->_data_end = access->data_init + (size_t)(verts->vertex_ct * format->stride);
+#endif
+	}
+
+
 static void VertexBuffer_prime(Gwn_VertBuf* verts)
 	{
 	const unsigned buffer_sz = GWN_vertbuf_size_get(verts);