/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    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 2.1 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, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

/* General (mostly internal) pixel/color manipulation routines for SDL */

#include "SDL_endian.h"
#include "SDL_video.h"
#include "SDL_sysvideo.h"
#include "SDL_blit.h"
#include "SDL_pixels_c.h"
#include "SDL_RLEaccel_c.h"

/* Helper functions */

SDL_bool
SDL_PixelFormatEnumToMasks (Uint32 format, int *bpp, Uint32 * Rmask,
                            Uint32 * Gmask, Uint32 * Bmask, Uint32 * Amask)
{
    Uint32 masks[4];

    /* Initialize the values here */
    if (SDL_BITSPERPIXEL (format) == 24) {
        *bpp = SDL_BYTESPERPIXEL (format) * 8;
    } else {
        *bpp = SDL_BITSPERPIXEL (format);
    }
    *Rmask = *Gmask = *Bmask = *Amask = 0;

    if (SDL_PIXELTYPE (format) != SDL_PixelType_Packed8 &&
        SDL_PIXELTYPE (format) != SDL_PixelType_Packed16 &&
        SDL_PIXELTYPE (format) != SDL_PixelType_Packed32) {
        /* Not a format that uses masks */
        return SDL_TRUE;
    }

    switch (SDL_PIXELLAYOUT (format)) {
    case SDL_PackedLayout_332:
        masks[0] = 0x00000000;
        masks[1] = 0x000000E0;
        masks[2] = 0x0000001C;
        masks[3] = 0x00000003;
        break;
    case SDL_PackedLayout_4444:
        masks[0] = 0x0000F000;
        masks[1] = 0x00000F00;
        masks[2] = 0x000000F0;
        masks[3] = 0x0000000F;
        break;
    case SDL_PackedLayout_1555:
        masks[0] = 0x00008000;
        masks[1] = 0x00007C00;
        masks[2] = 0x000003E0;
        masks[3] = 0x0000001F;
        break;
    case SDL_PackedLayout_565:
        masks[0] = 0x00000000;
        masks[1] = 0x0000F800;
        masks[2] = 0x000007E0;
        masks[3] = 0x0000001F;
        break;
    case SDL_PackedLayout_8888:
        masks[0] = 0xFF000000;
        masks[1] = 0x00FF0000;
        masks[2] = 0x0000FF00;
        masks[3] = 0x000000FF;
        break;
    case SDL_PackedLayout_2101010:
        masks[0] = 0xC0000000;
        masks[1] = 0x3FF00000;
        masks[2] = 0x000FFC00;
        masks[3] = 0x000003FF;
        break;
    default:
        /* Unknown layout */
        return SDL_FALSE;
    }

    switch (SDL_PIXELORDER (format)) {
    case SDL_PackedOrder_XRGB:
        *Rmask = masks[1];
        *Gmask = masks[2];
        *Bmask = masks[3];
        break;
    case SDL_PackedOrder_RGBX:
        *Rmask = masks[0];
        *Gmask = masks[1];
        *Bmask = masks[2];
        break;
    case SDL_PackedOrder_ARGB:
        *Amask = masks[0];
        *Rmask = masks[1];
        *Gmask = masks[2];
        *Bmask = masks[3];
        break;
    case SDL_PackedOrder_RGBA:
        *Rmask = masks[0];
        *Gmask = masks[1];
        *Bmask = masks[2];
        *Amask = masks[3];
        break;
    case SDL_PackedOrder_XBGR:
        *Bmask = masks[1];
        *Gmask = masks[2];
        *Rmask = masks[3];
        break;
    case SDL_PackedOrder_BGRX:
        *Bmask = masks[0];
        *Gmask = masks[1];
        *Rmask = masks[2];
        break;
    case SDL_PackedOrder_BGRA:
        *Bmask = masks[0];
        *Gmask = masks[1];
        *Rmask = masks[2];
        *Amask = masks[3];
        break;
    case SDL_PackedOrder_ABGR:
        *Amask = masks[0];
        *Bmask = masks[1];
        *Gmask = masks[2];
        *Rmask = masks[3];
        break;
    default:
        /* Unknown order */
        return SDL_FALSE;
    }
    return SDL_TRUE;
}

Uint32
SDL_MasksToPixelFormatEnum (int bpp, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask,
                            Uint32 Amask)
{
    switch (bpp) {
    case 8:
        switch (Rmask) {
        case 0:
            return SDL_PixelFormat_Index8;
        case 0xE0:
            return SDL_PixelFormat_RGB332;
        }
        break;
    case 12:
        switch (Rmask) {
        case 0x0F00:
            return SDL_PixelFormat_RGB444;
        }
        break;
    case 15:
        switch (Rmask) {
        case 0x7C00:
            return SDL_PixelFormat_RGB555;
        }
        break;
    case 16:
        switch (Rmask) {
        case 0x0F00:
            return SDL_PixelFormat_ARGB4444;
        case 0x7C00:
            return SDL_PixelFormat_ARGB1555;
        case 0xF800:
            return SDL_PixelFormat_RGB565;
        }
        break;
    case 32:
        switch (Rmask) {
        case 0xFF000000:
            if (Amask == 0x000000FF) {
                return SDL_PixelFormat_RGBA8888;
            }
            break;
        case 0x00FF0000:
            if (Amask == 0xFF000000) {
                return SDL_PixelFormat_ARGB8888;
            } else {
                return SDL_PixelFormat_RGB888;
            }
            break;
        case 0x0000FF00:
            if (Amask == 0x000000FF) {
                return SDL_PixelFormat_BGRA8888;
            }
            break;
        case 0x000000FF:
            if (Amask == 0xFF000000) {
                return SDL_PixelFormat_ABGR8888;
            } else {
                return SDL_PixelFormat_BGR888;
            }
            break;
        case 0x3FF00000:
            return SDL_PixelFormat_ARGB2101010;
        }
    }
    return SDL_PixelFormat_Unknown;
}

/*
 * Allocate a pixel format structure and fill it according to the given info.
 */
SDL_PixelFormat *
SDL_AllocFormat (int bpp,
                 Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
{
    SDL_PixelFormat *format;
    Uint32 mask;

    /* Allocate an empty pixel format structure */
    format = SDL_malloc (sizeof (*format));
    if (format == NULL) {
        SDL_OutOfMemory ();
        return (NULL);
    }
    SDL_memset (format, 0, sizeof (*format));
    format->alpha = SDL_ALPHA_OPAQUE;

    /* Set up the format */
    format->BitsPerPixel = bpp;
    format->BytesPerPixel = (bpp + 7) / 8;
    if (Rmask || Bmask || Gmask) {      /* Packed pixels with custom mask */
        format->palette = NULL;
        format->Rshift = 0;
        format->Rloss = 8;
        if (Rmask) {
            for (mask = Rmask; !(mask & 0x01); mask >>= 1)
                ++format->Rshift;
            for (; (mask & 0x01); mask >>= 1)
                --format->Rloss;
        }
        format->Gshift = 0;
        format->Gloss = 8;
        if (Gmask) {
            for (mask = Gmask; !(mask & 0x01); mask >>= 1)
                ++format->Gshift;
            for (; (mask & 0x01); mask >>= 1)
                --format->Gloss;
        }
        format->Bshift = 0;
        format->Bloss = 8;
        if (Bmask) {
            for (mask = Bmask; !(mask & 0x01); mask >>= 1)
                ++format->Bshift;
            for (; (mask & 0x01); mask >>= 1)
                --format->Bloss;
        }
        format->Ashift = 0;
        format->Aloss = 8;
        if (Amask) {
            for (mask = Amask; !(mask & 0x01); mask >>= 1)
                ++format->Ashift;
            for (; (mask & 0x01); mask >>= 1)
                --format->Aloss;
        }
        format->Rmask = Rmask;
        format->Gmask = Gmask;
        format->Bmask = Bmask;
        format->Amask = Amask;
    } else if (bpp > 8) {       /* Packed pixels with standard mask */
        /* R-G-B */
        if (bpp > 24)
            bpp = 24;
        format->Rloss = 8 - (bpp / 3);
        format->Gloss = 8 - (bpp / 3) - (bpp % 3);
        format->Bloss = 8 - (bpp / 3);
        format->Rshift = ((bpp / 3) + (bpp % 3)) + (bpp / 3);
        format->Gshift = (bpp / 3);
        format->Bshift = 0;
        format->Rmask = ((0xFF >> format->Rloss) << format->Rshift);
        format->Gmask = ((0xFF >> format->Gloss) << format->Gshift);
        format->Bmask = ((0xFF >> format->Bloss) << format->Bshift);
    } else {
        /* Palettized formats have no mask info */
        format->Rloss = 8;
        format->Gloss = 8;
        format->Bloss = 8;
        format->Aloss = 8;
        format->Rshift = 0;
        format->Gshift = 0;
        format->Bshift = 0;
        format->Ashift = 0;
        format->Rmask = 0;
        format->Gmask = 0;
        format->Bmask = 0;
        format->Amask = 0;
    }
    if (bpp <= 8) {             /* Palettized mode */
        int ncolors = 1 << bpp;
#ifdef DEBUG_PALETTE
        fprintf (stderr, "bpp=%d ncolors=%d\n", bpp, ncolors);
#endif
        format->palette = (SDL_Palette *) SDL_malloc (sizeof (SDL_Palette));
        if (format->palette == NULL) {
            SDL_FreeFormat (format);
            SDL_OutOfMemory ();
            return (NULL);
        }
        (format->palette)->ncolors = ncolors;
        (format->palette)->colors = (SDL_Color *) SDL_malloc ((format->
                                                               palette)->
                                                              ncolors *
                                                              sizeof
                                                              (SDL_Color));
        if ((format->palette)->colors == NULL) {
            SDL_FreeFormat (format);
            SDL_OutOfMemory ();
            return (NULL);
        }
        if (Rmask || Bmask || Gmask) {
            /* create palette according to masks */
            int i;
            int Rm = 0, Gm = 0, Bm = 0;
            int Rw = 0, Gw = 0, Bw = 0;
#ifdef ENABLE_PALETTE_ALPHA
            int Am = 0, Aw = 0;
#endif
            if (Rmask) {
                Rw = 8 - format->Rloss;
                for (i = format->Rloss; i > 0; i -= Rw)
                    Rm |= 1 << i;
            }
#ifdef DEBUG_PALETTE
            fprintf (stderr, "Rw=%d Rm=0x%02X\n", Rw, Rm);
#endif
            if (Gmask) {
                Gw = 8 - format->Gloss;
                for (i = format->Gloss; i > 0; i -= Gw)
                    Gm |= 1 << i;
            }
#ifdef DEBUG_PALETTE
            fprintf (stderr, "Gw=%d Gm=0x%02X\n", Gw, Gm);
#endif
            if (Bmask) {
                Bw = 8 - format->Bloss;
                for (i = format->Bloss; i > 0; i -= Bw)
                    Bm |= 1 << i;
            }
#ifdef DEBUG_PALETTE
            fprintf (stderr, "Bw=%d Bm=0x%02X\n", Bw, Bm);
#endif
#ifdef ENABLE_PALETTE_ALPHA
            if (Amask) {
                Aw = 8 - format->Aloss;
                for (i = format->Aloss; i > 0; i -= Aw)
                    Am |= 1 << i;
            }
# ifdef DEBUG_PALETTE
            fprintf (stderr, "Aw=%d Am=0x%02X\n", Aw, Am);
# endif
#endif
            for (i = 0; i < ncolors; ++i) {
                int r, g, b;
                r = (i & Rmask) >> format->Rshift;
                r = (r << format->Rloss) | ((r * Rm) >> Rw);
                format->palette->colors[i].r = r;

                g = (i & Gmask) >> format->Gshift;
                g = (g << format->Gloss) | ((g * Gm) >> Gw);
                format->palette->colors[i].g = g;

                b = (i & Bmask) >> format->Bshift;
                b = (b << format->Bloss) | ((b * Bm) >> Bw);
                format->palette->colors[i].b = b;

#ifdef ENABLE_PALETTE_ALPHA
                a = (i & Amask) >> format->Ashift;
                a = (a << format->Aloss) | ((a * Am) >> Aw);
                format->palette->colors[i].unused = a;
#else
                format->palette->colors[i].unused = 0;
#endif
            }
        } else if (ncolors == 2) {
            /* Create a black and white bitmap palette */
            format->palette->colors[0].r = 0xFF;
            format->palette->colors[0].g = 0xFF;
            format->palette->colors[0].b = 0xFF;
            format->palette->colors[1].r = 0x00;
            format->palette->colors[1].g = 0x00;
            format->palette->colors[1].b = 0x00;
        } else {
            /* Create an empty palette */
            SDL_memset ((format->palette)->colors, 0,
                        (format->palette)->ncolors * sizeof (SDL_Color));
        }
    }
    return (format);
}

SDL_PixelFormat *
SDL_ReallocFormat (SDL_Surface * surface, int bpp,
                   Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
{
    if (surface->format) {
        SDL_FreeFormat (surface->format);
        SDL_FormatChanged (surface);
    }
    surface->format = SDL_AllocFormat (bpp, Rmask, Gmask, Bmask, Amask);
    return surface->format;
}

/*
 * Change any previous mappings from/to the new surface format
 */
void
SDL_FormatChanged (SDL_Surface * surface)
{
    static int format_version = 0;
    ++format_version;
    if (format_version < 0) {   /* It wrapped... */
        format_version = 1;
    }
    surface->format_version = format_version;
    SDL_InvalidateMap (surface->map);
}

/*
 * Free a previously allocated format structure
 */
void
SDL_FreeFormat (SDL_PixelFormat * format)
{
    if (format) {
        if (format->palette) {
            if (format->palette->colors) {
                SDL_free (format->palette->colors);
            }
            SDL_free (format->palette);
        }
        SDL_free (format);
    }
}

/*
 * Calculate an 8-bit (3 red, 3 green, 2 blue) dithered palette of colors
 */
void
SDL_DitherColors (SDL_Color * colors, int bpp)
{
    int i;
    if (bpp != 8)
        return;                 /* only 8bpp supported right now */

    for (i = 0; i < 256; i++) {
        int r, g, b;
        /* map each bit field to the full [0, 255] interval,
           so 0 is mapped to (0, 0, 0) and 255 to (255, 255, 255) */
        r = i & 0xe0;
        r |= r >> 3 | r >> 6;
        colors[i].r = r;
        g = (i << 3) & 0xe0;
        g |= g >> 3 | g >> 6;
        colors[i].g = g;
        b = i & 0x3;
        b |= b << 2;
        b |= b << 4;
        colors[i].b = b;
    }
}

/* 
 * Calculate the pad-aligned scanline width of a surface
 */
Uint16
SDL_CalculatePitch (SDL_Surface * surface)
{
    Uint16 pitch;

    /* Surface should be 4-byte aligned for speed */
    pitch = surface->w * surface->format->BytesPerPixel;
    switch (surface->format->BitsPerPixel) {
    case 1:
        pitch = (pitch + 7) / 8;
        break;
    case 4:
        pitch = (pitch + 1) / 2;
        break;
    default:
        break;
    }
    pitch = (pitch + 3) & ~3;   /* 4-byte aligning */
    return (pitch);
}

/*
 * Match an RGB value to a particular palette index
 */
Uint8
SDL_FindColor (SDL_Palette * pal, Uint8 r, Uint8 g, Uint8 b)
{
    /* Do colorspace distance matching */
    unsigned int smallest;
    unsigned int distance;
    int rd, gd, bd;
    int i;
    Uint8 pixel = 0;

    smallest = ~0;
    for (i = 0; i < pal->ncolors; ++i) {
        rd = pal->colors[i].r - r;
        gd = pal->colors[i].g - g;
        bd = pal->colors[i].b - b;
        distance = (rd * rd) + (gd * gd) + (bd * bd);
        if (distance < smallest) {
            pixel = i;
            if (distance == 0) {        /* Perfect match! */
                break;
            }
            smallest = distance;
        }
    }
    return (pixel);
}

/* Find the opaque pixel value corresponding to an RGB triple */
Uint32
SDL_MapRGB (SDL_PixelFormat * format, Uint8 r, Uint8 g, Uint8 b)
{
    if (format->palette == NULL) {
        return (r >> format->Rloss) << format->Rshift
            | (g >> format->Gloss) << format->Gshift
            | (b >> format->Bloss) << format->Bshift | format->Amask;
    } else {
        return SDL_FindColor (format->palette, r, g, b);
    }
}

/* Find the pixel value corresponding to an RGBA quadruple */
Uint32
SDL_MapRGBA (SDL_PixelFormat * format, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    if (format->palette == NULL) {
        return (r >> format->Rloss) << format->Rshift
            | (g >> format->Gloss) << format->Gshift
            | (b >> format->Bloss) << format->Bshift
            | ((a >> format->Aloss) << format->Ashift & format->Amask);
    } else {
        return SDL_FindColor (format->palette, r, g, b);
    }
}

void
SDL_GetRGBA (Uint32 pixel, SDL_PixelFormat * fmt,
             Uint8 * r, Uint8 * g, Uint8 * b, Uint8 * a)
{
    if (fmt->palette == NULL) {
        /*
         * This makes sure that the result is mapped to the
         * interval [0..255], and the maximum value for each
         * component is 255. This is important to make sure
         * that white is indeed reported as (255, 255, 255),
         * and that opaque alpha is 255.
         * This only works for RGB bit fields at least 4 bit
         * wide, which is almost always the case.
         */
        unsigned v;
        v = (pixel & fmt->Rmask) >> fmt->Rshift;
        *r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
        v = (pixel & fmt->Gmask) >> fmt->Gshift;
        *g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
        v = (pixel & fmt->Bmask) >> fmt->Bshift;
        *b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
        if (fmt->Amask) {
            v = (pixel & fmt->Amask) >> fmt->Ashift;
            *a = (v << fmt->Aloss) + (v >> (8 - (fmt->Aloss << 1)));
        } else {
            *a = SDL_ALPHA_OPAQUE;
        }
    } else {
        *r = fmt->palette->colors[pixel].r;
        *g = fmt->palette->colors[pixel].g;
        *b = fmt->palette->colors[pixel].b;
        *a = SDL_ALPHA_OPAQUE;
    }
}

void
SDL_GetRGB (Uint32 pixel, SDL_PixelFormat * fmt, Uint8 * r, Uint8 * g,
            Uint8 * b)
{
    if (fmt->palette == NULL) {
        /* the note for SDL_GetRGBA above applies here too */
        unsigned v;
        v = (pixel & fmt->Rmask) >> fmt->Rshift;
        *r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
        v = (pixel & fmt->Gmask) >> fmt->Gshift;
        *g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
        v = (pixel & fmt->Bmask) >> fmt->Bshift;
        *b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
    } else {
        *r = fmt->palette->colors[pixel].r;
        *g = fmt->palette->colors[pixel].g;
        *b = fmt->palette->colors[pixel].b;
    }
}

/* Apply gamma to a set of colors - this is easy. :) */
void
SDL_ApplyGamma (Uint16 * gamma, SDL_Color * colors, SDL_Color * output,
                int ncolors)
{
    int i;

    for (i = 0; i < ncolors; ++i) {
        output[i].r = gamma[0 * 256 + colors[i].r] >> 8;
        output[i].g = gamma[1 * 256 + colors[i].g] >> 8;
        output[i].b = gamma[2 * 256 + colors[i].b] >> 8;
    }
}

/* Map from Palette to Palette */
static Uint8 *
Map1to1 (SDL_Palette * src, SDL_Palette * dst, int *identical)
{
    Uint8 *map;
    int i;

    if (identical) {
        if (src->ncolors <= dst->ncolors) {
            /* If an identical palette, no need to map */
            if (SDL_memcmp (src->colors, dst->colors, src->ncolors *
                            sizeof (SDL_Color)) == 0) {
                *identical = 1;
                return (NULL);
            }
        }
        *identical = 0;
    }
    map = (Uint8 *) SDL_malloc (src->ncolors);
    if (map == NULL) {
        SDL_OutOfMemory ();
        return (NULL);
    }
    for (i = 0; i < src->ncolors; ++i) {
        map[i] = SDL_FindColor (dst,
                                src->colors[i].r, src->colors[i].g,
                                src->colors[i].b);
    }
    return (map);
}

/* Map from Palette to BitField */
static Uint8 *
Map1toN (SDL_PixelFormat * src, SDL_PixelFormat * dst)
{
    Uint8 *map;
    int i;
    int bpp;
    unsigned alpha;
    SDL_Palette *pal = src->palette;

    bpp = ((dst->BytesPerPixel == 3) ? 4 : dst->BytesPerPixel);
    map = (Uint8 *) SDL_malloc (pal->ncolors * bpp);
    if (map == NULL) {
        SDL_OutOfMemory ();
        return (NULL);
    }

    alpha = dst->Amask ? src->alpha : 0;
    /* We memory copy to the pixel map so the endianness is preserved */
    for (i = 0; i < pal->ncolors; ++i) {
        ASSEMBLE_RGBA (&map[i * bpp], dst->BytesPerPixel, dst,
                       pal->colors[i].r, pal->colors[i].g,
                       pal->colors[i].b, alpha);
    }
    return (map);
}

/* Map from BitField to Dithered-Palette to Palette */
static Uint8 *
MapNto1 (SDL_PixelFormat * src, SDL_PixelFormat * dst, int *identical)
{
    /* Generate a 256 color dither palette */
    SDL_Palette dithered;
    SDL_Color colors[256];
    SDL_Palette *pal = dst->palette;

    /* SDL_DitherColors does not initialize the 'unused' component of colors,
       but Map1to1 compares it against pal, so we should initialize it. */
    SDL_memset (colors, 0, sizeof (colors));

    dithered.ncolors = 256;
    SDL_DitherColors (colors, 8);
    dithered.colors = colors;
    return (Map1to1 (&dithered, pal, identical));
}

SDL_BlitMap *
SDL_AllocBlitMap (void)
{
    SDL_BlitMap *map;

    /* Allocate the empty map */
    map = (SDL_BlitMap *) SDL_malloc (sizeof (*map));
    if (map == NULL) {
        SDL_OutOfMemory ();
        return (NULL);
    }
    SDL_memset (map, 0, sizeof (*map));

    /* Allocate the software blit data */
    map->sw_data =
        (struct private_swaccel *) SDL_malloc (sizeof (*map->sw_data));
    if (map->sw_data == NULL) {
        SDL_FreeBlitMap (map);
        SDL_OutOfMemory ();
        return (NULL);
    }
    SDL_memset (map->sw_data, 0, sizeof (*map->sw_data));

    /* It's ready to go */
    return (map);
}

void
SDL_InvalidateMap (SDL_BlitMap * map)
{
    if (!map) {
        return;
    }
    map->dst = NULL;
    map->format_version = (unsigned int) -1;
    if (map->table) {
        SDL_free (map->table);
        map->table = NULL;
    }
}
int
SDL_MapSurface (SDL_Surface * src, SDL_Surface * dst)
{
    SDL_PixelFormat *srcfmt;
    SDL_PixelFormat *dstfmt;
    SDL_BlitMap *map;

    /* Clear out any previous mapping */
    map = src->map;
    if ((src->flags & SDL_RLEACCEL) == SDL_RLEACCEL) {
        SDL_UnRLESurface (src, 1);
    }
    SDL_InvalidateMap (map);

    /* Figure out what kind of mapping we're doing */
    map->identity = 0;
    srcfmt = src->format;
    dstfmt = dst->format;
    switch (srcfmt->BytesPerPixel) {
    case 1:
        switch (dstfmt->BytesPerPixel) {
        case 1:
            /* Palette --> Palette */
            /* If both SDL_HWSURFACE, assume have same palette */
            if (((src->flags & SDL_HWSURFACE) == SDL_HWSURFACE) &&
                ((dst->flags & SDL_HWSURFACE) == SDL_HWSURFACE)) {
                map->identity = 1;
            } else {
                map->table = Map1to1 (srcfmt->palette,
                                      dstfmt->palette, &map->identity);
            }
            if (!map->identity) {
                if (map->table == NULL) {
                    return (-1);
                }
            }
            if (srcfmt->BitsPerPixel != dstfmt->BitsPerPixel)
                map->identity = 0;
            break;

        default:
            /* Palette --> BitField */
            map->table = Map1toN (srcfmt, dstfmt);
            if (map->table == NULL) {
                return (-1);
            }
            break;
        }
        break;
    default:
        switch (dstfmt->BytesPerPixel) {
        case 1:
            /* BitField --> Palette */
            map->table = MapNto1 (srcfmt, dstfmt, &map->identity);
            if (!map->identity) {
                if (map->table == NULL) {
                    return (-1);
                }
            }
            map->identity = 0;  /* Don't optimize to copy */
            break;
        default:
            /* BitField --> BitField */
            if (FORMAT_EQUAL (srcfmt, dstfmt))
                map->identity = 1;
            break;
        }
        break;
    }

    map->dst = dst;
    map->format_version = dst->format_version;

    /* Choose your blitters wisely */
    return (SDL_CalculateBlit (src));
}

void
SDL_FreeBlitMap (SDL_BlitMap * map)
{
    if (map) {
        SDL_InvalidateMap (map);
        if (map->sw_data != NULL) {
            SDL_free (map->sw_data);
        }
        SDL_free (map);
    }
}

/* vi: set ts=4 sw=4 expandtab: */