/*
 * 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.
 */

/**
 * \file glapi_getproc.c
 *
 * Code for implementing glXGetProcAddress(), etc.
 * This was originally in glapi.c but refactored out.
 */


#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include "glapi/glapi_priv.h"
#include "glapi/glapitable.h"


#define FIRST_DYNAMIC_OFFSET (sizeof(struct _glapi_table) / sizeof(void *))



/**********************************************************************
 * Static function management.
 */


#if !defined(DISPATCH_FUNCTION_SIZE) 
# define NEED_FUNCTION_POINTER
#endif
#include "glapi/glprocs.h"


/**
 * Search the table of static entrypoint functions for the named function
 * and return the corresponding glprocs_table_t entry.
 */
static const glprocs_table_t *
get_static_proc( const char * n )
{
   GLuint i;
   for (i = 0; static_functions[i].Name_offset >= 0; i++) {
      const char *testName = gl_string_table + static_functions[i].Name_offset;
      if (strcmp(testName, n) == 0)
      {
	 return &static_functions[i];
      }
   }
   return NULL;
}


/**
 * Return dispatch table offset of the named static (built-in) function.
 * Return -1 if function not found.
 */
static GLint
get_static_proc_offset(const char *funcName)
{
   const glprocs_table_t * const f = get_static_proc( funcName );
   if (f == NULL) {
      return -1;
   }

   return f->Offset;
}



/**
 * Return dispatch function address for the named static (built-in) function.
 * Return NULL if function not found.
 */
static _glapi_proc
get_static_proc_address(const char *funcName)
{
   const glprocs_table_t * const f = get_static_proc( funcName );
   if (f == NULL) {
      return NULL;
   }

#if defined(DISPATCH_FUNCTION_SIZE) && defined(GLX_INDIRECT_RENDERING)
   return (f->Address == NULL)
      ? get_entrypoint_address(f->Offset)
      : f->Address;
#elif defined(DISPATCH_FUNCTION_SIZE)
   return get_entrypoint_address(f->Offset);
#else
   return f->Address;
#endif
}



/**
 * Return the name of the function at the given offset in the dispatch
 * table.  For debugging only.
 */
static const char *
get_static_proc_name( GLuint offset )
{
   GLuint i;
   for (i = 0; static_functions[i].Name_offset >= 0; i++) {
      if (static_functions[i].Offset == offset) {
	 return gl_string_table + static_functions[i].Name_offset;
      }
   }
   return NULL;
}



/**********************************************************************
 * Extension function management.
 */


/**
 * Track information about a function added to the GL API.
 */
struct _glapi_function {
   /**
    * Name of the function.
    */
   const char * name;


   /**
    * Text string that describes the types of the parameters passed to the
    * named function.   Parameter types are converted to characters using the
    * following rules:
    *   - 'i' for \c GLint, \c GLuint, and \c GLenum
    *   - 'p' for any pointer type
    *   - 'f' for \c GLfloat and \c GLclampf
    *   - 'd' for \c GLdouble and \c GLclampd
    */
   const char * parameter_signature;


   /**
    * Offset in the dispatch table where the pointer to the real function is
    * located.  If the driver has not requested that the named function be
    * added to the dispatch table, this will have the value ~0.
    */
   unsigned dispatch_offset;


   /**
    * Pointer to the dispatch stub for the named function.
    * 
    * \todo
    * The semantic of this field should be changed slightly.  Currently, it
    * is always expected to be non-\c NULL.  However, it would be better to
    * only allocate the entry-point stub when the application requests the
    * function via \c glXGetProcAddress.  This would save memory for all the
    * functions that the driver exports but that the application never wants
    * to call.
    */
   _glapi_proc dispatch_stub;
};


static struct _glapi_function ExtEntryTable[MAX_EXTENSION_FUNCS];
static GLuint NumExtEntryPoints = 0;


static struct _glapi_function *
get_extension_proc(const char *funcName)
{
   GLuint i;
   for (i = 0; i < NumExtEntryPoints; i++) {
      if (strcmp(ExtEntryTable[i].name, funcName) == 0) {
         return & ExtEntryTable[i];
      }
   }
   return NULL;
}


static GLint
get_extension_proc_offset(const char *funcName)
{
   const struct _glapi_function * const f = get_extension_proc( funcName );
   if (f == NULL) {
      return -1;
   }

   return f->dispatch_offset;
}


static _glapi_proc
get_extension_proc_address(const char *funcName)
{
   const struct _glapi_function * const f = get_extension_proc( funcName );
   if (f == NULL) {
      return NULL;
   }

   return f->dispatch_stub;
}


static const char *
get_extension_proc_name(GLuint offset)
{
   GLuint i;
   for (i = 0; i < NumExtEntryPoints; i++) {
      if (ExtEntryTable[i].dispatch_offset == offset) {
         return ExtEntryTable[i].name;
      }
   }
   return NULL;
}


/**
 * strdup() is actually not a standard ANSI C or POSIX routine.
 * Irix will not define it if ANSI mode is in effect.
 */
static char *
str_dup(const char *str)
{
   char *copy;
   copy = malloc(strlen(str) + 1);
   if (!copy)
      return NULL;
   strcpy(copy, str);
   return copy;
}


/**
 * Generate new entrypoint
 *
 * Use a temporary dispatch offset of ~0 (i.e. -1).  Later, when the driver
 * calls \c _glapi_add_dispatch we'll put in the proper offset.  If that
 * never happens, and the user calls this function, he'll segfault.  That's
 * what you get when you try calling a GL function that doesn't really exist.
 * 
 * \param funcName  Name of the function to create an entry-point for.
 * 
 * \sa _glapi_add_entrypoint
 */

static struct _glapi_function *
add_function_name( const char * funcName )
{
   struct _glapi_function * entry = NULL;
   _glapi_proc entrypoint = NULL;
   char * name_dup = NULL;

   if (NumExtEntryPoints >= MAX_EXTENSION_FUNCS)
      return NULL;

   if (funcName == NULL)
      return NULL;

   name_dup = str_dup(funcName);
   if (name_dup == NULL)
      return NULL;

   entrypoint = generate_entrypoint(~0);

   if (entrypoint == NULL) {
      free(name_dup);
      return NULL;
   }

   entry = & ExtEntryTable[NumExtEntryPoints];
   NumExtEntryPoints++;

   entry->name = name_dup;
   entry->parameter_signature = NULL;
   entry->dispatch_offset = ~0;
   entry->dispatch_stub = entrypoint;

   return entry;
}


static struct _glapi_function *
set_entry_info( struct _glapi_function * entry, const char * signature, unsigned offset )
{
   char * sig_dup = NULL;

   if (signature == NULL)
      return NULL;

   sig_dup = str_dup(signature);
   if (sig_dup == NULL)
      return NULL;

   fill_in_entrypoint_offset(entry->dispatch_stub, offset);

   entry->parameter_signature = sig_dup;
   entry->dispatch_offset = offset;

   return entry;
}


/**
 * Fill-in the dispatch stub for the named function.
 * 
 * This function is intended to be called by a hardware driver.  When called,
 * a dispatch stub may be created for the function.  A pointer to this
 * dispatch function will be returned by glXGetProcAddress.
 *
 * \param function_names       Array of pointers to function names that should
 *                             share a common dispatch offset.
 * \param parameter_signature  String representing the types of the parameters
 *                             passed to the named function.  Parameter types
 *                             are converted to characters using the following
 *                             rules:
 *                               - 'i' for \c GLint, \c GLuint, and \c GLenum
 *                               - 'p' for any pointer type
 *                               - 'f' for \c GLfloat and \c GLclampf
 *                               - 'd' for \c GLdouble and \c GLclampd
 *
 * \returns
 * The offset in the dispatch table of the named function.  A pointer to the
 * driver's implementation of the named function should be stored at
 * \c dispatch_table[\c offset].  Return -1 if error/problem.
 *
 * \sa glXGetProcAddress
 *
 * \warning
 * This function can only handle up to 8 names at a time.  As far as I know,
 * the maximum number of names ever associated with an existing GL function is
 * 4 (\c glPointParameterfSGIS, \c glPointParameterfEXT,
 * \c glPointParameterfARB, and \c glPointParameterf), so this should not be
 * too painful of a limitation.
 *
 * \todo
 * Determine whether or not \c parameter_signature should be allowed to be
 * \c NULL.  It doesn't seem like much of a hardship for drivers to have to
 * pass in an empty string.
 *
 * \todo
 * Determine if code should be added to reject function names that start with
 * 'glX'.
 * 
 * \bug
 * Add code to compare \c parameter_signature with the parameter signature of
 * a static function.  In order to do that, we need to find a way to \b get
 * the parameter signature of a static function.
 */

int
_glapi_add_dispatch( const char * const * function_names,
		     const char * parameter_signature )
{
   static int next_dynamic_offset = FIRST_DYNAMIC_OFFSET;
   const char * const real_sig = (parameter_signature != NULL)
     ? parameter_signature : "";
   struct _glapi_function * entry[8];
   GLboolean is_static[8];
   unsigned i;
   int offset = ~0;

   init_glapi_relocs_once();

   (void) memset( is_static, 0, sizeof( is_static ) );
   (void) memset( entry, 0, sizeof( entry ) );

   /* Find the _single_ dispatch offset for all function names that already
    * exist (and have a dispatch offset).
    */

   for ( i = 0 ; function_names[i] != NULL ; i++ ) {
      const char * funcName = function_names[i];
      int static_offset;
      int extension_offset;

      if (funcName[0] != 'g' || funcName[1] != 'l')
         return -1;

      /* search built-in functions */
      static_offset = get_static_proc_offset(funcName);

      if (static_offset >= 0) {

	 is_static[i] = GL_TRUE;

	 /* FIXME: Make sure the parameter signatures match!  How do we get
	  * FIXME: the parameter signature for static functions?
	  */

	 if ( (offset != ~0) && (static_offset != offset) ) {
	    return -1;
	 }

	 offset = static_offset;

	 continue;
      }

      /* search added extension functions */
      entry[i] = get_extension_proc(funcName);

      if (entry[i] != NULL) {
	 extension_offset = entry[i]->dispatch_offset;

	 /* The offset may be ~0 if the function name was added by
	  * glXGetProcAddress but never filled in by the driver.
	  */

	 if (extension_offset == ~0) {
	    continue;
	 }

	 if (strcmp(real_sig, entry[i]->parameter_signature) != 0) {
	    return -1;
	 }

	 if ( (offset != ~0) && (extension_offset != offset) ) {
	    return -1;
	 }

	 offset = extension_offset;
      }
   }

   /* If all function names are either new (or with no dispatch offset),
    * allocate a new dispatch offset.
    */

   if (offset == ~0) {
      offset = next_dynamic_offset;
      next_dynamic_offset++;
   }

   /* Fill in the dispatch offset for the new function names (and those with
    * no dispatch offset).
    */

   for ( i = 0 ; function_names[i] != NULL ; i++ ) {
      if (is_static[i]) {
	 continue;
      }

      /* generate entrypoints for new function names */
      if (entry[i] == NULL) {
	 entry[i] = add_function_name( function_names[i] );
	 if (entry[i] == NULL) {
	    /* FIXME: Possible memory leak here. */
	    return -1;
	 }
      }

      if (entry[i]->dispatch_offset == ~0) {
	 set_entry_info( entry[i], real_sig, offset );
      }
   }

   return offset;
}


/**
 * Return offset of entrypoint for named function within dispatch table.
 */
GLint
_glapi_get_proc_offset(const char *funcName)
{
   GLint offset;

   /* search extension functions first */
   offset = get_extension_proc_offset(funcName);
   if (offset >= 0)
      return offset;

   /* search static functions */
   return get_static_proc_offset(funcName);
}



/**
 * Return pointer to the named function.  If the function name isn't found
 * in the name of static functions, try generating a new API entrypoint on
 * the fly with assembly language.
 */
_glapi_proc
_glapi_get_proc_address(const char *funcName)
{
   _glapi_proc func;
   struct _glapi_function * entry;

   init_glapi_relocs_once();

#ifdef USE_MGL_NAMESPACE
   if (funcName && funcName[0] == 'm')
      funcName++;
#endif

  if (!funcName || funcName[0] != 'g' || funcName[1] != 'l')
      return NULL;

   /* search extension functions first */
   func = get_extension_proc_address(funcName);
   if (func)
      return func;

   /* search static functions */
   func = get_static_proc_address(funcName);
   if (func)
      return func;

   /* generate entrypoint, dispatch offset must be filled in by the driver */
   entry = add_function_name(funcName);
   if (entry == NULL)
      return NULL;

   return entry->dispatch_stub;
}



/**
 * Return the name of the function at the given dispatch offset.
 * This is only intended for debugging.
 */
const char *
_glapi_get_proc_name(GLuint offset)
{
   const char * n;

   /* search built-in functions */
   n = get_static_proc_name(offset);
   if ( n != NULL ) {
      return n;
   }

   /* search added extension functions */
   return get_extension_proc_name(offset);
}



/**********************************************************************
 * GL API table functions.
 */


/**
 * Return size of dispatch table struct as number of functions (or
 * slots).
 */
GLuint
_glapi_get_dispatch_table_size(void)
{
   /*
    * The dispatch table size (number of entries) is the size of the
    * _glapi_table struct plus the number of dynamic entries we can add.
    * The extra slots can be filled in by DRI drivers that register new
    * extension functions.
    */
   return FIRST_DYNAMIC_OFFSET + MAX_EXTENSION_FUNCS;
}
