jdhuff.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"
#include "jdhuff.h" /* Declarations shared with jdphuff.c */

/*
 * Expanded entropy decoder object for Huffman decoding.
 *
 * The savable_state subrecord contains fields that change within an MCU,
 * but must not be updated permanently until we complete the MCU.
 */

typedef struct
{
        int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
} savable_state;

/* This macro is to work around compilers with missing or broken
 * structure assignment.  You'll need to fix this code if you have
 * such a compiler and you change MAX_COMPS_IN_SCAN.
 */

#ifndef NO_STRUCT_ASSIGN
#define ASSIGN_STATE(dest, src) ((dest) = (src))
#else
#if MAX_COMPS_IN_SCAN == 4
#define ASSIGN_STATE(dest, src)                    \
        ((dest).last_dc_val[0] = (src).last_dc_val[0], \
         (dest).last_dc_val[1] = (src).last_dc_val[1], \
         (dest).last_dc_val[2] = (src).last_dc_val[2], \
         (dest).last_dc_val[3] = (src).last_dc_val[3])
#endif
#endif

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

        /* These fields are loaded into local variables at start of each MCU.
         * In case of suspension, we exit WITHOUT updating them.
         */
        bitread_perm_state bitstate; /* Bit buffer at start of MCU */
        savable_state saved; /* Other state at start of MCU */

        /* These fields are NOT loaded into local working state. */
        unsigned int restarts_to_go; /* MCUs left in this restart interval */

        /* Pointers to derived tables (these workspaces have image lifespan) */
        d_derived_tbl* dc_derived_tbls[NUM_HUFF_TBLS];
        d_derived_tbl* ac_derived_tbls[NUM_HUFF_TBLS];

        /* Precalculated info set up by start_pass for use in decode_mcu: */

        /* Pointers to derived tables to be used for each block within an MCU */
        d_derived_tbl* dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
        d_derived_tbl* ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
        /* Whether we care about the DC and AC coefficient values for each block */
        boolean dc_needed[D_MAX_BLOCKS_IN_MCU];
        boolean ac_needed[D_MAX_BLOCKS_IN_MCU];
} huff_entropy_decoder;

typedef huff_entropy_decoder* huff_entropy_ptr;

/*
 * Initialize for a Huffman-compressed scan.
 */

METHODDEF(void)
start_pass_huff_decoder(j_decompress_ptr cinfo)
{
        huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
        int ci, blkn, dctbl, actbl;
        jpeg_component_info* compptr;

        /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
         * This ought to be an error condition, but we make it a warning because
         * there are some baseline files out there with all zeroes in these bytes.
         */
        if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2 - 1 || cinfo->Ah != 0 ||
                cinfo->Al != 0)
                WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);

        for (ci = 0; ci < cinfo->comps_in_scan; ci++)
        {
                compptr = cinfo->cur_comp_info[ci];
                dctbl = compptr->dc_tbl_no;
                actbl = compptr->ac_tbl_no;
                /* Compute derived values for Huffman tables */
                /* We may do this more than once for a table, but it's not expensive */
                jpeg_make_d_derived_tbl(
                        cinfo, TRUE, dctbl, &entropy->dc_derived_tbls[dctbl]);
                jpeg_make_d_derived_tbl(
                        cinfo, FALSE, actbl, &entropy->ac_derived_tbls[actbl]);
                /* Initialize DC predictions to 0 */
                entropy->saved.last_dc_val[ci] = 0;
        }

        /* Precalculate decoding info for each block in an MCU of this scan */
        for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++)
        {
                ci = cinfo->MCU_membership[blkn];
                compptr = cinfo->cur_comp_info[ci];
                /* Precalculate which table to use for each block */
                entropy->dc_cur_tbls[blkn] =
                        entropy->dc_derived_tbls[compptr->dc_tbl_no];
                entropy->ac_cur_tbls[blkn] =
                        entropy->ac_derived_tbls[compptr->ac_tbl_no];
                /* Decide whether we really care about the coefficient values */
                if (compptr->component_needed)
                {
                        entropy->dc_needed[blkn] = TRUE;
                        /* we don't need the ACs if producing a 1/8th-size image */
                        entropy->ac_needed[blkn] = (compptr->DCT_scaled_size > 1);
                }
                else
                {
                        entropy->dc_needed[blkn] = entropy->ac_needed[blkn] = FALSE;
                }
        }

        /* Initialize bitread state variables */
        entropy->bitstate.bits_left = 0;
        entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
        entropy->pub.insufficient_data = FALSE;

        /* Initialize restart counter */
        entropy->restarts_to_go = cinfo->restart_interval;
}

/*
 * Compute the derived values for a Huffman table.
 * This routine also performs some validation checks on the table.
 *
 * Note this is also used by jdphuff.c.
 */

GLOBAL(void)
jpeg_make_d_derived_tbl(
        j_decompress_ptr cinfo, boolean isDC, int tblno, d_derived_tbl** pdtbl)
{
        JHUFF_TBL* htbl;
        d_derived_tbl* dtbl;
        int p, i, l, si, numsymbols;
        int lookbits, ctr;
        char huffsize[257];
        unsigned int huffcode[257];
        unsigned int code;

        /* Note that huffsize[] and huffcode[] are filled in code-length order,
         * paralleling the order of the symbols themselves in htbl->huffval[].
         */

        /* Find the input Huffman table */
        if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
                ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
        htbl =
                isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
        if (htbl == nullptr) ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);

        /* Allocate a workspace if we haven't already done so. */
        if (*pdtbl == nullptr)
                *pdtbl = (d_derived_tbl*)(*cinfo->mem->alloc_small)(
                        (j_common_ptr)cinfo, JPOOL_IMAGE, SIZEOF(d_derived_tbl));
        dtbl = *pdtbl;
        dtbl->pub = htbl; /* fill in back link */

        /* Figure C.1: make table of Huffman code length for each symbol */

        p = 0;
        for (l = 1; l <= 16; l++)
        {
                i = (int)htbl->bits[l];
                if (i < 0 || p + i > 256) /* protect against table overrun */
                        ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
                while (i--) huffsize[p++] = (char)l;
        }
        huffsize[p] = 0;
        numsymbols = p;

        /* Figure C.2: generate the codes themselves */
        /* We also validate that the counts represent a legal Huffman code tree. */

        code = 0;
        si = huffsize[0];
        p = 0;
        while (huffsize[p])
        {
                while (((int)huffsize[p]) == si)
                {
                        huffcode[p++] = code;
                        code++;
                }
                /* code is now 1 more than the last code used for codelength si; but
                 * it must still fit in si bits, since no code is allowed to be all
                 * ones.
                 */
                if (((INT32)code) >= (((INT32)1) << si))
                        ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
                code <<= 1;
                si++;
        }

        /* Figure F.15: generate decoding tables for bit-sequential decoding */

        p = 0;
        for (l = 1; l <= 16; l++)
        {
                if (htbl->bits[l])
                {
                        /* valoffset[l] = huffval[] index of 1st symbol of code length l,
                         * minus the minimum code of length l
                         */
                        dtbl->valoffset[l] = (INT32)p - (INT32)huffcode[p];
                        p += htbl->bits[l];
                        dtbl->maxcode[l] = huffcode[p - 1]; /* maximum code of length l */
                }
                else
                {
                        dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
                }
        }
        dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */

        /* Compute lookahead tables to speed up decoding.
         * First we set all the table entries to 0, indicating "too long";
         * then we iterate through the Huffman codes that are short enough and
         * fill in all the entries that correspond to bit sequences starting
         * with that code.
         */

        MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));

        p = 0;
        for (l = 1; l <= HUFF_LOOKAHEAD; l++)
        {
                for (i = 1; i <= (int)htbl->bits[l]; i++, p++)
                {
                        /* l = current code's length, p = its index in huffcode[] &
                         * huffval[]. */
                        /* Generate left-justified code followed by all possible bit
                         * sequences */
                        lookbits = huffcode[p] << (HUFF_LOOKAHEAD - l);
                        for (ctr = 1 << (HUFF_LOOKAHEAD - l); ctr > 0; ctr--)
                        {
                                dtbl->look_nbits[lookbits] = l;
                                dtbl->look_sym[lookbits] = htbl->huffval[p];
                                lookbits++;
                        }
                }
        }

        /* Validate symbols as being reasonable.
         * For AC tables, we make no check, but accept all byte values 0..255.
         * For DC tables, we require the symbols to be in range 0..15.
         * (Tighter bounds could be applied depending on the data depth and mode,
         * but this is sufficient to ensure safe decoding.)
         */
        if (isDC)
        {
                for (i = 0; i < numsymbols; i++)
                {
                        int sym = htbl->huffval[i];
                        if (sym < 0 || sym > 15) ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
                }
        }
}

/*
 * Out-of-line code for bit fetching (shared with jdphuff.c).
 * See jdhuff.h for info about usage.
 * Note: current values of get_buffer and bits_left are passed as parameters,
 * but are returned in the corresponding fields of the state struct.
 *
 * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
 * of get_buffer to be used.  (On machines with wider words, an even larger
 * buffer could be used.)  However, on some machines 32-bit shifts are
 * quite slow and take time proportional to the number of places shifted.
 * (This is true with most PC compilers, for instance.)  In this case it may
 * be a win to set MIN_GET_BITS to the minimum value of 15.  This reduces the
 * average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
 */

#ifdef SLOW_SHIFT_32
#define MIN_GET_BITS 15 /* minimum allowable value */
#else
#define MIN_GET_BITS (BIT_BUF_SIZE - 7)
#endif

GLOBAL(boolean)
jpeg_fill_bit_buffer(
        bitread_working_state* state, bit_buf_type get_buffer, int bits_left,
        int nbits)
/* Load up the bit buffer to a depth of at least nbits */
{
        /* Copy heavily used state fields into locals (hopefully registers) */
        const JOCTET* next_input_byte = state->next_input_byte;
        size_t bytes_in_buffer = state->bytes_in_buffer;
        j_decompress_ptr cinfo = state->cinfo;

        /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
        /* (It is assumed that no request will be for more than that many bits.) */
        /* We fail to do so only if we hit a marker or are forced to suspend. */

        if (cinfo->unread_marker == 0)
        { /* cannot advance past a marker */
                while (bits_left < MIN_GET_BITS)
                {
                        int c;

                        /* Attempt to read a byte */
                        if (bytes_in_buffer == 0)
                        {
                                if (!(*cinfo->src->fill_input_buffer)(cinfo)) return FALSE;
                                next_input_byte = cinfo->src->next_input_byte;
                                bytes_in_buffer = cinfo->src->bytes_in_buffer;
                        }
                        bytes_in_buffer--;
                        c = GETJOCTET(*next_input_byte++);

                        /* If it's 0xFF, check and discard stuffed zero byte */
                        if (c == 0xFF)
                        {
                                /* Loop here to discard any padding FF's on terminating marker,
                                 * so that we can save a valid unread_marker value.  NOTE: we
                                 * will
                                 * accept multiple FF's followed by a 0 as meaning a single FF
                                 * data
                                 * byte.  This data pattern is not valid according to the
                                 * standard.
                                 */
                                do
                                {
                                        if (bytes_in_buffer == 0)
                                        {
                                                if (!(*cinfo->src->fill_input_buffer)(cinfo))
                                                        return FALSE;
                                                next_input_byte = cinfo->src->next_input_byte;
                                                bytes_in_buffer = cinfo->src->bytes_in_buffer;
                                        }
                                        bytes_in_buffer--;
                                        c = GETJOCTET(*next_input_byte++);
                                } while (c == 0xFF);

                                if (c == 0)
                                {
                                        /* Found FF/00, which represents an FF data byte */
                                        c = 0xFF;
                                }
                                else
                                {
                                        /* Oops, it's actually a marker indicating end of compressed
                                         * data.
                                         * Save the marker code for later use.
                                         * Fine point: it might appear that we should save the
                                         * marker into
                                         * bitread working state, not straight into permanent state.
                                         * But
                                         * once we have hit a marker, we cannot need to suspend
                                         * within the
                                         * current MCU, because we will read no more bytes from the
                                         * data
                                         * source.  So it is OK to update permanent state right
                                         * away.
                                         */
                                        cinfo->unread_marker = c;
                                        /* See if we need to insert some fake zero bits. */
                                        goto no_more_bytes;
                                }
                        }

                        /* OK, load c into get_buffer */
                        get_buffer = (get_buffer << 8) | c;
                        bits_left += 8;
                } /* end while */
        }
        else
        {
        no_more_bytes:
                /* We get here if we've read the marker that terminates the compressed
                 * data segment.  There should be enough bits in the buffer register
                 * to satisfy the request; if so, no problem.
                 */
                if (nbits > bits_left)
                {
                        /* Uh-oh.  Report corrupted data to user and stuff zeroes into
                         * the data stream, so that we can produce some kind of image.
                         * We use a nonvolatile flag to ensure that only one warning message
                         * appears per data segment.
                         */
                        if (!cinfo->entropy->insufficient_data)
                        {
                                WARNMS(cinfo, JWRN_HIT_MARKER);
                                cinfo->entropy->insufficient_data = TRUE;
                        }
                        /* Fill the buffer with zero bits */
                        get_buffer <<= MIN_GET_BITS - bits_left;
                        bits_left = MIN_GET_BITS;
                }
        }

        /* Unload the local registers */
        state->next_input_byte = next_input_byte;
        state->bytes_in_buffer = bytes_in_buffer;
        state->get_buffer = get_buffer;
        state->bits_left = bits_left;

        return TRUE;
}

/*
 * Out-of-line code for Huffman code decoding.
 * See jdhuff.h for info about usage.
 */

GLOBAL(int)
jpeg_huff_decode(
        bitread_working_state* state, bit_buf_type get_buffer, int bits_left,
        d_derived_tbl* htbl, int min_bits)
{
        int l = min_bits;
        INT32 code;

        /* HUFF_DECODE has determined that the code is at least min_bits */
        /* bits long, so fetch that many bits in one swoop. */

        CHECK_BIT_BUFFER(*state, l, return -1);
        code = GET_BITS(l);

        /* Collect the rest of the Huffman code one bit at a time. */
        /* This is per Figure F.16 in the JPEG spec. */

        while (code > htbl->maxcode[l])
        {
                code <<= 1;
                CHECK_BIT_BUFFER(*state, 1, return -1);
                code |= GET_BITS(1);
                l++;
        }

        /* Unload the local registers */
        state->get_buffer = get_buffer;
        state->bits_left = bits_left;

        /* With garbage input we may reach the sentinel value l = 17. */

        if (l > 16)
        {
                WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
                return 0; /* fake a zero as the safest result */
        }

        return htbl->pub->huffval[(int)(code + htbl->valoffset[l])];
}

/*
 * Figure F.12: extend sign bit.
 * On some machines, a shift and add will be faster than a table lookup.
 */

#ifdef AVOID_TABLES

#define HUFF_EXTEND(x, s) \
        ((x) < (1 << ((s)-1)) ? (x) + (((-1) << (s)) + 1) : (x))

#else

#define HUFF_EXTEND(x, s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))

static const int extend_test[16] = /* entry n is 2**(n-1) */
        {0,              0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040,
         0x0080, 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000};

static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
        {0,     -1,   -3,       -7,     -15,   -31,   -63,      -127,
         -255, -511, -1023, -2047, -4095, -8191, -16383, -32767};

#endif /* AVOID_TABLES */

/*
 * Check for a restart marker & resynchronize decoder.
 * Returns FALSE if must suspend.
 */

LOCAL(boolean)
process_restart(j_decompress_ptr cinfo)
{
        huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
        int ci;

        /* Throw away any unused bits remaining in bit buffer; */
        /* include any full bytes in next_marker's count of discarded bytes */
        cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
        entropy->bitstate.bits_left = 0;

        /* Advance past the RSTn marker */
        if (!(*cinfo->marker->read_restart_marker)(cinfo)) return FALSE;

        /* Re-initialize DC predictions to 0 */
        for (ci = 0; ci < cinfo->comps_in_scan; ci++)
                entropy->saved.last_dc_val[ci] = 0;

        /* Reset restart counter */
        entropy->restarts_to_go = cinfo->restart_interval;

        /* Reset out-of-data flag, unless read_restart_marker left us smack up
         * against a marker.  In that case we will end up treating the next data
         * segment as empty, and we can avoid producing bogus output pixels by
         * leaving the flag set.
         */
        if (cinfo->unread_marker == 0) entropy->pub.insufficient_data = FALSE;

        return TRUE;
}

/*
 * Decode and return one MCU's worth of Huffman-compressed coefficients.
 * The coefficients are reordered from zigzag order into natural array order,
 * but are not dequantized.
 *
 * The i'th block of the MCU is stored into the block pointed to by
 * MCU_data[i].  WE ASSUME THIS AREA HAS BEEN ZEROED BY THE CALLER.
 * (Wholesale zeroing is usually a little faster than retail...)
 *
 * Returns FALSE if data source requested suspension.  In that case no
 * changes have been made to permanent state.  (Exception: some output
 * coefficients may already have been assigned.  This is harmless for
 * this module, since we'll just re-assign them on the next call.)
 */

METHODDEF(boolean)
decode_mcu(j_decompress_ptr cinfo, JBLOCKROW* MCU_data)
{
        huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
        int blkn;
        BITREAD_STATE_VARS;
        savable_state state;

        /* Process restart marker if needed; may have to suspend */
        if (cinfo->restart_interval)
        {
                if (entropy->restarts_to_go == 0)
                        if (!process_restart(cinfo)) return FALSE;
        }

        /* If we've run out of data, just leave the MCU set to zeroes.
         * This way, we return uniform gray for the remainder of the segment.
         */
        if (!entropy->pub.insufficient_data)
        {
                /* Load up working state */
                BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
                ASSIGN_STATE(state, entropy->saved);

                /* Outer loop handles each block in the MCU */

                for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++)
                {
                        JBLOCKROW block = MCU_data[blkn];
                        d_derived_tbl* dctbl = entropy->dc_cur_tbls[blkn];
                        d_derived_tbl* actbl = entropy->ac_cur_tbls[blkn];
                        int s, k, r;

                        /* Decode a single block's worth of coefficients */

                        /* Section F.2.2.1: decode the DC coefficient difference */
                        HUFF_DECODE(s, br_state, dctbl, return FALSE, label1);
                        if (s)
                        {
                                CHECK_BIT_BUFFER(br_state, s, return FALSE);
                                r = GET_BITS(s);
                                s = HUFF_EXTEND(r, s);
                        }

                        if (entropy->dc_needed[blkn])
                        {
                                /* Convert DC difference to actual value, update last_dc_val */
                                int ci = cinfo->MCU_membership[blkn];
                                s += state.last_dc_val[ci];
                                state.last_dc_val[ci] = s;
                                /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0)
                                 */
                                (*block)[0] = (JCOEF)s;
                        }

                        if (entropy->ac_needed[blkn])
                        {
                                /* Section F.2.2.2: decode the AC coefficients */
                                /* Since zeroes are skipped, output area must be cleared
                                 * beforehand */
                                for (k = 1; k < DCTSIZE2; k++)
                                {
                                        HUFF_DECODE(s, br_state, actbl, return FALSE, label2);

                                        r = s >> 4;
                                        s &= 15;

                                        if (s)
                                        {
                                                k += r;
                                                CHECK_BIT_BUFFER(br_state, s, return FALSE);
                                                r = GET_BITS(s);
                                                s = HUFF_EXTEND(r, s);
                                                /* Output coefficient in natural (dezigzagged) order.
                                                 * Note: the extra entries in jpeg_natural_order[] will
                                                 * save us
                                                 * if k >= DCTSIZE2, which could happen if the data is
                                                 * corrupted.
                                                 */
                                                (*block)[jpeg_natural_order[k]] = (JCOEF)s;
                                        }
                                        else
                                        {
                                                if (r != 15) break;
                                                k += 15;
                                        }
                                }
                        }
                        else
                        {
                                /* Section F.2.2.2: decode the AC coefficients */
                                /* In this path we just discard the values */
                                for (k = 1; k < DCTSIZE2; k++)
                                {
                                        HUFF_DECODE(s, br_state, actbl, return FALSE, label3);

                                        r = s >> 4;
                                        s &= 15;

                                        if (s)
                                        {
                                                k += r;
                                                CHECK_BIT_BUFFER(br_state, s, return FALSE);
                                                DROP_BITS(s);
                                        }
                                        else
                                        {
                                                if (r != 15) break;
                                                k += 15;
                                        }
                                }
                        }
                }

                /* Completed MCU, so update state */
                BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
                ASSIGN_STATE(entropy->saved, state);
        }

        /* Account for restart interval (no-op if not using restarts) */
        entropy->restarts_to_go--;

        return TRUE;
}

/*
 * Module initialization routine for Huffman entropy decoding.
 */

GLOBAL(void)
jinit_huff_decoder(j_decompress_ptr cinfo)
{
        huff_entropy_ptr entropy;
        int i;

        entropy = (huff_entropy_ptr)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE, SIZEOF(huff_entropy_decoder));
        cinfo->entropy = (struct jpeg_entropy_decoder*)entropy;
        entropy->pub.start_pass = start_pass_huff_decoder;
        entropy->pub.decode_mcu = decode_mcu;

        /* Mark tables unallocated */
        for (i = 0; i < NUM_HUFF_TBLS; i++)
        {
                entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = nullptr;
        }
}