Gawain: flesh out VertexBuffer

create, specify, fill with data

source/blender/gpu/gawain/vertex_buffer.c

@@ -10,5 +10,82 @@
 // the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 #include "vertex_buffer.h"
+#include <stdlib.h>
+#include <string.h>
 
-// TODO: implement C functions
+VertexBuffer* create_VertexBuffer()
+	{
+	VertexBuffer* verts = malloc(sizeof(VertexBuffer));
+	init_VertexBuffer(verts);
+	return verts;
+	}
+
+void init_VertexBuffer(VertexBuffer* verts)
+	{
+	memset(verts, 0, sizeof(VertexBuffer));
+	}
+
+void allocate_vertex_data(VertexBuffer* verts, unsigned v_ct)
+	{
+	VertexFormat* format = &verts->format;
+	if (!format->packed)
+		pack(format);
+
+	verts->vertex_ct = v_ct;
+
+	// Data initially lives in main memory. Will be transferred to VRAM when we "prime" it.
+	verts->data = malloc(vertex_buffer_size(format, v_ct));
+	}
+
+void setAttrib(VertexBuffer* verts, unsigned a_idx, unsigned v_idx, const void* data)
+	{
+	const VertexFormat* format = &verts->format;
+	const Attrib* a = format->attribs + a_idx;
+
+#if TRUST_NO_ONE
+	assert(a_idx < format->attrib_ct);
+	assert(v_idx < verts->vertex_ct);
+	assert(verts->data != NULL); // data must be in main mem
+#endif
+
+	memcpy((GLubyte*)verts->data + a->offset + v_idx * format->stride, data, a->sz);
+	}
+
+void fillAttrib(VertexBuffer* verts, unsigned a_idx, const void* data)
+	{
+	const VertexFormat* format = &verts->format;
+	const Attrib* a = format->attribs + a_idx;
+
+#if TRUST_NO_ONE
+	assert(a_idx < format->attrib_ct);
+#endif
+
+	const unsigned stride = a->sz; // tightly packed input data
+
+	fillAttribStride(verts, a_idx, stride, data);
+	}
+
+void fillAttribStride(VertexBuffer* verts, unsigned a_idx, unsigned stride, const void* data)
+	{
+	const VertexFormat* format = &verts->format;
+	const Attrib* 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
+
+	const unsigned vertex_ct = verts->vertex_ct;
+
+	if (format->attrib_ct == 1 && stride == format->stride)
+		{
+		// we can copy it all at once
+		memcpy(verts->data, data, vertex_ct * a->sz);
+		}
+	else
+		{
+		// we must copy it per vertex
+		for (unsigned v = 0; v < vertex_ct; ++v)
+			memcpy((GLubyte*)verts->data + a->offset + v * format->stride, (const GLubyte*)data + v * stride, a->sz);
+		}
+	}

source/blender/gpu/gawain/vertex_buffer.h

@@ -13,6 +13,15 @@
 
 #include "vertex_format.h"
 
+// How to create a VertexBuffer:
+// 1) verts = create_VertexBuffer() or init_VertexBuffer(verts)
+// 2) add_attrib(verts->format, ...)
+// 3) allocate_vertex_data(verts, vertex_ct) <-- finalizes/packs vertex format
+// 4) fillAttrib(verts, pos, application_pos_buffer)
+// 5) prime_VertexBuffer(verts);
+
+// Is VertexBuffer always used as part of a Batch?
+
 typedef struct {
 	VertexFormat format;
 	unsigned vertex_ct;
@@ -20,8 +29,13 @@ typedef struct {
 	GLuint vbo_id; // 0 indicates not yet sent to VRAM
 } VertexBuffer;
 
-VertexBuffer* create_VertexBuffer(VertexFormat*, unsigned v_ct); // create means allocate, then init
-void init_VertexBuffer(VertexBuffer*, VertexFormat*, unsigned v_ct);
+VertexBuffer* create_VertexBuffer(void); // create means allocate, then init
+void init_VertexBuffer(VertexBuffer*);
+
+// TODO: use copy of existing format
+// void init_VertexBuffer_with_format(VertexBuffer*, VertexFormat*);
+
+void allocate_vertex_data(VertexBuffer*, unsigned v_ct);
 
 // The most important setAttrib variant is the untyped one. Get it right first.
 // It takes a void* so the app developer is responsible for matching their app data types
@@ -29,9 +43,12 @@ void init_VertexBuffer(VertexBuffer*, VertexFormat*, unsigned v_ct);
 // should not be a problem.
 
 void setAttrib(VertexBuffer*, unsigned a_idx, unsigned v_idx, const void* data);
-void fillAttrib(VertexBuffer*, unsigned a_idx, const void* data);
+void fillAttrib(VertexBuffer*, unsigned a_idx, const void* data); // tightly packed, non interleaved input data
 void fillAttribStride(VertexBuffer*, unsigned a_idx, unsigned stride, const void* data);
 
+// TODO: decide whether to keep the functions below
+// doesn't immediate mode satisfy these needs?
+
 //	void setAttrib1f(unsigned a_idx, unsigned v_idx, float x);
 //	void setAttrib2f(unsigned a_idx, unsigned v_idx, float x, float y);
 //	void setAttrib3f(unsigned a_idx, unsigned v_idx, float x, float y, float z);