DOOM-3-BFG

jdhuff.cpp (20233B)

---

 /*
  * jdhuff.c
  *
  * Copyright (C) 1991-1995, 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 decoding routines.
  *
  * Much of the complexity here has to do with supporting input suspension.
  * If the data source module demands suspension, we want to be able to back
  * up to the start of the current MCU.  To do this, we copy state variables
  * into local working storage, and update them back to the permanent
  * storage only upon successful completion of an MCU.
  */
 
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "jdhuff.h"      /* Declarations shared with jdphuff.c */
 
 
 /*
  * Expanded entropy decoder object for Huffman decoding.
  *
  * The savable_state subrecord contains fields that change within an MCU,
  * but must not be updated permanently until we complete the MCU.
  */
 
 typedef struct {
     int last_dc_val[MAX_COMPS_IN_SCAN];/* last DC coef for each component */
 } savable_state;
 
 /* This macro is to work around compilers with missing or broken
  * structure assignment.  You'll need to fix this code if you have
  * such a compiler and you change MAX_COMPS_IN_SCAN.
  */
 
 #ifndef NO_STRUCT_ASSIGN
 #define ASSIGN_STATE( dest, src )  ( ( dest ) = ( src ) )
 #else
 #if MAX_COMPS_IN_SCAN == 4
 #define ASSIGN_STATE( dest, src )  \
     ( ( dest ).last_dc_val[0] = ( src ).last_dc_val[0], \
      ( dest ).last_dc_val[1] = ( src ).last_dc_val[1], \
      ( dest ).last_dc_val[2] = ( src ).last_dc_val[2], \
      ( dest ).last_dc_val[3] = ( src ).last_dc_val[3] )
 #endif
 #endif
 
 
 typedef struct {
     struct jpeg_entropy_decoder pub;/* public fields */
 
     /* These fields are loaded into local variables at start of each MCU.
      * In case of suspension, we exit WITHOUT updating them.
      */
     bitread_perm_state bitstate;/* Bit buffer at start of MCU */
     savable_state      saved; /* Other state at start of MCU */
 
     /* These fields are NOT loaded into local working state. */
     unsigned int restarts_to_go;/* MCUs left in this restart interval */
 
     /* Pointers to derived tables (these workspaces have image lifespan) */
     d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
     d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
 } huff_entropy_decoder;
 
 typedef huff_entropy_decoder * huff_entropy_ptr;
 
 
 /*
  * Initialize for a Huffman-compressed scan.
  */
 
 METHODDEF void
 start_pass_huff_decoder( j_decompress_ptr cinfo ) {
     huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
     int ci, dctbl, actbl;
     jpeg_component_info * compptr;
 
     /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
      * This ought to be an error condition, but we make it a warning because
      * there are some baseline files out there with all zeroes in these bytes.
      */
     if ( ( cinfo->Ss != 0 ) || ( cinfo->Se != DCTSIZE2 - 1 ) ||
         ( cinfo->Ah != 0 ) || ( cinfo->Al != 0 ) ) {
         WARNMS( cinfo, JWRN_NOT_SEQUENTIAL );
     }
 
     for ( ci = 0; ci < cinfo->comps_in_scan; ci++ ) {
         compptr = cinfo->cur_comp_info[ci];
         dctbl = compptr->dc_tbl_no;
         actbl = compptr->ac_tbl_no;
         /* Make sure requested tables are present */
         if ( ( dctbl < 0 ) || ( dctbl >= NUM_HUFF_TBLS ) ||
             ( cinfo->dc_huff_tbl_ptrs[dctbl] == NULL ) ) {
             ERREXIT1( cinfo, JERR_NO_HUFF_TABLE, dctbl );
         }
         if ( ( actbl < 0 ) || ( actbl >= NUM_HUFF_TBLS ) ||
             ( cinfo->ac_huff_tbl_ptrs[actbl] == NULL ) ) {
             ERREXIT1( cinfo, JERR_NO_HUFF_TABLE, actbl );
         }
         /* Compute derived values for Huffman tables */
         /* We may do this more than once for a table, but it's not expensive */
         jpeg_make_d_derived_tbl( cinfo, cinfo->dc_huff_tbl_ptrs[dctbl],
                                  &entropy->dc_derived_tbls[dctbl] );
         jpeg_make_d_derived_tbl( cinfo, cinfo->ac_huff_tbl_ptrs[actbl],
                                  &entropy->ac_derived_tbls[actbl] );
         /* Initialize DC predictions to 0 */
         entropy->saved.last_dc_val[ci] = 0;
     }
 
     /* Initialize bitread state variables */
     entropy->bitstate.bits_left = 0;
     entropy->bitstate.get_buffer = 0;/* unnecessary, but keeps Purify quiet */
     entropy->bitstate.printed_eod = FALSE;
 
     /* Initialize restart counter */
     entropy->restarts_to_go = cinfo->restart_interval;
 }
 
 
 /*
  * Compute the derived values for a Huffman table.
  * Note this is also used by jdphuff.c.
  */
 
 GLOBAL void
 jpeg_make_d_derived_tbl( j_decompress_ptr cinfo, JHUFF_TBL * htbl,
                          d_derived_tbl ** pdtbl ) {
     d_derived_tbl * dtbl;
     int p, i, l, si;
     int lookbits, ctr;
     char huffsize[257];
     unsigned int huffcode[257];
     unsigned int code;
 
     /* Allocate a workspace if we haven't already done so. */
     if ( *pdtbl == NULL ) {
         *pdtbl = (d_derived_tbl *)
                  ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                               SIZEOF( d_derived_tbl ) );
     }
     dtbl = *pdtbl;
     dtbl->pub = htbl;   /* fill in back link */
 
     /* Figure C.1: make table of Huffman code length for each symbol */
     /* Note that this is in code-length order. */
 
     p = 0;
     for ( l = 1; l <= 16; l++ ) {
         for ( i = 1; i <= (int) htbl->bits[l]; i++ ) {
             huffsize[p++] = (char) l;
         }
     }
     huffsize[p] = 0;
 
     /* Figure C.2: generate the codes themselves */
     /* Note that this is in code-length order. */
 
     code = 0;
     si = huffsize[0];
     p = 0;
     while ( huffsize[p] ) {
         while ( ( (int) huffsize[p] ) == si ) {
             huffcode[p++] = code;
             code++;
         }
         code <<= 1;
         si++;
     }
 
     /* Figure F.15: generate decoding tables for bit-sequential decoding */
 
     p = 0;
     for ( l = 1; l <= 16; l++ ) {
         if ( htbl->bits[l] ) {
             dtbl->valptr[l] = p;/* huffval[] index of 1st symbol of code length l */
             dtbl->mincode[l] = huffcode[p];/* minimum code of length l */
             p += htbl->bits[l];
             dtbl->maxcode[l] = huffcode[p - 1];/* maximum code of length l */
         } else {
             dtbl->maxcode[l] = -1;/* -1 if no codes of this length */
         }
     }
     dtbl->maxcode[17] = 0xFFFFFL;/* ensures jpeg_huff_decode terminates */
 
     /* Compute lookahead tables to speed up decoding.
      * First we set all the table entries to 0, indicating "too long";
      * then we iterate through the Huffman codes that are short enough and
      * fill in all the entries that correspond to bit sequences starting
      * with that code.
      */
 
     MEMZERO( dtbl->look_nbits, SIZEOF( dtbl->look_nbits ) );
 
     p = 0;
     for ( l = 1; l <= HUFF_LOOKAHEAD; l++ ) {
         for ( i = 1; i <= (int) htbl->bits[l]; i++, p++ ) {
             /* l = current code's length, p = its index in huffcode[] & huffval[]. */
             /* Generate left-justified code followed by all possible bit sequences */
             lookbits = huffcode[p] << ( HUFF_LOOKAHEAD - l );
             for ( ctr = 1 << ( HUFF_LOOKAHEAD - l ); ctr > 0; ctr-- ) {
                 dtbl->look_nbits[lookbits] = l;
                 dtbl->look_sym[lookbits] = htbl->huffval[p];
                 lookbits++;
             }
         }
     }
 }
 
 
 /*
  * Out-of-line code for bit fetching (shared with jdphuff.c).
  * See jdhuff.h for info about usage.
  * Note: current values of get_buffer and bits_left are passed as parameters,
  * but are returned in the corresponding fields of the state struct.
  *
  * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
  * of get_buffer to be used.  (On machines with wider words, an even larger
  * buffer could be used.)  However, on some machines 32-bit shifts are
  * quite slow and take time proportional to the number of places shifted.
  * (This is true with most PC compilers, for instance.)  In this case it may
  * be a win to set MIN_GET_BITS to the minimum value of 15.  This reduces the
  * average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
  */
 
 #ifdef SLOW_SHIFT_32
 #define MIN_GET_BITS  15    /* minimum allowable value */
 #else
 #define MIN_GET_BITS  ( BIT_BUF_SIZE - 7 )
 #endif
 
 
 GLOBAL boolean
 jpeg_fill_bit_buffer( bitread_working_state * state,
                       register bit_buf_type get_buffer, register int bits_left,
                       int nbits ) {
 /* Load up the bit buffer to a depth of at least nbits */
 /* Copy heavily used state fields into locals (hopefully registers) */
     register const JOCTET * next_input_byte = state->next_input_byte;
     register size_t bytes_in_buffer = state->bytes_in_buffer;
     register int c;
 
     /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
     /* (It is assumed that no request will be for more than that many bits.) */
 
     while ( bits_left < MIN_GET_BITS ) {
         /* Attempt to read a byte */
         if ( state->unread_marker != 0 ) {
             goto no_more_data;
         }                   /* can't advance past a marker */
 
         if ( bytes_in_buffer == 0 ) {
             if ( !( *state->cinfo->src->fill_input_buffer )( state->cinfo ) ) {
                 return FALSE;
             }
             next_input_byte = state->cinfo->src->next_input_byte;
             bytes_in_buffer = state->cinfo->src->bytes_in_buffer;
         }
         bytes_in_buffer--;
         c = GETJOCTET( *next_input_byte++ );
 
         /* If it's 0xFF, check and discard stuffed zero byte */
         if ( c == 0xFF ) {
             do {
                 if ( bytes_in_buffer == 0 ) {
                     if ( !( *state->cinfo->src->fill_input_buffer )( state->cinfo ) ) {
                         return FALSE;
                     }
                     next_input_byte = state->cinfo->src->next_input_byte;
                     bytes_in_buffer = state->cinfo->src->bytes_in_buffer;
                 }
                 bytes_in_buffer--;
                 c = GETJOCTET( *next_input_byte++ );
             } while ( c == 0xFF );
 
             if ( c == 0 ) {
                 /* Found FF/00, which represents an FF data byte */
                 c = 0xFF;
             } else {
                 /* Oops, it's actually a marker indicating end of compressed data. */
                 /* Better put it back for use later */
                 state->unread_marker = c;
 
 no_more_data:
                 /* There should be enough bits still left in the data segment; */
                 /* if so, just break out of the outer while loop. */
                 if ( bits_left >= nbits ) {
                     break;
                 }
                 /* Uh-oh.  Report corrupted data to user and stuff zeroes into
                  * the data stream, so that we can produce some kind of image.
                  * Note that this code will be repeated for each byte demanded
                  * for the rest of the segment.  We use a nonvolatile flag to ensure
                  * that only one warning message appears.
                  */
                 if ( ! * ( state->printed_eod_ptr ) ) {
                     WARNMS( state->cinfo, JWRN_HIT_MARKER );
                     *( state->printed_eod_ptr ) = TRUE;
                 }
                 c = 0;/* insert a zero byte into bit buffer */
             }
         }
 
         /* OK, load c into get_buffer */
         get_buffer = ( get_buffer << 8 ) | c;
         bits_left += 8;
     }
 
     /* Unload the local registers */
     state->next_input_byte = next_input_byte;
     state->bytes_in_buffer = bytes_in_buffer;
     state->get_buffer = get_buffer;
     state->bits_left = bits_left;
 
     return TRUE;
 }
 
 
 /*
  * Out-of-line code for Huffman code decoding.
  * See jdhuff.h for info about usage.
  */
 
 GLOBAL int
 jpeg_huff_decode( bitread_working_state * state,
                   register bit_buf_type get_buffer, register int bits_left,
                   d_derived_tbl * htbl, int min_bits ) {
     register int l = min_bits;
     register INT32 code;
 
     /* HUFF_DECODE has determined that the code is at least min_bits */
     /* bits long, so fetch that many bits in one swoop. */
 
     CHECK_BIT_BUFFER( *state, l, return -1 );
     code = GET_BITS( l );
 
     /* Collect the rest of the Huffman code one bit at a time. */
     /* This is per Figure F.16 in the JPEG spec. */
 
     while ( code > htbl->maxcode[l] ) {
         code <<= 1;
 
         CHECK_BIT_BUFFER( *state, 1, return -1 );
         code |= GET_BITS( 1 );
         l++;
     }
 
     /* Unload the local registers */
     state->get_buffer = get_buffer;
     state->bits_left = bits_left;
 
     /* With garbage input we may reach the sentinel value l = 17. */
 
     if ( l > 16 ) {
         WARNMS( state->cinfo, JWRN_HUFF_BAD_CODE );
         return 0;       /* fake a zero as the safest result */
     }
 
     return htbl->pub->huffval[ htbl->valptr[l] +
                                ( (int) ( code - htbl->mincode[l] ) ) ];
 }
 
 
 /*
  * Figure F.12: extend sign bit.
  * On some machines, a shift and add will be faster than a table lookup.
  */
 
 #ifdef AVOID_TABLES
 
 #define HUFF_EXTEND( x, s )  ( ( x ) < ( 1 << ( ( s ) - 1 ) ) ? ( x ) + ( ( ( -1 ) << ( s ) ) + 1 ) : ( x ) )
 
 #else
 
 #define HUFF_EXTEND( x, s )  ( ( x ) < extend_test[s] ? ( x ) + extend_offset[s] : ( x ) )
 
 static const int extend_test[16] =   /* entry n is 2**(n-1) */
 { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
   0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
 
 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
 { 0, ( ( -1 ) << 1 ) + 1, ( ( -1 ) << 2 ) + 1, ( ( -1 ) << 3 ) + 1, ( ( -1 ) << 4 ) + 1,
   ( ( -1 ) << 5 ) + 1, ( ( -1 ) << 6 ) + 1, ( ( -1 ) << 7 ) + 1, ( ( -1 ) << 8 ) + 1,
   ( ( -1 ) << 9 ) + 1, ( ( -1 ) << 10 ) + 1, ( ( -1 ) << 11 ) + 1, ( ( -1 ) << 12 ) + 1,
   ( ( -1 ) << 13 ) + 1, ( ( -1 ) << 14 ) + 1, ( ( -1 ) << 15 ) + 1 };
 
 #endif /* AVOID_TABLES */
 
 
 /*
  * Check for a restart marker & resynchronize decoder.
  * Returns FALSE if must suspend.
  */
 
 LOCAL boolean
 process_restart( j_decompress_ptr cinfo ) {
     huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
     int ci;
 
     /* Throw away any unused bits remaining in bit buffer; */
     /* include any full bytes in next_marker's count of discarded bytes */
     cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
     entropy->bitstate.bits_left = 0;
 
     /* Advance past the RSTn marker */
     if ( !( *cinfo->marker->read_restart_marker )( cinfo ) ) {
         return FALSE;
     }
 
     /* Re-initialize DC predictions to 0 */
     for ( ci = 0; ci < cinfo->comps_in_scan; ci++ ) {
         entropy->saved.last_dc_val[ci] = 0;
     }
 
     /* Reset restart counter */
     entropy->restarts_to_go = cinfo->restart_interval;
 
     /* Next segment can get another out-of-data warning */
     entropy->bitstate.printed_eod = FALSE;
 
     return TRUE;
 }
 
 
 /*
  * Decode and return one MCU's worth of Huffman-compressed coefficients.
  * The coefficients are reordered from zigzag order into natural array order,
  * but are not dequantized.
  *
  * The i'th block of the MCU is stored into the block pointed to by
  * MCU_data[i].  WE ASSUME THIS AREA HAS BEEN ZEROED BY THE CALLER.
  * (Wholesale zeroing is usually a little faster than retail...)
  *
  * Returns FALSE if data source requested suspension.  In that case no
  * changes have been made to permanent state.  (Exception: some output
  * coefficients may already have been assigned.  This is harmless for
  * this module, since we'll just re-assign them on the next call.)
  */
 
 METHODDEF boolean
 decode_mcu( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) {
     huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
     register int s, k, r;
     int blkn, ci;
     JBLOCKROW block;
     BITREAD_STATE_VARS;
     savable_state state;
     d_derived_tbl * dctbl;
     d_derived_tbl * actbl;
     jpeg_component_info * compptr;
 
     /* Process restart marker if needed; may have to suspend */
     if ( cinfo->restart_interval ) {
         if ( entropy->restarts_to_go == 0 ) {
             if ( !process_restart( cinfo ) ) {
                 return FALSE;
             }
         }
     }
 
     /* Load up working state */
     BITREAD_LOAD_STATE( cinfo, entropy->bitstate );
     ASSIGN_STATE( state, entropy->saved );
 
     /* Outer loop handles each block in the MCU */
 
     for ( blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++ ) {
         block = MCU_data[blkn];
         ci = cinfo->MCU_membership[blkn];
         compptr = cinfo->cur_comp_info[ci];
         dctbl = entropy->dc_derived_tbls[compptr->dc_tbl_no];
         actbl = entropy->ac_derived_tbls[compptr->ac_tbl_no];
 
         /* Decode a single block's worth of coefficients */
 
         /* Section F.2.2.1: decode the DC coefficient difference */
         HUFF_DECODE( s, br_state, dctbl, return FALSE, label1 );
         if ( s ) {
             CHECK_BIT_BUFFER( br_state, s, return FALSE );
 
             r = GET_BITS( s );
             s = HUFF_EXTEND( r, s );
         }
 
         /* Shortcut if component's values are not interesting */
         if ( !compptr->component_needed ) {
             goto skip_ACs;
         }
 
         /* Convert DC difference to actual value, update last_dc_val */
         s += state.last_dc_val[ci];
         state.last_dc_val[ci] = s;
         /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */
         ( *block )[0] = (JCOEF) s;
 
         /* Do we need to decode the AC coefficients for this component? */
         if ( compptr->DCT_scaled_size > 1 ) {
 
             /* Section F.2.2.2: decode the AC coefficients */
             /* Since zeroes are skipped, output area must be cleared beforehand */
             for ( k = 1; k < DCTSIZE2; k++ ) {
                 HUFF_DECODE( s, br_state, actbl, return FALSE, label2 );
 
                 r = s >> 4;
                 s &= 15;
 
                 if ( s ) {
                     k += r;
 
                     CHECK_BIT_BUFFER( br_state, s, return FALSE );
                     r = GET_BITS( s );
                     s = HUFF_EXTEND( r, s );
                     /* Output coefficient in natural (dezigzagged) order.
                      * Note: the extra entries in jpeg_natural_order[] will save us
                      * if k >= DCTSIZE2, which could happen if the data is corrupted.
                      */
                     ( *block )[jpeg_natural_order[k]] = (JCOEF) s;
                 } else {
                     if ( r != 15 ) {
                         break;
                     }
                     k += 15;
                 }
             }
 
         } else {
 skip_ACs:
 
             /* Section F.2.2.2: decode the AC coefficients */
             /* In this path we just discard the values */
             for ( k = 1; k < DCTSIZE2; k++ ) {
                 HUFF_DECODE( s, br_state, actbl, return FALSE, label3 );
 
                 r = s >> 4;
                 s &= 15;
 
                 if ( s ) {
                     k += r;
 
                     CHECK_BIT_BUFFER( br_state, s, return FALSE );
                     DROP_BITS( s );
                 } else {
                     if ( r != 15 ) {
                         break;
                     }
                     k += 15;
                 }
             }
 
         }
     }
 
     /* Completed MCU, so update state */
     BITREAD_SAVE_STATE( cinfo, entropy->bitstate );
     ASSIGN_STATE( entropy->saved, state );
 
     /* Account for restart interval (no-op if not using restarts) */
     entropy->restarts_to_go--;
 
     return TRUE;
 }
 
 
 /*
  * Module initialization routine for Huffman entropy decoding.
  */
 
 GLOBAL void
 jinit_huff_decoder( j_decompress_ptr cinfo ) {
     huff_entropy_ptr entropy;
     int i;
 
     entropy = (huff_entropy_ptr)
               ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                            SIZEOF( huff_entropy_decoder ) );
     cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
     entropy->pub.start_pass = start_pass_huff_decoder;
     entropy->pub.decode_mcu = decode_mcu;
 
     /* Mark tables unallocated */
     for ( i = 0; i < NUM_HUFF_TBLS; i++ ) {
         entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
     }
 }