SDL_stretch.c

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/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2013 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"

/* This a stretch blit implementation based on ideas given to me by
   Tomasz Cejner - thanks! :)

   April 27, 2000 - Sam Lantinga
*/

#include "SDL_video.h"
#include "SDL_blit.h"

/* This isn't ready for general consumption yet - it should be folded
   into the general blitting mechanism.
*/

#if ((defined(_MFC_VER) && defined(_M_IX86)) || \
     defined(__WATCOMC__) || \
     (defined(__GNUC__) && defined(__i386__))) && SDL_ASSEMBLY_ROUTINES
/* There's a bug with gcc 4.4.1 and -O2 where srcp doesn't get the correct
 * value after the first scanline.  FIXME? */
/* #define USE_ASM_STRETCH */
#endif

#ifdef USE_ASM_STRETCH

#ifdef HAVE_MPROTECT
#include <sys/types.h>
#include <sys/mman.h>
#endif
#ifdef __GNUC__
#define PAGE_ALIGNED __attribute__((__aligned__(4096)))
#else
#define PAGE_ALIGNED
#endif

#if defined(_M_IX86) || defined(i386)
#define PREFIX16    0x66
#define STORE_BYTE  0xAA
#define STORE_WORD  0xAB
#define LOAD_BYTE   0xAC
#define LOAD_WORD   0xAD
#define RETURN      0xC3
#else
#error Need assembly opcodes for this architecture
#endif

static unsigned char copy_row[4096] PAGE_ALIGNED;

static int
generate_rowbytes(int src_w, int dst_w, int bpp)
{
    static struct
    {
        int bpp;
        int src_w;
        int dst_w;
        int status;
    } last;

    int i;
    int pos, inc;
    unsigned char *eip, *fence;
    unsigned char load, store;

    /* See if we need to regenerate the copy buffer */
    if ((src_w == last.src_w) && (dst_w == last.dst_w) && (bpp == last.bpp)) {
        return (last.status);
    }
    last.bpp = bpp;
    last.src_w = src_w;
    last.dst_w = dst_w;
    last.status = -1;

    switch (bpp) {
    case 1:
        load = LOAD_BYTE;
        store = STORE_BYTE;
        break;
    case 2:
    case 4:
        load = LOAD_WORD;
        store = STORE_WORD;
        break;
    default:
        return SDL_SetError("ASM stretch of %d bytes isn't supported\n", bpp);
    }
#ifdef HAVE_MPROTECT
    /* Make the code writeable */
    if (mprotect(copy_row, sizeof(copy_row), PROT_READ | PROT_WRITE) < 0) {
        return SDL_SetError("Couldn't make copy buffer writeable");
    }
#endif
    pos = 0x10000;
    inc = (src_w << 16) / dst_w;
    eip = copy_row;
    fence = copy_row + sizeof(copy_row)-2;
    for (i = 0; i < dst_w; ++i) {
        while (pos >= 0x10000L) {
            if (eip == fence) {
                return -1;
            }
            if (bpp == 2) {
                *eip++ = PREFIX16;
            }
            *eip++ = load;
            pos -= 0x10000L;
        }
        if (eip == fence) {
            return -1;
        }
        if (bpp == 2) {
            *eip++ = PREFIX16;
        }
        *eip++ = store;
        pos += inc;
    }
    *eip++ = RETURN;

#ifdef HAVE_MPROTECT
    /* Make the code executable but not writeable */
    if (mprotect(copy_row, sizeof(copy_row), PROT_READ | PROT_EXEC) < 0) {
        return SDL_SetError("Couldn't make copy buffer executable");
    }
#endif
    last.status = 0;
    return (0);
}

#endif /* USE_ASM_STRETCH */

#define DEFINE_COPY_ROW(name, type)         \
static void name(type *src, int src_w, type *dst, int dst_w)    \
{                                           \
    int i;                                  \
    int pos, inc;                           \
    type pixel = 0;                         \
                                            \
    pos = 0x10000;                          \
    inc = (src_w << 16) / dst_w;            \
    for ( i=dst_w; i>0; --i ) {             \
        while ( pos >= 0x10000L ) {         \
            pixel = *src++;                 \
            pos -= 0x10000L;                \
        }                                   \
        *dst++ = pixel;                     \
        pos += inc;                         \
    }                                       \
}
/* *INDENT-OFF* */
DEFINE_COPY_ROW(copy_row1, Uint8)
DEFINE_COPY_ROW(copy_row2, Uint16)
DEFINE_COPY_ROW(copy_row4, Uint32)
/* *INDENT-ON* */

/* The ASM code doesn't handle 24-bpp stretch blits */
static void
copy_row3(Uint8 * src, int src_w, Uint8 * dst, int dst_w)
{
    int i;
    int pos, inc;
    Uint8 pixel[3] = { 0, 0, 0 };

    pos = 0x10000;
    inc = (src_w << 16) / dst_w;
    for (i = dst_w; i > 0; --i) {
        while (pos >= 0x10000L) {
            pixel[0] = *src++;
            pixel[1] = *src++;
            pixel[2] = *src++;
            pos -= 0x10000L;
        }
        *dst++ = pixel[0];
        *dst++ = pixel[1];
        *dst++ = pixel[2];
        pos += inc;
    }
}

/* Perform a stretch blit between two surfaces of the same format.
   NOTE:  This function is not safe to call from multiple threads!
*/
int
SDL_SoftStretch(SDL_Surface * src, const SDL_Rect * srcrect,
                SDL_Surface * dst, const SDL_Rect * dstrect)
{
    int src_locked;
    int dst_locked;
    int pos, inc;
    int dst_maxrow;
    int src_row, dst_row;
    Uint8 *srcp = NULL;
    Uint8 *dstp;
    SDL_Rect full_src;
    SDL_Rect full_dst;
#ifdef USE_ASM_STRETCH
    SDL_bool use_asm = SDL_TRUE;
#ifdef __GNUC__
    int u1, u2;
#endif
#endif /* USE_ASM_STRETCH */
    const int bpp = dst->format->BytesPerPixel;

    if (src->format->format != dst->format->format) {
        return SDL_SetError("Only works with same format surfaces");
    }

    /* Verify the blit rectangles */
    if (srcrect) {
        if ((srcrect->x < 0) || (srcrect->y < 0) ||
            ((srcrect->x + srcrect->w) > src->w) ||
            ((srcrect->y + srcrect->h) > src->h)) {
            return SDL_SetError("Invalid source blit rectangle");
        }
    } else {
        full_src.x = 0;
        full_src.y = 0;
        full_src.w = src->w;
        full_src.h = src->h;
        srcrect = &full_src;
    }
    if (dstrect) {
        if ((dstrect->x < 0) || (dstrect->y < 0) ||
            ((dstrect->x + dstrect->w) > dst->w) ||
            ((dstrect->y + dstrect->h) > dst->h)) {
            return SDL_SetError("Invalid destination blit rectangle");
        }
    } else {
        full_dst.x = 0;
        full_dst.y = 0;
        full_dst.w = dst->w;
        full_dst.h = dst->h;
        dstrect = &full_dst;
    }

    /* Lock the destination if it's in hardware */
    dst_locked = 0;
    if (SDL_MUSTLOCK(dst)) {
        if (SDL_LockSurface(dst) < 0) {
            return SDL_SetError("Unable to lock destination surface");
        }
        dst_locked = 1;
    }
    /* Lock the source if it's in hardware */
    src_locked = 0;
    if (SDL_MUSTLOCK(src)) {
        if (SDL_LockSurface(src) < 0) {
            if (dst_locked) {
                SDL_UnlockSurface(dst);
            }
            return SDL_SetError("Unable to lock source surface");
        }
        src_locked = 1;
    }

    /* Set up the data... */
    pos = 0x10000;
    inc = (srcrect->h << 16) / dstrect->h;
    src_row = srcrect->y;
    dst_row = dstrect->y;

#ifdef USE_ASM_STRETCH
    /* Write the opcodes for this stretch */
    if ((bpp == 3) || (generate_rowbytes(srcrect->w, dstrect->w, bpp) < 0)) {
        use_asm = SDL_FALSE;
    }
#endif

    /* Perform the stretch blit */
    for (dst_maxrow = dst_row + dstrect->h; dst_row < dst_maxrow; ++dst_row) {
        dstp = (Uint8 *) dst->pixels + (dst_row * dst->pitch)
            + (dstrect->x * bpp);
        while (pos >= 0x10000L) {
            srcp = (Uint8 *) src->pixels + (src_row * src->pitch)
                + (srcrect->x * bpp);
            ++src_row;
            pos -= 0x10000L;
        }
#ifdef USE_ASM_STRETCH
        if (use_asm) {
#ifdef __GNUC__
            __asm__ __volatile__("call *%4":"=&D"(u1), "=&S"(u2)
                                 :"0"(dstp), "1"(srcp), "r"(copy_row)
                                 :"memory");
#elif defined(_MSC_VER) || defined(__WATCOMC__)
            /* *INDENT-OFF* */
            {
                void *code = copy_row;
                __asm {
                    push edi
                    push esi
                    mov edi, dstp
                    mov esi, srcp
                    call dword ptr code
                    pop esi
                    pop edi
                }
            }
            /* *INDENT-ON* */
#else
#error Need inline assembly for this compiler
#endif
        } else
#endif
            switch (bpp) {
            case 1:
                copy_row1(srcp, srcrect->w, dstp, dstrect->w);
                break;
            case 2:
                copy_row2((Uint16 *) srcp, srcrect->w,
                          (Uint16 *) dstp, dstrect->w);
                break;
            case 3:
                copy_row3(srcp, srcrect->w, dstp, dstrect->w);
                break;
            case 4:
                copy_row4((Uint32 *) srcp, srcrect->w,
                          (Uint32 *) dstp, dstrect->w);
                break;
            }
        pos += inc;
    }

    /* We need to unlock the surfaces if they're locked */
    if (dst_locked) {
        SDL_UnlockSurface(dst);
    }
    if (src_locked) {
        SDL_UnlockSurface(src);
    }
    return (0);
}

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