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Annotation of hatari/src/convert/low320x16_spec.c, revision 1.1

1.1     ! root        1: /*
        !             2:   Hatari - low320x16_spec.c
        !             3: 
        !             4:   This file is distributed under the GNU Public License, version 2 or at your
        !             5:   option any later version. Read the file gpl.txt for details.
        !             6: 
        !             7:   Screen Conversion, Low Res Spec512 to 320x16Bit
        !             8: */
        !             9: 
        !            10: static void ConvertLowRes_320x16Bit_Spec(void)
        !            11: {
        !            12:        Uint32 *edi, *ebp;
        !            13:        Uint16 *esi;
        !            14:        Uint32 eax, ebx, ecx, edx;
        !            15:        Uint32 pixelspace[5]; /* Workspace to store pixels to so can print in right order for Spec512 */
        !            16:        int y, x;
        !            17: 
        !            18:        /* on x86, unaligned access macro touches also
        !            19:         * next byte, zero it for code checkers
        !            20:         */
        !            21:        pixelspace[4] = 0;
        !            22: 
        !            23:        Spec512_StartFrame();            /* Start frame, track palettes */
        !            24: 
        !            25:        edx = 0;                         /* Clear index for loop */
        !            26: 
        !            27:        for (y = STScreenStartHorizLine; y < STScreenEndHorizLine; y++)
        !            28:        {
        !            29: 
        !            30:                Spec512_StartScanLine();        /* Build up palettes for every 4 pixels, store in 'ScanLinePalettes' */
        !            31:                edx = 0;                        /* Clear index for loop */
        !            32: 
        !            33:                /* Get screen addresses, 'edi'-ST screen, 'ebp'-Previous ST screen, 'esi'-PC screen */
        !            34:                eax = STScreenLineOffset[y] + STScreenLeftSkipBytes;  /* Offset for this line + Amount to skip on left hand side */
        !            35:                edi = (Uint32 *)((Uint8 *)pSTScreen + eax);       /* ST format screen 4-plane 16 colors */
        !            36:                ebp = (Uint32 *)((Uint8 *)pSTScreenCopy + eax);   /* Previous ST format screen */
        !            37:                esi = (Uint16 *)pPCScreenDest;                    /* PC format screen */
        !            38: 
        !            39:                x = STScreenWidthBytes >> 3;    /* Amount to draw across in 16-pixels (8 bytes) */
        !            40: 
        !            41:                do  /* x-loop */
        !            42:                {
        !            43:                        ebx = *edi;                 /* Do 16 pixels at one time */
        !            44:                        ecx = *(edi+1);
        !            45: 
        !            46: #if SDL_BYTEORDER == SDL_BIG_ENDIAN
        !            47:                        /* Convert planes to byte indices - as works in wrong order store to workspace so can read back in order! */
        !            48:                        LOW_BUILD_PIXELS_0 ;        /* Generate 'ecx' as pixels [12,13,14,15] */
        !            49:                        pixelspace[3] = ecx;
        !            50:                        LOW_BUILD_PIXELS_1 ;        /* Generate 'ecx' as pixels [4,5,6,7] */
        !            51:                        pixelspace[1] = ecx;
        !            52:                        LOW_BUILD_PIXELS_2 ;        /* Generate 'ecx' as pixels [8,9,10,11] */
        !            53:                        pixelspace[2] = ecx;
        !            54:                        LOW_BUILD_PIXELS_3 ;        /* Generate 'ecx' as pixels [0,1,2,3] */
        !            55:                        pixelspace[0] = ecx;
        !            56: #else
        !            57:                        LOW_BUILD_PIXELS_0 ;        /* Generate 'ecx' as pixels [4,5,6,7] */
        !            58:                        pixelspace[1] = ecx;
        !            59:                        LOW_BUILD_PIXELS_1 ;        /* Generate 'ecx' as pixels [12,13,14,15] */
        !            60:                        pixelspace[3] = ecx;
        !            61:                        LOW_BUILD_PIXELS_2 ;        /* Generate 'ecx' as pixels [0,1,2,3] */
        !            62:                        pixelspace[0] = ecx;
        !            63:                        LOW_BUILD_PIXELS_3 ;        /* Generate 'ecx' as pixels [8,9,10,11] */
        !            64:                        pixelspace[2] = ecx;
        !            65: #endif
        !            66:                        /* And plot, the Spec512 is offset by 1 pixel and works on 'chunks' of 4 pixels */
        !            67:                        /* So, we plot 1_4_4_4_3 to give 16 pixels, changing palette between */
        !            68:                        /* (last one is used for first of next 16-pixels) */
        !            69:                        ecx = pixelspace[0];
        !            70:                        PLOT_SPEC512_LEFT_LOW_320_16BIT(0);
        !            71:                        Spec512_UpdatePaletteSpan();
        !            72: 
        !            73:                        ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 1);
        !            74:                        PLOT_SPEC512_MID_320_16BIT(1);
        !            75:                        Spec512_UpdatePaletteSpan();
        !            76: 
        !            77:                        ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 5);
        !            78:                        PLOT_SPEC512_MID_320_16BIT(5);
        !            79:                        Spec512_UpdatePaletteSpan();
        !            80: 
        !            81:                        ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 9);
        !            82:                        PLOT_SPEC512_MID_320_16BIT(9);
        !            83:                        Spec512_UpdatePaletteSpan();
        !            84: 
        !            85:                        ecx = GET_SPEC512_OFFSET_FINAL_PIXELS(pixelspace);
        !            86:                        PLOT_SPEC512_END_LOW_320_16BIT(13);
        !            87: 
        !            88:                        esi += 16;                  /* Next PC pixels */
        !            89:                        edi += 2;                   /* Next ST pixels */
        !            90:                        ebp += 2;                   /* Next ST copy pixels */
        !            91:                }
        !            92:                while (--x);                    /* Loop on X */
        !            93: 
        !            94:                Spec512_EndScanLine();
        !            95: 
        !            96:                /* Offset to next line */
        !            97:                pPCScreenDest = (((Uint8 *)pPCScreenDest) + PCScreenBytesPerLine);
        !            98:        }
        !            99: 
        !           100:        bScreenContentsChanged = true;
        !           101: }

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