main: Add entry point for TextureBufferRange.

v2: Review by Martin Peres
   - Get rid of difficult-to-follow code copied and pasted from
     the original TexBufferRange

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>

src/mapi/glapi/gen/ARB_direct_state_access.xml

@@ -21,6 +21,14 @@
       <param name="buffer" type="GLuint" />
    </function>
 
+   <function name="TextureBufferRange" offset="assign">
+      <param name="texture" type="GLuint" />
+      <param name="internalformat" type="GLenum" />
+      <param name="buffer" type="GLuint" />
+      <param name="offset" type="GLintptr" />
+      <param name="size" type="GLsizeiptr" />
+   </function>
+
    <function name="TextureStorage1D" offset="assign">
       <param name="texture" type="GLuint" />
       <param name="levels" type="GLsizei" />

src/mesa/main/tests/dispatch_sanity.cpp

@@ -985,6 +985,7 @@ const struct function gl_core_functions_possible[] = {
    { "glTextureStorage2DMultisample", 45, -1 },
    { "glTextureStorage3DMultisample", 45, -1 },
    { "glTextureBuffer", 45, -1 },
+   { "glTextureBufferRange", 45, -1 },
 
    /* GL_EXT_polygon_offset_clamp */
    { "glPolygonOffsetClampEXT", 11, -1 },

src/mesa/main/teximage.c

@@ -5463,6 +5463,52 @@ _mesa_TextureBuffer(GLuint texture, GLenum internalFormat, GLuint buffer)
                               bufObj, 0, buffer ? -1 : 0, "glTextureBuffer");
 }
 
+void GLAPIENTRY
+_mesa_TextureBufferRange(GLuint texture, GLenum internalFormat, GLuint buffer,
+                         GLintptr offset, GLsizeiptr size)
+{
+   struct gl_texture_object *texObj;
+   struct gl_buffer_object *bufObj;
+
+   GET_CURRENT_CONTEXT(ctx);
+
+   if (buffer) {
+      bufObj = _mesa_lookup_bufferobj_err(ctx, buffer,
+                                          "glTextureBufferRange");
+      if (!bufObj)
+         return;
+
+      if (!check_texture_buffer_range(ctx, bufObj, offset, size,
+          "glTextureBufferRange"))
+         return;
+
+   } else {
+
+      /* OpenGL 4.5 core spec (02.02.2015) says in Section 8.9 Buffer
+       * Textures (PDF page 254):
+       *    "If buffer is zero, then any buffer object attached to the buffer
+       *    texture is detached, the values offset and size are ignored and
+       *    the state for offset and size for the buffer texture are reset to
+       *    zero."
+       */
+      offset = 0;
+      size = 0;
+      bufObj = NULL;
+   }
+
+   /* Get the texture object by Name. */
+   texObj = _mesa_lookup_texture_err(ctx, texture, "glTextureBufferRange");
+   if (!texObj)
+      return;
+
+   if (!check_texture_buffer_target(ctx, texObj->Target,
+       "glTextureBufferRange"))
+      return;
+
+   _mesa_texture_buffer_range(ctx, texObj, internalFormat,
+                              bufObj, offset, size, "glTextureBufferRange");
+}
+
 static GLboolean
 is_renderable_texture_format(struct gl_context *ctx, GLenum internalformat)
 {

src/mesa/main/teximage.h

@@ -409,6 +409,10 @@ _mesa_TexBufferRange(GLenum target, GLenum internalFormat, GLuint buffer,
 extern void GLAPIENTRY
 _mesa_TextureBuffer(GLuint texture, GLenum internalFormat, GLuint buffer);
 
+extern void GLAPIENTRY
+_mesa_TextureBufferRange(GLuint texture, GLenum internalFormat, GLuint buffer,
+                         GLintptr offset, GLsizeiptr size);
+
 
 extern void GLAPIENTRY
 _mesa_TexImage2DMultisample(GLenum target, GLsizei samples,