nuclear@2: /*
nuclear@2:  * jchuff.c
nuclear@2:  *
nuclear@2:  * Copyright (C) 1991-1997, Thomas G. Lane.
nuclear@2:  * This file is part of the Independent JPEG Group's software.
nuclear@2:  * For conditions of distribution and use, see the accompanying README file.
nuclear@2:  *
nuclear@2:  * This file contains Huffman entropy encoding routines.
nuclear@2:  *
nuclear@2:  * Much of the complexity here has to do with supporting output suspension.
nuclear@2:  * If the data destination module demands suspension, we want to be able to
nuclear@2:  * back up to the start of the current MCU.  To do this, we copy state
nuclear@2:  * variables into local working storage, and update them back to the
nuclear@2:  * permanent JPEG objects only upon successful completion of an MCU.
nuclear@2:  */
nuclear@2: 
nuclear@2: #define JPEG_INTERNALS
nuclear@2: #include "jinclude.h"
nuclear@2: #include "jpeglib.h"
nuclear@2: #include "jchuff.h"		/* Declarations shared with jcphuff.c */
nuclear@2: 
nuclear@2: 
nuclear@2: /* Expanded entropy encoder object for Huffman encoding.
nuclear@2:  *
nuclear@2:  * The savable_state subrecord contains fields that change within an MCU,
nuclear@2:  * but must not be updated permanently until we complete the MCU.
nuclear@2:  */
nuclear@2: 
nuclear@2: typedef struct {
nuclear@2:   INT32 put_buffer;		/* current bit-accumulation buffer */
nuclear@2:   int put_bits;			/* # of bits now in it */
nuclear@2:   int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
nuclear@2: } savable_state;
nuclear@2: 
nuclear@2: /* This macro is to work around compilers with missing or broken
nuclear@2:  * structure assignment.  You'll need to fix this code if you have
nuclear@2:  * such a compiler and you change MAX_COMPS_IN_SCAN.
nuclear@2:  */
nuclear@2: 
nuclear@2: #ifndef NO_STRUCT_ASSIGN
nuclear@2: #define ASSIGN_STATE(dest,src)  ((dest) = (src))
nuclear@2: #else
nuclear@2: #if MAX_COMPS_IN_SCAN == 4
nuclear@2: #define ASSIGN_STATE(dest,src)  \
nuclear@2: 	((dest).put_buffer = (src).put_buffer, \
nuclear@2: 	 (dest).put_bits = (src).put_bits, \
nuclear@2: 	 (dest).last_dc_val[0] = (src).last_dc_val[0], \
nuclear@2: 	 (dest).last_dc_val[1] = (src).last_dc_val[1], \
nuclear@2: 	 (dest).last_dc_val[2] = (src).last_dc_val[2], \
nuclear@2: 	 (dest).last_dc_val[3] = (src).last_dc_val[3])
nuclear@2: #endif
nuclear@2: #endif
nuclear@2: 
nuclear@2: 
nuclear@2: typedef struct {
nuclear@2:   struct jpeg_entropy_encoder pub; /* public fields */
nuclear@2: 
nuclear@2:   savable_state saved;		/* Bit buffer & DC state at start of MCU */
nuclear@2: 
nuclear@2:   /* These fields are NOT loaded into local working state. */
nuclear@2:   unsigned int restarts_to_go;	/* MCUs left in this restart interval */
nuclear@2:   int next_restart_num;		/* next restart number to write (0-7) */
nuclear@2: 
nuclear@2:   /* Pointers to derived tables (these workspaces have image lifespan) */
nuclear@2:   c_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
nuclear@2:   c_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
nuclear@2: 
nuclear@2: #ifdef ENTROPY_OPT_SUPPORTED	/* Statistics tables for optimization */
nuclear@2:   long * dc_count_ptrs[NUM_HUFF_TBLS];
nuclear@2:   long * ac_count_ptrs[NUM_HUFF_TBLS];
nuclear@2: #endif
nuclear@2: } huff_entropy_encoder;
nuclear@2: 
nuclear@2: typedef huff_entropy_encoder * huff_entropy_ptr;
nuclear@2: 
nuclear@2: /* Working state while writing an MCU.
nuclear@2:  * This struct contains all the fields that are needed by subroutines.
nuclear@2:  */
nuclear@2: 
nuclear@2: typedef struct {
nuclear@2:   JOCTET * next_output_byte;	/* => next byte to write in buffer */
nuclear@2:   size_t free_in_buffer;	/* # of byte spaces remaining in buffer */
nuclear@2:   savable_state cur;		/* Current bit buffer & DC state */
nuclear@2:   j_compress_ptr cinfo;		/* dump_buffer needs access to this */
nuclear@2: } working_state;
nuclear@2: 
nuclear@2: 
nuclear@2: /* Forward declarations */
nuclear@2: METHODDEF(boolean) encode_mcu_huff JPP((j_compress_ptr cinfo,
nuclear@2: 					JBLOCKROW *MCU_data));
nuclear@2: METHODDEF(void) finish_pass_huff JPP((j_compress_ptr cinfo));
nuclear@2: #ifdef ENTROPY_OPT_SUPPORTED
nuclear@2: METHODDEF(boolean) encode_mcu_gather JPP((j_compress_ptr cinfo,
nuclear@2: 					  JBLOCKROW *MCU_data));
nuclear@2: METHODDEF(void) finish_pass_gather JPP((j_compress_ptr cinfo));
nuclear@2: #endif
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Initialize for a Huffman-compressed scan.
nuclear@2:  * If gather_statistics is TRUE, we do not output anything during the scan,
nuclear@2:  * just count the Huffman symbols used and generate Huffman code tables.
nuclear@2:  */
nuclear@2: 
nuclear@2: METHODDEF(void)
nuclear@2: start_pass_huff (j_compress_ptr cinfo, boolean gather_statistics)
nuclear@2: {
nuclear@2:   huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
nuclear@2:   int ci, dctbl, actbl;
nuclear@2:   jpeg_component_info * compptr;
nuclear@2: 
nuclear@2:   if (gather_statistics) {
nuclear@2: #ifdef ENTROPY_OPT_SUPPORTED
nuclear@2:     entropy->pub.encode_mcu = encode_mcu_gather;
nuclear@2:     entropy->pub.finish_pass = finish_pass_gather;
nuclear@2: #else
nuclear@2:     ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@2: #endif
nuclear@2:   } else {
nuclear@2:     entropy->pub.encode_mcu = encode_mcu_huff;
nuclear@2:     entropy->pub.finish_pass = finish_pass_huff;
nuclear@2:   }
nuclear@2: 
nuclear@2:   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
nuclear@2:     compptr = cinfo->cur_comp_info[ci];
nuclear@2:     dctbl = compptr->dc_tbl_no;
nuclear@2:     actbl = compptr->ac_tbl_no;
nuclear@2:     if (gather_statistics) {
nuclear@2: #ifdef ENTROPY_OPT_SUPPORTED
nuclear@2:       /* Check for invalid table indexes */
nuclear@2:       /* (make_c_derived_tbl does this in the other path) */
nuclear@2:       if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS)
nuclear@2: 	ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);
nuclear@2:       if (actbl < 0 || actbl >= NUM_HUFF_TBLS)
nuclear@2: 	ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, actbl);
nuclear@2:       /* Allocate and zero the statistics tables */
nuclear@2:       /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
nuclear@2:       if (entropy->dc_count_ptrs[dctbl] == NULL)
nuclear@2: 	entropy->dc_count_ptrs[dctbl] = (long *)
nuclear@2: 	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@2: 				      257 * SIZEOF(long));
nuclear@2:       MEMZERO(entropy->dc_count_ptrs[dctbl], 257 * SIZEOF(long));
nuclear@2:       if (entropy->ac_count_ptrs[actbl] == NULL)
nuclear@2: 	entropy->ac_count_ptrs[actbl] = (long *)
nuclear@2: 	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@2: 				      257 * SIZEOF(long));
nuclear@2:       MEMZERO(entropy->ac_count_ptrs[actbl], 257 * SIZEOF(long));
nuclear@2: #endif
nuclear@2:     } else {
nuclear@2:       /* Compute derived values for Huffman tables */
nuclear@2:       /* We may do this more than once for a table, but it's not expensive */
nuclear@2:       jpeg_make_c_derived_tbl(cinfo, TRUE, dctbl,
nuclear@2: 			      & entropy->dc_derived_tbls[dctbl]);
nuclear@2:       jpeg_make_c_derived_tbl(cinfo, FALSE, actbl,
nuclear@2: 			      & entropy->ac_derived_tbls[actbl]);
nuclear@2:     }
nuclear@2:     /* Initialize DC predictions to 0 */
nuclear@2:     entropy->saved.last_dc_val[ci] = 0;
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* Initialize bit buffer to empty */
nuclear@2:   entropy->saved.put_buffer = 0;
nuclear@2:   entropy->saved.put_bits = 0;
nuclear@2: 
nuclear@2:   /* Initialize restart stuff */
nuclear@2:   entropy->restarts_to_go = cinfo->restart_interval;
nuclear@2:   entropy->next_restart_num = 0;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Compute the derived values for a Huffman table.
nuclear@2:  * This routine also performs some validation checks on the table.
nuclear@2:  *
nuclear@2:  * Note this is also used by jcphuff.c.
nuclear@2:  */
nuclear@2: 
nuclear@2: GLOBAL(void)
nuclear@2: jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno,
nuclear@2: 			 c_derived_tbl ** pdtbl)
nuclear@2: {
nuclear@2:   JHUFF_TBL *htbl;
nuclear@2:   c_derived_tbl *dtbl;
nuclear@2:   int p, i, l, lastp, si, maxsymbol;
nuclear@2:   char huffsize[257];
nuclear@2:   unsigned int huffcode[257];
nuclear@2:   unsigned int code;
nuclear@2: 
nuclear@2:   /* Note that huffsize[] and huffcode[] are filled in code-length order,
nuclear@2:    * paralleling the order of the symbols themselves in htbl->huffval[].
nuclear@2:    */
nuclear@2: 
nuclear@2:   /* Find the input Huffman table */
nuclear@2:   if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
nuclear@2:     ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
nuclear@2:   htbl =
nuclear@2:     isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
nuclear@2:   if (htbl == NULL)
nuclear@2:     ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
nuclear@2: 
nuclear@2:   /* Allocate a workspace if we haven't already done so. */
nuclear@2:   if (*pdtbl == NULL)
nuclear@2:     *pdtbl = (c_derived_tbl *)
nuclear@2:       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@2: 				  SIZEOF(c_derived_tbl));
nuclear@2:   dtbl = *pdtbl;
nuclear@2:   
nuclear@2:   /* Figure C.1: make table of Huffman code length for each symbol */
nuclear@2: 
nuclear@2:   p = 0;
nuclear@2:   for (l = 1; l <= 16; l++) {
nuclear@2:     i = (int) htbl->bits[l];
nuclear@2:     if (i < 0 || p + i > 256)	/* protect against table overrun */
nuclear@2:       ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
nuclear@2:     while (i--)
nuclear@2:       huffsize[p++] = (char) l;
nuclear@2:   }
nuclear@2:   huffsize[p] = 0;
nuclear@2:   lastp = p;
nuclear@2:   
nuclear@2:   /* Figure C.2: generate the codes themselves */
nuclear@2:   /* We also validate that the counts represent a legal Huffman code tree. */
nuclear@2: 
nuclear@2:   code = 0;
nuclear@2:   si = huffsize[0];
nuclear@2:   p = 0;
nuclear@2:   while (huffsize[p]) {
nuclear@2:     while (((int) huffsize[p]) == si) {
nuclear@2:       huffcode[p++] = code;
nuclear@2:       code++;
nuclear@2:     }
nuclear@2:     /* code is now 1 more than the last code used for codelength si; but
nuclear@2:      * it must still fit in si bits, since no code is allowed to be all ones.
nuclear@2:      */
nuclear@2:     if (((INT32) code) >= (((INT32) 1) << si))
nuclear@2:       ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
nuclear@2:     code <<= 1;
nuclear@2:     si++;
nuclear@2:   }
nuclear@2:   
nuclear@2:   /* Figure C.3: generate encoding tables */
nuclear@2:   /* These are code and size indexed by symbol value */
nuclear@2: 
nuclear@2:   /* Set all codeless symbols to have code length 0;
nuclear@2:    * this lets us detect duplicate VAL entries here, and later
nuclear@2:    * allows emit_bits to detect any attempt to emit such symbols.
nuclear@2:    */
nuclear@2:   MEMZERO(dtbl->ehufsi, SIZEOF(dtbl->ehufsi));
nuclear@2: 
nuclear@2:   /* This is also a convenient place to check for out-of-range
nuclear@2:    * and duplicated VAL entries.  We allow 0..255 for AC symbols
nuclear@2:    * but only 0..15 for DC.  (We could constrain them further
nuclear@2:    * based on data depth and mode, but this seems enough.)
nuclear@2:    */
nuclear@2:   maxsymbol = isDC ? 15 : 255;
nuclear@2: 
nuclear@2:   for (p = 0; p < lastp; p++) {
nuclear@2:     i = htbl->huffval[p];
nuclear@2:     if (i < 0 || i > maxsymbol || dtbl->ehufsi[i])
nuclear@2:       ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
nuclear@2:     dtbl->ehufco[i] = huffcode[p];
nuclear@2:     dtbl->ehufsi[i] = huffsize[p];
nuclear@2:   }
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /* Outputting bytes to the file */
nuclear@2: 
nuclear@2: /* Emit a byte, taking 'action' if must suspend. */
nuclear@2: #define emit_byte(state,val,action)  \
nuclear@2: 	{ *(state)->next_output_byte++ = (JOCTET) (val);  \
nuclear@2: 	  if (--(state)->free_in_buffer == 0)  \
nuclear@2: 	    if (! dump_buffer(state))  \
nuclear@2: 	      { action; } }
nuclear@2: 
nuclear@2: 
nuclear@2: LOCAL(boolean)
nuclear@2: dump_buffer (working_state * state)
nuclear@2: /* Empty the output buffer; return TRUE if successful, FALSE if must suspend */
nuclear@2: {
nuclear@2:   struct jpeg_destination_mgr * dest = state->cinfo->dest;
nuclear@2: 
nuclear@2:   if (! (*dest->empty_output_buffer) (state->cinfo))
nuclear@2:     return FALSE;
nuclear@2:   /* After a successful buffer dump, must reset buffer pointers */
nuclear@2:   state->next_output_byte = dest->next_output_byte;
nuclear@2:   state->free_in_buffer = dest->free_in_buffer;
nuclear@2:   return TRUE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /* Outputting bits to the file */
nuclear@2: 
nuclear@2: /* Only the right 24 bits of put_buffer are used; the valid bits are
nuclear@2:  * left-justified in this part.  At most 16 bits can be passed to emit_bits
nuclear@2:  * in one call, and we never retain more than 7 bits in put_buffer
nuclear@2:  * between calls, so 24 bits are sufficient.
nuclear@2:  */
nuclear@2: 
nuclear@2: INLINE
nuclear@2: LOCAL(boolean)
nuclear@2: emit_bits (working_state * state, unsigned int code, int size)
nuclear@2: /* Emit some bits; return TRUE if successful, FALSE if must suspend */
nuclear@2: {
nuclear@2:   /* This routine is heavily used, so it's worth coding tightly. */
nuclear@2:   register INT32 put_buffer = (INT32) code;
nuclear@2:   register int put_bits = state->cur.put_bits;
nuclear@2: 
nuclear@2:   /* if size is 0, caller used an invalid Huffman table entry */
nuclear@2:   if (size == 0)
nuclear@2:     ERREXIT(state->cinfo, JERR_HUFF_MISSING_CODE);
nuclear@2: 
nuclear@2:   put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
nuclear@2:   
nuclear@2:   put_bits += size;		/* new number of bits in buffer */
nuclear@2:   
nuclear@2:   put_buffer <<= 24 - put_bits; /* align incoming bits */
nuclear@2: 
nuclear@2:   put_buffer |= state->cur.put_buffer; /* and merge with old buffer contents */
nuclear@2:   
nuclear@2:   while (put_bits >= 8) {
nuclear@2:     int c = (int) ((put_buffer >> 16) & 0xFF);
nuclear@2:     
nuclear@2:     emit_byte(state, c, return FALSE);
nuclear@2:     if (c == 0xFF) {		/* need to stuff a zero byte? */
nuclear@2:       emit_byte(state, 0, return FALSE);
nuclear@2:     }
nuclear@2:     put_buffer <<= 8;
nuclear@2:     put_bits -= 8;
nuclear@2:   }
nuclear@2: 
nuclear@2:   state->cur.put_buffer = put_buffer; /* update state variables */
nuclear@2:   state->cur.put_bits = put_bits;
nuclear@2: 
nuclear@2:   return TRUE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: LOCAL(boolean)
nuclear@2: flush_bits (working_state * state)
nuclear@2: {
nuclear@2:   if (! emit_bits(state, 0x7F, 7)) /* fill any partial byte with ones */
nuclear@2:     return FALSE;
nuclear@2:   state->cur.put_buffer = 0;	/* and reset bit-buffer to empty */
nuclear@2:   state->cur.put_bits = 0;
nuclear@2:   return TRUE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /* Encode a single block's worth of coefficients */
nuclear@2: 
nuclear@2: LOCAL(boolean)
nuclear@2: encode_one_block (working_state * state, JCOEFPTR block, int last_dc_val,
nuclear@2: 		  c_derived_tbl *dctbl, c_derived_tbl *actbl)
nuclear@2: {
nuclear@2:   register int temp, temp2;
nuclear@2:   register int nbits;
nuclear@2:   register int k, r, i;
nuclear@2:   
nuclear@2:   /* Encode the DC coefficient difference per section F.1.2.1 */
nuclear@2:   
nuclear@2:   temp = temp2 = block[0] - last_dc_val;
nuclear@2: 
nuclear@2:   if (temp < 0) {
nuclear@2:     temp = -temp;		/* temp is abs value of input */
nuclear@2:     /* For a negative input, want temp2 = bitwise complement of abs(input) */
nuclear@2:     /* This code assumes we are on a two's complement machine */
nuclear@2:     temp2--;
nuclear@2:   }
nuclear@2:   
nuclear@2:   /* Find the number of bits needed for the magnitude of the coefficient */
nuclear@2:   nbits = 0;
nuclear@2:   while (temp) {
nuclear@2:     nbits++;
nuclear@2:     temp >>= 1;
nuclear@2:   }
nuclear@2:   /* Check for out-of-range coefficient values.
nuclear@2:    * Since we're encoding a difference, the range limit is twice as much.
nuclear@2:    */
nuclear@2:   if (nbits > MAX_COEF_BITS+1)
nuclear@2:     ERREXIT(state->cinfo, JERR_BAD_DCT_COEF);
nuclear@2:   
nuclear@2:   /* Emit the Huffman-coded symbol for the number of bits */
nuclear@2:   if (! emit_bits(state, dctbl->ehufco[nbits], dctbl->ehufsi[nbits]))
nuclear@2:     return FALSE;
nuclear@2: 
nuclear@2:   /* Emit that number of bits of the value, if positive, */
nuclear@2:   /* or the complement of its magnitude, if negative. */
nuclear@2:   if (nbits)			/* emit_bits rejects calls with size 0 */
nuclear@2:     if (! emit_bits(state, (unsigned int) temp2, nbits))
nuclear@2:       return FALSE;
nuclear@2: 
nuclear@2:   /* Encode the AC coefficients per section F.1.2.2 */
nuclear@2:   
nuclear@2:   r = 0;			/* r = run length of zeros */
nuclear@2:   
nuclear@2:   for (k = 1; k < DCTSIZE2; k++) {
nuclear@2:     if ((temp = block[jpeg_natural_order[k]]) == 0) {
nuclear@2:       r++;
nuclear@2:     } else {
nuclear@2:       /* if run length > 15, must emit special run-length-16 codes (0xF0) */
nuclear@2:       while (r > 15) {
nuclear@2: 	if (! emit_bits(state, actbl->ehufco[0xF0], actbl->ehufsi[0xF0]))
nuclear@2: 	  return FALSE;
nuclear@2: 	r -= 16;
nuclear@2:       }
nuclear@2: 
nuclear@2:       temp2 = temp;
nuclear@2:       if (temp < 0) {
nuclear@2: 	temp = -temp;		/* temp is abs value of input */
nuclear@2: 	/* This code assumes we are on a two's complement machine */
nuclear@2: 	temp2--;
nuclear@2:       }
nuclear@2:       
nuclear@2:       /* Find the number of bits needed for the magnitude of the coefficient */
nuclear@2:       nbits = 1;		/* there must be at least one 1 bit */
nuclear@2:       while ((temp >>= 1))
nuclear@2: 	nbits++;
nuclear@2:       /* Check for out-of-range coefficient values */
nuclear@2:       if (nbits > MAX_COEF_BITS)
nuclear@2: 	ERREXIT(state->cinfo, JERR_BAD_DCT_COEF);
nuclear@2:       
nuclear@2:       /* Emit Huffman symbol for run length / number of bits */
nuclear@2:       i = (r << 4) + nbits;
nuclear@2:       if (! emit_bits(state, actbl->ehufco[i], actbl->ehufsi[i]))
nuclear@2: 	return FALSE;
nuclear@2: 
nuclear@2:       /* Emit that number of bits of the value, if positive, */
nuclear@2:       /* or the complement of its magnitude, if negative. */
nuclear@2:       if (! emit_bits(state, (unsigned int) temp2, nbits))
nuclear@2: 	return FALSE;
nuclear@2:       
nuclear@2:       r = 0;
nuclear@2:     }
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* If the last coef(s) were zero, emit an end-of-block code */
nuclear@2:   if (r > 0)
nuclear@2:     if (! emit_bits(state, actbl->ehufco[0], actbl->ehufsi[0]))
nuclear@2:       return FALSE;
nuclear@2: 
nuclear@2:   return TRUE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Emit a restart marker & resynchronize predictions.
nuclear@2:  */
nuclear@2: 
nuclear@2: LOCAL(boolean)
nuclear@2: emit_restart (working_state * state, int restart_num)
nuclear@2: {
nuclear@2:   int ci;
nuclear@2: 
nuclear@2:   if (! flush_bits(state))
nuclear@2:     return FALSE;
nuclear@2: 
nuclear@2:   emit_byte(state, 0xFF, return FALSE);
nuclear@2:   emit_byte(state, JPEG_RST0 + restart_num, return FALSE);
nuclear@2: 
nuclear@2:   /* Re-initialize DC predictions to 0 */
nuclear@2:   for (ci = 0; ci < state->cinfo->comps_in_scan; ci++)
nuclear@2:     state->cur.last_dc_val[ci] = 0;
nuclear@2: 
nuclear@2:   /* The restart counter is not updated until we successfully write the MCU. */
nuclear@2: 
nuclear@2:   return TRUE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Encode and output one MCU's worth of Huffman-compressed coefficients.
nuclear@2:  */
nuclear@2: 
nuclear@2: METHODDEF(boolean)
nuclear@2: encode_mcu_huff (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
nuclear@2: {
nuclear@2:   huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
nuclear@2:   working_state state;
nuclear@2:   int blkn, ci;
nuclear@2:   jpeg_component_info * compptr;
nuclear@2: 
nuclear@2:   /* Load up working state */
nuclear@2:   state.next_output_byte = cinfo->dest->next_output_byte;
nuclear@2:   state.free_in_buffer = cinfo->dest->free_in_buffer;
nuclear@2:   ASSIGN_STATE(state.cur, entropy->saved);
nuclear@2:   state.cinfo = cinfo;
nuclear@2: 
nuclear@2:   /* Emit restart marker if needed */
nuclear@2:   if (cinfo->restart_interval) {
nuclear@2:     if (entropy->restarts_to_go == 0)
nuclear@2:       if (! emit_restart(&state, entropy->next_restart_num))
nuclear@2: 	return FALSE;
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* Encode the MCU data blocks */
nuclear@2:   for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
nuclear@2:     ci = cinfo->MCU_membership[blkn];
nuclear@2:     compptr = cinfo->cur_comp_info[ci];
nuclear@2:     if (! encode_one_block(&state,
nuclear@2: 			   MCU_data[blkn][0], state.cur.last_dc_val[ci],
nuclear@2: 			   entropy->dc_derived_tbls[compptr->dc_tbl_no],
nuclear@2: 			   entropy->ac_derived_tbls[compptr->ac_tbl_no]))
nuclear@2:       return FALSE;
nuclear@2:     /* Update last_dc_val */
nuclear@2:     state.cur.last_dc_val[ci] = MCU_data[blkn][0][0];
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* Completed MCU, so update state */
nuclear@2:   cinfo->dest->next_output_byte = state.next_output_byte;
nuclear@2:   cinfo->dest->free_in_buffer = state.free_in_buffer;
nuclear@2:   ASSIGN_STATE(entropy->saved, state.cur);
nuclear@2: 
nuclear@2:   /* Update restart-interval state too */
nuclear@2:   if (cinfo->restart_interval) {
nuclear@2:     if (entropy->restarts_to_go == 0) {
nuclear@2:       entropy->restarts_to_go = cinfo->restart_interval;
nuclear@2:       entropy->next_restart_num++;
nuclear@2:       entropy->next_restart_num &= 7;
nuclear@2:     }
nuclear@2:     entropy->restarts_to_go--;
nuclear@2:   }
nuclear@2: 
nuclear@2:   return TRUE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Finish up at the end of a Huffman-compressed scan.
nuclear@2:  */
nuclear@2: 
nuclear@2: METHODDEF(void)
nuclear@2: finish_pass_huff (j_compress_ptr cinfo)
nuclear@2: {
nuclear@2:   huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
nuclear@2:   working_state state;
nuclear@2: 
nuclear@2:   /* Load up working state ... flush_bits needs it */
nuclear@2:   state.next_output_byte = cinfo->dest->next_output_byte;
nuclear@2:   state.free_in_buffer = cinfo->dest->free_in_buffer;
nuclear@2:   ASSIGN_STATE(state.cur, entropy->saved);
nuclear@2:   state.cinfo = cinfo;
nuclear@2: 
nuclear@2:   /* Flush out the last data */
nuclear@2:   if (! flush_bits(&state))
nuclear@2:     ERREXIT(cinfo, JERR_CANT_SUSPEND);
nuclear@2: 
nuclear@2:   /* Update state */
nuclear@2:   cinfo->dest->next_output_byte = state.next_output_byte;
nuclear@2:   cinfo->dest->free_in_buffer = state.free_in_buffer;
nuclear@2:   ASSIGN_STATE(entropy->saved, state.cur);
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Huffman coding optimization.
nuclear@2:  *
nuclear@2:  * We first scan the supplied data and count the number of uses of each symbol
nuclear@2:  * that is to be Huffman-coded. (This process MUST agree with the code above.)
nuclear@2:  * Then we build a Huffman coding tree for the observed counts.
nuclear@2:  * Symbols which are not needed at all for the particular image are not
nuclear@2:  * assigned any code, which saves space in the DHT marker as well as in
nuclear@2:  * the compressed data.
nuclear@2:  */
nuclear@2: 
nuclear@2: #ifdef ENTROPY_OPT_SUPPORTED
nuclear@2: 
nuclear@2: 
nuclear@2: /* Process a single block's worth of coefficients */
nuclear@2: 
nuclear@2: LOCAL(void)
nuclear@2: htest_one_block (j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val,
nuclear@2: 		 long dc_counts[], long ac_counts[])
nuclear@2: {
nuclear@2:   register int temp;
nuclear@2:   register int nbits;
nuclear@2:   register int k, r;
nuclear@2:   
nuclear@2:   /* Encode the DC coefficient difference per section F.1.2.1 */
nuclear@2:   
nuclear@2:   temp = block[0] - last_dc_val;
nuclear@2:   if (temp < 0)
nuclear@2:     temp = -temp;
nuclear@2:   
nuclear@2:   /* Find the number of bits needed for the magnitude of the coefficient */
nuclear@2:   nbits = 0;
nuclear@2:   while (temp) {
nuclear@2:     nbits++;
nuclear@2:     temp >>= 1;
nuclear@2:   }
nuclear@2:   /* Check for out-of-range coefficient values.
nuclear@2:    * Since we're encoding a difference, the range limit is twice as much.
nuclear@2:    */
nuclear@2:   if (nbits > MAX_COEF_BITS+1)
nuclear@2:     ERREXIT(cinfo, JERR_BAD_DCT_COEF);
nuclear@2: 
nuclear@2:   /* Count the Huffman symbol for the number of bits */
nuclear@2:   dc_counts[nbits]++;
nuclear@2:   
nuclear@2:   /* Encode the AC coefficients per section F.1.2.2 */
nuclear@2:   
nuclear@2:   r = 0;			/* r = run length of zeros */
nuclear@2:   
nuclear@2:   for (k = 1; k < DCTSIZE2; k++) {
nuclear@2:     if ((temp = block[jpeg_natural_order[k]]) == 0) {
nuclear@2:       r++;
nuclear@2:     } else {
nuclear@2:       /* if run length > 15, must emit special run-length-16 codes (0xF0) */
nuclear@2:       while (r > 15) {
nuclear@2: 	ac_counts[0xF0]++;
nuclear@2: 	r -= 16;
nuclear@2:       }
nuclear@2:       
nuclear@2:       /* Find the number of bits needed for the magnitude of the coefficient */
nuclear@2:       if (temp < 0)
nuclear@2: 	temp = -temp;
nuclear@2:       
nuclear@2:       /* Find the number of bits needed for the magnitude of the coefficient */
nuclear@2:       nbits = 1;		/* there must be at least one 1 bit */
nuclear@2:       while ((temp >>= 1))
nuclear@2: 	nbits++;
nuclear@2:       /* Check for out-of-range coefficient values */
nuclear@2:       if (nbits > MAX_COEF_BITS)
nuclear@2: 	ERREXIT(cinfo, JERR_BAD_DCT_COEF);
nuclear@2:       
nuclear@2:       /* Count Huffman symbol for run length / number of bits */
nuclear@2:       ac_counts[(r << 4) + nbits]++;
nuclear@2:       
nuclear@2:       r = 0;
nuclear@2:     }
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* If the last coef(s) were zero, emit an end-of-block code */
nuclear@2:   if (r > 0)
nuclear@2:     ac_counts[0]++;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Trial-encode one MCU's worth of Huffman-compressed coefficients.
nuclear@2:  * No data is actually output, so no suspension return is possible.
nuclear@2:  */
nuclear@2: 
nuclear@2: METHODDEF(boolean)
nuclear@2: encode_mcu_gather (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
nuclear@2: {
nuclear@2:   huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
nuclear@2:   int blkn, ci;
nuclear@2:   jpeg_component_info * compptr;
nuclear@2: 
nuclear@2:   /* Take care of restart intervals if needed */
nuclear@2:   if (cinfo->restart_interval) {
nuclear@2:     if (entropy->restarts_to_go == 0) {
nuclear@2:       /* Re-initialize DC predictions to 0 */
nuclear@2:       for (ci = 0; ci < cinfo->comps_in_scan; ci++)
nuclear@2: 	entropy->saved.last_dc_val[ci] = 0;
nuclear@2:       /* Update restart state */
nuclear@2:       entropy->restarts_to_go = cinfo->restart_interval;
nuclear@2:     }
nuclear@2:     entropy->restarts_to_go--;
nuclear@2:   }
nuclear@2: 
nuclear@2:   for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
nuclear@2:     ci = cinfo->MCU_membership[blkn];
nuclear@2:     compptr = cinfo->cur_comp_info[ci];
nuclear@2:     htest_one_block(cinfo, MCU_data[blkn][0], entropy->saved.last_dc_val[ci],
nuclear@2: 		    entropy->dc_count_ptrs[compptr->dc_tbl_no],
nuclear@2: 		    entropy->ac_count_ptrs[compptr->ac_tbl_no]);
nuclear@2:     entropy->saved.last_dc_val[ci] = MCU_data[blkn][0][0];
nuclear@2:   }
nuclear@2: 
nuclear@2:   return TRUE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Generate the best Huffman code table for the given counts, fill htbl.
nuclear@2:  * Note this is also used by jcphuff.c.
nuclear@2:  *
nuclear@2:  * The JPEG standard requires that no symbol be assigned a codeword of all
nuclear@2:  * one bits (so that padding bits added at the end of a compressed segment
nuclear@2:  * can't look like a valid code).  Because of the canonical ordering of
nuclear@2:  * codewords, this just means that there must be an unused slot in the
nuclear@2:  * longest codeword length category.  Section K.2 of the JPEG spec suggests
nuclear@2:  * reserving such a slot by pretending that symbol 256 is a valid symbol
nuclear@2:  * with count 1.  In theory that's not optimal; giving it count zero but
nuclear@2:  * including it in the symbol set anyway should give a better Huffman code.
nuclear@2:  * But the theoretically better code actually seems to come out worse in
nuclear@2:  * practice, because it produces more all-ones bytes (which incur stuffed
nuclear@2:  * zero bytes in the final file).  In any case the difference is tiny.
nuclear@2:  *
nuclear@2:  * The JPEG standard requires Huffman codes to be no more than 16 bits long.
nuclear@2:  * If some symbols have a very small but nonzero probability, the Huffman tree
nuclear@2:  * must be adjusted to meet the code length restriction.  We currently use
nuclear@2:  * the adjustment method suggested in JPEG section K.2.  This method is *not*
nuclear@2:  * optimal; it may not choose the best possible limited-length code.  But
nuclear@2:  * typically only very-low-frequency symbols will be given less-than-optimal
nuclear@2:  * lengths, so the code is almost optimal.  Experimental comparisons against
nuclear@2:  * an optimal limited-length-code algorithm indicate that the difference is
nuclear@2:  * microscopic --- usually less than a hundredth of a percent of total size.
nuclear@2:  * So the extra complexity of an optimal algorithm doesn't seem worthwhile.
nuclear@2:  */
nuclear@2: 
nuclear@2: GLOBAL(void)
nuclear@2: jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])
nuclear@2: {
nuclear@2: #define MAX_CLEN 32		/* assumed maximum initial code length */
nuclear@2:   UINT8 bits[MAX_CLEN+1];	/* bits[k] = # of symbols with code length k */
nuclear@2:   int codesize[257];		/* codesize[k] = code length of symbol k */
nuclear@2:   int others[257];		/* next symbol in current branch of tree */
nuclear@2:   int c1, c2;
nuclear@2:   int p, i, j;
nuclear@2:   long v;
nuclear@2: 
nuclear@2:   /* This algorithm is explained in section K.2 of the JPEG standard */
nuclear@2: 
nuclear@2:   MEMZERO(bits, SIZEOF(bits));
nuclear@2:   MEMZERO(codesize, SIZEOF(codesize));
nuclear@2:   for (i = 0; i < 257; i++)
nuclear@2:     others[i] = -1;		/* init links to empty */
nuclear@2:   
nuclear@2:   freq[256] = 1;		/* make sure 256 has a nonzero count */
nuclear@2:   /* Including the pseudo-symbol 256 in the Huffman procedure guarantees
nuclear@2:    * that no real symbol is given code-value of all ones, because 256
nuclear@2:    * will be placed last in the largest codeword category.
nuclear@2:    */
nuclear@2: 
nuclear@2:   /* Huffman's basic algorithm to assign optimal code lengths to symbols */
nuclear@2: 
nuclear@2:   for (;;) {
nuclear@2:     /* Find the smallest nonzero frequency, set c1 = its symbol */
nuclear@2:     /* In case of ties, take the larger symbol number */
nuclear@2:     c1 = -1;
nuclear@2:     v = 1000000000L;
nuclear@2:     for (i = 0; i <= 256; i++) {
nuclear@2:       if (freq[i] && freq[i] <= v) {
nuclear@2: 	v = freq[i];
nuclear@2: 	c1 = i;
nuclear@2:       }
nuclear@2:     }
nuclear@2: 
nuclear@2:     /* Find the next smallest nonzero frequency, set c2 = its symbol */
nuclear@2:     /* In case of ties, take the larger symbol number */
nuclear@2:     c2 = -1;
nuclear@2:     v = 1000000000L;
nuclear@2:     for (i = 0; i <= 256; i++) {
nuclear@2:       if (freq[i] && freq[i] <= v && i != c1) {
nuclear@2: 	v = freq[i];
nuclear@2: 	c2 = i;
nuclear@2:       }
nuclear@2:     }
nuclear@2: 
nuclear@2:     /* Done if we've merged everything into one frequency */
nuclear@2:     if (c2 < 0)
nuclear@2:       break;
nuclear@2:     
nuclear@2:     /* Else merge the two counts/trees */
nuclear@2:     freq[c1] += freq[c2];
nuclear@2:     freq[c2] = 0;
nuclear@2: 
nuclear@2:     /* Increment the codesize of everything in c1's tree branch */
nuclear@2:     codesize[c1]++;
nuclear@2:     while (others[c1] >= 0) {
nuclear@2:       c1 = others[c1];
nuclear@2:       codesize[c1]++;
nuclear@2:     }
nuclear@2:     
nuclear@2:     others[c1] = c2;		/* chain c2 onto c1's tree branch */
nuclear@2:     
nuclear@2:     /* Increment the codesize of everything in c2's tree branch */
nuclear@2:     codesize[c2]++;
nuclear@2:     while (others[c2] >= 0) {
nuclear@2:       c2 = others[c2];
nuclear@2:       codesize[c2]++;
nuclear@2:     }
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* Now count the number of symbols of each code length */
nuclear@2:   for (i = 0; i <= 256; i++) {
nuclear@2:     if (codesize[i]) {
nuclear@2:       /* The JPEG standard seems to think that this can't happen, */
nuclear@2:       /* but I'm paranoid... */
nuclear@2:       if (codesize[i] > MAX_CLEN)
nuclear@2: 	ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
nuclear@2: 
nuclear@2:       bits[codesize[i]]++;
nuclear@2:     }
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
nuclear@2:    * Huffman procedure assigned any such lengths, we must adjust the coding.
nuclear@2:    * Here is what the JPEG spec says about how this next bit works:
nuclear@2:    * Since symbols are paired for the longest Huffman code, the symbols are
nuclear@2:    * removed from this length category two at a time.  The prefix for the pair
nuclear@2:    * (which is one bit shorter) is allocated to one of the pair; then,
nuclear@2:    * skipping the BITS entry for that prefix length, a code word from the next
nuclear@2:    * shortest nonzero BITS entry is converted into a prefix for two code words
nuclear@2:    * one bit longer.
nuclear@2:    */
nuclear@2:   
nuclear@2:   for (i = MAX_CLEN; i > 16; i--) {
nuclear@2:     while (bits[i] > 0) {
nuclear@2:       j = i - 2;		/* find length of new prefix to be used */
nuclear@2:       while (bits[j] == 0)
nuclear@2: 	j--;
nuclear@2:       
nuclear@2:       bits[i] -= 2;		/* remove two symbols */
nuclear@2:       bits[i-1]++;		/* one goes in this length */
nuclear@2:       bits[j+1] += 2;		/* two new symbols in this length */
nuclear@2:       bits[j]--;		/* symbol of this length is now a prefix */
nuclear@2:     }
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* Remove the count for the pseudo-symbol 256 from the largest codelength */
nuclear@2:   while (bits[i] == 0)		/* find largest codelength still in use */
nuclear@2:     i--;
nuclear@2:   bits[i]--;
nuclear@2:   
nuclear@2:   /* Return final symbol counts (only for lengths 0..16) */
nuclear@2:   MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits));
nuclear@2:   
nuclear@2:   /* Return a list of the symbols sorted by code length */
nuclear@2:   /* It's not real clear to me why we don't need to consider the codelength
nuclear@2:    * changes made above, but the JPEG spec seems to think this works.
nuclear@2:    */
nuclear@2:   p = 0;
nuclear@2:   for (i = 1; i <= MAX_CLEN; i++) {
nuclear@2:     for (j = 0; j <= 255; j++) {
nuclear@2:       if (codesize[j] == i) {
nuclear@2: 	htbl->huffval[p] = (UINT8) j;
nuclear@2: 	p++;
nuclear@2:       }
nuclear@2:     }
nuclear@2:   }
nuclear@2: 
nuclear@2:   /* Set sent_table FALSE so updated table will be written to JPEG file. */
nuclear@2:   htbl->sent_table = FALSE;
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Finish up a statistics-gathering pass and create the new Huffman tables.
nuclear@2:  */
nuclear@2: 
nuclear@2: METHODDEF(void)
nuclear@2: finish_pass_gather (j_compress_ptr cinfo)
nuclear@2: {
nuclear@2:   huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
nuclear@2:   int ci, dctbl, actbl;
nuclear@2:   jpeg_component_info * compptr;
nuclear@2:   JHUFF_TBL **htblptr;
nuclear@2:   boolean did_dc[NUM_HUFF_TBLS];
nuclear@2:   boolean did_ac[NUM_HUFF_TBLS];
nuclear@2: 
nuclear@2:   /* It's important not to apply jpeg_gen_optimal_table more than once
nuclear@2:    * per table, because it clobbers the input frequency counts!
nuclear@2:    */
nuclear@2:   MEMZERO(did_dc, SIZEOF(did_dc));
nuclear@2:   MEMZERO(did_ac, SIZEOF(did_ac));
nuclear@2: 
nuclear@2:   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
nuclear@2:     compptr = cinfo->cur_comp_info[ci];
nuclear@2:     dctbl = compptr->dc_tbl_no;
nuclear@2:     actbl = compptr->ac_tbl_no;
nuclear@2:     if (! did_dc[dctbl]) {
nuclear@2:       htblptr = & cinfo->dc_huff_tbl_ptrs[dctbl];
nuclear@2:       if (*htblptr == NULL)
nuclear@2: 	*htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
nuclear@2:       jpeg_gen_optimal_table(cinfo, *htblptr, entropy->dc_count_ptrs[dctbl]);
nuclear@2:       did_dc[dctbl] = TRUE;
nuclear@2:     }
nuclear@2:     if (! did_ac[actbl]) {
nuclear@2:       htblptr = & cinfo->ac_huff_tbl_ptrs[actbl];
nuclear@2:       if (*htblptr == NULL)
nuclear@2: 	*htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
nuclear@2:       jpeg_gen_optimal_table(cinfo, *htblptr, entropy->ac_count_ptrs[actbl]);
nuclear@2:       did_ac[actbl] = TRUE;
nuclear@2:     }
nuclear@2:   }
nuclear@2: }
nuclear@2: 
nuclear@2: 
nuclear@2: #endif /* ENTROPY_OPT_SUPPORTED */
nuclear@2: 
nuclear@2: 
nuclear@2: /*
nuclear@2:  * Module initialization routine for Huffman entropy encoding.
nuclear@2:  */
nuclear@2: 
nuclear@2: GLOBAL(void)
nuclear@2: jinit_huff_encoder (j_compress_ptr cinfo)
nuclear@2: {
nuclear@2:   huff_entropy_ptr entropy;
nuclear@2:   int i;
nuclear@2: 
nuclear@2:   entropy = (huff_entropy_ptr)
nuclear@2:     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@2: 				SIZEOF(huff_entropy_encoder));
nuclear@2:   cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
nuclear@2:   entropy->pub.start_pass = start_pass_huff;
nuclear@2: 
nuclear@2:   /* Mark tables unallocated */
nuclear@2:   for (i = 0; i < NUM_HUFF_TBLS; i++) {
nuclear@2:     entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
nuclear@2: #ifdef ENTROPY_OPT_SUPPORTED
nuclear@2:     entropy->dc_count_ptrs[i] = entropy->ac_count_ptrs[i] = NULL;
nuclear@2: #endif
nuclear@2:   }
nuclear@2: }