Attachment 2753 Details for Bug 3377 – Generate dynamic offsets, handle GLuint ~0 values properly

[patch] Generate dynamic offsets, handle GLuint ~0 values properly

add_entrypoint-01.patch (text/plain), 6.68 KB, created by Ian Romanick on 2005-05-23 16:13:43 UTC

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Creator: Ian Romanick

Created: 2005-05-23 16:13:43 UTC

Size: 6.68 KB

patch

obsolete

>Index: src/mesa/glapi/glapi.c
>===================================================================
>RCS file: /cvs/mesa/Mesa/src/mesa/glapi/glapi.c,v
>retrieving revision 1.92
>diff -u -d -r1.92 glapi.c
>--- src/mesa/glapi/glapi.c	28 Apr 2005 13:16:23 -0000	1.92
>+++ src/mesa/glapi/glapi.c	23 May 2005 23:04:09 -0000
>@@ -815,11 +815,59 @@
> 
> /**
>  * Add a new extension function entrypoint.
>- * Return: GL_TRUE = success or GL_FALSE = failure
>+ * 
>+ * This function is used by dynamically loaded drivers to add entrypoints
>+ * for new functions.  New offsets are assigned to functions in gl_API.xml.
>+ * If a driver needs work with libGL versions from before a function had an
>+ * offset assigned, it must call this function with the assigned offset.
>+ * 
>+ * If a driver wants to extend the GL API with functions that do not have
>+ * assigned API offsets (e.g., a new vendor-specific extension), this
>+ * function should be called with an offset of ~0.
>+ * 
>+ * The rule is: if you know an offset from gl_API.xml, use it for the
>+ * \c offset parameter.  If you do not know an offset from gl_API.xml, use
>+ * ~0.
>+ *
>+ * \param funcName  Name of the function to be added
>+ * \param offset    Offset in the dispatch table for the function.  If the
>+ *                  function does \b not have a registered offset, then the
>+ *                  value ~0 should be used.
>+ * \returns
>+ * On success \c GL_TRUE is returned, otherwise \c GL_FALSE is returned.
>+ *
>+ * \bug
>+ * Dynamic offsets are assigned starting with the highest possible value
>+ * working towards the lowest (i.e., working towards the statically assigned
>+ * offsets).  This is done to prevent a potential problem where a driver could
>+ * request a dynamic offset, then request a static offset and have the two
>+ * conflict.  However, if \c _glapi_add_entrypoint is called too many times
>+ * requesting dynamic offsets, the value of \c next_dynamic_offset can get
>+ * down into the range of the static offsets.  If the incoming offset is ~0,
>+ * \c next_dynamic_offset needs to be validated against the largest known
>+ * static offset.
>+ *
>+ * \bug
>+ * It is possible for libGL to load two (or more) different drivers.  One
>+ * driver could call '_glapi_add_entrypoint("glFooIHV", ~0)'.  Another
>+ * driver could later call
>+ * '_glapi_add_entrypoint("glFooIHV", _gloffset_glFooIHV)'.  If the libGL
>+ * version does not know about \c _gloffset_glFooIHV, the second call to
>+ * \c _glapi_add_entrypoint will fail.  This is an unfortunate side-effect of
>+ * this interface.  I believe that this bug will rarely, if ever, occur in the
>+ * real world.  If it does, the fix is to upgrade to a more recent libGL.
>+ * The issue is documented here for completeness.
>  */
>+
> PUBLIC GLboolean
> _glapi_add_entrypoint(const char *funcName, GLuint offset)
> {
>+   const GLint index = _glapi_get_proc_offset( funcName );
>+   static unsigned next_dynamic_offset = DISPATCH_TABLE_SIZE - 1;
>+   _glapi_proc entrypoint;
>+   GLuint i;
>+
>+
>    /* trivial rejection test */
> #ifdef MANGLE
>    if (!funcName || funcName[0] != 'm' || funcName[1] != 'g' || funcName[2] != 'l')
>@@ -829,61 +877,70 @@
>       return GL_FALSE;
> #endif
> 
>-   /* first check if the named function is already statically present */
>-   {
>-      GLint index = get_static_proc_offset(funcName);
>-      if (index >= 0) {
>-         return (GLboolean) ((GLuint) index == offset);  /* bad offset! */
>-      }
>+
>+   /* Check if the named function is already present.
>+    */
>+
>+   if ( index != ~0 ) {
>+      return (((GLuint) index == offset) || (offset == (GLuint)~0));
>    }
> 
>-   /* See if this function has already been dynamically added */
>-   {
>-      GLuint i;
>-      for (i = 0; i < NumExtEntryPoints; i++) {
>-         if (strcmp(ExtEntryTable[i].Name, funcName) == 0) {
>-            /* function already registered */
>-            if (ExtEntryTable[i].Offset == offset) {
>-               return GL_TRUE;  /* offsets match */
>-            }
>-            else if (ExtEntryTable[i].Offset == (GLuint) ~0
>-                     && offset < DISPATCH_TABLE_SIZE) {
>-               /* need to patch-up the dispatch code */
>-               if (offset != (GLuint) ~0) {
>-                  fill_in_entrypoint_offset(ExtEntryTable[i].Address, offset);
>-                  ExtEntryTable[i].Offset = offset;
>-               }
>-               return GL_TRUE;
>-            }
>-            else {
>-               return GL_FALSE;  /* bad offset! */
>-            }
>-         }
>+
>+   /* If the supplied offset is ~0, we need to select an appropriate offset
>+    * to use.
>+    */
>+
>+   if ( offset == (GLuint) ~0 ) {
>+      offset = next_dynamic_offset;
>+      next_dynamic_offset--;
>+   }
>+   else if ( offset >= next_dynamic_offset ) {
>+      /* The requested offset has already been given to a dynamic offset
>+       * request.
>+       */
>+      return GL_FALSE;
>+   }
>+
>+
>+   /* See if this function has already been dynamically added via
>+    * glXGetProcAddress (or similar funciton).  If this has happened, the
>+    * function will be listed in the ExtEntryTable, but it will have an offset
>+    * of ~0.
>+    */
>+   for (i = 0; i < NumExtEntryPoints; i++) {
>+      if (strcmp(ExtEntryTable[i].Name, funcName) == 0) {
>+	 /* If the offset is not ~0, then this function should have already
>+	  * exited above when testing the return value of
>+	  * _glapi_get_proc_offset.
>+	  */
>+	 assert( ExtEntryTable[i].Offset == ~0 );
>+
>+	 fill_in_entrypoint_offset(ExtEntryTable[i].Address, offset);
>+	 ExtEntryTable[i].Offset = offset;
>+	 return GL_TRUE;
>       }
>    }
> 
>-   /* This is a new function, try to add it.  */
>-   if (NumExtEntryPoints >= MAX_EXTENSION_FUNCS ||
>-       offset >= DISPATCH_TABLE_SIZE) {
>-      /* No space left */
>+
>+   if (NumExtEntryPoints >= MAX_EXTENSION_FUNCS) {
>+      /* No space left in the internal extension entrypoint table.
>+       */
>       return GL_FALSE;
>    }
>-   else {
>-      _glapi_proc entrypoint = generate_entrypoint(offset);
>-      if (!entrypoint)
>-         return GL_FALSE; /* couldn't generate assembly */
>-
>-      /* OK! */
>-      ExtEntryTable[NumExtEntryPoints].Name = str_dup(funcName);
>-      ExtEntryTable[NumExtEntryPoints].Offset = offset;
>-      ExtEntryTable[NumExtEntryPoints].Address = entrypoint;
>-      NumExtEntryPoints++;
> 
>-      return GL_TRUE;  /* success */
>+   /* This is a new function, try to add it.  */
>+   entrypoint = generate_entrypoint(offset);
>+   if (!entrypoint) {
>+      return GL_FALSE; /* couldn't generate assembly */
>    }
> 
>-   /* should never get here, silence compiler warnings */
>-   return GL_FALSE;
>+   /* OK! */
>+   ExtEntryTable[NumExtEntryPoints].Name = str_dup(funcName);
>+   ExtEntryTable[NumExtEntryPoints].Offset = offset;
>+   ExtEntryTable[NumExtEntryPoints].Address = entrypoint;
>+   NumExtEntryPoints++;
>+
>+   return GL_TRUE;  /* success */
> }
> 
>

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