The Tor Browser: media/libjpeg/jcphuff.c@b8a032363ba2 (annotated)

media/libjpeg/jcphuff.c@b8a032363ba2 (annotated)

media/libjpeg/jcphuff.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /*
  * jcphuff.c
  *
  * Copyright (C) 1995-1997, Thomas G. Lane.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains Huffman entropy encoding routines for progressive JPEG.
  *
  * We do not support output suspension in this module, since the library
  * currently does not allow multiple-scan files to be written with output
  * suspension.
  */
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "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 == NULL)
 	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] == NULL)
 	entropy->count_ptrs[tbl] = (long *)
 	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 * 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.
  */
 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. */
   register INT32 put_buffer = (INT32) code;
   register 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.
  */
 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)
 {
   register 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;
   register int temp, temp2;
   register 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;
   register int temp, temp2;
   register int nbits;
   register 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;
   register 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;
   register int temp;
   register 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 == NULL)
         *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] = NULL;
     entropy->count_ptrs[i] = NULL;
   }
   entropy->bit_buffer = NULL;	/* needed only in AC refinement scan */
 }
 #endif /* C_PROGRESSIVE_SUPPORTED */

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media/libjpeg/jcphuff.c@b8a032363ba2 (annotated)

media/libjpeg/jcphuff.c