diff options
Diffstat (limited to 'jdhuff.c')
| -rw-r--r-- | jdhuff.c | 849 |
1 files changed, 747 insertions, 102 deletions
@@ -6,6 +6,7 @@ * For conditions of distribution and use, see the accompanying README file. * * This file contains Huffman entropy decoding routines. + * Both sequential and progressive modes are supported in this single module. * * 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 @@ -17,7 +18,173 @@ #define JPEG_INTERNALS #include "jinclude.h" #include "jpeglib.h" -#include "jdhuff.h" /* Declarations shared with jdphuff.c */ + + +/* Derived data constructed for each Huffman table */ + +#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */ + +typedef struct { + /* Basic tables: (element [0] of each array is unused) */ + INT32 maxcode[18]; /* largest code of length k (-1 if none) */ + /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */ + INT32 valoffset[17]; /* huffval[] offset for codes of length k */ + /* valoffset[k] = huffval[] index of 1st symbol of code length k, less + * the smallest code of length k; so given a code of length k, the + * corresponding symbol is huffval[code + valoffset[k]] + */ + + /* Link to public Huffman table (needed only in jpeg_huff_decode) */ + JHUFF_TBL *pub; + + /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of + * the input data stream. If the next Huffman code is no more + * than HUFF_LOOKAHEAD bits long, we can obtain its length and + * the corresponding symbol directly from these tables. + */ + int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */ + UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */ +} d_derived_tbl; + + +/* + * Fetching the next N bits from the input stream is a time-critical operation + * for the Huffman decoders. We implement it with a combination of inline + * macros and out-of-line subroutines. Note that N (the number of bits + * demanded at one time) never exceeds 15 for JPEG use. + * + * We read source bytes into get_buffer and dole out bits as needed. + * If get_buffer already contains enough bits, they are fetched in-line + * by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough + * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer + * as full as possible (not just to the number of bits needed; this + * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer). + * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension. + * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains + * at least the requested number of bits --- dummy zeroes are inserted if + * necessary. + */ + +typedef INT32 bit_buf_type; /* type of bit-extraction buffer */ +#define BIT_BUF_SIZE 32 /* size of buffer in bits */ + +/* If long is > 32 bits on your machine, and shifting/masking longs is + * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE + * appropriately should be a win. Unfortunately we can't define the size + * with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8) + * because not all machines measure sizeof in 8-bit bytes. + */ + +typedef struct { /* Bitreading state saved across MCUs */ + bit_buf_type get_buffer; /* current bit-extraction buffer */ + int bits_left; /* # of unused bits in it */ +} bitread_perm_state; + +typedef struct { /* Bitreading working state within an MCU */ + /* Current data source location */ + /* We need a copy, rather than munging the original, in case of suspension */ + const JOCTET * next_input_byte; /* => next byte to read from source */ + size_t bytes_in_buffer; /* # of bytes remaining in source buffer */ + /* Bit input buffer --- note these values are kept in register variables, + * not in this struct, inside the inner loops. + */ + bit_buf_type get_buffer; /* current bit-extraction buffer */ + int bits_left; /* # of unused bits in it */ + /* Pointer needed by jpeg_fill_bit_buffer. */ + j_decompress_ptr cinfo; /* back link to decompress master record */ +} bitread_working_state; + +/* Macros to declare and load/save bitread local variables. */ +#define BITREAD_STATE_VARS \ + register bit_buf_type get_buffer; \ + register int bits_left; \ + bitread_working_state br_state + +#define BITREAD_LOAD_STATE(cinfop,permstate) \ + br_state.cinfo = cinfop; \ + br_state.next_input_byte = cinfop->src->next_input_byte; \ + br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \ + get_buffer = permstate.get_buffer; \ + bits_left = permstate.bits_left; + +#define BITREAD_SAVE_STATE(cinfop,permstate) \ + cinfop->src->next_input_byte = br_state.next_input_byte; \ + cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \ + permstate.get_buffer = get_buffer; \ + permstate.bits_left = bits_left + +/* + * These macros provide the in-line portion of bit fetching. + * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer + * before using GET_BITS, PEEK_BITS, or DROP_BITS. + * The variables get_buffer and bits_left are assumed to be locals, + * but the state struct might not be (jpeg_huff_decode needs this). + * CHECK_BIT_BUFFER(state,n,action); + * Ensure there are N bits in get_buffer; if suspend, take action. + * val = GET_BITS(n); + * Fetch next N bits. + * val = PEEK_BITS(n); + * Fetch next N bits without removing them from the buffer. + * DROP_BITS(n); + * Discard next N bits. + * The value N should be a simple variable, not an expression, because it + * is evaluated multiple times. + */ + +#define CHECK_BIT_BUFFER(state,nbits,action) \ + { if (bits_left < (nbits)) { \ + if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \ + { action; } \ + get_buffer = (state).get_buffer; bits_left = (state).bits_left; } } + +#define GET_BITS(nbits) \ + (((int) (get_buffer >> (bits_left -= (nbits)))) & BIT_MASK(nbits)) + +#define PEEK_BITS(nbits) \ + (((int) (get_buffer >> (bits_left - (nbits)))) & BIT_MASK(nbits)) + +#define DROP_BITS(nbits) \ + (bits_left -= (nbits)) + + +/* + * Code for extracting next Huffman-coded symbol from input bit stream. + * Again, this is time-critical and we make the main paths be macros. + * + * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits + * without looping. Usually, more than 95% of the Huffman codes will be 8 + * or fewer bits long. The few overlength codes are handled with a loop, + * which need not be inline code. + * + * Notes about the HUFF_DECODE macro: + * 1. Near the end of the data segment, we may fail to get enough bits + * for a lookahead. In that case, we do it the hard way. + * 2. If the lookahead table contains no entry, the next code must be + * more than HUFF_LOOKAHEAD bits long. + * 3. jpeg_huff_decode returns -1 if forced to suspend. + */ + +#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \ +{ register int nb, look; \ + if (bits_left < HUFF_LOOKAHEAD) { \ + if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \ + get_buffer = state.get_buffer; bits_left = state.bits_left; \ + if (bits_left < HUFF_LOOKAHEAD) { \ + nb = 1; goto slowlabel; \ + } \ + } \ + look = PEEK_BITS(HUFF_LOOKAHEAD); \ + if ((nb = htbl->look_nbits[look]) != 0) { \ + DROP_BITS(nb); \ + result = htbl->look_sym[look]; \ + } else { \ + nb = HUFF_LOOKAHEAD+1; \ +slowlabel: \ + if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \ + { failaction; } \ + get_buffer = state.get_buffer; bits_left = state.bits_left; \ + } \ +} /* @@ -28,7 +195,8 @@ */ typedef struct { - int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ + 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 @@ -41,7 +209,8 @@ typedef struct { #else #if MAX_COMPS_IN_SCAN == 4 #define ASSIGN_STATE(dest,src) \ - ((dest).last_dc_val[0] = (src).last_dc_val[0], \ + ((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]) @@ -61,6 +230,15 @@ typedef struct { /* These fields are NOT loaded into local working state. */ unsigned int restarts_to_go; /* MCUs left in this restart interval */ + /* Following two fields used only in progressive mode */ + + /* 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 */ + + /* Following fields used only in sequential mode */ + /* 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]; @@ -77,7 +255,7 @@ typedef struct { typedef huff_entropy_decoder * huff_entropy_ptr; -static const int jpeg_zigzag_order[DCTSIZE2] = { +static const int jpeg_zigzag_order[8][8] = { 0, 1, 5, 6, 14, 15, 27, 28, 2, 4, 7, 13, 16, 26, 29, 42, 3, 8, 12, 17, 25, 30, 41, 43, @@ -90,75 +268,11 @@ static const int jpeg_zigzag_order[DCTSIZE2] = { /* - * 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, blkn, dctbl, actbl, i; - 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; - /* 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, TRUE, dctbl, - & entropy->dc_derived_tbls[dctbl]); - jpeg_make_d_derived_tbl(cinfo, FALSE, actbl, - & entropy->ac_derived_tbls[actbl]); - /* Initialize DC predictions to 0 */ - entropy->saved.last_dc_val[ci] = 0; - } - - /* Precalculate decoding info for each block in an MCU of this scan */ - for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { - ci = cinfo->MCU_membership[blkn]; - compptr = cinfo->cur_comp_info[ci]; - /* Precalculate which table to use for each block */ - entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no]; - entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no]; - /* Decide whether we really care about the coefficient values */ - if (compptr->component_needed) { - ci = compptr->DCT_v_scaled_size; - if (ci <= 0 || ci > 8) ci = 8; - i = compptr->DCT_h_scaled_size; - if (i <= 0 || i > 8) i = 8; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[(ci - 1) * DCTSIZE + i - 1]; - } else { - entropy->coef_limit[blkn] = 0; - } - } - - /* Initialize bitread state variables */ - entropy->bitstate.bits_left = 0; - entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ - entropy->pub.insufficient_data = FALSE; - - /* Initialize restart counter */ - entropy->restarts_to_go = cinfo->restart_interval; -} - - -/* * Compute the derived values for a Huffman table. * This routine also performs some validation checks on the table. - * - * Note this is also used by jdphuff.c. */ -GLOBAL(void) +LOCAL(void) jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno, d_derived_tbl ** pdtbl) { @@ -280,8 +394,7 @@ jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno, /* - * Out-of-line code for bit fetching (shared with jdphuff.c). - * See jdhuff.h for info about usage. + * Out-of-line code for bit fetching. * Note: current values of get_buffer and bits_left are passed as parameters, * but are returned in the corresponding fields of the state struct. * @@ -301,7 +414,7 @@ jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno, #endif -GLOBAL(boolean) +LOCAL(boolean) jpeg_fill_bit_buffer (bitread_working_state * state, register bit_buf_type get_buffer, register int bits_left, int nbits) @@ -403,11 +516,32 @@ jpeg_fill_bit_buffer (bitread_working_state * state, /* + * Figure F.12: extend sign bit. + * On some machines, a shift and sub will be faster than a table lookup. + */ + +#ifdef AVOID_TABLES + +#define BIT_MASK(nbits) ((1<<(nbits))-1) +#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x)) + +#else + +#define BIT_MASK(nbits) bmask[nbits] +#define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x)) + +static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */ + { 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, + 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF }; + +#endif /* AVOID_TABLES */ + + +/* * Out-of-line code for Huffman code decoding. - * See jdhuff.h for info about usage. */ -GLOBAL(int) +LOCAL(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) @@ -447,26 +581,6 @@ jpeg_huff_decode (bitread_working_state * state, /* - * Figure F.12: extend sign bit. - * On some machines, a shift and sub 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) <= bmask[(s) - 1] ? (x) - bmask[s] : (x)) - -static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */ - { 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, - 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF }; - -#endif /* AVOID_TABLES */ - - -/* * Check for a restart marker & resynchronize decoder. * Returns FALSE if must suspend. */ @@ -489,6 +603,8 @@ process_restart (j_decompress_ptr cinfo) /* 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; @@ -506,18 +622,381 @@ process_restart (j_decompress_ptr cinfo) /* - * Decode and return one MCU's worth of Huffman-compressed coefficients. + * 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 HAS BEEN ZEROED BY THE CALLER. + * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. * (Wholesale zeroing is usually a little faster than retail...) * - * Returns FALSE if data source requested suspension. In that case no + * 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 - * this module, since we'll just re-assign them on the next call.) + * 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) +{ + huff_entropy_ptr entropy = (huff_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; + } + + /* If we've run out of data, just leave the MCU set to zeroes. + * This way, we return uniform gray for the remainder of the segment. + */ + if (! entropy->pub.insufficient_data) { + + /* 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 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) +{ + huff_entropy_ptr entropy = (huff_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; + } + + /* If we've run out of data, just leave the MCU set to zeroes. + * This way, we return uniform gray for the remainder of the segment. + */ + if (! entropy->pub.insufficient_data) { + + /* 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 need */ + + /* 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 need */ + } + + /* 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) +{ + huff_entropy_ptr entropy = (huff_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; + } + + /* Not worth the cycles to check insufficient_data here, + * since we will not change the data anyway if we read zeroes. + */ + + /* 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) +{ + huff_entropy_ptr entropy = (huff_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; + } + + /* If we've run out of data, don't modify the MCU. + */ + if (! entropy->pub.insufficient_data) { + + /* Load up working state */ + BITREAD_LOAD_STATE(cinfo,entropy->bitstate); + EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ + + /* 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 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 set 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 need */ + } + + /* 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; +} + + +/* + * Decode one MCU's worth of Huffman-compressed coefficients. */ METHODDEF(boolean) @@ -640,6 +1119,156 @@ decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) /* + * 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, blkn, dctbl, actbl, i; + jpeg_component_info * compptr; + + if (cinfo->progressive_mode) { + /* Validate progressive scan parameters */ + if (cinfo->Ss == 0) { + if (cinfo->Se != 0) + goto bad; + } else { + /* need not check Ss/Se < 0 since they came from unsigned bytes */ + if (cinfo->Se < cinfo->Ss || cinfo->Se >= DCTSIZE2) + goto bad; + /* AC scans may have only one component */ + if (cinfo->comps_in_scan != 1) + goto bad; + } + if (cinfo->Ah != 0) { + /* Successive approximation refinement scan: must have Al = Ah-1. */ + if (cinfo->Ah-1 != cinfo->Al) + goto bad; + } + if (cinfo->Al > 13) { /* need not check for < 0 */ + /* Arguably the maximum Al value should be less than 13 for 8-bit precision, + * but the spec doesn't say so, and we try to be liberal about what we + * accept. Note: large Al values could result in out-of-range DC + * coefficients during early scans, leading to bizarre displays due to + * overflows in the IDCT math. But we won't crash. + */ + 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 coefi, cindex = cinfo->cur_comp_info[ci]->component_index; + int *coef_bit_ptr = & cinfo->coef_bits[cindex][0]; + if (cinfo->Ss && 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 (cinfo->Ss == 0) + entropy->pub.decode_mcu = decode_mcu_DC_first; + else + entropy->pub.decode_mcu = decode_mcu_AC_first; + } else { + if (cinfo->Ss == 0) + 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 (cinfo->Ss == 0) { + if (cinfo->Ah == 0) { /* DC refinement needs no table */ + i = compptr->dc_tbl_no; + jpeg_make_d_derived_tbl(cinfo, TRUE, i, + & entropy->derived_tbls[i]); + } + } else { + i = compptr->ac_tbl_no; + jpeg_make_d_derived_tbl(cinfo, FALSE, i, + & entropy->derived_tbls[i]); + /* remember the single active table */ + entropy->ac_derived_tbl = entropy->derived_tbls[i]; + } + /* Initialize DC predictions to 0 */ + entropy->saved.last_dc_val[ci] = 0; + } + + /* Initialize private state variables */ + entropy->saved.EOBRUN = 0; + } else { + /* 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); + + /* Select MCU decoding routine */ + entropy->pub.decode_mcu = decode_mcu; + + 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; + /* 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, TRUE, dctbl, + & entropy->dc_derived_tbls[dctbl]); + jpeg_make_d_derived_tbl(cinfo, FALSE, actbl, + & entropy->ac_derived_tbls[actbl]); + /* Initialize DC predictions to 0 */ + entropy->saved.last_dc_val[ci] = 0; + } + + /* Precalculate decoding info for each block in an MCU of this scan */ + for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { + ci = cinfo->MCU_membership[blkn]; + compptr = cinfo->cur_comp_info[ci]; + /* Precalculate which table to use for each block */ + entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no]; + entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no]; + /* Decide whether we really care about the coefficient values */ + if (compptr->component_needed) { + ci = compptr->DCT_v_scaled_size; + if (ci <= 0 || ci > 8) ci = 8; + i = compptr->DCT_h_scaled_size; + if (i <= 0 || i > 8) i = 8; + entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1]; + } else { + entropy->coef_limit[blkn] = 0; + } + } + } + + /* Initialize bitread state variables */ + entropy->bitstate.bits_left = 0; + entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ + entropy->pub.insufficient_data = FALSE; + + /* Initialize restart counter */ + entropy->restarts_to_go = cinfo->restart_interval; +} + + +/* * Module initialization routine for Huffman entropy decoding. */ @@ -654,10 +1283,26 @@ jinit_huff_decoder (j_decompress_ptr cinfo) 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; + if (cinfo->progressive_mode) { + /* Create progression status table */ + int *coef_bit_ptr, ci; + 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; + + /* Mark derived tables unallocated */ + for (i = 0; i < NUM_HUFF_TBLS; i++) { + entropy->derived_tbls[i] = NULL; + } + } else { + /* Mark tables unallocated */ + for (i = 0; i < NUM_HUFF_TBLS; i++) { + entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL; + } } } |