c# - 这行 C 代码在 C# 中相当于什么？

Question

我需要在 C# 上重写一些 C 函数，我已经取得了一些进展，但遇到了一些我不明白的事情。通常我会问“这是什么？”，但在这种情况下我必须问“这到底是什么？!”

我在我不明白的行上方添加了注释。

static enumError conv_from_CMPR
(
    Image_t     * dest_img, // valid destination
    const Image_t   * src_img,  // valid source
    image_format_t  iform       // new image format, only valid IMG_X_*
)
{
    DASSERT(dest_img);
    DASSERT(src_img);
    DASSERT( src_img->iform == IMG_CMPR );
    DASSERT( iform >= IMG_X__MIN && iform <= IMG_X__MAX );

    const uint bits_per_pixel   = 4;
    const uint block_width  = 8;
    const uint block_height = 8;

    uint h_blocks, v_blocks, img_size;
    enumError err = CalcImageBlock(src_img,
                bits_per_pixel, block_width, block_height,
                &h_blocks, &v_blocks, &img_size, false );
    if (err)
    return err;

    //This is the line that I don't know how to convert to C#.
    //Ok, u16 is looks like a numeric type, but what happens next I don't have any idea. I don't see where is variable name.
    u16 (*rd16) ( const void * data_ptr ) = src_img->endian->rd16;

    uint data_size;
    u8 * data = AllocDataIMG(src_img,4,&data_size);
    u8 * dest1 = data;
    const u8 *src = src_img->data;

    const uint block_size = block_width * 4;
    const uint line_size  = EXPAND8(src_img->width) * 4;
    const uint delta[] = { 0, 16, 4*line_size, 4*line_size+16 };

    while ( v_blocks-- > 0 )
    {
    u8 * dest2 = dest1;
    uint hblk = h_blocks;
    while ( hblk-- > 0 )
    {
        uint subb;
        for ( subb = 0; subb < 4; subb++ )
        {
        u8 palette[4][4], *pal = palette[0];

        const u16 val1 = rd16(src);
        src += 2;
        *pal++ = cc58[ val1 >> 11 & 0x1f ];
        *pal++ = cc68[ val1 >>  5 & 0x3f ];
        *pal++ = cc58[ val1       & 0x1f ];
        *pal++ = 0xff;

        const u16 val2 = rd16(src);
        src += 2;
        *pal++ = cc58[ val2 >> 11 & 0x1f ];
        *pal++ = cc68[ val2 >>  5 & 0x3f ];
        *pal++ = cc58[ val2       & 0x1f ];
        *pal++ = 0xff;

        if ( val1 > val2 )
        {
            *pal++ = ( 2 * palette[0][0] + palette[1][0] ) / 3;
            *pal++ = ( 2 * palette[0][1] + palette[1][1] ) / 3;
            *pal++ = ( 2 * palette[0][2] + palette[1][2] ) / 3;
            *pal++ = 0xff;

            *pal++ = ( 2 * palette[1][0] + palette[0][0] ) / 3;
            *pal++ = ( 2 * palette[1][1] + palette[0][1] ) / 3;
            *pal++ = ( 2 * palette[1][2] + palette[0][2] ) / 3;
            *pal++ = 0xff;
        }
        else
        {
            *pal++ = ( palette[0][0] + palette[1][0] ) / 2;
            *pal++ = ( palette[0][1] + palette[1][1] ) / 2;
            *pal++ = ( palette[0][2] + palette[1][2] ) / 2;
            *pal++ = 0xff;

            *pal++ = 0;
            *pal++ = 0;
            *pal++ = 0;
            *pal++ = 0;
        }

        u8 *dest3 = dest2 + delta[subb];
        uint i;
        for ( i = 0; i < 4; i++ )
        {
            u8 val = *src++;
            memcpy(dest3+12, palette[ val & 3 ], 4); val >>= 2;
            memcpy(dest3+ 8, palette[ val & 3 ], 4); val >>= 2;
            memcpy(dest3+ 4, palette[ val & 3 ], 4); val >>= 2;
            memcpy(dest3   , palette[ val & 3 ], 4);
            dest3 += line_size;
        }
        }
        dest2 += block_size;
    }
    dest1 += line_size * block_height;
    }

    DASSERT( src == src_img->data + img_size );
    DASSERT( dest1 <= data + data_size );
    AssignDataRGB(dest_img,src_img,data);
    dest_img->alpha_status = 0;
    return ERR_OK;
}

Answer 1

您的代码行将成为 C# 中的委托(delegate) See here

如果您有大量 C 代码(作为 DLL)并且需要从 C# 使用它们，那么您可能需要考虑保留 C 并通过 tlbimp 使用 COM Interop。 See here