//========================================================================
// GLFW - An OpenGL framework
// File:        glext.c
// Platform:    Any
// API version: 2.7
// WWW:         http://glfw.sourceforge.net
//------------------------------------------------------------------------
// Copyright (c) 2002-2006 Camilla Berglund
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgment in the product documentation would
//    be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
//    be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
//    distribution.
//
//========================================================================

#include "internal.h"


//************************************************************************
//****                  GLFW internal functions                       ****
//************************************************************************

//========================================================================
// Parses the OpenGL version string and extracts the version number
//========================================================================

void _glfwParseGLVersion( int *major, int *minor, int *rev )
{
    GLuint _major, _minor = 0, _rev = 0;
    const GLubyte *version;
    const GLubyte *ptr;

    // Get OpenGL version string
    version = glGetString( GL_VERSION );
    if( !version )
    {
        return;
    }

    // Parse string
    ptr = version;
    for( _major = 0; *ptr >= '0' && *ptr <= '9'; ptr ++ )
    {
        _major = 10*_major + (*ptr - '0');
    }
    if( *ptr == '.' )
    {
        ptr ++;
        for( _minor = 0; *ptr >= '0' && *ptr <= '9'; ptr ++ )
        {
            _minor = 10*_minor + (*ptr - '0');
        }
        if( *ptr == '.' )
        {
            ptr ++;
            for( _rev = 0; *ptr >= '0' && *ptr <= '9'; ptr ++ )
            {
                _rev = 10*_rev + (*ptr - '0');
            }
        }
    }

    // Return parsed values
    *major = _major;
    *minor = _minor;
    *rev = _rev;
}

//========================================================================
// _glfwStringInExtensionString() - Check if a string can be found in an
// OpenGL extension string
//========================================================================

int _glfwStringInExtensionString( const char *string,
                                  const GLubyte *extensions )
{
    const GLubyte *start;
    GLubyte *where, *terminator;

    // It takes a bit of care to be fool-proof about parsing the
    // OpenGL extensions string. Don't be fooled by sub-strings,
    // etc.
    start = extensions;
    while( 1 )
    {
        where = (GLubyte *) strstr( (const char *) start, string );
        if( !where )
        {
            return GL_FALSE;
        }
        terminator = where + strlen( string );
        if( where == start || *(where - 1) == ' ' )
        {
            if( *terminator == ' ' || *terminator == '\0' )
            {
                break;
            }
        }
        start = terminator;
    }

    return GL_TRUE;
}



//************************************************************************
//****                    GLFW user functions                         ****
//************************************************************************

//========================================================================
// glfwExtensionSupported() - Check if an OpenGL extension is available
// at runtime
//========================================================================

GLFWAPI int GLFWAPIENTRY glfwExtensionSupported( const char *extension )
{
    const GLubyte *extensions;
    GLubyte *where;

    // Is GLFW initialized?
    if( !_glfwInitialized || !_glfwWin.opened )
    {
        return GL_FALSE;
    }

    // Extension names should not have spaces
    where = (GLubyte *) strchr( extension, ' ' );
    if( where || *extension == '\0' )
    {
        return GL_FALSE;
    }

    // Check if extension is in the standard OpenGL extensions string
    extensions = glGetString( GL_EXTENSIONS );
    if( extensions != NULL )
    {
        if( _glfwStringInExtensionString( extension, extensions ) )
        {
            return GL_TRUE;
        }
    }

    // Additional platform specific extension checking (e.g. WGL)
    if( _glfwPlatformExtensionSupported( extension ) )
    {
        return GL_TRUE;
    }

    return GL_FALSE;
}


//========================================================================
// glfwGetProcAddress() - Get the function pointer to an OpenGL function.
// This function can be used to get access to extended OpenGL functions.
//========================================================================

GLFWAPI void * GLFWAPIENTRY glfwGetProcAddress( const char *procname )
{
    // Is GLFW initialized?
    if( !_glfwInitialized || !_glfwWin.opened )
    {
        return NULL;
    }

    return _glfwPlatformGetProcAddress( procname );
}


//========================================================================
// Returns the OpenGL version
//========================================================================

GLFWAPI void GLFWAPIENTRY glfwGetGLVersion( int *major, int *minor, int *rev )
{
    // Is GLFW initialized?
    if( !_glfwInitialized || !_glfwWin.opened )
    {
        return;
    }

    if( major != NULL )
    {
        *major = _glfwWin.glMajor;
    }
    if( minor != NULL )
    {
        *minor = _glfwWin.glMinor;
    }
    if( rev != NULL )
    {
        *rev = _glfwWin.glRevision;
    }
}