BitMiracle.LibJpeg.Classic.Internal.jpeg_marker_reader.examine_app0 C# (CSharp) Method

        private static void examine_app0(jpeg_decompress_struct cinfo, byte[] data, int datalen, int remaining)
        {
            int totallen = datalen + remaining;

            if (datalen >= APP0_DATA_LEN &&
                data[0] == 0x4A &&
                data[1] == 0x46 &&
                data[2] == 0x49 &&
                data[3] == 0x46 &&
                data[4] == 0)
            {
                /* Found JFIF APP0 marker: save info */
                cinfo.m_saw_JFIF_marker = true;
                cinfo.m_JFIF_major_version = data[5];
                cinfo.m_JFIF_minor_version = data[6];
                cinfo.m_density_unit = (DensityUnit)data[7];
                cinfo.m_X_density = (short)((data[8] << 8) + data[9]);
                cinfo.m_Y_density = (short)((data[10] << 8) + data[11]);

                /* Check version.
                 * Major version must be 1 or 2, anything else signals an incompatible change.
                 * (We used to treat this as an error, but now it's a nonfatal warning,
                 * because some bozo at Hijaak couldn't read the spec.)
                 * Minor version should be 0..2, but process anyway if newer.
                 */
                if (cinfo.m_JFIF_major_version != 1 && cinfo.m_JFIF_major_version != 2)
                    cinfo.WARNMS(J_MESSAGE_CODE.JWRN_JFIF_MAJOR, cinfo.m_JFIF_major_version, cinfo.m_JFIF_minor_version);

                /* Generate trace messages */
                cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_JFIF, cinfo.m_JFIF_major_version, cinfo.m_JFIF_minor_version, cinfo.m_X_density,
                                cinfo.m_Y_density, cinfo.m_density_unit);

                /* Validate thumbnail dimensions and issue appropriate messages */
                if ((data[12] | data[13]) != 0)
                    cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_JFIF_THUMBNAIL, data[12], data[13]);

                totallen -= APP0_DATA_LEN;
                if (totallen != ((int)data[12] * (int)data[13] * 3))
                    cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_JFIF_BADTHUMBNAILSIZE, totallen);
            }
            else if (datalen >= 6 && data[0] == 0x4A && data[1] == 0x46 && data[2] == 0x58 && data[3] == 0x58 && data[4] == 0)
            {
                /* Found JFIF "JFXX" extension APP0 marker */
                /* The library doesn't actually do anything with these,
                 * but we try to produce a helpful trace message.
                 */
                switch (data[5])
                {
                    case 0x10:
                        cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_THUMB_JPEG, totallen);
                        break;
                    case 0x11:
                        cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_THUMB_PALETTE, totallen);
                        break;
                    case 0x13:
                        cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_THUMB_RGB, totallen);
                        break;
                    default:
                        cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_JFIF_EXTENSION, data[5], totallen);
                        break;
                }
            }
            else
            {
                /* Start of APP0 does not match "JFIF" or "JFXX", or too short */
                cinfo.TRACEMS(1, J_MESSAGE_CODE.JTRC_APP0, totallen);
            }
        }