path: root/src/mesa/main/format_utils.c

/*
 * Mesa 3-D graphics library
 *
 * Copyright (C) 2014  Intel Corporation  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.
 */

#include "format_utils.h"
#include "glformats.h"
#include "format_pack.h"
#include "format_unpack.h"

const mesa_array_format RGBA8888_FLOAT =
   MESA_ARRAY_FORMAT(4, 1, 1, 1, 4, 0, 1, 2, 3);

const mesa_array_format RGBA8888_UBYTE =
   MESA_ARRAY_FORMAT(1, 0, 0, 1, 4, 0, 1, 2, 3);

const mesa_array_format RGBA8888_UINT =
   MESA_ARRAY_FORMAT(4, 0, 0, 0, 4, 0, 1, 2, 3);

const mesa_array_format RGBA8888_INT =
   MESA_ARRAY_FORMAT(4, 1, 0, 0, 4, 0, 1, 2, 3);

static void
invert_swizzle(uint8_t dst[4], const uint8_t src[4])
{
   int i, j;

   dst[0] = MESA_FORMAT_SWIZZLE_NONE;
   dst[1] = MESA_FORMAT_SWIZZLE_NONE;
   dst[2] = MESA_FORMAT_SWIZZLE_NONE;
   dst[3] = MESA_FORMAT_SWIZZLE_NONE;

   for (i = 0; i < 4; ++i)
      for (j = 0; j < 4; ++j)
         if (src[j] == i && dst[i] == MESA_FORMAT_SWIZZLE_NONE)
            dst[i] = j;
}

static GLenum
gl_type_for_array_format_datatype(enum mesa_array_format_datatype type)
{
   switch (type) {
   case MESA_ARRAY_FORMAT_TYPE_UBYTE:
      return GL_UNSIGNED_BYTE;
   case MESA_ARRAY_FORMAT_TYPE_USHORT:
      return GL_UNSIGNED_SHORT;
   case MESA_ARRAY_FORMAT_TYPE_UINT:
      return GL_UNSIGNED_INT;
   case MESA_ARRAY_FORMAT_TYPE_BYTE:
      return GL_BYTE;
   case MESA_ARRAY_FORMAT_TYPE_SHORT:
      return GL_SHORT;
   case MESA_ARRAY_FORMAT_TYPE_INT:
      return GL_INT;
   case MESA_ARRAY_FORMAT_TYPE_HALF:
      return GL_HALF_FLOAT;
   case MESA_ARRAY_FORMAT_TYPE_FLOAT:
      return GL_FLOAT;
   default:
      assert(!"Invalid datatype");
      return GL_NONE;
   }
}

/**
 * This can be used to convert between most color formats.
 *
 * Limitations:
 * - This function doesn't handle GL_COLOR_INDEX or YCBCR formats.
 * - This function doesn't handle byte-swapping or transferOps, these should
 *   be handled by the caller.
 *
 * \param void_dst  The address where converted color data will be stored.
 *                  The caller must ensure that the buffer is large enough
 *                  to hold the converted pixel data.
 * \param dst_format  The destination color format. It can be a mesa_format
 *                    or a mesa_array_format represented as an uint32_t.
 * \param dst_stride  The stride of the destination format in bytes.
 * \param void_src  The address of the source color data to convert.
 * \param src_format  The source color format. It can be a mesa_format
 *                    or a mesa_array_format represented as an uint32_t.
 * \param src_stride  The stride of the source format in bytes.
 * \param width  The width, in pixels, of the source image to convert.
 * \param height  The height, in pixels, of the source image to convert.
 */
void
_mesa_format_convert(void *void_dst, uint32_t dst_format, size_t dst_stride,
                     void *void_src, uint32_t src_format, size_t src_stride,
                     size_t width, size_t height)
{
   uint8_t *dst = (uint8_t *)void_dst;
   uint8_t *src = (uint8_t *)void_src;
   mesa_array_format src_array_format, dst_array_format;
   bool src_format_is_mesa_array_format, dst_format_is_mesa_array_format;
   uint8_t src2dst[4], src2rgba[4], rgba2dst[4], dst2rgba[4];
   GLenum src_gl_type, dst_gl_type, common_gl_type;
   bool normalized, dst_integer, src_integer, is_signed;
   int src_num_channels = 0, dst_num_channels = 0;
   uint8_t (*tmp_ubyte)[4];
   float (*tmp_float)[4];
   uint32_t (*tmp_uint)[4];
   int i, bits;
   size_t row;

   if (_mesa_format_is_mesa_array_format(src_format)) {
      src_format_is_mesa_array_format = true;
      src_array_format = src_format;
   } else {
      assert(_mesa_is_format_color_format(src_format));
      src_format_is_mesa_array_format = false;
      src_array_format = _mesa_format_to_array_format(src_format);
   }

   if (_mesa_format_is_mesa_array_format(dst_format)) {
      dst_format_is_mesa_array_format = true;
      dst_array_format = dst_format;
   } else {
      assert(_mesa_is_format_color_format(dst_format));
      dst_format_is_mesa_array_format = false;
      dst_array_format = _mesa_format_to_array_format(dst_format);
   }

   /* Handle the cases where we can directly unpack */
   if (!src_format_is_mesa_array_format) {
      if (dst_array_format == RGBA8888_FLOAT) {
         for (row = 0; row < height; ++row) {
            _mesa_unpack_rgba_row(src_format, width,
                                  src, (float (*)[4])dst);
            src += src_stride;
            dst += dst_stride;
         }
         return;
      } else if (dst_array_format == RGBA8888_UBYTE) {
         assert(!_mesa_is_format_integer_color(src_format));
         for (row = 0; row < height; ++row) {
            _mesa_unpack_ubyte_rgba_row(src_format, width,
                                        src, (uint8_t (*)[4])dst);
            src += src_stride;
            dst += dst_stride;
         }
         return;
      } else if (dst_array_format == RGBA8888_UINT &&
                 _mesa_is_format_unsigned(src_format)) {
         assert(_mesa_is_format_integer_color(src_format));
         for (row = 0; row < height; ++row) {
            _mesa_unpack_uint_rgba_row(src_format, width,
                                       src, (uint32_t (*)[4])dst);
            src += src_stride;
            dst += dst_stride;
         }
         return;
      }
   }

   /* Handle the cases where we can directly pack */
   if (!dst_format_is_mesa_array_format) {
      if (src_array_format == RGBA8888_FLOAT) {
         for (row = 0; row < height; ++row) {
            _mesa_pack_float_rgba_row(dst_format, width,
                                      (const float (*)[4])src, dst);
            src += src_stride;
            dst += dst_stride;
         }
         return;
      } else if (src_array_format == RGBA8888_UBYTE) {
         assert(!_mesa_is_format_integer_color(dst_format));
         for (row = 0; row < height; ++row) {
            _mesa_pack_ubyte_rgba_row(dst_format, width,
                                      (const uint8_t (*)[4])src, dst);
            src += src_stride;
            dst += dst_stride;
         }
         return;
      } else if (src_array_format == RGBA8888_UINT &&
                 _mesa_is_format_unsigned(dst_format)) {
         assert(_mesa_is_format_integer_color(dst_format));
         for (row = 0; row < height; ++row) {
            _mesa_pack_uint_rgba_row(dst_format, width,
                                     (const uint32_t (*)[4])src, dst);
            src += src_stride;
            dst += dst_stride;
         }
         return;
      }
   }

   /* Handle conversions between array formats */
   normalized = false;
   if (src_array_format) {
      enum mesa_array_format_datatype datatype =
         _mesa_array_format_get_datatype(src_array_format);
      src_gl_type = gl_type_for_array_format_datatype(datatype);

      src_num_channels = _mesa_array_format_get_num_channels(src_array_format);

      _mesa_array_format_get_swizzle(src_array_format, src2rgba);

      normalized = _mesa_array_format_is_normalized(src_array_format);
   }

   if (dst_array_format) {
      enum mesa_array_format_datatype datatype =
         _mesa_array_format_get_datatype(dst_array_format);
      dst_gl_type = gl_type_for_array_format_datatype(datatype);

      dst_num_channels = _mesa_array_format_get_num_channels(dst_array_format);

      _mesa_array_format_get_swizzle(dst_array_format, dst2rgba);
      invert_swizzle(rgba2dst, dst2rgba);

      normalized |= _mesa_array_format_is_normalized(dst_array_format);
   }

   if (src_array_format && dst_array_format) {
      assert(_mesa_array_format_is_normalized(src_array_format) ==
             _mesa_array_format_is_normalized(dst_array_format));

      for (i = 0; i < 4; i++) {
         if (rgba2dst[i] > MESA_FORMAT_SWIZZLE_W) {
            src2dst[i] = rgba2dst[i];
         } else {
            src2dst[i] = src2rgba[rgba2dst[i]];
         }
      }

      for (row = 0; row < height; ++row) {
         _mesa_swizzle_and_convert(dst, dst_gl_type, dst_num_channels,
                                   src, src_gl_type, src_num_channels,
                                   src2dst, normalized, width);
         src += src_stride;
         dst += dst_stride;
      }
      return;
   }

   /* At this point, we're fresh out of fast-paths and we need to convert
    * to float, uint32, or, if we're lucky, uint8.
    */
   dst_integer = false;
   src_integer = false;

   if (src_array_format) {
      if (!_mesa_array_format_is_float(src_array_format) &&
          !_mesa_array_format_is_normalized(src_array_format))
         src_integer = true;
   } else {
      switch (_mesa_get_format_datatype(src_format)) {
      case GL_UNSIGNED_INT:
      case GL_INT:
         src_integer = true;
         break;
      }
   }

   /* If the destination format is signed but the source is unsigned, then we
    * don't loose any data by converting to a signed intermediate format above
    * and beyond the precision that we loose in the conversion itself. If the
    * destination is unsigned then, by using an unsigned intermediate format,
    * we make the conversion function that converts from the source to the
    * intermediate format take care of truncating at zero. The exception here
    * is if the intermediate format is float, in which case the first
    * conversion will leave it signed and the second conversion will truncate
    * at zero.
    */
   is_signed = false;
   if (dst_array_format) {
      if (!_mesa_array_format_is_float(dst_array_format) &&
          !_mesa_array_format_is_normalized(dst_array_format))
         dst_integer = true;
      is_signed = _mesa_array_format_is_signed(dst_array_format);
      bits = 8 * _mesa_array_format_get_type_size(dst_array_format);
   } else {
      switch (_mesa_get_format_datatype(dst_format)) {
      case GL_UNSIGNED_NORMALIZED:
         is_signed = false;
         break;
      case GL_SIGNED_NORMALIZED:
         is_signed = true;
         break;
      case GL_FLOAT:
         is_signed = true;
         break;
      case GL_UNSIGNED_INT:
         is_signed = false;
         dst_integer = true;
         break;
      case GL_INT:
         is_signed = true;
         dst_integer = true;
         break;
      }
      bits = _mesa_get_format_max_bits(dst_format);
   }

   assert(src_integer == dst_integer);

   if (src_integer && dst_integer) {
      tmp_uint = malloc(width * height * sizeof(*tmp_uint));

      /* The [un]packing functions for unsigned datatypes treat the 32-bit
       * integer array as signed for signed formats and as unsigned for
       * unsigned formats. This is a bit of a problem if we ever convert from
       * a signed to an unsigned format because the unsigned packing function
       * doesn't know that the input is signed and will treat it as unsigned
       * and not do the trunctation. The thing that saves us here is that all
       * of the packed formats are unsigned, so we can just always use
       * _mesa_swizzle_and_convert for signed formats, which is aware of the
       * truncation problem.
       */
      common_gl_type = is_signed ? GL_INT : GL_UNSIGNED_INT;
      if (src_array_format) {
         for (row = 0; row < height; ++row) {
            _mesa_swizzle_and_convert(tmp_uint + row * width, common_gl_type, 4,
                                      src, src_gl_type, src_num_channels,
                                      src2rgba, normalized, width);
            src += src_stride;
         }
      } else {
         for (row = 0; row < height; ++row) {
            _mesa_unpack_uint_rgba_row(src_format, width,
                                       src, tmp_uint + row * width);
            src += src_stride;
         }
      }

      /* At this point, we have already done the truncation if the source is
       * signed but the destination is unsigned, so no need to force the
       * _mesa_swizzle_and_convert path.
       */
      if (dst_format_is_mesa_array_format) {
         for (row = 0; row < height; ++row) {
            _mesa_swizzle_and_convert(dst, dst_gl_type, dst_num_channels,
                                      tmp_uint + row * width, common_gl_type, 4,
                                      rgba2dst, normalized, width);
            dst += dst_stride;
         }
      } else {
         for (row = 0; row < height; ++row) {
            _mesa_pack_uint_rgba_row(dst_format, width,
                                     (const uint32_t (*)[4])tmp_uint + row * width, dst);
            dst += dst_stride;
         }
      }

      free(tmp_uint);
   } else if (is_signed || bits > 8) {
      tmp_float = malloc(width * height * sizeof(*tmp_float));

      if (src_format_is_mesa_array_format) {
         for (row = 0; row < height; ++row) {
            _mesa_swizzle_and_convert(tmp_float + row * width, GL_FLOAT, 4,
                                      src, src_gl_type, src_num_channels,
                                      src2rgba, normalized, width);
            src += src_stride;
         }
      } else {
         for (row = 0; row < height; ++row) {
            _mesa_unpack_rgba_row(src_format, width,
                                  src, tmp_float + row * width);
            src += src_stride;
         }
      }

      if (dst_format_is_mesa_array_format) {
         for (row = 0; row < height; ++row) {
            _mesa_swizzle_and_convert(dst, dst_gl_type, dst_num_channels,
                                      tmp_float + row * width, GL_FLOAT, 4,
                                      rgba2dst, normalized, width);
            dst += dst_stride;
         }
      } else {
         for (row = 0; row < height; ++row) {
            _mesa_pack_float_rgba_row(dst_format, width,
                                      (const float (*)[4])tmp_float + row * width, dst);
            dst += dst_stride;
         }
      }

      free(tmp_float);
   } else {
      tmp_ubyte = malloc(width * height * sizeof(*tmp_ubyte));

      if (src_format_is_mesa_array_format) {
         for (row = 0; row < height; ++row) {
            _mesa_swizzle_and_convert(tmp_ubyte + row * width, GL_UNSIGNED_BYTE, 4,
                                      src, src_gl_type, src_num_channels,
                                      src2rgba, normalized, width);
            src += src_stride;
         }
      } else {
         for (row = 0; row < height; ++row) {
            _mesa_unpack_ubyte_rgba_row(src_format, width,
                                        src, tmp_ubyte + row * width);
            src += src_stride;
         }
      }

      if (dst_format_is_mesa_array_format) {
         for (row = 0; row < height; ++row) {
            _mesa_swizzle_and_convert(dst, dst_gl_type, dst_num_channels,
                                      tmp_ubyte + row * width, GL_UNSIGNED_BYTE, 4,
                                      rgba2dst, normalized, width);
            dst += dst_stride;
         }
      } else {
         for (row = 0; row < height; ++row) {
            _mesa_pack_ubyte_rgba_row(dst_format, width,
                                      (const uint8_t (*)[4])tmp_ubyte + row * width, dst);
            dst += dst_stride;
         }
      }

      free(tmp_ubyte);
   }
}

static const uint8_t map_identity[7] = { 0, 1, 2, 3, 4, 5, 6 };
static const uint8_t map_3210[7] = { 3, 2, 1, 0, 4, 5, 6 };
static const uint8_t map_1032[7] = { 1, 0, 3, 2, 4, 5, 6 };

/**
 * Describes a format as an array format, if possible
 *
 * A helper function for figuring out if a (possibly packed) format is
 * actually an array format and, if so, what the array parameters are.
 *
 * \param[in]  format         the mesa format
 * \param[out] type           the GL type of the array (GL_BYTE, etc.)
 * \param[out] num_components the number of components in the array
 * \param[out] swizzle        a swizzle describing how to get from the
 *                            given format to RGBA
 * \param[out] normalized     for integer formats, this represents whether
 *                            the format is a normalized integer or a
 *                            regular integer
 * \return  true if this format is an array format, false otherwise
 */
bool
_mesa_format_to_array(mesa_format format, GLenum *type, int *num_components,
                      uint8_t swizzle[4], bool *normalized)
{
   int i;
   GLuint format_components;
   uint8_t packed_swizzle[4];
   const uint8_t *endian;

   if (_mesa_is_format_compressed(format))
      return false;

   *normalized = !_mesa_is_format_integer(format);

   _mesa_format_to_type_and_comps(format, type, &format_components);

   switch (_mesa_get_format_layout(format)) {
   case MESA_FORMAT_LAYOUT_ARRAY:
      *num_components = format_components;
      _mesa_get_format_swizzle(format, swizzle);
      return true;
   case MESA_FORMAT_LAYOUT_PACKED:
      switch (*type) {
      case GL_UNSIGNED_BYTE:
      case GL_BYTE:
         if (_mesa_get_format_max_bits(format) != 8)
            return false;
         *num_components = _mesa_get_format_bytes(format);
         switch (*num_components) {
         case 1:
            endian = map_identity;
            break;
         case 2:
            endian = _mesa_little_endian() ? map_identity : map_1032;
            break;
         case 4:
            endian = _mesa_little_endian() ? map_identity : map_3210;
            break;
         default:
            endian = map_identity;
            assert(!"Invalid number of components");
         }
         break;
      case GL_UNSIGNED_SHORT:
      case GL_SHORT:
      case GL_HALF_FLOAT:
         if (_mesa_get_format_max_bits(format) != 16)
            return false;
         *num_components = _mesa_get_format_bytes(format) / 2;
         switch (*num_components) {
         case 1:
            endian = map_identity;
            break;
         case 2:
            endian = _mesa_little_endian() ? map_identity : map_1032;
            break;
         default:
            endian = map_identity;
            assert(!"Invalid number of components");
         }
         break;
      case GL_UNSIGNED_INT:
      case GL_INT:
      case GL_FLOAT:
         /* This isn't packed.  At least not really. */
         assert(format_components == 1);
         if (_mesa_get_format_max_bits(format) != 32)
            return false;
         *num_components = format_components;
         endian = map_identity;
         break;
      default:
         return false;
      }

      _mesa_get_format_swizzle(format, packed_swizzle);

      for (i = 0; i < 4; ++i)
         swizzle[i] = endian[packed_swizzle[i]];

      return true;
   case MESA_FORMAT_LAYOUT_OTHER:
   default:
      return false;
   }
}

/**
 * Attempts to perform the given swizzle-and-convert operation with memcpy
 *
 * This function determines if the given swizzle-and-convert operation can
 * be done with a simple memcpy and, if so, does the memcpy.  If not, it
 * returns false and we fall back to the standard version below.
 *
 * The arguments are exactly the same as for _mesa_swizzle_and_convert
 *
 * \return  true if it successfully performed the swizzle-and-convert
 *          operation with memcpy, false otherwise
 */
static bool
swizzle_convert_try_memcpy(void *dst, GLenum dst_type, int num_dst_channels,
                           const void *src, GLenum src_type, int num_src_channels,
                           const uint8_t swizzle[4], bool normalized, int count)
{
   int i;

   if (src_type != dst_type)
      return false;
   if (num_src_channels != num_dst_channels)
      return false;

   for (i = 0; i < num_dst_channels; ++i)
      if (swizzle[i] != i && swizzle[i] != MESA_FORMAT_SWIZZLE_NONE)
         return false;

   memcpy(dst, src, count * num_src_channels * _mesa_sizeof_type(src_type));

   return true;
}

/**
 * Represents a single instance of the standard swizzle-and-convert loop
 *
 * Any swizzle-and-convert operation simply loops through the pixels and
 * performs the transformation operation one pixel at a time.  This macro
 * embodies one instance of the conversion loop.  This way we can do all
 * control flow outside of the loop and allow the compiler to unroll
 * everything inside the loop.
 *
 * Note: This loop is carefully crafted for performance.  Be careful when
 * changing it and run some benchmarks to ensure no performance regressions
 * if you do.
 *
 * \param   DST_TYPE    the C datatype of the destination
 * \param   DST_CHANS   the number of destination channels
 * \param   SRC_TYPE    the C datatype of the source
 * \param   SRC_CHANS   the number of source channels
 * \param   CONV        an expression for converting from the source data,
 *                      storred in the variable "src", to the destination
 *                      format
 */
#define SWIZZLE_CONVERT_LOOP(DST_TYPE, DST_CHANS, SRC_TYPE, SRC_CHANS, CONV) \
   do {                                           \
      int s, j;                                   \
      for (s = 0; s < count; ++s) {               \
         for (j = 0; j < SRC_CHANS; ++j) {        \
            SRC_TYPE src = typed_src[j];          \
            tmp[j] = CONV;                        \
         }                                        \
                                                  \
         typed_dst[0] = tmp[swizzle_x];           \
         if (DST_CHANS > 1) {                     \
            typed_dst[1] = tmp[swizzle_y];        \
            if (DST_CHANS > 2) {                  \
               typed_dst[2] = tmp[swizzle_z];     \
               if (DST_CHANS > 3) {               \
                  typed_dst[3] = tmp[swizzle_w];  \
               }                                  \
            }                                     \
         }                                        \
         typed_src += SRC_CHANS;                  \
         typed_dst += DST_CHANS;                  \
      }                                           \
   } while (0)

/**
 * Represents a single swizzle-and-convert operation
 *
 * This macro represents everything done in a single swizzle-and-convert
 * operation.  The actual work is done by the SWIZZLE_CONVERT_LOOP macro.
 * This macro acts as a wrapper that uses a nested switch to ensure that
 * all looping parameters get unrolled.
 *
 * This macro makes assumptions about variables etc. in the calling
 * function.  Changes to _mesa_swizzle_and_convert may require changes to
 * this macro.
 *
 * \param   DST_TYPE    the C datatype of the destination
 * \param   SRC_TYPE    the C datatype of the source
 * \param   CONV        an expression for converting from the source data,
 *                      storred in the variable "src", to the destination
 *                      format
 */
#define SWIZZLE_CONVERT(DST_TYPE, SRC_TYPE, CONV)                 \
   do {                                                           \
      const uint8_t swizzle_x = swizzle[0];                       \
      const uint8_t swizzle_y = swizzle[1];                       \
      const uint8_t swizzle_z = swizzle[2];                       \
      const uint8_t swizzle_w = swizzle[3];                       \
      const SRC_TYPE *typed_src = void_src;                       \
      DST_TYPE *typed_dst = void_dst;                             \
      DST_TYPE tmp[7];                                            \
      tmp[4] = 0;                                                 \
      tmp[5] = one;                                               \
      switch (num_dst_channels) {                                 \
      case 1:                                                     \
         switch (num_src_channels) {                              \
         case 1:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 1, SRC_TYPE, 1, CONV); \
            break;                                                \
         case 2:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 1, SRC_TYPE, 2, CONV); \
            break;                                                \
         case 3:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 1, SRC_TYPE, 3, CONV); \
            break;                                                \
         case 4:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 1, SRC_TYPE, 4, CONV); \
            break;                                                \
         }                                                        \
         break;                                                   \
      case 2:                                                     \
         switch (num_src_channels) {                              \
         case 1:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 2, SRC_TYPE, 1, CONV); \
            break;                                                \
         case 2:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 2, SRC_TYPE, 2, CONV); \
            break;                                                \
         case 3:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 2, SRC_TYPE, 3, CONV); \
            break;                                                \
         case 4:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 2, SRC_TYPE, 4, CONV); \
            break;                                                \
         }                                                        \
         break;                                                   \
      case 3:                                                     \
         switch (num_src_channels) {                              \
         case 1:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 3, SRC_TYPE, 1, CONV); \
            break;                                                \
         case 2:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 3, SRC_TYPE, 2, CONV); \
            break;                                                \
         case 3:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 3, SRC_TYPE, 3, CONV); \
            break;                                                \
         case 4:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 3, SRC_TYPE, 4, CONV); \
            break;                                                \
         }                                                        \
         break;                                                   \
      case 4:                                                     \
         switch (num_src_channels) {                              \
         case 1:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 4, SRC_TYPE, 1, CONV); \
            break;                                                \
         case 2:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 4, SRC_TYPE, 2, CONV); \
            break;                                                \
         case 3:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 4, SRC_TYPE, 3, CONV); \
            break;                                                \
         case 4:                                                  \
            SWIZZLE_CONVERT_LOOP(DST_TYPE, 4, SRC_TYPE, 4, CONV); \
            break;                                                \
         }                                                        \
         break;                                                   \
      }                                                           \
   } while (0)


static void
convert_float(void *void_dst, int num_dst_channels,
              const void *void_src, GLenum src_type, int num_src_channels,
              const uint8_t swizzle[4], bool normalized, int count)
{
   const float one = 1.0f;

   switch (src_type) {
   case GL_FLOAT:
      SWIZZLE_CONVERT(float, float, src);
      break;
   case GL_HALF_FLOAT:
      SWIZZLE_CONVERT(float, uint16_t, _mesa_half_to_float(src));
      break;
   case GL_UNSIGNED_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(float, uint8_t, _mesa_unorm_to_float(src, 8));
      } else {
         SWIZZLE_CONVERT(float, uint8_t, src);
      }
      break;
   case GL_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(float, int8_t, _mesa_snorm_to_float(src, 8));
      } else {
         SWIZZLE_CONVERT(float, int8_t, src);
      }
      break;
   case GL_UNSIGNED_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(float, uint16_t, _mesa_unorm_to_float(src, 16));
      } else {
         SWIZZLE_CONVERT(float, uint16_t, src);
      }
      break;
   case GL_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(float, int16_t, _mesa_snorm_to_float(src, 16));
      } else {
         SWIZZLE_CONVERT(float, int16_t, src);
      }
      break;
   case GL_UNSIGNED_INT:
      if (normalized) {
         SWIZZLE_CONVERT(float, uint32_t, _mesa_unorm_to_float(src, 32));
      } else {
         SWIZZLE_CONVERT(float, uint32_t, src);
      }
      break;
   case GL_INT:
      if (normalized) {
         SWIZZLE_CONVERT(float, int32_t, _mesa_snorm_to_float(src, 32));
      } else {
         SWIZZLE_CONVERT(float, int32_t, src);
      }
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}


static void
convert_half_float(void *void_dst, int num_dst_channels,
                   const void *void_src, GLenum src_type, int num_src_channels,
                   const uint8_t swizzle[4], bool normalized, int count)
{
   const uint16_t one = _mesa_float_to_half(1.0f);

   switch (src_type) {
   case GL_FLOAT:
      SWIZZLE_CONVERT(uint16_t, float, _mesa_float_to_half(src));
      break;
   case GL_HALF_FLOAT:
      SWIZZLE_CONVERT(uint16_t, uint16_t, src);
      break;
   case GL_UNSIGNED_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, uint8_t, _mesa_unorm_to_half(src, 8));
      } else {
         SWIZZLE_CONVERT(uint16_t, uint8_t, _mesa_float_to_half(src));
      }
      break;
   case GL_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, int8_t, _mesa_snorm_to_half(src, 8));
      } else {
         SWIZZLE_CONVERT(uint16_t, int8_t, _mesa_float_to_half(src));
      }
      break;
   case GL_UNSIGNED_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, uint16_t, _mesa_unorm_to_half(src, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, uint16_t, _mesa_float_to_half(src));
      }
      break;
   case GL_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, int16_t, _mesa_snorm_to_half(src, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, int16_t, _mesa_float_to_half(src));
      }
      break;
   case GL_UNSIGNED_INT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, uint32_t, _mesa_unorm_to_half(src, 32));
      } else {
         SWIZZLE_CONVERT(uint16_t, uint32_t, _mesa_float_to_half(src));
      }
      break;
   case GL_INT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, int32_t, _mesa_snorm_to_half(src, 32));
      } else {
         SWIZZLE_CONVERT(uint16_t, int32_t, _mesa_float_to_half(src));
      }
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}

static void
convert_ubyte(void *void_dst, int num_dst_channels,
              const void *void_src, GLenum src_type, int num_src_channels,
              const uint8_t swizzle[4], bool normalized, int count)
{
   const uint8_t one = normalized ? UINT8_MAX : 1;

   switch (src_type) {
   case GL_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, float, _mesa_float_to_unorm(src, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, float, _mesa_float_to_unsigned(src, 8));
      }
      break;
   case GL_HALF_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, uint16_t, _mesa_half_to_unorm(src, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, uint16_t, _mesa_half_to_unsigned(src, 8));
      }
      break;
   case GL_UNSIGNED_BYTE:
      SWIZZLE_CONVERT(uint8_t, uint8_t, src);
      break;
   case GL_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, int8_t, _mesa_snorm_to_unorm(src, 8, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, int8_t, _mesa_signed_to_unsigned(src, 8));
      }
      break;
   case GL_UNSIGNED_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, uint16_t, _mesa_unorm_to_unorm(src, 16, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, uint16_t, _mesa_unsigned_to_unsigned(src, 8));
      }
      break;
   case GL_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, int16_t, _mesa_snorm_to_unorm(src, 16, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, int16_t, _mesa_signed_to_unsigned(src, 8));
      }
      break;
   case GL_UNSIGNED_INT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, uint32_t, _mesa_unorm_to_unorm(src, 32, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, uint32_t, _mesa_unsigned_to_unsigned(src, 8));
      }
      break;
   case GL_INT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, int32_t, _mesa_snorm_to_unorm(src, 32, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, int32_t, _mesa_signed_to_unsigned(src, 8));
      }
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}


static void
convert_byte(void *void_dst, int num_dst_channels,
             const void *void_src, GLenum src_type, int num_src_channels,
             const uint8_t swizzle[4], bool normalized, int count)
{
   const int8_t one = normalized ? INT8_MAX : 1;

   switch (src_type) {
   case GL_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, float, _mesa_float_to_snorm(src, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, float, _mesa_float_to_signed(src, 8));
      }
      break;
   case GL_HALF_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint8_t, uint16_t, _mesa_half_to_snorm(src, 8));
      } else {
         SWIZZLE_CONVERT(uint8_t, uint16_t, _mesa_half_to_signed(src, 8));
      }
      break;
   case GL_UNSIGNED_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(int8_t, uint8_t, _mesa_unorm_to_snorm(src, 8, 8));
      } else {
         SWIZZLE_CONVERT(int8_t, uint8_t, _mesa_unsigned_to_signed(src, 8));
      }
      break;
   case GL_BYTE:
      SWIZZLE_CONVERT(int8_t, int8_t, src);
      break;
   case GL_UNSIGNED_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(int8_t, uint16_t, _mesa_unorm_to_snorm(src, 16, 8));
      } else {
         SWIZZLE_CONVERT(int8_t, uint16_t, _mesa_unsigned_to_signed(src, 8));
      }
      break;
   case GL_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(int8_t, int16_t, _mesa_snorm_to_snorm(src, 16, 8));
      } else {
         SWIZZLE_CONVERT(int8_t, int16_t, _mesa_signed_to_signed(src, 8));
      }
      break;
   case GL_UNSIGNED_INT:
      if (normalized) {
         SWIZZLE_CONVERT(int8_t, uint32_t, _mesa_unorm_to_snorm(src, 32, 8));
      } else {
         SWIZZLE_CONVERT(int8_t, uint32_t, _mesa_unsigned_to_signed(src, 8));
      }
      break;
   case GL_INT:
      if (normalized) {
         SWIZZLE_CONVERT(int8_t, int32_t, _mesa_snorm_to_snorm(src, 32, 8));
      } else {
         SWIZZLE_CONVERT(int8_t, int32_t, _mesa_signed_to_signed(src, 8));
      }
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}


static void
convert_ushort(void *void_dst, int num_dst_channels,
               const void *void_src, GLenum src_type, int num_src_channels,
               const uint8_t swizzle[4], bool normalized, int count)
{
   const uint16_t one = normalized ? UINT16_MAX : 1;
   
   switch (src_type) {
   case GL_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, float, _mesa_float_to_unorm(src, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, float, _mesa_float_to_unsigned(src, 16));
      }
      break;
   case GL_HALF_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, uint16_t, _mesa_half_to_unorm(src, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, uint16_t, _mesa_half_to_unsigned(src, 16));
      }
      break;
   case GL_UNSIGNED_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, uint8_t, _mesa_unorm_to_unorm(src, 8, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, uint8_t, src);
      }
      break;
   case GL_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, int8_t, _mesa_snorm_to_unorm(src, 8, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, int8_t, _mesa_signed_to_unsigned(src, 16));
      }
      break;
   case GL_UNSIGNED_SHORT:
      SWIZZLE_CONVERT(uint16_t, uint16_t, src);
      break;
   case GL_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, int16_t, _mesa_snorm_to_unorm(src, 16, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, int16_t, _mesa_signed_to_unsigned(src, 16));
      }
      break;
   case GL_UNSIGNED_INT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, uint32_t, _mesa_unorm_to_unorm(src, 32, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, uint32_t, _mesa_unsigned_to_unsigned(src, 16));
      }
      break;
   case GL_INT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, int32_t, _mesa_snorm_to_unorm(src, 32, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, int32_t, _mesa_signed_to_unsigned(src, 16));
      }
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}


static void
convert_short(void *void_dst, int num_dst_channels,
              const void *void_src, GLenum src_type, int num_src_channels,
              const uint8_t swizzle[4], bool normalized, int count)
{
   const int16_t one = normalized ? INT16_MAX : 1;

   switch (src_type) {
   case GL_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, float, _mesa_float_to_snorm(src, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, float, _mesa_float_to_signed(src, 16));
      }
      break;
   case GL_HALF_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint16_t, uint16_t, _mesa_half_to_snorm(src, 16));
      } else {
         SWIZZLE_CONVERT(uint16_t, uint16_t, _mesa_half_to_signed(src, 16));
      }
      break;
   case GL_UNSIGNED_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(int16_t, uint8_t, _mesa_unorm_to_snorm(src, 8, 16));
      } else {
         SWIZZLE_CONVERT(int16_t, uint8_t, src);
      }
      break;
   case GL_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(int16_t, int8_t, _mesa_snorm_to_snorm(src, 8, 16));
      } else {
         SWIZZLE_CONVERT(int16_t, int8_t, src);
      }
      break;
   case GL_UNSIGNED_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(int16_t, uint16_t, _mesa_unorm_to_snorm(src, 16, 16));
      } else {
         SWIZZLE_CONVERT(int16_t, uint16_t, _mesa_unsigned_to_signed(src, 16));
      }
      break;
   case GL_SHORT:
      SWIZZLE_CONVERT(int16_t, int16_t, src);
      break;
   case GL_UNSIGNED_INT:
      if (normalized) {
         SWIZZLE_CONVERT(int16_t, uint32_t, _mesa_unorm_to_snorm(src, 32, 16));
      } else {
         SWIZZLE_CONVERT(int16_t, uint32_t, _mesa_unsigned_to_signed(src, 16));
      }
      break;
   case GL_INT:
      if (normalized) {
         SWIZZLE_CONVERT(int16_t, int32_t, _mesa_snorm_to_snorm(src, 32, 16));
      } else {
         SWIZZLE_CONVERT(int16_t, int32_t, _mesa_signed_to_signed(src, 16));
      }
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}

static void
convert_uint(void *void_dst, int num_dst_channels,
             const void *void_src, GLenum src_type, int num_src_channels,
             const uint8_t swizzle[4], bool normalized, int count)
{
   const uint32_t one = normalized ? UINT32_MAX : 1;

   switch (src_type) {
   case GL_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, float, _mesa_float_to_unorm(src, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, float, _mesa_float_to_unsigned(src, 32));
      }
      break;
   case GL_HALF_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, uint16_t, _mesa_half_to_unorm(src, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, uint16_t, _mesa_half_to_unsigned(src, 32));
      }
      break;
   case GL_UNSIGNED_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, uint8_t, _mesa_unorm_to_unorm(src, 8, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, uint8_t, src);
      }
      break;
   case GL_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, int8_t, _mesa_snorm_to_unorm(src, 8, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, int8_t, _mesa_signed_to_unsigned(src, 32));
      }
      break;
   case GL_UNSIGNED_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, uint16_t, _mesa_unorm_to_unorm(src, 16, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, uint16_t, src);
      }
      break;
   case GL_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, int16_t, _mesa_snorm_to_unorm(src, 16, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, int16_t, _mesa_signed_to_unsigned(src, 32));
      }
      break;
   case GL_UNSIGNED_INT:
      SWIZZLE_CONVERT(uint32_t, uint32_t, src);
      break;
   case GL_INT:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, int32_t, _mesa_snorm_to_unorm(src, 32, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, int32_t, _mesa_signed_to_unsigned(src, 32));
      }
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}


static void
convert_int(void *void_dst, int num_dst_channels,
            const void *void_src, GLenum src_type, int num_src_channels,
            const uint8_t swizzle[4], bool normalized, int count)
{
   const int32_t one = normalized ? INT32_MAX : 1;

   switch (src_type) {
   case GL_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, float, _mesa_float_to_snorm(src, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, float, _mesa_float_to_signed(src, 32));
      }
      break;
   case GL_HALF_FLOAT:
      if (normalized) {
         SWIZZLE_CONVERT(uint32_t, uint16_t, _mesa_half_to_snorm(src, 32));
      } else {
         SWIZZLE_CONVERT(uint32_t, uint16_t, _mesa_half_to_signed(src, 32));
      }
      break;
   case GL_UNSIGNED_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(int32_t, uint8_t, _mesa_unorm_to_snorm(src, 8, 32));
      } else {
         SWIZZLE_CONVERT(int32_t, uint8_t, src);
      }
      break;
   case GL_BYTE:
      if (normalized) {
         SWIZZLE_CONVERT(int32_t, int8_t, _mesa_snorm_to_snorm(src, 8, 32));
      } else {
         SWIZZLE_CONVERT(int32_t, int8_t, src);
      }
      break;
   case GL_UNSIGNED_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(int32_t, uint16_t, _mesa_unorm_to_snorm(src, 16, 32));
      } else {
         SWIZZLE_CONVERT(int32_t, uint16_t, src);
      }
      break;
   case GL_SHORT:
      if (normalized) {
         SWIZZLE_CONVERT(int32_t, int16_t, _mesa_snorm_to_snorm(src, 16, 32));
      } else {
         SWIZZLE_CONVERT(int32_t, int16_t, src);
      }
      break;
   case GL_UNSIGNED_INT:
      if (normalized) {
         SWIZZLE_CONVERT(int32_t, uint32_t, _mesa_unorm_to_snorm(src, 32, 32));
      } else {
         SWIZZLE_CONVERT(int32_t, uint32_t, _mesa_unsigned_to_signed(src, 32));
      }
      break;
   case GL_INT:
      SWIZZLE_CONVERT(int32_t, int32_t, src);
      break;
   default:
      assert(!"Invalid channel type combination");
   }
}


/**
 * Convert between array-based color formats.
 *
 * Most format conversion operations required by GL can be performed by
 * converting one channel at a time, shuffling the channels around, and
 * optionally filling missing channels with zeros and ones.  This function
 * does just that in a general, yet efficient, way.
 *
 * The swizzle parameter is an array of 4 numbers (see
 * _mesa_get_format_swizzle) that describes where each channel in the
 * destination should come from in the source.  If swizzle[i] < 4 then it
 * means that dst[i] = CONVERT(src[swizzle[i]]).  If swizzle[i] is
 * MESA_FORMAT_SWIZZLE_ZERO or MESA_FORMAT_SWIZZLE_ONE, the corresponding
 * dst[i] will be filled with the appropreate representation of zero or one
 * respectively.
 *
 * Under most circumstances, the source and destination images must be
 * different as no care is taken not to clobber one with the other.
 * However, if they have the same number of bits per pixel, it is safe to
 * do an in-place conversion.
 *
 * \param[out] dst               pointer to where the converted data should
 *                               be stored
 *
 * \param[in]  dst_type          the destination GL type of the converted
 *                               data (GL_BYTE, etc.)
 *
 * \param[in]  num_dst_channels  the number of channels in the converted
 *                               data
 *
 * \param[in]  src               pointer to the source data
 *
 * \param[in]  src_type          the GL type of the source data (GL_BYTE,
 *                               etc.)
 *
 * \param[in]  num_src_channels  the number of channels in the source data
 *                               (the number of channels total, not just
 *                               the number used)
 *
 * \param[in]  swizzle           describes how to get the destination data
 *                               from the source data.
 *
 * \param[in]  normalized        for integer types, this indicates whether
 *                               the data should be considered as integers
 *                               or as normalized integers;
 *
 * \param[in]  count             the number of pixels to convert
 */
void
_mesa_swizzle_and_convert(void *void_dst, GLenum dst_type, int num_dst_channels,
                          const void *void_src, GLenum src_type, int num_src_channels,
                          const uint8_t swizzle[4], bool normalized, int count)
{
   if (swizzle_convert_try_memcpy(void_dst, dst_type, num_dst_channels,
                                  void_src, src_type, num_src_channels,
                                  swizzle, normalized, count))
      return;

   switch (dst_type) {
   case GL_FLOAT:
      convert_float(void_dst, num_dst_channels, void_src, src_type,
                    num_src_channels, swizzle, normalized, count);
      break;
   case GL_HALF_FLOAT:
      convert_half_float(void_dst, num_dst_channels, void_src, src_type,
                    num_src_channels, swizzle, normalized, count);
      break;
   case GL_UNSIGNED_BYTE:
      convert_ubyte(void_dst, num_dst_channels, void_src, src_type,
                    num_src_channels, swizzle, normalized, count);
      break;
   case GL_BYTE:
      convert_byte(void_dst, num_dst_channels, void_src, src_type,
                   num_src_channels, swizzle, normalized, count);
      break;
   case GL_UNSIGNED_SHORT:
      convert_ushort(void_dst, num_dst_channels, void_src, src_type,
                     num_src_channels, swizzle, normalized, count);
      break;
   case GL_SHORT:
      convert_short(void_dst, num_dst_channels, void_src, src_type,
                    num_src_channels, swizzle, normalized, count);
      break;
   case GL_UNSIGNED_INT:
      convert_uint(void_dst, num_dst_channels, void_src, src_type,
                   num_src_channels, swizzle, normalized, count);
      break;
   case GL_INT:
      convert_int(void_dst, num_dst_channels, void_src, src_type,
                  num_src_channels, swizzle, normalized, count);
      break;
   default:
      assert(!"Invalid channel type");
   }
}