jcphuff.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 "jchuff.h" /* Declarations shared with jchuff.c */

#ifdef C_PROGRESSIVE_SUPPORTED

/* Expanded entropy encoder object for progressive Huffman encoding. */

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

        /* Mode flag: TRUE for optimization, FALSE for actual data output */
        boolean gather_statistics;

        /* Bit-level coding status.
         * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
         */
        JOCTET* next_output_byte; /* => next byte to write in buffer */
        size_t free_in_buffer; /* # of byte spaces remaining in buffer */
        INT32 put_buffer; /* current bit-accumulation buffer */
        int put_bits; /* # of bits now in it */
        j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */

        /* Coding status for DC components */
        int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */

        /* Coding status for AC components */
        int ac_tbl_no; /* the table number of the single component */
        unsigned int EOBRUN; /* run length of EOBs */
        unsigned int BE; /* # of buffered correction bits before MCU */
        char* bit_buffer; /* buffer for correction bits (1 per char) */
        /* packing correction bits tightly would save some space but cost time... */

        unsigned int restarts_to_go; /* MCUs left in this restart interval */
        int next_restart_num; /* next restart number to write (0-7) */

        /* Pointers to derived tables (these workspaces have image lifespan).
         * Since any one scan codes only DC or only AC, we only need one set
         * of tables, not one for DC and one for AC.
         */
        c_derived_tbl* derived_tbls[NUM_HUFF_TBLS];

        /* Statistics tables for optimization; again, one set is enough */
        long* count_ptrs[NUM_HUFF_TBLS];
} phuff_entropy_encoder;

typedef phuff_entropy_encoder* phuff_entropy_ptr;

/* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
 * buffer can hold.  Larger sizes may slightly improve compression, but
 * 1000 is already well into the realm of overkill.
 * The minimum safe size is 64 bits.
 */

#define MAX_CORR_BITS 1000 /* Max # of correction bits I can buffer */

/* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
 * We assume that int right shift is unsigned if INT32 right shift is,
 * which should be safe.
 */

#ifdef RIGHT_SHIFT_IS_UNSIGNED
#define ISHIFT_TEMPS int ishift_temp;
#define IRIGHT_SHIFT(x, shft)                                \
        ((ishift_temp = (x)) < 0                                 \
                 ? (ishift_temp >> (shft)) | ((~0) << (16 - (shft))) \
                 : (ishift_temp >> (shft)))
#else
#define ISHIFT_TEMPS
#define IRIGHT_SHIFT(x, shft) ((x) >> (shft))
#endif

/* Forward declarations */
METHODDEF(boolean)
encode_mcu_DC_first JPP((j_compress_ptr cinfo, JBLOCKROW* MCU_data));
METHODDEF(boolean)
encode_mcu_AC_first JPP((j_compress_ptr cinfo, JBLOCKROW* MCU_data));
METHODDEF(boolean)
encode_mcu_DC_refine JPP((j_compress_ptr cinfo, JBLOCKROW* MCU_data));
METHODDEF(boolean)
encode_mcu_AC_refine JPP((j_compress_ptr cinfo, JBLOCKROW* MCU_data));
METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo));

/*
 * Initialize for a Huffman-compressed scan using progressive JPEG.
 */

METHODDEF(void)
start_pass_phuff(j_compress_ptr cinfo, boolean gather_statistics)
{
        phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;
        boolean is_DC_band;
        int ci, tbl;
        jpeg_component_info* compptr;

        entropy->cinfo = cinfo;
        entropy->gather_statistics = gather_statistics;

        is_DC_band = (cinfo->Ss == 0);

        /* We assume jcmaster.c already validated the scan parameters. */

        /* Select execution routines */
        if (cinfo->Ah == 0)
        {
                if (is_DC_band)
                        entropy->pub.encode_mcu = encode_mcu_DC_first;
                else
                        entropy->pub.encode_mcu = encode_mcu_AC_first;
        }
        else
        {
                if (is_DC_band)
                        entropy->pub.encode_mcu = encode_mcu_DC_refine;
                else
                {
                        entropy->pub.encode_mcu = encode_mcu_AC_refine;
                        /* AC refinement needs a correction bit buffer */
                        if (entropy->bit_buffer == nullptr)
                                entropy->bit_buffer = (char*)(*cinfo->mem->alloc_small)(
                                        (j_common_ptr)cinfo, JPOOL_IMAGE,
                                        MAX_CORR_BITS * SIZEOF(char));
                }
        }
        if (gather_statistics)
                entropy->pub.finish_pass = finish_pass_gather_phuff;
        else
                entropy->pub.finish_pass = finish_pass_phuff;

        /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1
         * for AC coefficients.
         */
        for (ci = 0; ci < cinfo->comps_in_scan; ci++)
        {
                compptr = cinfo->cur_comp_info[ci];
                /* Initialize DC predictions to 0 */
                entropy->last_dc_val[ci] = 0;
                /* Get table index */
                if (is_DC_band)
                {
                        if (cinfo->Ah != 0) /* DC refinement needs no table */
                                continue;
                        tbl = compptr->dc_tbl_no;
                }
                else
                {
                        entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
                }
                if (gather_statistics)
                {
                        /* Check for invalid table index */
                        /* (make_c_derived_tbl does this in the other path) */
                        if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
                                ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
                        /* Allocate and zero the statistics tables */
                        /* Note that jpeg_gen_optimal_table expects 257 entries in each
                         * table! */
                        if (entropy->count_ptrs[tbl] == nullptr)
                                entropy->count_ptrs[tbl] = (long*)(*cinfo->mem->alloc_small)(
                                        (j_common_ptr)cinfo, JPOOL_IMAGE, 257 * SIZEOF(long));
                        MEMZERO(entropy->count_ptrs[tbl], 257 * SIZEOF(long));
                }
                else
                {
                        /* Compute derived values for Huffman table */
                        /* We may do this more than once for a table, but it's not expensive
                         */
                        jpeg_make_c_derived_tbl(
                                cinfo, is_DC_band, tbl, &entropy->derived_tbls[tbl]);
                }
        }

        /* Initialize AC stuff */
        entropy->EOBRUN = 0;
        entropy->BE = 0;

        /* Initialize bit buffer to empty */
        entropy->put_buffer = 0;
        entropy->put_bits = 0;

        /* Initialize restart stuff */
        entropy->restarts_to_go = cinfo->restart_interval;
        entropy->next_restart_num = 0;
}

/* Outputting bytes to the file.
 * NB: these must be called only when actually outputting,
 * that is, entropy->gather_statistics == FALSE.
 */

/* Emit a byte */
#define emit_byte(entropy, val)                                     \
        {                                                               \
                *(entropy)->next_output_byte++ = (JOCTET)(val);             \
                if (--(entropy)->free_in_buffer == 0) dump_buffer(entropy); \
        }

LOCAL(void)
dump_buffer(phuff_entropy_ptr entropy)
/* Empty the output buffer; we do not support suspension in this module. */
{
        struct jpeg_destination_mgr* dest = entropy->cinfo->dest;

        if (!(*dest->empty_output_buffer)(entropy->cinfo))
                ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);
        /* After a successful buffer dump, must reset buffer pointers */
        entropy->next_output_byte = dest->next_output_byte;
        entropy->free_in_buffer = dest->free_in_buffer;
}

/* Outputting bits to the file */

/* Only the right 24 bits of put_buffer are used; the valid bits are
 * left-justified in this part.  At most 16 bits can be passed to emit_bits
 * in one call, and we never retain more than 7 bits in put_buffer
 * between calls, so 24 bits are sufficient.
 */

INLINE
LOCAL(void)
emit_bits(phuff_entropy_ptr entropy, unsigned int code, int size)
/* Emit some bits, unless we are in gather mode */
{
        /* This routine is heavily used, so it's worth coding tightly. */
        INT32 put_buffer = (INT32)code;
        int put_bits = entropy->put_bits;

        /* if size is 0, caller used an invalid Huffman table entry */
        if (size == 0) ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);

        if (entropy->gather_statistics)
                return; /* do nothing if we're only getting stats */

        put_buffer &=
                (((INT32)1) << size) - 1; /* mask off any extra bits in code */

        put_bits += size; /* new number of bits in buffer */

        put_buffer <<= 24 - put_bits; /* align incoming bits */

        put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */

        while (put_bits >= 8)
        {
                int c = (int)((put_buffer >> 16) & 0xFF);

                emit_byte(entropy, c);
                if (c == 0xFF)
                { /* need to stuff a zero byte? */
                        emit_byte(entropy, 0);
                }
                put_buffer <<= 8;
                put_bits -= 8;
        }

        entropy->put_buffer = put_buffer; /* update variables */
        entropy->put_bits = put_bits;
}

LOCAL(void)
flush_bits(phuff_entropy_ptr entropy)
{
        emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */
        entropy->put_buffer = 0; /* and reset bit-buffer to empty */
        entropy->put_bits = 0;
}

/*
 * Emit (or just count) a Huffman symbol.
 */

INLINE
LOCAL(void)
emit_symbol(phuff_entropy_ptr entropy, int tbl_no, int symbol)
{
        if (entropy->gather_statistics)
                entropy->count_ptrs[tbl_no][symbol]++;
        else
        {
                c_derived_tbl* tbl = entropy->derived_tbls[tbl_no];
                emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
        }
}

/*
 * Emit bits from a correction bit buffer.
 */

LOCAL(void)
emit_buffered_bits(
        phuff_entropy_ptr entropy, char* bufstart, unsigned int nbits)
{
        if (entropy->gather_statistics) return; /* no real work */

        while (nbits > 0)
        {
                emit_bits(entropy, (unsigned int)(*bufstart), 1);
                bufstart++;
                nbits--;
        }
}

/*
 * Emit any pending EOBRUN symbol.
 */

LOCAL(void)
emit_eobrun(phuff_entropy_ptr entropy)
{
        int temp, nbits;

        if (entropy->EOBRUN > 0)
        { /* if there is any pending EOBRUN */
                temp = entropy->EOBRUN;
                nbits = 0;
                while ((temp >>= 1)) nbits++;
                /* safety check: shouldn't happen given limited correction-bit buffer */
                if (nbits > 14) ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);

                emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
                if (nbits) emit_bits(entropy, entropy->EOBRUN, nbits);

                entropy->EOBRUN = 0;

                /* Emit any buffered correction bits */
                emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
                entropy->BE = 0;
        }
}

/*
 * Emit a restart marker & resynchronize predictions.
 */

LOCAL(void)
emit_restart(phuff_entropy_ptr entropy, int restart_num)
{
        int ci;

        emit_eobrun(entropy);

        if (!entropy->gather_statistics)
        {
                flush_bits(entropy);
                emit_byte(entropy, 0xFF);
                emit_byte(entropy, JPEG_RST0 + restart_num);
        }

        if (entropy->cinfo->Ss == 0)
        {
                /* Re-initialize DC predictions to 0 */
                for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
                        entropy->last_dc_val[ci] = 0;
        }
        else
        {
                /* Re-initialize all AC-related fields to 0 */
                entropy->EOBRUN = 0;
                entropy->BE = 0;
        }
}

/*
 * MCU encoding for DC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF(boolean)
encode_mcu_DC_first(j_compress_ptr cinfo, JBLOCKROW* MCU_data)
{
        phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;
        int temp, temp2;
        int nbits;
        int blkn, ci;
        int Al = cinfo->Al;
        JBLOCKROW block;
        jpeg_component_info* compptr;
        ISHIFT_TEMPS

        entropy->next_output_byte = cinfo->dest->next_output_byte;
        entropy->free_in_buffer = cinfo->dest->free_in_buffer;

        /* Emit restart marker if needed */
        if (cinfo->restart_interval)
                if (entropy->restarts_to_go == 0)
                        emit_restart(entropy, entropy->next_restart_num);

        /* Encode the MCU data blocks */
        for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++)
        {
                block = MCU_data[blkn];
                ci = cinfo->MCU_membership[blkn];
                compptr = cinfo->cur_comp_info[ci];

                /* Compute the DC value after the required point transform by Al.
                 * This is simply an arithmetic right shift.
                 */
                temp2 = IRIGHT_SHIFT((int)((*block)[0]), Al);

                /* DC differences are figured on the point-transformed values. */
                temp = temp2 - entropy->last_dc_val[ci];
                entropy->last_dc_val[ci] = temp2;

                /* Encode the DC coefficient difference per section G.1.2.1 */
                temp2 = temp;
                if (temp < 0)
                {
                        temp = -temp; /* temp is abs value of input */
                        /* For a negative input, want temp2 = bitwise complement of
                         * abs(input) */
                        /* This code assumes we are on a two's complement machine */
                        temp2--;
                }

                /* Find the number of bits needed for the magnitude of the coefficient
                 */
                nbits = 0;
                while (temp)
                {
                        nbits++;
                        temp >>= 1;
                }
                /* Check for out-of-range coefficient values.
                 * Since we're encoding a difference, the range limit is twice as much.
                 */
                if (nbits > MAX_COEF_BITS + 1) ERREXIT(cinfo, JERR_BAD_DCT_COEF);

                /* Count/emit the Huffman-coded symbol for the number of bits */
                emit_symbol(entropy, compptr->dc_tbl_no, nbits);

                /* Emit that number of bits of the value, if positive, */
                /* or the complement of its magnitude, if negative. */
                if (nbits) /* emit_bits rejects calls with size 0 */
                        emit_bits(entropy, (unsigned int)temp2, nbits);
        }

        cinfo->dest->next_output_byte = entropy->next_output_byte;
        cinfo->dest->free_in_buffer = entropy->free_in_buffer;

        /* Update restart-interval state too */
        if (cinfo->restart_interval)
        {
                if (entropy->restarts_to_go == 0)
                {
                        entropy->restarts_to_go = cinfo->restart_interval;
                        entropy->next_restart_num++;
                        entropy->next_restart_num &= 7;
                }
                entropy->restarts_to_go--;
        }

        return TRUE;
}

/*
 * MCU encoding for AC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF(boolean)
encode_mcu_AC_first(j_compress_ptr cinfo, JBLOCKROW* MCU_data)
{
        phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;
        int temp, temp2;
        int nbits;
        int r, k;
        int Se = cinfo->Se;
        int Al = cinfo->Al;
        JBLOCKROW block;

        entropy->next_output_byte = cinfo->dest->next_output_byte;
        entropy->free_in_buffer = cinfo->dest->free_in_buffer;

        /* Emit restart marker if needed */
        if (cinfo->restart_interval)
                if (entropy->restarts_to_go == 0)
                        emit_restart(entropy, entropy->next_restart_num);

        /* Encode the MCU data block */
        block = MCU_data[0];

        /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */

        r = 0; /* r = run length of zeros */

        for (k = cinfo->Ss; k <= Se; k++)
        {
                if ((temp = (*block)[jpeg_natural_order[k]]) == 0)
                {
                        r++;
                        continue;
                }
                /* We must apply the point transform by Al.  For AC coefficients this
                 * is an integer division with rounding towards 0.  To do this portably
                 * in C, we shift after obtaining the absolute value; so the code is
                 * interwoven with finding the abs value (temp) and output bits (temp2).
                 */
                if (temp < 0)
                {
                        temp = -temp; /* temp is abs value of input */
                        temp >>= Al; /* apply the point transform */
                        /* For a negative coef, want temp2 = bitwise complement of abs(coef)
                         */
                        temp2 = ~temp;
                }
                else
                {
                        temp >>= Al; /* apply the point transform */
                        temp2 = temp;
                }
                /* Watch out for case that nonzero coef is zero after point transform */
                if (temp == 0)
                {
                        r++;
                        continue;
                }

                /* Emit any pending EOBRUN */
                if (entropy->EOBRUN > 0) emit_eobrun(entropy);
                /* if run length > 15, must emit special run-length-16 codes (0xF0) */
                while (r > 15)
                {
                        emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
                        r -= 16;
                }

                /* Find the number of bits needed for the magnitude of the coefficient
                 */
                nbits = 1; /* there must be at least one 1 bit */
                while ((temp >>= 1)) nbits++;
                /* Check for out-of-range coefficient values */
                if (nbits > MAX_COEF_BITS) ERREXIT(cinfo, JERR_BAD_DCT_COEF);

                /* Count/emit Huffman symbol for run length / number of bits */
                emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);

                /* Emit that number of bits of the value, if positive, */
                /* or the complement of its magnitude, if negative. */
                emit_bits(entropy, (unsigned int)temp2, nbits);

                r = 0; /* reset zero run length */
        }

        if (r > 0)
        { /* If there are trailing zeroes, */
                entropy->EOBRUN++; /* count an EOB */
                if (entropy->EOBRUN == 0x7FFF)
                        emit_eobrun(entropy); /* force it out to avoid overflow */
        }

        cinfo->dest->next_output_byte = entropy->next_output_byte;
        cinfo->dest->free_in_buffer = entropy->free_in_buffer;

        /* Update restart-interval state too */
        if (cinfo->restart_interval)
        {
                if (entropy->restarts_to_go == 0)
                {
                        entropy->restarts_to_go = cinfo->restart_interval;
                        entropy->next_restart_num++;
                        entropy->next_restart_num &= 7;
                }
                entropy->restarts_to_go--;
        }

        return TRUE;
}

/*
 * MCU encoding for DC successive approximation refinement scan.
 * Note: we assume such scans can be multi-component, although the spec
 * is not very clear on the point.
 */

METHODDEF(boolean)
encode_mcu_DC_refine(j_compress_ptr cinfo, JBLOCKROW* MCU_data)
{
        phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;
        int temp;
        int blkn;
        int Al = cinfo->Al;
        JBLOCKROW block;

        entropy->next_output_byte = cinfo->dest->next_output_byte;
        entropy->free_in_buffer = cinfo->dest->free_in_buffer;

        /* Emit restart marker if needed */
        if (cinfo->restart_interval)
                if (entropy->restarts_to_go == 0)
                        emit_restart(entropy, entropy->next_restart_num);

        /* Encode the MCU data blocks */
        for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++)
        {
                block = MCU_data[blkn];

                /* We simply emit the Al'th bit of the DC coefficient value. */
                temp = (*block)[0];
                emit_bits(entropy, (unsigned int)(temp >> Al), 1);
        }

        cinfo->dest->next_output_byte = entropy->next_output_byte;
        cinfo->dest->free_in_buffer = entropy->free_in_buffer;

        /* Update restart-interval state too */
        if (cinfo->restart_interval)
        {
                if (entropy->restarts_to_go == 0)
                {
                        entropy->restarts_to_go = cinfo->restart_interval;
                        entropy->next_restart_num++;
                        entropy->next_restart_num &= 7;
                }
                entropy->restarts_to_go--;
        }

        return TRUE;
}

/*
 * MCU encoding for AC successive approximation refinement scan.
 */

METHODDEF(boolean)
encode_mcu_AC_refine(j_compress_ptr cinfo, JBLOCKROW* MCU_data)
{
        phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;
        int temp;
        int r, k;
        int EOB;
        char* BR_buffer;
        unsigned int BR;
        int Se = cinfo->Se;
        int Al = cinfo->Al;
        JBLOCKROW block;
        int absvalues[DCTSIZE2];

        entropy->next_output_byte = cinfo->dest->next_output_byte;
        entropy->free_in_buffer = cinfo->dest->free_in_buffer;

        /* Emit restart marker if needed */
        if (cinfo->restart_interval)
                if (entropy->restarts_to_go == 0)
                        emit_restart(entropy, entropy->next_restart_num);

        /* Encode the MCU data block */
        block = MCU_data[0];

        /* It is convenient to make a pre-pass to determine the transformed
         * coefficients' absolute values and the EOB position.
         */
        EOB = 0;
        for (k = cinfo->Ss; k <= Se; k++)
        {
                temp = (*block)[jpeg_natural_order[k]];
                /* We must apply the point transform by Al.  For AC coefficients this
                 * is an integer division with rounding towards 0.  To do this portably
                 * in C, we shift after obtaining the absolute value.
                 */
                if (temp < 0) temp = -temp; /* temp is abs value of input */
                temp >>= Al; /* apply the point transform */
                absvalues[k] = temp; /* save abs value for main pass */
                if (temp == 1) EOB = k; /* EOB = index of last newly-nonzero coef */
        }

        /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */

        r = 0; /* r = run length of zeros */
        BR = 0; /* BR = count of buffered bits added now */
        BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */

        for (k = cinfo->Ss; k <= Se; k++)
        {
                if ((temp = absvalues[k]) == 0)
                {
                        r++;
                        continue;
                }

                /* Emit any required ZRLs, but not if they can be folded into EOB */
                while (r > 15 && k <= EOB)
                {
                        /* emit any pending EOBRUN and the BE correction bits */
                        emit_eobrun(entropy);
                        /* Emit ZRL */
                        emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
                        r -= 16;
                        /* Emit buffered correction bits that must be associated with ZRL */
                        emit_buffered_bits(entropy, BR_buffer, BR);
                        BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
                        BR = 0;
                }

                /* If the coef was previously nonzero, it only needs a correction bit.
                 * NOTE: a straight translation of the spec's figure G.7 would suggest
                 * that we also need to test r > 15.  But if r > 15, we can only get
                 * here
                 * if k > EOB, which implies that this coefficient is not 1.
                 */
                if (temp > 1)
                {
                        /* The correction bit is the next bit of the absolute value. */
                        BR_buffer[BR++] = (char)(temp & 1);
                        continue;
                }

                /* Emit any pending EOBRUN and the BE correction bits */
                emit_eobrun(entropy);

                /* Count/emit Huffman symbol for run length / number of bits */
                emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);

                /* Emit output bit for newly-nonzero coef */
                temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
                emit_bits(entropy, (unsigned int)temp, 1);

                /* Emit buffered correction bits that must be associated with this code
                 */
                emit_buffered_bits(entropy, BR_buffer, BR);
                BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
                BR = 0;
                r = 0; /* reset zero run length */
        }

        if (r > 0 || BR > 0)
        { /* If there are trailing zeroes, */
                entropy->EOBRUN++; /* count an EOB */
                entropy->BE += BR; /* concat my correction bits to older ones */
                /* We force out the EOB if we risk either:
                 * 1. overflow of the EOB counter;
                 * 2. overflow of the correction bit buffer during the next MCU.
                 */
                if (entropy->EOBRUN == 0x7FFF ||
                        entropy->BE > (MAX_CORR_BITS - DCTSIZE2 + 1))
                        emit_eobrun(entropy);
        }

        cinfo->dest->next_output_byte = entropy->next_output_byte;
        cinfo->dest->free_in_buffer = entropy->free_in_buffer;

        /* Update restart-interval state too */
        if (cinfo->restart_interval)
        {
                if (entropy->restarts_to_go == 0)
                {
                        entropy->restarts_to_go = cinfo->restart_interval;
                        entropy->next_restart_num++;
                        entropy->next_restart_num &= 7;
                }
                entropy->restarts_to_go--;
        }

        return TRUE;
}

/*
 * Finish up at the end of a Huffman-compressed progressive scan.
 */

METHODDEF(void)
finish_pass_phuff(j_compress_ptr cinfo)
{
        phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;

        entropy->next_output_byte = cinfo->dest->next_output_byte;
        entropy->free_in_buffer = cinfo->dest->free_in_buffer;

        /* Flush out any buffered data */
        emit_eobrun(entropy);
        flush_bits(entropy);

        cinfo->dest->next_output_byte = entropy->next_output_byte;
        cinfo->dest->free_in_buffer = entropy->free_in_buffer;
}

/*
 * Finish up a statistics-gathering pass and create the new Huffman tables.
 */

METHODDEF(void)
finish_pass_gather_phuff(j_compress_ptr cinfo)
{
        phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;
        boolean is_DC_band;
        int ci, tbl;
        jpeg_component_info* compptr;
        JHUFF_TBL** htblptr;
        boolean did[NUM_HUFF_TBLS];

        /* Flush out buffered data (all we care about is counting the EOB symbol) */
        emit_eobrun(entropy);

        is_DC_band = (cinfo->Ss == 0);

        /* It's important not to apply jpeg_gen_optimal_table more than once
         * per table, because it clobbers the input frequency counts!
         */
        MEMZERO(did, SIZEOF(did));

        for (ci = 0; ci < cinfo->comps_in_scan; ci++)
        {
                compptr = cinfo->cur_comp_info[ci];
                if (is_DC_band)
                {
                        if (cinfo->Ah != 0) /* DC refinement needs no table */
                                continue;
                        tbl = compptr->dc_tbl_no;
                }
                else
                {
                        tbl = compptr->ac_tbl_no;
                }
                if (!did[tbl])
                {
                        if (is_DC_band)
                                htblptr = &cinfo->dc_huff_tbl_ptrs[tbl];
                        else
                                htblptr = &cinfo->ac_huff_tbl_ptrs[tbl];
                        if (*htblptr == nullptr)
                                *htblptr = jpeg_alloc_huff_table((j_common_ptr)cinfo);
                        jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
                        did[tbl] = TRUE;
                }
        }
}

/*
 * Module initialization routine for progressive Huffman entropy encoding.
 */

GLOBAL(void)
jinit_phuff_encoder(j_compress_ptr cinfo)
{
        phuff_entropy_ptr entropy;
        int i;

        entropy = (phuff_entropy_ptr)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE, SIZEOF(phuff_entropy_encoder));
        cinfo->entropy = (struct jpeg_entropy_encoder*)entropy;
        entropy->pub.start_pass = start_pass_phuff;

        /* Mark tables unallocated */
        for (i = 0; i < NUM_HUFF_TBLS; i++)
        {
                entropy->derived_tbls[i] = nullptr;
                entropy->count_ptrs[i] = nullptr;
        }
        entropy->bit_buffer = nullptr; /* needed only in AC refinement scan */
}

#endif /* C_PROGRESSIVE_SUPPORTED */