xref: /aosp_15_r20/external/mesa3d/src/mapi/u_current.c (revision 6104692788411f58d303aa86923a9ff6ecaded22)

/*
 * Mesa 3-D graphics library
 *
 * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */


/*
 * This file manages the OpenGL API dispatch layer.
 * The dispatch table (struct _glapi_table) is basically just a list
 * of function pointers.
 * There are functions to set/get the current dispatch table for the
 * current thread and to manage registration/dispatch of dynamically
 * added extension functions.
 *
 * It's intended that this file and the other glapi*.[ch] files are
 * flexible enough to be reused in several places:  XFree86, DRI-
 * based libGL.so, and perhaps the SGI SI.
 *
 * NOTE: There are no dependencies on Mesa in this code.
 *
 * Versions (API changes):
 *   2000/02/23  - original version for Mesa 3.3 and XFree86 4.0
 *   2001/01/16  - added dispatch override feature for Mesa 3.5
 *   2002/06/28  - added _glapi_set_warning_func(), Mesa 4.1.
 *   2002/10/01  - _glapi_get_proc_address() will now generate new entrypoints
 *                 itself (using offset ~0).  _glapi_add_entrypoint() can be
 *                 called afterward and it'll fill in the correct dispatch
 *                 offset.  This allows DRI libGL to avoid probing for DRI
 *                 drivers!  No changes to the public glapi interface.
 */

#include "c11/threads.h"
#include "util/u_thread.h"
#include "u_current.h"

#ifndef MAPI_MODE_UTIL

#include "table.h"
#include "stub.h"

#else

extern void init_glapi_relocs_once(void);
extern void (*__glapi_noop_table[])(void);

#define table_noop_array __glapi_noop_table
#define stub_init_once() init_glapi_relocs_once()

#endif

/**
 * \name Current dispatch and current context control variables
 *
 * Depending on whether or not multithreading is support, and the type of
 * support available, several variables are used to store the current context
 * pointer and the current dispatch table pointer. In the non-threaded case,
 * the variables \c _glapi_Dispatch and \c _glapi_Context are used for this
 * purpose.
 *
 * In multi threaded case, The TLS variables \c _glapi_tls_Dispatch and
 * \c _glapi_tls_Context are used. Having \c _glapi_Dispatch and \c _glapi_Context
 * be hardcoded to \c NULL maintains binary compatability between TLS enabled
 * loaders and non-TLS DRI drivers. When \c _glapi_Dispatch and \c _glapi_Context
 * are \c NULL, the thread state data \c ContextTSD are used. Drivers and the
 * static dispatch functions access these variables via \c _glapi_get_dispatch
 * and \c _glapi_get_context.
 */
/*@{*/

__THREAD_INITIAL_EXEC struct _glapi_table *_glapi_tls_Dispatch
   = (struct _glapi_table *) table_noop_array;

__THREAD_INITIAL_EXEC void *_glapi_tls_Context;

/* not used, but defined for compatibility */
const struct _glapi_table *_glapi_Dispatch;
const void *_glapi_Context;

/*@}*/

/* not used, but defined for compatibility */
void
_glapi_destroy_multithread(void)
{
}

/* not used, but defined for compatibility */
void
_glapi_check_multithread(void)
{
}

/**
 * Set the current context pointer for this thread.
 * The context pointer is an opaque type which should be cast to
 * void from the real context pointer type.
 */
void
_glapi_set_context(void *ptr)
{
   _glapi_tls_Context = ptr;
}

/**
 * Get the current context pointer for this thread.
 * The context pointer is an opaque type which should be cast from
 * void to the real context pointer type.
 */
void *
_glapi_get_context(void)
{
   return _glapi_tls_Context;
}

/**
 * Set the global or per-thread dispatch table pointer.
 * If the dispatch parameter is NULL we'll plug in the no-op dispatch
 * table (__glapi_noop_table).
 */
void
_glapi_set_dispatch(struct _glapi_table *tbl)
{
   stub_init_once();

   if (!tbl)
      tbl = (struct _glapi_table *) table_noop_array;

   _glapi_tls_Dispatch = tbl;
}

/**
 * Return pointer to current dispatch table for calling thread.
 */
struct _glapi_table *
_glapi_get_dispatch(void)
{
   return _glapi_tls_Dispatch;
}