jdmarker.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "mrpt_jpeglib.h"

typedef enum { /* JPEG marker codes */
                           M_SOF0 = 0xc0,
                           M_SOF1 = 0xc1,
                           M_SOF2 = 0xc2,
                           M_SOF3 = 0xc3,

                           M_SOF5 = 0xc5,
                           M_SOF6 = 0xc6,
                           M_SOF7 = 0xc7,

                           M_JPG = 0xc8,
                           M_SOF9 = 0xc9,
                           M_SOF10 = 0xca,
                           M_SOF11 = 0xcb,

                           M_SOF13 = 0xcd,
                           M_SOF14 = 0xce,
                           M_SOF15 = 0xcf,

                           M_DHT = 0xc4,

                           M_DAC = 0xcc,

                           M_RST0 = 0xd0,
                           M_RST1 = 0xd1,
                           M_RST2 = 0xd2,
                           M_RST3 = 0xd3,
                           M_RST4 = 0xd4,
                           M_RST5 = 0xd5,
                           M_RST6 = 0xd6,
                           M_RST7 = 0xd7,

                           M_SOI = 0xd8,
                           M_EOI = 0xd9,
                           M_SOS = 0xda,
                           M_DQT = 0xdb,
                           M_DNL = 0xdc,
                           M_DRI = 0xdd,
                           M_DHP = 0xde,
                           M_EXP = 0xdf,

                           M_APP0 = 0xe0,
                           M_APP1 = 0xe1,
                           M_APP2 = 0xe2,
                           M_APP3 = 0xe3,
                           M_APP4 = 0xe4,
                           M_APP5 = 0xe5,
                           M_APP6 = 0xe6,
                           M_APP7 = 0xe7,
                           M_APP8 = 0xe8,
                           M_APP9 = 0xe9,
                           M_APP10 = 0xea,
                           M_APP11 = 0xeb,
                           M_APP12 = 0xec,
                           M_APP13 = 0xed,
                           M_APP14 = 0xee,
                           M_APP15 = 0xef,

                           M_JPG0 = 0xf0,
                           M_JPG13 = 0xfd,
                           M_COM = 0xfe,

                           M_TEM = 0x01,

                           M_ERROR = 0x100
} JPEG_MARKER;

/* Private state */

typedef struct
{
        struct jpeg_marker_reader pub; /* public fields */

        /* Application-overridable marker processing methods */
        jpeg_marker_parser_method process_COM;
        jpeg_marker_parser_method process_APPn[16];

        /* Limit on marker data length to save for each marker type */
        unsigned int length_limit_COM;
        unsigned int length_limit_APPn[16];

        /* Status of COM/APPn marker saving */
        jpeg_saved_marker_ptr cur_marker; /* nullptr if not processing a marker */
        unsigned int bytes_read; /* data bytes read so far in marker */
        /* Note: cur_marker is not linked into marker_list until it's all read. */
} my_marker_reader;

typedef my_marker_reader* my_marker_ptr;

/*
 * Macros for fetching data from the data source module.
 *
 * At all times, cinfo->src->next_input_byte and ->bytes_in_buffer reflect
 * the current restart point; we update them only when we have reached a
 * suitable place to restart if a suspension occurs.
 */

/* Declare and initialize local copies of input pointer/count */
#define INPUT_VARS(cinfo)                                     \
        struct jpeg_source_mgr* datasrc = (cinfo)->src;           \
        const JOCTET* next_input_byte = datasrc->next_input_byte; \
        size_t bytes_in_buffer = datasrc->bytes_in_buffer

/* Unload the local copies --- do this only at a restart boundary */
#define INPUT_SYNC(cinfo)                        \
        (datasrc->next_input_byte = next_input_byte, \
         datasrc->bytes_in_buffer = bytes_in_buffer)

/* Reload the local copies --- used only in MAKE_BYTE_AVAIL */
#define INPUT_RELOAD(cinfo)                      \
        (next_input_byte = datasrc->next_input_byte, \
         bytes_in_buffer = datasrc->bytes_in_buffer)

/* Internal macro for INPUT_BYTE and INPUT_2BYTES: make a byte available.
 * Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
 * but we must reload the local copies after a successful fill.
 */
#define MAKE_BYTE_AVAIL(cinfo, action)             \
        if (bytes_in_buffer == 0)                      \
        {                                              \
                if (!(*datasrc->fill_input_buffer)(cinfo)) \
                {                                          \
                        action;                                \
                }                                          \
                INPUT_RELOAD(cinfo);                       \
        }

/* Read a byte into variable V.
 * If must suspend, take the specified action (typically "return FALSE").
 */
#define INPUT_BYTE(cinfo, V, action)                       \
        MAKESTMT(                                              \
                MAKE_BYTE_AVAIL(cinfo, action); bytes_in_buffer--; \
                V = GETJOCTET(*next_input_byte++);)

/* As above, but read two bytes interpreted as an unsigned 16-bit integer.
 * V should be declared unsigned int or perhaps INT32.
 */
#define INPUT_2BYTES(cinfo, V, action)                          \
        MAKESTMT(                                                   \
                MAKE_BYTE_AVAIL(cinfo, action); bytes_in_buffer--;      \
                V = ((unsigned int)GETJOCTET(*next_input_byte++)) << 8; \
                MAKE_BYTE_AVAIL(cinfo, action); bytes_in_buffer--;      \
                V += GETJOCTET(*next_input_byte++);)

/*
 * Routines to process JPEG markers.
 *
 * Entry condition: JPEG marker itself has been read and its code saved
 *   in cinfo->unread_marker; input restart point is just after the marker.
 *
 * Exit: if return TRUE, have read and processed any parameters, and have
 *   updated the restart point to point after the parameters.
 *   If return FALSE, was forced to suspend before reaching end of
 *   marker parameters; restart point has not been moved.  Same routine
 *   will be called again after application supplies more input data.
 *
 * This approach to suspension assumes that all of a marker's parameters
 * can fit into a single input bufferload.  This should hold for "normal"
 * markers.  Some COM/APPn markers might have large parameter segments
 * that might not fit.  If we are simply dropping such a marker, we use
 * skip_input_data to get past it, and thereby put the problem on the
 * source manager's shoulders.  If we are saving the marker's contents
 * into memory, we use a slightly different convention: when forced to
 * suspend, the marker processor updates the restart point to the end of
 * what it's consumed (ie, the end of the buffer) before returning FALSE.
 * On resumption, cinfo->unread_marker still contains the marker code,
 * but the data source will point to the next chunk of marker data.
 * The marker processor must retain internal state to deal with this.
 *
 * Note that we don't bother to avoid duplicate trace messages if a
 * suspension occurs within marker parameters.  Other side effects
 * require more care.
 */

LOCAL(boolean)
get_soi(j_decompress_ptr cinfo)
/* Process an SOI marker */
{
        int i;

        TRACEMS(cinfo, 1, JTRC_SOI);

        if (cinfo->marker->saw_SOI) ERREXIT(cinfo, JERR_SOI_DUPLICATE);

        /* Reset all parameters that are defined to be reset by SOI */

        for (i = 0; i < NUM_ARITH_TBLS; i++)
        {
                cinfo->arith_dc_L[i] = 0;
                cinfo->arith_dc_U[i] = 1;
                cinfo->arith_ac_K[i] = 5;
        }
        cinfo->restart_interval = 0;

        /* Set initial assumptions for colorspace etc */

        cinfo->jpeg_color_space = JCS_UNKNOWN;
        cinfo->CCIR601_sampling = FALSE; /* Assume non-CCIR sampling??? */

        cinfo->saw_JFIF_marker = FALSE;
        cinfo->JFIF_major_version = 1; /* set default JFIF APP0 values */
        cinfo->JFIF_minor_version = 1;
        cinfo->density_unit = 0;
        cinfo->X_density = 1;
        cinfo->Y_density = 1;
        cinfo->saw_Adobe_marker = FALSE;
        cinfo->Adobe_transform = 0;

        cinfo->marker->saw_SOI = TRUE;

        return TRUE;
}

LOCAL(boolean)
get_sof(j_decompress_ptr cinfo, boolean is_prog, boolean is_arith)
/* Process a SOFn marker */
{
        INT32 length;
        int c, ci;
        jpeg_component_info* compptr;
        INPUT_VARS(cinfo);

        cinfo->progressive_mode = is_prog;
        cinfo->arith_code = is_arith;

        INPUT_2BYTES(cinfo, length, return FALSE);

        INPUT_BYTE(cinfo, cinfo->data_precision, return FALSE);
        INPUT_2BYTES(cinfo, cinfo->image_height, return FALSE);
        INPUT_2BYTES(cinfo, cinfo->image_width, return FALSE);
        INPUT_BYTE(cinfo, cinfo->num_components, return FALSE);

        length -= 8;

        TRACEMS4(
                cinfo, 1, JTRC_SOF, cinfo->unread_marker, (int)cinfo->image_width,
                (int)cinfo->image_height, cinfo->num_components);

        if (cinfo->marker->saw_SOF) ERREXIT(cinfo, JERR_SOF_DUPLICATE);

        /* We don't support files in which the image height is initially specified
         */
        /* as 0 and is later redefined by DNL.  As long as we have to check that, */
        /* might as well have a general sanity check. */
        if (cinfo->image_height <= 0 || cinfo->image_width <= 0 ||
                cinfo->num_components <= 0)
                ERREXIT(cinfo, JERR_EMPTY_IMAGE);

        if (length != (cinfo->num_components * 3)) ERREXIT(cinfo, JERR_BAD_LENGTH);

        if (cinfo->comp_info == nullptr) /* do only once, even if suspend */
                cinfo->comp_info = (jpeg_component_info*)(*cinfo->mem->alloc_small)(
                        (j_common_ptr)cinfo, JPOOL_IMAGE,
                        cinfo->num_components * SIZEOF(jpeg_component_info));

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                compptr->component_index = ci;
                INPUT_BYTE(cinfo, compptr->component_id, return FALSE);
                INPUT_BYTE(cinfo, c, return FALSE);
                compptr->h_samp_factor = (c >> 4) & 15;
                compptr->v_samp_factor = (c)&15;
                INPUT_BYTE(cinfo, compptr->quant_tbl_no, return FALSE);

                TRACEMS4(
                        cinfo, 1, JTRC_SOF_COMPONENT, compptr->component_id,
                        compptr->h_samp_factor, compptr->v_samp_factor,
                        compptr->quant_tbl_no);
        }

        cinfo->marker->saw_SOF = TRUE;

        INPUT_SYNC(cinfo);
        return TRUE;
}

LOCAL(boolean)
get_sos(j_decompress_ptr cinfo)
/* Process a SOS marker */
{
        INT32 length;
        int i, ci, n, c, cc;
        jpeg_component_info* compptr;
        INPUT_VARS(cinfo);

        if (!cinfo->marker->saw_SOF) ERREXIT(cinfo, JERR_SOS_NO_SOF);

        INPUT_2BYTES(cinfo, length, return FALSE);

        INPUT_BYTE(cinfo, n, return FALSE); /* Number of components */

        TRACEMS1(cinfo, 1, JTRC_SOS, n);

        if (length != (n * 2 + 6) || n < 1 || n > MAX_COMPS_IN_SCAN)
                ERREXIT(cinfo, JERR_BAD_LENGTH);

        cinfo->comps_in_scan = n;

        /* Collect the component-spec parameters */

        for (i = 0; i < n; i++)
        {
                INPUT_BYTE(cinfo, cc, return FALSE);
                INPUT_BYTE(cinfo, c, return FALSE);

                for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                         ci++, compptr++)
                {
                        if (cc == compptr->component_id) goto id_found;
                }

                ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, cc);

        id_found:

                cinfo->cur_comp_info[i] = compptr;
                compptr->dc_tbl_no = (c >> 4) & 15;
                compptr->ac_tbl_no = (c)&15;

                TRACEMS3(
                        cinfo, 1, JTRC_SOS_COMPONENT, cc, compptr->dc_tbl_no,
                        compptr->ac_tbl_no);
        }

        /* Collect the additional scan parameters Ss, Se, Ah/Al. */
        INPUT_BYTE(cinfo, c, return FALSE);
        cinfo->Ss = c;
        INPUT_BYTE(cinfo, c, return FALSE);
        cinfo->Se = c;
        INPUT_BYTE(cinfo, c, return FALSE);
        cinfo->Ah = (c >> 4) & 15;
        cinfo->Al = (c)&15;

        TRACEMS4(
                cinfo, 1, JTRC_SOS_PARAMS, cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);

        /* Prepare to scan data & restart markers */
        cinfo->marker->next_restart_num = 0;

        /* Count another SOS marker */
        cinfo->input_scan_number++;

        INPUT_SYNC(cinfo);
        return TRUE;
}

#ifdef D_ARITH_CODING_SUPPORTED

LOCAL(boolean)
get_dac(j_decompress_ptr cinfo)
/* Process a DAC marker */
{
        INT32 length;
        int index, val;
        INPUT_VARS(cinfo);

        INPUT_2BYTES(cinfo, length, return FALSE);
        length -= 2;

        while (length > 0)
        {
                INPUT_BYTE(cinfo, index, return FALSE);
                INPUT_BYTE(cinfo, val, return FALSE);

                length -= 2;

                TRACEMS2(cinfo, 1, JTRC_DAC, index, val);

                if (index < 0 || index >= (2 * NUM_ARITH_TBLS))
                        ERREXIT1(cinfo, JERR_DAC_INDEX, index);

                if (index >= NUM_ARITH_TBLS)
                { /* define AC table */
                        cinfo->arith_ac_K[index - NUM_ARITH_TBLS] = (UINT8)val;
                }
                else
                { /* define DC table */
                        cinfo->arith_dc_L[index] = (UINT8)(val & 0x0F);
                        cinfo->arith_dc_U[index] = (UINT8)(val >> 4);
                        if (cinfo->arith_dc_L[index] > cinfo->arith_dc_U[index])
                                ERREXIT1(cinfo, JERR_DAC_VALUE, val);
                }
        }

        if (length != 0) ERREXIT(cinfo, JERR_BAD_LENGTH);

        INPUT_SYNC(cinfo);
        return TRUE;
}

#else /* ! D_ARITH_CODING_SUPPORTED */

#define get_dac(cinfo) skip_variable(cinfo)

#endif /* D_ARITH_CODING_SUPPORTED */

LOCAL(boolean)
get_dht(j_decompress_ptr cinfo)
/* Process a DHT marker */
{
        INT32 length;
        UINT8 bits[17];
        UINT8 huffval[256];
        int i, index, count;
        JHUFF_TBL** htblptr;
        INPUT_VARS(cinfo);

        INPUT_2BYTES(cinfo, length, return FALSE);
        length -= 2;

        while (length > 16)
        {
                INPUT_BYTE(cinfo, index, return FALSE);

                TRACEMS1(cinfo, 1, JTRC_DHT, index);

                bits[0] = 0;
                count = 0;
                for (i = 1; i <= 16; i++)
                {
                        INPUT_BYTE(cinfo, bits[i], return FALSE);
                        count += bits[i];
                }

                length -= 1 + 16;

                TRACEMS8(
                        cinfo, 2, JTRC_HUFFBITS, bits[1], bits[2], bits[3], bits[4],
                        bits[5], bits[6], bits[7], bits[8]);
                TRACEMS8(
                        cinfo, 2, JTRC_HUFFBITS, bits[9], bits[10], bits[11], bits[12],
                        bits[13], bits[14], bits[15], bits[16]);

                /* Here we just do minimal validation of the counts to avoid walking
                 * off the end of our table space.  jdhuff.c will check more carefully.
                 */
                if (count > 256 || ((INT32)count) > length)
                        ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);

                for (i = 0; i < count; i++) INPUT_BYTE(cinfo, huffval[i], return FALSE);

                length -= count;

                if (index & 0x10)
                { /* AC table definition */
                        index -= 0x10;
                        htblptr = &cinfo->ac_huff_tbl_ptrs[index];
                }
                else
                { /* DC table definition */
                        htblptr = &cinfo->dc_huff_tbl_ptrs[index];
                }

                if (index < 0 || index >= NUM_HUFF_TBLS)
                        ERREXIT1(cinfo, JERR_DHT_INDEX, index);

                if (*htblptr == nullptr)
                        *htblptr = jpeg_alloc_huff_table((j_common_ptr)cinfo);

                MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));
                MEMCOPY((*htblptr)->huffval, huffval, SIZEOF((*htblptr)->huffval));
        }

        if (length != 0) ERREXIT(cinfo, JERR_BAD_LENGTH);

        INPUT_SYNC(cinfo);
        return TRUE;
}

LOCAL(boolean)
get_dqt(j_decompress_ptr cinfo)
/* Process a DQT marker */
{
        INT32 length;
        int n, i, prec;
        unsigned int tmp;
        JQUANT_TBL* quant_ptr;
        INPUT_VARS(cinfo);

        INPUT_2BYTES(cinfo, length, return FALSE);
        length -= 2;

        while (length > 0)
        {
                INPUT_BYTE(cinfo, n, return FALSE);
                prec = n >> 4;
                n &= 0x0F;

                TRACEMS2(cinfo, 1, JTRC_DQT, n, prec);

                if (n >= NUM_QUANT_TBLS) ERREXIT1(cinfo, JERR_DQT_INDEX, n);

                if (cinfo->quant_tbl_ptrs[n] == nullptr)
                        cinfo->quant_tbl_ptrs[n] =
                                jpeg_alloc_quant_table((j_common_ptr)cinfo);
                quant_ptr = cinfo->quant_tbl_ptrs[n];

                for (i = 0; i < DCTSIZE2; i++)
                {
                        if (prec)
                                INPUT_2BYTES(cinfo, tmp, return FALSE);
                        else
                                INPUT_BYTE(cinfo, tmp, return FALSE);
                        /* We convert the zigzag-order table to natural array order. */
                        quant_ptr->quantval[jpeg_natural_order[i]] = (UINT16)tmp;
                }

                if (cinfo->err->trace_level >= 2)
                {
                        for (i = 0; i < DCTSIZE2; i += 8)
                        {
                                TRACEMS8(
                                        cinfo, 2, JTRC_QUANTVALS, quant_ptr->quantval[i],
                                        quant_ptr->quantval[i + 1], quant_ptr->quantval[i + 2],
                                        quant_ptr->quantval[i + 3], quant_ptr->quantval[i + 4],
                                        quant_ptr->quantval[i + 5], quant_ptr->quantval[i + 6],
                                        quant_ptr->quantval[i + 7]);
                        }
                }

                length -= DCTSIZE2 + 1;
                if (prec) length -= DCTSIZE2;
        }

        if (length != 0) ERREXIT(cinfo, JERR_BAD_LENGTH);

        INPUT_SYNC(cinfo);
        return TRUE;
}

LOCAL(boolean)
get_dri(j_decompress_ptr cinfo)
/* Process a DRI marker */
{
        INT32 length;
        unsigned int tmp;
        INPUT_VARS(cinfo);

        INPUT_2BYTES(cinfo, length, return FALSE);

        if (length != 4) ERREXIT(cinfo, JERR_BAD_LENGTH);

        INPUT_2BYTES(cinfo, tmp, return FALSE);

        TRACEMS1(cinfo, 1, JTRC_DRI, tmp);

        cinfo->restart_interval = tmp;

        INPUT_SYNC(cinfo);
        return TRUE;
}

/*
 * Routines for processing APPn and COM markers.
 * These are either saved in memory or discarded, per application request.
 * APP0 and APP14 are specially checked to see if they are
 * JFIF and Adobe markers, respectively.
 */

#define APP0_DATA_LEN 14 /* Length of interesting data in APP0 */
#define APP14_DATA_LEN 12 /* Length of interesting data in APP14 */
#define APPN_DATA_LEN 14 /* Must be the largest of the above!! */

LOCAL(void)
examine_app0(
        j_decompress_ptr cinfo, JOCTET FAR* data, unsigned int datalen,
        INT32 remaining)
/* Examine first few bytes from an APP0.
 * Take appropriate action if it is a JFIF marker.
 * datalen is # of bytes at data[], remaining is length of rest of marker data.
 */
{
        INT32 totallen = (INT32)datalen + remaining;

        if (datalen >= APP0_DATA_LEN && GETJOCTET(data[0]) == 0x4A &&
                GETJOCTET(data[1]) == 0x46 && GETJOCTET(data[2]) == 0x49 &&
                GETJOCTET(data[3]) == 0x46 && GETJOCTET(data[4]) == 0)
        {
                /* Found JFIF APP0 marker: save info */
                cinfo->saw_JFIF_marker = TRUE;
                cinfo->JFIF_major_version = GETJOCTET(data[5]);
                cinfo->JFIF_minor_version = GETJOCTET(data[6]);
                cinfo->density_unit = GETJOCTET(data[7]);
                cinfo->X_density = (GETJOCTET(data[8]) << 8) + GETJOCTET(data[9]);
                cinfo->Y_density = (GETJOCTET(data[10]) << 8) + GETJOCTET(data[11]);
                /* Check version.
                 * Major version must be 1, 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->JFIF_major_version != 1)
                        WARNMS2(
                                cinfo, JWRN_JFIF_MAJOR, cinfo->JFIF_major_version,
                                cinfo->JFIF_minor_version);
                /* Generate trace messages */
                TRACEMS5(
                        cinfo, 1, JTRC_JFIF, cinfo->JFIF_major_version,
                        cinfo->JFIF_minor_version, cinfo->X_density, cinfo->Y_density,
                        cinfo->density_unit);
                /* Validate thumbnail dimensions and issue appropriate messages */
                if (GETJOCTET(data[12]) | GETJOCTET(data[13]))
                        TRACEMS2(
                                cinfo, 1, JTRC_JFIF_THUMBNAIL, GETJOCTET(data[12]),
                                GETJOCTET(data[13]));
                totallen -= APP0_DATA_LEN;
                if (totallen != ((INT32)GETJOCTET(data[12]) *
                                                 (INT32)GETJOCTET(data[13]) * (INT32)3))
                        TRACEMS1(cinfo, 1, JTRC_JFIF_BADTHUMBNAILSIZE, (int)totallen);
        }
        else if (
                datalen >= 6 && GETJOCTET(data[0]) == 0x4A &&
                GETJOCTET(data[1]) == 0x46 && GETJOCTET(data[2]) == 0x58 &&
                GETJOCTET(data[3]) == 0x58 && GETJOCTET(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 (GETJOCTET(data[5]))
                {
                        case 0x10:
                                TRACEMS1(cinfo, 1, JTRC_THUMB_JPEG, (int)totallen);
                                break;
                        case 0x11:
                                TRACEMS1(cinfo, 1, JTRC_THUMB_PALETTE, (int)totallen);
                                break;
                        case 0x13:
                                TRACEMS1(cinfo, 1, JTRC_THUMB_RGB, (int)totallen);
                                break;
                        default:
                                TRACEMS2(
                                        cinfo, 1, JTRC_JFIF_EXTENSION, GETJOCTET(data[5]),
                                        (int)totallen);
                                break;
                }
        }
        else
        {
                /* Start of APP0 does not match "JFIF" or "JFXX", or too short */
                TRACEMS1(cinfo, 1, JTRC_APP0, (int)totallen);
        }
}

LOCAL(void)
examine_app14(
        j_decompress_ptr cinfo, JOCTET FAR* data, unsigned int datalen,
        INT32 remaining)
/* Examine first few bytes from an APP14.
 * Take appropriate action if it is an Adobe marker.
 * datalen is # of bytes at data[], remaining is length of rest of marker data.
 */
{
        unsigned int version, flags0, flags1, transform;

        if (datalen >= APP14_DATA_LEN && GETJOCTET(data[0]) == 0x41 &&
                GETJOCTET(data[1]) == 0x64 && GETJOCTET(data[2]) == 0x6F &&
                GETJOCTET(data[3]) == 0x62 && GETJOCTET(data[4]) == 0x65)
        {
                /* Found Adobe APP14 marker */
                version = (GETJOCTET(data[5]) << 8) + GETJOCTET(data[6]);
                flags0 = (GETJOCTET(data[7]) << 8) + GETJOCTET(data[8]);
                flags1 = (GETJOCTET(data[9]) << 8) + GETJOCTET(data[10]);
                transform = GETJOCTET(data[11]);
                TRACEMS4(cinfo, 1, JTRC_ADOBE, version, flags0, flags1, transform);
                cinfo->saw_Adobe_marker = TRUE;
                cinfo->Adobe_transform = (UINT8)transform;
        }
        else
        {
                /* Start of APP14 does not match "Adobe", or too short */
                TRACEMS1(cinfo, 1, JTRC_APP14, (int)(datalen + remaining));
        }
}

METHODDEF(boolean)
get_interesting_appn(j_decompress_ptr cinfo)
/* Process an APP0 or APP14 marker without saving it */
{
        INT32 length;
        JOCTET b[APPN_DATA_LEN];
        unsigned int i, numtoread;
        INPUT_VARS(cinfo);

        INPUT_2BYTES(cinfo, length, return FALSE);
        length -= 2;

        /* get the interesting part of the marker data */
        if (length >= APPN_DATA_LEN)
                numtoread = APPN_DATA_LEN;
        else if (length > 0)
                numtoread = (unsigned int)length;
        else
                numtoread = 0;
        for (i = 0; i < numtoread; i++) INPUT_BYTE(cinfo, b[i], return FALSE);
        length -= numtoread;

        /* process it */
        switch (cinfo->unread_marker)
        {
                case M_APP0:
                        examine_app0(cinfo, (JOCTET FAR*)b, numtoread, length);
                        break;
                case M_APP14:
                        examine_app14(cinfo, (JOCTET FAR*)b, numtoread, length);
                        break;
                default:
                        /* can't get here unless jpeg_save_markers chooses wrong processor
                         */
                        ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
                        break;
        }

        /* skip any remaining data -- could be lots */
        INPUT_SYNC(cinfo);
        if (length > 0) (*cinfo->src->skip_input_data)(cinfo, (long)length);

        return TRUE;
}

#ifdef SAVE_MARKERS_SUPPORTED

METHODDEF(boolean)
save_marker(j_decompress_ptr cinfo)
/* Save an APPn or COM marker into the marker list */
{
        my_marker_ptr marker = (my_marker_ptr)cinfo->marker;
        jpeg_saved_marker_ptr cur_marker = marker->cur_marker;
        unsigned int bytes_read, data_length;
        JOCTET FAR* data;
        INT32 length = 0;
        INPUT_VARS(cinfo);

        if (cur_marker == nullptr)
        {
                /* begin reading a marker */
                INPUT_2BYTES(cinfo, length, return FALSE);
                length -= 2;
                if (length >= 0)
                { /* watch out for bogus length word */
                        /* figure out how much we want to save */
                        unsigned int limit;
                        if (cinfo->unread_marker == (int)M_COM)
                                limit = marker->length_limit_COM;
                        else
                                limit =
                                        marker
                                                ->length_limit_APPn[cinfo->unread_marker - (int)M_APP0];
                        if ((unsigned int)length < limit) limit = (unsigned int)length;
                        /* allocate and initialize the marker item */
                        cur_marker = (jpeg_saved_marker_ptr)(*cinfo->mem->alloc_large)(
                                (j_common_ptr)cinfo, JPOOL_IMAGE,
                                SIZEOF(struct jpeg_marker_struct) + limit);
                        cur_marker->next = nullptr;
                        cur_marker->marker = (UINT8)cinfo->unread_marker;
                        cur_marker->original_length = (unsigned int)length;
                        cur_marker->data_length = limit;
                        /* data area is just beyond the jpeg_marker_struct */
                        data = cur_marker->data = (JOCTET FAR*)(cur_marker + 1);
                        marker->cur_marker = cur_marker;
                        marker->bytes_read = 0;
                        bytes_read = 0;
                        data_length = limit;
                }
                else
                {
                        /* deal with bogus length word */
                        bytes_read = data_length = 0;
                        data = nullptr;
                }
        }
        else
        {
                /* resume reading a marker */
                bytes_read = marker->bytes_read;
                data_length = cur_marker->data_length;
                data = cur_marker->data + bytes_read;
        }

        while (bytes_read < data_length)
        {
                INPUT_SYNC(cinfo); /* move the restart point to here */
                marker->bytes_read = bytes_read;
                /* If there's not at least one byte in buffer, suspend */
                MAKE_BYTE_AVAIL(cinfo, return FALSE);
                /* Copy bytes with reasonable rapidity */
                while (bytes_read < data_length && bytes_in_buffer > 0)
                {
                        *data++ = *next_input_byte++;
                        bytes_in_buffer--;
                        bytes_read++;
                }
        }

        /* Done reading what we want to read */
        if (cur_marker != nullptr)
        { /* will be nullptr if bogus length word */
                /* Add new marker to end of list */
                if (cinfo->marker_list == nullptr)
                {
                        cinfo->marker_list = cur_marker;
                }
                else
                {
                        jpeg_saved_marker_ptr prev = cinfo->marker_list;
                        while (prev->next != nullptr) prev = prev->next;
                        prev->next = cur_marker;
                }
                /* Reset pointer & calc remaining data length */
                data = cur_marker->data;
                length = cur_marker->original_length - data_length;
        }
        /* Reset to initial state for next marker */
        marker->cur_marker = nullptr;

        /* Process the marker if interesting; else just make a generic trace msg */
        switch (cinfo->unread_marker)
        {
                case M_APP0:
                        examine_app0(cinfo, data, data_length, length);
                        break;
                case M_APP14:
                        examine_app14(cinfo, data, data_length, length);
                        break;
                default:
                        TRACEMS2(
                                cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker,
                                (int)(data_length + length));
                        break;
        }

        /* skip any remaining data -- could be lots */
        INPUT_SYNC(cinfo); /* do before skip_input_data */
        if (length > 0) (*cinfo->src->skip_input_data)(cinfo, (long)length);

        return TRUE;
}

#endif /* SAVE_MARKERS_SUPPORTED */

METHODDEF(boolean)
skip_variable(j_decompress_ptr cinfo)
/* Skip over an unknown or uninteresting variable-length marker */
{
        INT32 length;
        INPUT_VARS(cinfo);

        INPUT_2BYTES(cinfo, length, return FALSE);
        length -= 2;

        TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker, (int)length);

        INPUT_SYNC(cinfo); /* do before skip_input_data */
        if (length > 0) (*cinfo->src->skip_input_data)(cinfo, (long)length);

        return TRUE;
}

/*
 * Find the next JPEG marker, save it in cinfo->unread_marker.
 * Returns FALSE if had to suspend before reaching a marker;
 * in that case cinfo->unread_marker is unchanged.
 *
 * Note that the result might not be a valid marker code,
 * but it will never be 0 or FF.
 */

LOCAL(boolean)
next_marker(j_decompress_ptr cinfo)
{
        int c;
        INPUT_VARS(cinfo);

        for (;;)
        {
                INPUT_BYTE(cinfo, c, return FALSE);
                /* Skip any non-FF bytes.
                 * This may look a bit inefficient, but it will not occur in a valid
                 * file.
                 * We sync after each discarded byte so that a suspending data source
                 * can discard the byte from its buffer.
                 */
                while (c != 0xFF)
                {
                        cinfo->marker->discarded_bytes++;
                        INPUT_SYNC(cinfo);
                        INPUT_BYTE(cinfo, c, return FALSE);
                }
                /* This loop swallows any duplicate FF bytes.  Extra FFs are legal as
                 * pad bytes, so don't count them in discarded_bytes.  We assume there
                 * will not be so many consecutive FF bytes as to overflow a suspending
                 * data source's input buffer.
                 */
                do
                {
                        INPUT_BYTE(cinfo, c, return FALSE);
                } while (c == 0xFF);
                if (c != 0) break; /* found a valid marker, exit loop */
                /* Reach here if we found a stuffed-zero data sequence (FF/00).
                 * Discard it and loop back to try again.
                 */
                cinfo->marker->discarded_bytes += 2;
                INPUT_SYNC(cinfo);
        }

        if (cinfo->marker->discarded_bytes != 0)
        {
                WARNMS2(cinfo, JWRN_EXTRANEOUS_DATA, cinfo->marker->discarded_bytes, c);
                cinfo->marker->discarded_bytes = 0;
        }

        cinfo->unread_marker = c;

        INPUT_SYNC(cinfo);
        return TRUE;
}

LOCAL(boolean)
first_marker(j_decompress_ptr cinfo)
/* Like next_marker, but used to obtain the initial SOI marker. */
/* For this marker, we do not allow preceding garbage or fill; otherwise,
 * we might well scan an entire input file before realizing it ain't JPEG.
 * If an application wants to process non-JFIF files, it must seek to the
 * SOI before calling the JPEG library.
 */
{
        int c, c2;
        INPUT_VARS(cinfo);

        INPUT_BYTE(cinfo, c, return FALSE);
        INPUT_BYTE(cinfo, c2, return FALSE);
        if (c != 0xFF || c2 != (int)M_SOI) ERREXIT2(cinfo, JERR_NO_SOI, c, c2);

        cinfo->unread_marker = c2;

        INPUT_SYNC(cinfo);
        return TRUE;
}

/*
 * Read markers until SOS or EOI.
 *
 * Returns same codes as are defined for jpeg_consume_input:
 * JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
 */

METHODDEF(int)
read_markers(j_decompress_ptr cinfo)
{
        /* Outer loop repeats once for each marker. */
        for (;;)
        {
                /* Collect the marker proper, unless we already did. */
                /* NB: first_marker() enforces the requirement that SOI appear first. */
                if (cinfo->unread_marker == 0)
                {
                        if (!cinfo->marker->saw_SOI)
                        {
                                if (!first_marker(cinfo)) return JPEG_SUSPENDED;
                        }
                        else
                        {
                                if (!next_marker(cinfo)) return JPEG_SUSPENDED;
                        }
                }
                /* At this point cinfo->unread_marker contains the marker code and the
                 * input point is just past the marker proper, but before any
                 * parameters.
                 * A suspension will cause us to return with this state still true.
                 */
                switch (cinfo->unread_marker)
                {
                        case M_SOI:
                                if (!get_soi(cinfo)) return JPEG_SUSPENDED;
                                break;

                        case M_SOF0: /* Baseline */
                        case M_SOF1: /* Extended sequential, Huffman */
                                if (!get_sof(cinfo, FALSE, FALSE)) return JPEG_SUSPENDED;
                                break;

                        case M_SOF2: /* Progressive, Huffman */
                                if (!get_sof(cinfo, TRUE, FALSE)) return JPEG_SUSPENDED;
                                break;

                        case M_SOF9: /* Extended sequential, arithmetic */
                                if (!get_sof(cinfo, FALSE, TRUE)) return JPEG_SUSPENDED;
                                break;

                        case M_SOF10: /* Progressive, arithmetic */
                                if (!get_sof(cinfo, TRUE, TRUE)) return JPEG_SUSPENDED;
                                break;

                        /* Currently unsupported SOFn types */
                        case M_SOF3: /* Lossless, Huffman */
                        case M_SOF5: /* Differential sequential, Huffman */
                        case M_SOF6: /* Differential progressive, Huffman */
                        case M_SOF7: /* Differential lossless, Huffman */
                        case M_JPG: /* Reserved for JPEG extensions */
                        case M_SOF11: /* Lossless, arithmetic */
                        case M_SOF13: /* Differential sequential, arithmetic */
                        case M_SOF14: /* Differential progressive, arithmetic */
                        case M_SOF15: /* Differential lossless, arithmetic */
                                ERREXIT1(cinfo, JERR_SOF_UNSUPPORTED, cinfo->unread_marker);
                                break;

                        case M_SOS:
                                if (!get_sos(cinfo)) return JPEG_SUSPENDED;
                                cinfo->unread_marker = 0; /* processed the marker */
                                return JPEG_REACHED_SOS;

                        case M_EOI:
                                TRACEMS(cinfo, 1, JTRC_EOI);
                                cinfo->unread_marker = 0; /* processed the marker */
                                return JPEG_REACHED_EOI;

                        case M_DAC:
                                if (!get_dac(cinfo)) return JPEG_SUSPENDED;
                                break;

                        case M_DHT:
                                if (!get_dht(cinfo)) return JPEG_SUSPENDED;
                                break;

                        case M_DQT:
                                if (!get_dqt(cinfo)) return JPEG_SUSPENDED;
                                break;

                        case M_DRI:
                                if (!get_dri(cinfo)) return JPEG_SUSPENDED;
                                break;

                        case M_APP0:
                        case M_APP1:
                        case M_APP2:
                        case M_APP3:
                        case M_APP4:
                        case M_APP5:
                        case M_APP6:
                        case M_APP7:
                        case M_APP8:
                        case M_APP9:
                        case M_APP10:
                        case M_APP11:
                        case M_APP12:
                        case M_APP13:
                        case M_APP14:
                        case M_APP15:
                                if (!(*((my_marker_ptr)cinfo->marker)
                                                   ->process_APPn[cinfo->unread_marker - (int)M_APP0])(
                                                cinfo))
                                        return JPEG_SUSPENDED;
                                break;

                        case M_COM:
                                if (!(*((my_marker_ptr)cinfo->marker)->process_COM)(cinfo))
                                        return JPEG_SUSPENDED;
                                break;

                        case M_RST0: /* these are all parameterless */
                        case M_RST1:
                        case M_RST2:
                        case M_RST3:
                        case M_RST4:
                        case M_RST5:
                        case M_RST6:
                        case M_RST7:
                        case M_TEM:
                                TRACEMS1(cinfo, 1, JTRC_PARMLESS_MARKER, cinfo->unread_marker);
                                break;

                        case M_DNL: /* Ignore DNL ... perhaps the wrong thing */
                                if (!skip_variable(cinfo)) return JPEG_SUSPENDED;
                                break;

                        default: /* must be DHP, EXP, JPGn, or RESn */
                                /* For now, we treat the reserved markers as fatal errors since
                                 * they are
                                 * likely to be used to signal incompatible JPEG Part 3
                                 * extensions.
                                 * Once the JPEG 3 version-number marker is well defined, this
                                 * code
                                 * ought to change!
                                 */
                                ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
                                break;
                }
                /* Successfully processed marker, so reset state variable */
                cinfo->unread_marker = 0;
        } /* end loop */
}

/*
 * Read a restart marker, which is expected to appear next in the datastream;
 * if the marker is not there, take appropriate recovery action.
 * Returns FALSE if suspension is required.
 *
 * This is called by the entropy decoder after it has read an appropriate
 * number of MCUs.  cinfo->unread_marker may be nonzero if the entropy decoder
 * has already read a marker from the data source.  Under normal conditions
 * cinfo->unread_marker will be reset to 0 before returning; if not reset,
 * it holds a marker which the decoder will be unable to read past.
 */

METHODDEF(boolean)
read_restart_marker(j_decompress_ptr cinfo)
{
        /* Obtain a marker unless we already did. */
        /* Note that next_marker will complain if it skips any data. */
        if (cinfo->unread_marker == 0)
        {
                if (!next_marker(cinfo)) return FALSE;
        }

        if (cinfo->unread_marker == ((int)M_RST0 + cinfo->marker->next_restart_num))
        {
                /* Normal case --- swallow the marker and let entropy decoder continue
                 */
                TRACEMS1(cinfo, 3, JTRC_RST, cinfo->marker->next_restart_num);
                cinfo->unread_marker = 0;
        }
        else
        {
                /* Uh-oh, the restart markers have been messed up. */
                /* Let the data source manager determine how to resync. */
                if (!(*cinfo->src->resync_to_restart)(
                                cinfo, cinfo->marker->next_restart_num))
                        return FALSE;
        }

        /* Update next-restart state */
        cinfo->marker->next_restart_num = (cinfo->marker->next_restart_num + 1) & 7;

        return TRUE;
}

/*
 * This is the default resync_to_restart method for data source managers
 * to use if they don't have any better approach.  Some data source managers
 * may be able to back up, or may have additional knowledge about the data
 * which permits a more intelligent recovery strategy; such managers would
 * presumably supply their own resync method.
 *
 * read_restart_marker calls resync_to_restart if it finds a marker other than
 * the restart marker it was expecting.  (This code is *not* used unless
 * a nonzero restart interval has been declared.)  cinfo->unread_marker is
 * the marker code actually found (might be anything, except 0 or FF).
 * The desired restart marker number (0..7) is passed as a parameter.
 * This routine is supposed to apply whatever error recovery strategy seems
 * appropriate in order to position the input stream to the next data segment.
 * Note that cinfo->unread_marker is treated as a marker appearing before
 * the current data-source input point; usually it should be reset to zero
 * before returning.
 * Returns FALSE if suspension is required.
 *
 * This implementation is substantially constrained by wanting to treat the
 * input as a data stream; this means we can't back up.  Therefore, we have
 * only the following actions to work with:
 *   1. Simply discard the marker and let the entropy decoder resume at next
 *      byte of file.
 *   2. Read forward until we find another marker, discarding intervening
 *      data.  (In theory we could look ahead within the current bufferload,
 *      without having to discard data if we don't find the desired marker.
 *      This idea is not implemented here, in part because it makes behavior
 *      dependent on buffer size and chance buffer-boundary positions.)
 *   3. Leave the marker unread (by failing to zero cinfo->unread_marker).
 *      This will cause the entropy decoder to process an empty data segment,
 *      inserting dummy zeroes, and then we will reprocess the marker.
 *
 * #2 is appropriate if we think the desired marker lies ahead, while #3 is
 * appropriate if the found marker is a future restart marker (indicating
 * that we have missed the desired restart marker, probably because it got
 * corrupted).
 * We apply #2 or #3 if the found marker is a restart marker no more than
 * two counts behind or ahead of the expected one.  We also apply #2 if the
 * found marker is not a legal JPEG marker code (it's certainly bogus data).
 * If the found marker is a restart marker more than 2 counts away, we do #1
 * (too much risk that the marker is erroneous; with luck we will be able to
 * resync at some future point).
 * For any valid non-restart JPEG marker, we apply #3.  This keeps us from
 * overrunning the end of a scan.  An implementation limited to single-scan
 * files might find it better to apply #2 for markers other than EOI, since
 * any other marker would have to be bogus data in that case.
 */

GLOBAL(boolean)
jpeg_resync_to_restart(j_decompress_ptr cinfo, int desired)
{
        int marker = cinfo->unread_marker;
        int action = 1;

        /* Always put up a warning. */
        WARNMS2(cinfo, JWRN_MUST_RESYNC, marker, desired);

        /* Outer loop handles repeated decision after scanning forward. */
        for (;;)
        {
                if (marker < (int)M_SOF0)
                        action = 2; /* invalid marker */
                else if (marker < (int)M_RST0 || marker > (int)M_RST7)
                        action = 3; /* valid non-restart marker */
                else
                {
                        if (marker == ((int)M_RST0 + ((desired + 1) & 7)) ||
                                marker == ((int)M_RST0 + ((desired + 2) & 7)))
                                action = 3; /* one of the next two expected restarts */
                        else if (
                                marker == ((int)M_RST0 + ((desired - 1) & 7)) ||
                                marker == ((int)M_RST0 + ((desired - 2) & 7)))
                                action = 2; /* a prior restart, so advance */
                        else
                                action = 1; /* desired restart or too far away */
                }
                TRACEMS2(cinfo, 4, JTRC_RECOVERY_ACTION, marker, action);
                switch (action)
                {
                        case 1:
                                /* Discard marker and let entropy decoder resume processing. */
                                cinfo->unread_marker = 0;
                                return TRUE;
                        case 2:
                                /* Scan to the next marker, and repeat the decision loop. */
                                if (!next_marker(cinfo)) return FALSE;
                                marker = cinfo->unread_marker;
                                break;
                        case 3:
                                /* Return without advancing past this marker. */
                                /* Entropy decoder will be forced to process an empty segment.
                                 */
                                return TRUE;
                }
        } /* end loop */
}

/*
 * Reset marker processing state to begin a fresh datastream.
 */

METHODDEF(void)
reset_marker_reader(j_decompress_ptr cinfo)
{
        my_marker_ptr marker = (my_marker_ptr)cinfo->marker;

        cinfo->comp_info = nullptr; /* until allocated by get_sof */
        cinfo->input_scan_number = 0; /* no SOS seen yet */
        cinfo->unread_marker = 0; /* no pending marker */
        marker->pub.saw_SOI = FALSE; /* set internal state too */
        marker->pub.saw_SOF = FALSE;
        marker->pub.discarded_bytes = 0;
        marker->cur_marker = nullptr;
}

/*
 * Initialize the marker reader module.
 * This is called only once, when the decompression object is created.
 */

GLOBAL(void)
jinit_marker_reader(j_decompress_ptr cinfo)
{
        my_marker_ptr marker;
        int i;

        /* Create subobject in permanent pool */
        marker = (my_marker_ptr)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_PERMANENT, SIZEOF(my_marker_reader));
        cinfo->marker = (struct jpeg_marker_reader*)marker;
        /* Initialize public method pointers */
        marker->pub.reset_marker_reader = reset_marker_reader;
        marker->pub.read_markers = read_markers;
        marker->pub.read_restart_marker = read_restart_marker;
        /* Initialize COM/APPn processing.
         * By default, we examine and then discard APP0 and APP14,
         * but simply discard COM and all other APPn.
         */
        marker->process_COM = skip_variable;
        marker->length_limit_COM = 0;
        for (i = 0; i < 16; i++)
        {
                marker->process_APPn[i] = skip_variable;
                marker->length_limit_APPn[i] = 0;
        }
        marker->process_APPn[0] = get_interesting_appn;
        marker->process_APPn[14] = get_interesting_appn;
        /* Reset marker processing state */
        reset_marker_reader(cinfo);
}

/*
 * Control saving of COM and APPn markers into marker_list.
 */

#ifdef SAVE_MARKERS_SUPPORTED

GLOBAL(void)
jpeg_save_markers(
        j_decompress_ptr cinfo, int marker_code, unsigned int length_limit)
{
        my_marker_ptr marker = (my_marker_ptr)cinfo->marker;
        long maxlength;
        jpeg_marker_parser_method processor;

        /* Length limit mustn't be larger than what we can allocate
         * (should only be a concern in a 16-bit environment).
         */
        maxlength = cinfo->mem->max_alloc_chunk - SIZEOF(struct jpeg_marker_struct);
        if (((long)length_limit) > maxlength)
                length_limit = (unsigned int)maxlength;

        /* Choose processor routine to use.
         * APP0/APP14 have special requirements.
         */
        if (length_limit)
        {
                processor = save_marker;
                /* If saving APP0/APP14, save at least enough for our internal use. */
                if (marker_code == (int)M_APP0 && length_limit < APP0_DATA_LEN)
                        length_limit = APP0_DATA_LEN;
                else if (marker_code == (int)M_APP14 && length_limit < APP14_DATA_LEN)
                        length_limit = APP14_DATA_LEN;
        }
        else
        {
                processor = skip_variable;
                /* If discarding APP0/APP14, use our regular on-the-fly processor. */
                if (marker_code == (int)M_APP0 || marker_code == (int)M_APP14)
                        processor = get_interesting_appn;
        }

        if (marker_code == (int)M_COM)
        {
                marker->process_COM = processor;
                marker->length_limit_COM = length_limit;
        }
        else if (marker_code >= (int)M_APP0 && marker_code <= (int)M_APP15)
        {
                marker->process_APPn[marker_code - (int)M_APP0] = processor;
                marker->length_limit_APPn[marker_code - (int)M_APP0] = length_limit;
        }
        else
                ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, marker_code);
}

#endif /* SAVE_MARKERS_SUPPORTED */

/*
 * Install a special processing method for COM or APPn markers.
 */

GLOBAL(void)
jpeg_set_marker_processor(
        j_decompress_ptr cinfo, int marker_code, jpeg_marker_parser_method routine)
{
        my_marker_ptr marker = (my_marker_ptr)cinfo->marker;

        if (marker_code == (int)M_COM)
                marker->process_COM = routine;
        else if (marker_code >= (int)M_APP0 && marker_code <= (int)M_APP15)
                marker->process_APPn[marker_code - (int)M_APP0] = routine;
        else
                ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, marker_code);
}