mutter/cogl/cogl-util.c

/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2007,2008,2009,2010 Intel Corporation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "cogl-util.h"
#include "cogl-private.h"

/*
 * cogl_util_next_p2:
 * @a: Value to get the next power of two
 *
 * Calculates the next power of two greater than or equal to @a.
 *
 * Return value: @a if @a is already a power of two, otherwise returns
 *   the next nearest power of two.
 */
int
_cogl_util_next_p2 (int a)
{
  int rval = 1;

  while (rval < a)
    rval <<= 1;

  return rval;
}

unsigned int
_cogl_util_one_at_a_time_mix (unsigned int hash)
{
  hash += ( hash << 3 );
  hash ^= ( hash >> 11 );
  hash += ( hash << 15 );

  return hash;
}

/* The 'ffs' function is part of C99 so it isn't always available */
#ifndef HAVE_FFS

int
_cogl_util_ffs (int num)
{
  int i = 1;

  if (num == 0)
    return 0;

  while ((num & 1) == 0)
    {
      num >>= 1;
      i++;
    }

  return i;
}
#endif /* HAVE_FFS */

/* The 'ffsl' is non-standard but when building with GCC we'll use its
   builtin instead */
#ifndef COGL_UTIL_HAVE_BUILTIN_FFSL

int
_cogl_util_ffsl_wrapper (long int num)
{
  int i = 1;

  if (num == 0)
    return 0;

  while ((num & 1) == 0)
    {
      num >>= 1;
      i++;
    }

  return i;
}

#endif /* COGL_UTIL_HAVE_BUILTIN_FFSL */

#ifndef COGL_UTIL_HAVE_BUILTIN_POPCOUNTL

const unsigned char
_cogl_util_popcount_table[256] =
  {
    0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4,
    2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4,
    2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,
    4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5,
    3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,
    4, 5, 5, 6, 5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
    4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
  };

#endif /* COGL_UTIL_HAVE_BUILTIN_POPCOUNTL */

/* tests/conform/test-bitmask.c tests some cogl internals and includes this
 * file directly but since these functions depend on other internal Cogl
 * symbols we hide them from test-bitmask.c
 *
 * XXX: maybe there's a better way for us to handle internal testing
 * to avoid needing hacks like this.
 */
#ifndef _COGL_IN_TEST_BITMASK

/* Given a set of red, green and blue component masks, a depth and
 * bits per pixel this function tries to determine a corresponding
 * CoglPixelFormat.
 *
 * The depth is measured in bits not including padding for un-used
 * alpha. The bits per pixel (bpp) does include padding for un-used
 * alpha.
 *
 * This function firstly aims to match formats with RGB ordered
 * components and only considers alpha coming first, in the most
 * significant bits. If the function fails to match then it recurses
 * by either switching the r and b masks around to check for BGR
 * ordered formats or it recurses with the masks shifted to check for
 * formats where the alpha component is the least significant bits.
 */
static CoglPixelFormat
_cogl_util_pixel_format_from_masks_real (unsigned long r_mask,
                                         unsigned long g_mask,
                                         unsigned long b_mask,
                                         int depth, int bpp,
                                         gboolean check_bgr,
                                         gboolean check_afirst,
                                         int recursion_depth)
{
  CoglPixelFormat image_format;

  if (depth == 24 && bpp == 24 &&
      r_mask == 0xff0000 && g_mask == 0xff00 && b_mask == 0xff)
    {
      return COGL_PIXEL_FORMAT_RGB_888;
    }
  else if ((depth == 24 || depth == 32) && bpp == 32 &&
           r_mask == 0xff0000 && g_mask == 0xff00 && b_mask == 0xff)
    {
      return COGL_PIXEL_FORMAT_ARGB_8888_PRE;
    }
  else if (depth == 16 && bpp == 16 &&
           r_mask == 0xf800 && g_mask == 0x7e0 && b_mask == 0x1f)
    {
      return COGL_PIXEL_FORMAT_RGB_565;
    }

  if (recursion_depth == 2)
    return 0;

  /* Check for BGR ordering if we didn't find a match */
  if (check_bgr)
    {
      image_format =
        _cogl_util_pixel_format_from_masks_real (b_mask, g_mask, r_mask,
                                                 depth, bpp,
                                                 FALSE,
                                                 TRUE,
                                                 recursion_depth + 1);
      if (image_format)
        return image_format ^ COGL_BGR_BIT;
    }

  /* Check for alpha in the least significant bits if we still
   * haven't found a match... */
  if (check_afirst && depth != bpp)
    {
      int shift = bpp - depth;

      image_format =
        _cogl_util_pixel_format_from_masks_real (r_mask >> shift,
                                                 g_mask >> shift,
                                                 b_mask >> shift,
                                                 depth, bpp,
                                                 TRUE,
                                                 FALSE,
                                                 recursion_depth + 1);
      if (image_format)
        return image_format ^ COGL_AFIRST_BIT;
    }

  return 0;
}

CoglPixelFormat
_cogl_util_pixel_format_from_masks (unsigned long r_mask,
                                    unsigned long g_mask,
                                    unsigned long b_mask,
                                    int depth, int bpp,
                                    gboolean byte_order_is_lsb_first)
{
  CoglPixelFormat image_format =
    _cogl_util_pixel_format_from_masks_real (r_mask, g_mask, b_mask,
                                             depth, bpp,
                                             TRUE,
                                             TRUE,
                                             0);

  if (!image_format)
    {
      const char *byte_order[] = { "MSB first", "LSB first" };
      g_warning ("Could not find a matching pixel format for red mask=0x%lx,"
                 "green mask=0x%lx, blue mask=0x%lx at depth=%d, bpp=%d "
                 "and byte order=%s\n", r_mask, g_mask, b_mask, depth, bpp,
                 byte_order[!!byte_order_is_lsb_first]);
      return 0;
    }

  /* If the image is in little-endian then the order in memory is
     reversed */
  if (byte_order_is_lsb_first &&
      _cogl_pixel_format_is_endian_dependant (image_format))
    {
      image_format ^= COGL_BGR_BIT;
      if (image_format & COGL_A_BIT)
        image_format ^= COGL_AFIRST_BIT;
    }

  return image_format;
}

#endif /* _COGL_IN_TEST_BITMASK */