/* * jdphuff.c * * Copyright (C) 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 for progressive JPEG. * * 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 jdhuff.c */ #ifdef D_PROGRESSIVE_SUPPORTED /* * Expanded entropy decoder object for progressive 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 { unsigned int EOBRUN; /* remaining EOBs in EOBRUN */ 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 ).EOBRUN = ( src ).EOBRUN, \ ( 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 * derived_tbls[NUM_HUFF_TBLS]; d_derived_tbl * ac_derived_tbl;/* active table during an AC scan */ } phuff_entropy_decoder; typedef phuff_entropy_decoder * phuff_entropy_ptr; /* Forward declarations */ METHODDEF boolean decode_mcu_DC_first JPP( ( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) ); METHODDEF boolean decode_mcu_AC_first JPP( ( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) ); METHODDEF boolean decode_mcu_DC_refine JPP( ( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) ); METHODDEF boolean decode_mcu_AC_refine JPP( ( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) ); /* * Initialize for a Huffman-compressed scan. */ METHODDEF void start_pass_phuff_decoder( j_decompress_ptr cinfo ) { phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; boolean is_DC_band, bad; int ci, coefi, tbl; int * coef_bit_ptr; jpeg_component_info * compptr; is_DC_band = ( cinfo->Ss == 0 ); /* Validate scan parameters */ bad = FALSE; if ( is_DC_band ) { if ( cinfo->Se != 0 ) { bad = TRUE; } } else { /* need not check Ss/Se < 0 since they came from unsigned bytes */ if ( ( cinfo->Ss > cinfo->Se ) || ( cinfo->Se >= DCTSIZE2 ) ) { bad = TRUE; } /* AC scans may have only one component */ if ( cinfo->comps_in_scan != 1 ) { bad = TRUE; } } if ( cinfo->Ah != 0 ) { /* Successive approximation refinement scan: must have Al = Ah-1. */ if ( cinfo->Al != cinfo->Ah - 1 ) { bad = TRUE; } } if ( cinfo->Al > 13 ) { /* need not check for < 0 */ bad = TRUE; } if ( bad ) { ERREXIT4( cinfo, JERR_BAD_PROGRESSION, cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al ); } /* Update progression status, and verify that scan order is legal. * Note that inter-scan inconsistencies are treated as warnings * not fatal errors ... not clear if this is right way to behave. */ for ( ci = 0; ci < cinfo->comps_in_scan; ci++ ) { int cindex = cinfo->cur_comp_info[ci]->component_index; coef_bit_ptr = &cinfo->coef_bits[cindex][0]; if ( ( !is_DC_band ) && ( coef_bit_ptr[0] < 0 ) ) {/* AC without prior DC scan */ WARNMS2( cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0 ); } for ( coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++ ) { int expected = ( coef_bit_ptr[coefi] < 0 ) ? 0 : coef_bit_ptr[coefi]; if ( cinfo->Ah != expected ) { WARNMS2( cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi ); } coef_bit_ptr[coefi] = cinfo->Al; } } /* Select MCU decoding routine */ if ( cinfo->Ah == 0 ) { if ( is_DC_band ) { entropy->pub.decode_mcu = decode_mcu_DC_first; } else { entropy->pub.decode_mcu = decode_mcu_AC_first; } } else { if ( is_DC_band ) { entropy->pub.decode_mcu = decode_mcu_DC_refine; } else { entropy->pub.decode_mcu = decode_mcu_AC_refine; } } for ( ci = 0; ci < cinfo->comps_in_scan; ci++ ) { compptr = cinfo->cur_comp_info[ci]; /* Make sure requested tables are present, and compute derived tables. * We may build same derived table more than once, but it's not expensive. */ if ( is_DC_band ) { if ( cinfo->Ah == 0 ) {/* DC refinement needs no table */ tbl = compptr->dc_tbl_no; if ( ( tbl < 0 ) || ( tbl >= NUM_HUFF_TBLS ) || ( cinfo->dc_huff_tbl_ptrs[tbl] == NULL ) ) { ERREXIT1( cinfo, JERR_NO_HUFF_TABLE, tbl ); } jpeg_make_d_derived_tbl( cinfo, cinfo->dc_huff_tbl_ptrs[tbl], &entropy->derived_tbls[tbl] ); } } else { tbl = compptr->ac_tbl_no; if ( ( tbl < 0 ) || ( tbl >= NUM_HUFF_TBLS ) || ( cinfo->ac_huff_tbl_ptrs[tbl] == NULL ) ) { ERREXIT1( cinfo, JERR_NO_HUFF_TABLE, tbl ); } jpeg_make_d_derived_tbl( cinfo, cinfo->ac_huff_tbl_ptrs[tbl], &entropy->derived_tbls[tbl] ); /* remember the single active table */ entropy->ac_derived_tbl = entropy->derived_tbls[tbl]; } /* 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 private state variables */ entropy->saved.EOBRUN = 0; /* Initialize restart counter */ entropy->restarts_to_go = cinfo->restart_interval; } /* * 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 ) { phuff_entropy_ptr entropy = (phuff_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; } /* Re-init EOB run count, too */ entropy->saved.EOBRUN = 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; } /* * Huffman MCU decoding. * Each of these routines decodes and returns 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 IS INITIALLY ZEROED BY THE CALLER. * * We return 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 * spectral selection, since we'll just re-assign them on the next call. * Successive approximation AC refinement has to be more careful, however.) */ /* * MCU decoding for DC initial scan (either spectral selection, * or first pass of successive approximation). */ METHODDEF boolean decode_mcu_DC_first( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) { phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; int Al = cinfo->Al; register int s, r; int blkn, ci; JBLOCKROW block; BITREAD_STATE_VARS; savable_state state; d_derived_tbl * tbl; 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]; tbl = entropy->derived_tbls[compptr->dc_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, tbl, return FALSE, label1 ); if ( s ) { CHECK_BIT_BUFFER( br_state, s, return FALSE ); r = GET_BITS( s ); s = HUFF_EXTEND( r, s ); } /* Convert DC difference to actual value, update last_dc_val */ s += state.last_dc_val[ci]; state.last_dc_val[ci] = s; /* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */ ( *block )[0] = (JCOEF) ( s << Al ); } /* 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; } /* * MCU decoding for AC initial scan (either spectral selection, * or first pass of successive approximation). */ METHODDEF boolean decode_mcu_AC_first( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) { phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; int Se = cinfo->Se; int Al = cinfo->Al; register int s, k, r; unsigned int EOBRUN; JBLOCKROW block; BITREAD_STATE_VARS; d_derived_tbl * tbl; /* 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. * We can avoid loading/saving bitread state if in an EOB run. */ EOBRUN = entropy->saved.EOBRUN;/* only part of saved state we care about */ /* There is always only one block per MCU */ if ( EOBRUN > 0 ) { /* if it's a band of zeroes... */ EOBRUN--; } /* ...process it now (we do nothing) */ else { BITREAD_LOAD_STATE( cinfo, entropy->bitstate ); block = MCU_data[0]; tbl = entropy->ac_derived_tbl; for ( k = cinfo->Ss; k <= Se; k++ ) { HUFF_DECODE( s, br_state, tbl, 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 ); /* Scale and output coefficient in natural (dezigzagged) order */ ( *block )[jpeg_natural_order[k]] = (JCOEF) ( s << Al ); } else { if ( r == 15 ) {/* ZRL */ k += 15;/* skip 15 zeroes in band */ } else {/* EOBr, run length is 2^r + appended bits */ EOBRUN = 1 << r; if ( r ) {/* EOBr, r > 0 */ CHECK_BIT_BUFFER( br_state, r, return FALSE ); r = GET_BITS( r ); EOBRUN += r; } EOBRUN--; /* this band is processed at this moment */ break; /* force end-of-band */ } } } BITREAD_SAVE_STATE( cinfo, entropy->bitstate ); } /* Completed MCU, so update state */ entropy->saved.EOBRUN = EOBRUN;/* only part of saved state we care about */ /* Account for restart interval (no-op if not using restarts) */ entropy->restarts_to_go--; return TRUE; } /* * MCU decoding 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 decode_mcu_DC_refine( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) { phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; int p1 = 1 << cinfo->Al;/* 1 in the bit position being coded */ int blkn; JBLOCKROW block; BITREAD_STATE_VARS; /* 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 ); /* Outer loop handles each block in the MCU */ for ( blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++ ) { block = MCU_data[blkn]; /* Encoded data is simply the next bit of the two's-complement DC value */ CHECK_BIT_BUFFER( br_state, 1, return FALSE ); if ( GET_BITS( 1 ) ) { ( *block )[0] |= p1; } /* Note: since we use |=, repeating the assignment later is safe */ } /* Completed MCU, so update state */ BITREAD_SAVE_STATE( cinfo, entropy->bitstate ); /* Account for restart interval (no-op if not using restarts) */ entropy->restarts_to_go--; return TRUE; } /* * MCU decoding for AC successive approximation refinement scan. */ METHODDEF boolean decode_mcu_AC_refine( j_decompress_ptr cinfo, JBLOCKROW * MCU_data ) { phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; int Se = cinfo->Se; int p1 = 1 << cinfo->Al;/* 1 in the bit position being coded */ int m1 = ( -1 ) << cinfo->Al;/* -1 in the bit position being coded */ register int s, k, r; unsigned int EOBRUN; JBLOCKROW block; JCOEFPTR thiscoef; BITREAD_STATE_VARS; d_derived_tbl * tbl; int num_newnz; int newnz_pos[DCTSIZE2]; /* 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 ); EOBRUN = entropy->saved.EOBRUN;/* only part of saved state we care about */ /* There is always only one block per MCU */ block = MCU_data[0]; tbl = entropy->ac_derived_tbl; /* If we are forced to suspend, we must undo the assignments to any newly * nonzero coefficients in the block, because otherwise we'd get confused * next time about which coefficients were already nonzero. * But we need not undo addition of bits to already-nonzero coefficients; * instead, we can test the current bit position to see if we already did it. */ num_newnz = 0; /* initialize coefficient loop counter to start of band */ k = cinfo->Ss; if ( EOBRUN == 0 ) { for (; k <= Se; k++ ) { HUFF_DECODE( s, br_state, tbl, goto undoit, label3 ); r = s >> 4; s &= 15; if ( s ) { if ( s != 1 ) {/* size of new coef should always be 1 */ WARNMS( cinfo, JWRN_HUFF_BAD_CODE ); } CHECK_BIT_BUFFER( br_state, 1, goto undoit ); if ( GET_BITS( 1 ) ) { s = p1; } /* newly nonzero coef is positive */ else { s = m1; } /* newly nonzero coef is negative */ } else { if ( r != 15 ) { EOBRUN = 1 << r;/* EOBr, run length is 2^r + appended bits */ if ( r ) { CHECK_BIT_BUFFER( br_state, r, goto undoit ); r = GET_BITS( r ); EOBRUN += r; } break; /* rest of block is handled by EOB logic */ } /* note s = 0 for processing ZRL */ } /* Advance over already-nonzero coefs and r still-zero coefs, * appending correction bits to the nonzeroes. A correction bit is 1 * if the absolute value of the coefficient must be increased. */ do { thiscoef = *block + jpeg_natural_order[k]; if ( *thiscoef != 0 ) { CHECK_BIT_BUFFER( br_state, 1, goto undoit ); if ( GET_BITS( 1 ) ) { if ( ( *thiscoef & p1 ) == 0 ) {/* do nothing if already changed it */ if ( *thiscoef >= 0 ) { *thiscoef += p1; } else { *thiscoef += m1; } } } } else { if ( --r < 0 ) { break; } /* reached target zero coefficient */ } k++; } while ( k <= Se ); if ( s ) { int pos = jpeg_natural_order[k]; /* Output newly nonzero coefficient */ ( *block )[pos] = (JCOEF) s; /* Remember its position in case we have to suspend */ newnz_pos[num_newnz++] = pos; } } } if ( EOBRUN > 0 ) { /* Scan any remaining coefficient positions after the end-of-band * (the last newly nonzero coefficient, if any). Append a correction * bit to each already-nonzero coefficient. A correction bit is 1 * if the absolute value of the coefficient must be increased. */ for (; k <= Se; k++ ) { thiscoef = *block + jpeg_natural_order[k]; if ( *thiscoef != 0 ) { CHECK_BIT_BUFFER( br_state, 1, goto undoit ); if ( GET_BITS( 1 ) ) { if ( ( *thiscoef & p1 ) == 0 ) {/* do nothing if already changed it */ if ( *thiscoef >= 0 ) { *thiscoef += p1; } else { *thiscoef += m1; } } } } } /* Count one block completed in EOB run */ EOBRUN--; } /* Completed MCU, so update state */ BITREAD_SAVE_STATE( cinfo, entropy->bitstate ); entropy->saved.EOBRUN = EOBRUN;/* only part of saved state we care about */ /* Account for restart interval (no-op if not using restarts) */ entropy->restarts_to_go--; return TRUE; undoit: /* Re-zero any output coefficients that we made newly nonzero */ while ( num_newnz > 0 ) { ( *block )[newnz_pos[--num_newnz]] = 0; } return FALSE; } /* * Module initialization routine for progressive Huffman entropy decoding. */ GLOBAL void jinit_phuff_decoder( j_decompress_ptr cinfo ) { phuff_entropy_ptr entropy; int * coef_bit_ptr; int ci, i; entropy = (phuff_entropy_ptr) ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF( phuff_entropy_decoder ) ); cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; entropy->pub.start_pass = start_pass_phuff_decoder; /* Mark derived tables unallocated */ for ( i = 0; i < NUM_HUFF_TBLS; i++ ) { entropy->derived_tbls[i] = NULL; } /* Create progression status table */ cinfo->coef_bits = ( int ( * )[DCTSIZE2] ) ( *cinfo->mem->alloc_small ) ( (j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->num_components * DCTSIZE2 * SIZEOF( int ) ); coef_bit_ptr = &cinfo->coef_bits[0][0]; for ( ci = 0; ci < cinfo->num_components; ci++ ) { for ( i = 0; i < DCTSIZE2; i++ ) { *coef_bit_ptr++ = -1; } } } #endif /* D_PROGRESSIVE_SUPPORTED */