src/video/SDL_blit.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2011 Sam Lantinga <slouken@libsdl.org>

  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 "SDL_config.h"

#include "SDL_video.h"
#include "SDL_sysvideo.h"
#include "SDL_blit.h"
#include "SDL_blit_auto.h"
#include "SDL_blit_copy.h"
#include "SDL_blit_slow.h"
#include "SDL_RLEaccel_c.h"
#include "SDL_pixels_c.h"

/* The general purpose software blit routine */
static int
SDL_SoftBlit(SDL_Surface * src, SDL_Rect * srcrect,
             SDL_Surface * dst, SDL_Rect * dstrect)
{
    int okay;
    int src_locked;
    int dst_locked;

    /* Everything is okay at the beginning...  */
    okay = 1;

    /* Lock the destination if it's in hardware */
    dst_locked = 0;
    if (SDL_MUSTLOCK(dst)) {
        if (SDL_LockSurface(dst) < 0) {
            okay = 0;
        } else {
            dst_locked = 1;
        }
    }
    /* Lock the source if it's in hardware */
    src_locked = 0;
    if (SDL_MUSTLOCK(src)) {
        if (SDL_LockSurface(src) < 0) {
            okay = 0;
        } else {
            src_locked = 1;
        }
    }

    /* Set up source and destination buffer pointers, and BLIT! */
    if (okay && srcrect->w && srcrect->h) {
        SDL_BlitFunc RunBlit;
        SDL_BlitInfo *info = &src->map->info;

        /* Set up the blit information */
        info->src = (Uint8 *) src->pixels +
            (Uint16) srcrect->y * src->pitch +
            (Uint16) srcrect->x * info->src_fmt->BytesPerPixel;
        info->src_w = srcrect->w;
        info->src_h = srcrect->h;
        info->src_pitch = src->pitch;
        info->src_skip =
            info->src_pitch - info->src_w * info->src_fmt->BytesPerPixel;
        info->dst =
            (Uint8 *) dst->pixels + (Uint16) dstrect->y * dst->pitch +
            (Uint16) dstrect->x * info->dst_fmt->BytesPerPixel;
        info->dst_w = dstrect->w;
        info->dst_h = dstrect->h;
        info->dst_pitch = dst->pitch;
        info->dst_skip =
            info->dst_pitch - info->dst_w * info->dst_fmt->BytesPerPixel;
        RunBlit = (SDL_BlitFunc) src->map->data;

        /* Run the actual software blit */
        RunBlit(info);
    }

    /* We need to unlock the surfaces if they're locked */
    if (dst_locked) {
        SDL_UnlockSurface(dst);
    }
    if (src_locked) {
        SDL_UnlockSurface(src);
    }
    /* Blit is done! */
    return (okay ? 0 : -1);
}

#ifdef __MACOSX__
#include <sys/sysctl.h>

static SDL_bool
SDL_UseAltivecPrefetch()
{
    const char key[] = "hw.l3cachesize";
    u_int64_t result = 0;
    size_t typeSize = sizeof(result);

    if (sysctlbyname(key, &result, &typeSize, NULL, 0) == 0 && result > 0) {
        return SDL_TRUE;
    } else {
        return SDL_FALSE;
    }
}
#else
static SDL_bool
SDL_UseAltivecPrefetch()
{
    /* Just guess G4 */
    return SDL_TRUE;
}
#endif /* __MACOSX__ */

static SDL_BlitFunc
SDL_ChooseBlitFunc(Uint32 src_format, Uint32 dst_format, int flags,
                   SDL_BlitFuncEntry * entries)
{
    int i, flagcheck;
    static Uint32 features = 0xffffffff;

    /* Get the available CPU features */
    if (features == 0xffffffff) {
        const char *override = SDL_getenv("SDL_BLIT_CPU_FEATURES");

        features = SDL_CPU_ANY;

        /* Allow an override for testing .. */
        if (override) {
            SDL_sscanf(override, "%u", &features);
        } else {
            if (SDL_HasMMX()) {
                features |= SDL_CPU_MMX;
            }
            if (SDL_Has3DNow()) {
                features |= SDL_CPU_3DNOW;
            }
            if (SDL_HasSSE()) {
                features |= SDL_CPU_SSE;
            }
            if (SDL_HasSSE2()) {
                features |= SDL_CPU_SSE2;
            }
            if (SDL_HasAltiVec()) {
                if (SDL_UseAltivecPrefetch()) {
                    features |= SDL_CPU_ALTIVEC_PREFETCH;
                } else {
                    features |= SDL_CPU_ALTIVEC_NOPREFETCH;
                }
            }
        }
    }

    for (i = 0; entries[i].func; ++i) {
        /* Check for matching pixel formats */
        if (src_format != entries[i].src_format) {
            continue;
        }
        if (dst_format != entries[i].dst_format) {
            continue;
        }

        /* Check modulation flags */
        flagcheck =
            (flags & (SDL_COPY_MODULATE_COLOR | SDL_COPY_MODULATE_ALPHA));
        if ((flagcheck & entries[i].flags) != flagcheck) {
            continue;
        }

        /* Check blend flags */
        flagcheck =
            (flags &
             (SDL_COPY_BLEND | SDL_COPY_ADD | SDL_COPY_MOD));
        if ((flagcheck & entries[i].flags) != flagcheck) {
            continue;
        }

        /* Check colorkey flag */
        flagcheck = (flags & SDL_COPY_COLORKEY);
        if ((flagcheck & entries[i].flags) != flagcheck) {
            continue;
        }

        /* Check scaling flags */
        flagcheck = (flags & SDL_COPY_NEAREST);
        if ((flagcheck & entries[i].flags) != flagcheck) {
            continue;
        }

        /* Check CPU features */
        flagcheck = entries[i].cpu;
        if ((flagcheck & features) != flagcheck) {
            continue;
        }

        /* We found the best one! */
        return entries[i].func;
    }
    return NULL;
}

/* Figure out which of many blit routines to set up on a surface */
int
SDL_CalculateBlit(SDL_Surface * surface)
{
    SDL_BlitFunc blit = NULL;
    SDL_BlitMap *map = surface->map;
    SDL_Surface *dst = map->dst;

    /* Clean everything out to start */
    if ((surface->flags & SDL_RLEACCEL) == SDL_RLEACCEL) {
        SDL_UnRLESurface(surface, 1);
    }
    map->blit = SDL_SoftBlit;
    map->info.src_fmt = surface->format;
    map->info.src_pitch = surface->pitch;
    map->info.dst_fmt = dst->format;
    map->info.dst_pitch = dst->pitch;

    /* See if we can do RLE acceleration */
    if (map->info.flags & SDL_COPY_RLE_DESIRED) {
        if (SDL_RLESurface(surface) == 0) {
            return 0;
        }
    }

    /* Choose a standard blit function */
    if (map->identity && !(map->info.flags & ~SDL_COPY_RLE_DESIRED)) {
        blit = SDL_BlitCopy;
    } else if (surface->format->BitsPerPixel < 8) {
        blit = SDL_CalculateBlit0(surface);
    } else if (surface->format->BytesPerPixel == 1) {
        blit = SDL_CalculateBlit1(surface);
    } else if (map->info.flags & SDL_COPY_BLEND) {
        blit = SDL_CalculateBlitA(surface);
    } else {
        blit = SDL_CalculateBlitN(surface);
    }
    if (blit == NULL) {
        Uint32 src_format = surface->format->format;
        Uint32 dst_format = dst->format->format;

        blit =
            SDL_ChooseBlitFunc(src_format, dst_format, map->info.flags,
                               SDL_GeneratedBlitFuncTable);
    }
#ifndef TEST_SLOW_BLIT
    if (blit == NULL)
#endif
    {
        if (surface->format->BytesPerPixel > 1
            && dst->format->BytesPerPixel > 1) {
            blit = SDL_Blit_Slow;
        }
    }
    map->data = blit;

    /* Make sure we have a blit function */
    if (blit == NULL) {
        SDL_InvalidateMap(map);
        SDL_SetError("Blit combination not supported");
        return (-1);
    }

    return (0);
}

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