| /* |
| * jdhuff.c |
| * |
| * This file was part of the Independent JPEG Group's software: |
| * Copyright (C) 1991-1997, Thomas G. Lane. |
| * libjpeg-turbo Modifications: |
| * Copyright (C) 2009-2011, 2016, 2018-2019, D. R. Commander. |
| * Copyright (C) 2018, Matthias Räncker. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * 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. |
| * |
| * NOTE: All referenced figures are from |
| * Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994. |
| */ |
| |
| #define JPEG_INTERNALS |
| #include "jinclude.h" |
| #include "jpeglib.h" |
| #include "jdhuff.h" /* Declarations shared with jdphuff.c */ |
| #include "jpegcomp.h" |
| #include "jstdhuff.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; |
| |
| 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]; |
| |
| /* Precalculated info set up by start_pass for use in decode_mcu: */ |
| |
| /* Pointers to derived tables to be used for each block within an MCU */ |
| d_derived_tbl *dc_cur_tbls[D_MAX_BLOCKS_IN_MCU]; |
| d_derived_tbl *ac_cur_tbls[D_MAX_BLOCKS_IN_MCU]; |
| /* Whether we care about the DC and AC coefficient values for each block */ |
| boolean dc_needed[D_MAX_BLOCKS_IN_MCU]; |
| boolean ac_needed[D_MAX_BLOCKS_IN_MCU]; |
| } 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, blkn, dctbl, actbl; |
| d_derived_tbl **pdtbl; |
| 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 */ |
| pdtbl = (d_derived_tbl **)(entropy->dc_derived_tbls) + dctbl; |
| jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl, pdtbl); |
| pdtbl = (d_derived_tbl **)(entropy->ac_derived_tbls) + actbl; |
| jpeg_make_d_derived_tbl(cinfo, FALSE, actbl, pdtbl); |
| /* 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) { |
| entropy->dc_needed[blkn] = TRUE; |
| /* we don't need the ACs if producing a 1/8th-size image */ |
| entropy->ac_needed[blkn] = (compptr->_DCT_scaled_size > 1); |
| } else { |
| entropy->dc_needed[blkn] = entropy->ac_needed[blkn] = FALSE; |
| } |
| } |
| |
| /* 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) |
| jpeg_make_d_derived_tbl(j_decompress_ptr cinfo, boolean isDC, int tblno, |
| d_derived_tbl **pdtbl) |
| { |
| JHUFF_TBL *htbl; |
| d_derived_tbl *dtbl; |
| int p, i, l, si, numsymbols; |
| int lookbits, ctr; |
| char huffsize[257]; |
| unsigned int huffcode[257]; |
| unsigned int code; |
| |
| /* Note that huffsize[] and huffcode[] are filled in code-length order, |
| * paralleling the order of the symbols themselves in htbl->huffval[]. |
| */ |
| |
| /* Find the input Huffman table */ |
| if (tblno < 0 || tblno >= NUM_HUFF_TBLS) |
| ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); |
| htbl = |
| isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno]; |
| if (htbl == NULL) |
| ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); |
| |
| /* 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 */ |
| |
| p = 0; |
| for (l = 1; l <= 16; l++) { |
| i = (int)htbl->bits[l]; |
| if (i < 0 || p + i > 256) /* protect against table overrun */ |
| ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); |
| while (i--) |
| huffsize[p++] = (char)l; |
| } |
| huffsize[p] = 0; |
| numsymbols = p; |
| |
| /* Figure C.2: generate the codes themselves */ |
| /* We also validate that the counts represent a legal Huffman code tree. */ |
| |
| code = 0; |
| si = huffsize[0]; |
| p = 0; |
| while (huffsize[p]) { |
| while (((int)huffsize[p]) == si) { |
| huffcode[p++] = code; |
| code++; |
| } |
| /* code is now 1 more than the last code used for codelength si; but |
| * it must still fit in si bits, since no code is allowed to be all ones. |
| */ |
| if (((JLONG)code) >= (((JLONG)1) << si)) |
| ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); |
| 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]) { |
| /* valoffset[l] = huffval[] index of 1st symbol of code length l, |
| * minus the minimum code of length l |
| */ |
| dtbl->valoffset[l] = (JLONG)p - (JLONG)huffcode[p]; |
| 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->valoffset[17] = 0; |
| 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. |
| */ |
| |
| for (i = 0; i < (1 << HUFF_LOOKAHEAD); i++) |
| dtbl->lookup[i] = (HUFF_LOOKAHEAD + 1) << HUFF_LOOKAHEAD; |
| |
| 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->lookup[lookbits] = (l << HUFF_LOOKAHEAD) | htbl->huffval[p]; |
| lookbits++; |
| } |
| } |
| } |
| |
| /* Validate symbols as being reasonable. |
| * For AC tables, we make no check, but accept all byte values 0..255. |
| * For DC tables, we require the symbols to be in range 0..15. |
| * (Tighter bounds could be applied depending on the data depth and mode, |
| * but this is sufficient to ensure safe decoding.) |
| */ |
| if (isDC) { |
| for (i = 0; i < numsymbols; i++) { |
| int sym = htbl->huffval[i]; |
| if (sym < 0 || sym > 15) |
| ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); |
| } |
| } |
| } |
| |
| |
| /* |
| * 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; |
| j_decompress_ptr cinfo = state->cinfo; |
| |
| /* 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.) */ |
| /* We fail to do so only if we hit a marker or are forced to suspend. */ |
| |
| if (cinfo->unread_marker == 0) { /* cannot advance past a marker */ |
| while (bits_left < MIN_GET_BITS) { |
| register int c; |
| |
| /* Attempt to read a byte */ |
| if (bytes_in_buffer == 0) { |
| if (!(*cinfo->src->fill_input_buffer) (cinfo)) |
| return FALSE; |
| next_input_byte = cinfo->src->next_input_byte; |
| bytes_in_buffer = cinfo->src->bytes_in_buffer; |
| } |
| bytes_in_buffer--; |
| c = *next_input_byte++; |
| |
| /* If it's 0xFF, check and discard stuffed zero byte */ |
| if (c == 0xFF) { |
| /* Loop here to discard any padding FF's on terminating marker, |
| * so that we can save a valid unread_marker value. NOTE: we will |
| * accept multiple FF's followed by a 0 as meaning a single FF data |
| * byte. This data pattern is not valid according to the standard. |
| */ |
| do { |
| if (bytes_in_buffer == 0) { |
| if (!(*cinfo->src->fill_input_buffer) (cinfo)) |
| return FALSE; |
| next_input_byte = cinfo->src->next_input_byte; |
| bytes_in_buffer = cinfo->src->bytes_in_buffer; |
| } |
| bytes_in_buffer--; |
| c = *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. |
| * Save the marker code for later use. |
| * Fine point: it might appear that we should save the marker into |
| * bitread working state, not straight into permanent state. But |
| * once we have hit a marker, we cannot need to suspend within the |
| * current MCU, because we will read no more bytes from the data |
| * source. So it is OK to update permanent state right away. |
| */ |
| cinfo->unread_marker = c; |
| /* See if we need to insert some fake zero bits. */ |
| goto no_more_bytes; |
| } |
| } |
| |
| /* OK, load c into get_buffer */ |
| get_buffer = (get_buffer << 8) | c; |
| bits_left += 8; |
| } /* end while */ |
| } else { |
| no_more_bytes: |
| /* We get here if we've read the marker that terminates the compressed |
| * data segment. There should be enough bits in the buffer register |
| * to satisfy the request; if so, no problem. |
| */ |
| if (nbits > bits_left) { |
| /* Uh-oh. Report corrupted data to user and stuff zeroes into |
| * the data stream, so that we can produce some kind of image. |
| * We use a nonvolatile flag to ensure that only one warning message |
| * appears per data segment. |
| */ |
| if (!cinfo->entropy->insufficient_data) { |
| WARNMS(cinfo, JWRN_HIT_MARKER); |
| cinfo->entropy->insufficient_data = TRUE; |
| } |
| /* Fill the buffer with zero bits */ |
| get_buffer <<= MIN_GET_BITS - bits_left; |
| bits_left = MIN_GET_BITS; |
| } |
| } |
| |
| /* 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; |
| } |
| |
| |
| /* Macro version of the above, which performs much better but does not |
| handle markers. We have to hand off any blocks with markers to the |
| slower routines. */ |
| |
| #define GET_BYTE { \ |
| register int c0, c1; \ |
| c0 = *buffer++; \ |
| c1 = *buffer; \ |
| /* Pre-execute most common case */ \ |
| get_buffer = (get_buffer << 8) | c0; \ |
| bits_left += 8; \ |
| if (c0 == 0xFF) { \ |
| /* Pre-execute case of FF/00, which represents an FF data byte */ \ |
| buffer++; \ |
| if (c1 != 0) { \ |
| /* Oops, it's actually a marker indicating end of compressed data. */ \ |
| cinfo->unread_marker = c1; \ |
| /* Back out pre-execution and fill the buffer with zero bits */ \ |
| buffer -= 2; \ |
| get_buffer &= ~0xFF; \ |
| } \ |
| } \ |
| } |
| |
| #if SIZEOF_SIZE_T == 8 || defined(_WIN64) || (defined(__x86_64__) && defined(__ILP32__)) |
| |
| /* Pre-fetch 48 bytes, because the holding register is 64-bit */ |
| #define FILL_BIT_BUFFER_FAST \ |
| if (bits_left <= 16) { \ |
| GET_BYTE GET_BYTE GET_BYTE GET_BYTE GET_BYTE GET_BYTE \ |
| } |
| |
| #else |
| |
| /* Pre-fetch 16 bytes, because the holding register is 32-bit */ |
| #define FILL_BIT_BUFFER_FAST \ |
| if (bits_left <= 16) { \ |
| GET_BYTE GET_BYTE \ |
| } |
| |
| #endif |
| |
| |
| /* |
| * 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 JLONG 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. */ |
| |
| 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[(int)(code + htbl->valoffset[l])]; |
| } |
| |
| |
| /* |
| * Figure F.12: extend sign bit. |
| * On some machines, a shift and add will be faster than a table lookup. |
| */ |
| |
| #define AVOID_TABLES |
| #ifdef AVOID_TABLES |
| |
| #define NEG_1 ((unsigned int)-1) |
| #define HUFF_EXTEND(x, s) \ |
| ((x) + ((((x) - (1 << ((s) - 1))) >> 31) & (((NEG_1) << (s)) + 1))) |
| |
| #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; |
| |
| /* Reset out-of-data flag, unless read_restart_marker left us smack up |
| * against a marker. In that case we will end up treating the next data |
| * segment as empty, and we can avoid producing bogus output pixels by |
| * leaving the flag set. |
| */ |
| if (cinfo->unread_marker == 0) |
| entropy->pub.insufficient_data = FALSE; |
| |
| return TRUE; |
| } |
| |
| |
| LOCAL(boolean) |
| decode_mcu_slow(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
| { |
| huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy; |
| BITREAD_STATE_VARS; |
| int blkn; |
| savable_state state; |
| /* Outer loop handles each block in the MCU */ |
| |
| /* Load up working state */ |
| BITREAD_LOAD_STATE(cinfo, entropy->bitstate); |
| state = entropy->saved; |
| |
| for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
| JBLOCKROW block = MCU_data ? MCU_data[blkn] : NULL; |
| d_derived_tbl *dctbl = entropy->dc_cur_tbls[blkn]; |
| d_derived_tbl *actbl = entropy->ac_cur_tbls[blkn]; |
| register int s, k, r; |
| |
| /* 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); |
| } |
| |
| if (entropy->dc_needed[blkn]) { |
| /* Convert DC difference to actual value, update last_dc_val */ |
| int ci = cinfo->MCU_membership[blkn]; |
| /* This is really just |
| * s += state.last_dc_val[ci]; |
| * It is written this way in order to shut up UBSan. |
| */ |
| s = (int)((unsigned int)s + (unsigned int)state.last_dc_val[ci]); |
| state.last_dc_val[ci] = s; |
| if (block) { |
| /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */ |
| (*block)[0] = (JCOEF)s; |
| } |
| } |
| |
| if (entropy->ac_needed[blkn] && block) { |
| |
| /* 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 { |
| |
| /* 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); |
| entropy->saved = state; |
| return TRUE; |
| } |
| |
| |
| LOCAL(boolean) |
| decode_mcu_fast(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
| { |
| huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy; |
| BITREAD_STATE_VARS; |
| JOCTET *buffer; |
| int blkn; |
| savable_state state; |
| /* Outer loop handles each block in the MCU */ |
| |
| /* Load up working state */ |
| BITREAD_LOAD_STATE(cinfo, entropy->bitstate); |
| buffer = (JOCTET *)br_state.next_input_byte; |
| state = entropy->saved; |
| |
| for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
| JBLOCKROW block = MCU_data ? MCU_data[blkn] : NULL; |
| d_derived_tbl *dctbl = entropy->dc_cur_tbls[blkn]; |
| d_derived_tbl *actbl = entropy->ac_cur_tbls[blkn]; |
| register int s, k, r, l; |
| |
| HUFF_DECODE_FAST(s, l, dctbl); |
| if (s) { |
| FILL_BIT_BUFFER_FAST |
| r = GET_BITS(s); |
| s = HUFF_EXTEND(r, s); |
| } |
| |
| if (entropy->dc_needed[blkn]) { |
| int ci = cinfo->MCU_membership[blkn]; |
| s = (int)((unsigned int)s + (unsigned int)state.last_dc_val[ci]); |
| state.last_dc_val[ci] = s; |
| if (block) |
| (*block)[0] = (JCOEF)s; |
| } |
| |
| if (entropy->ac_needed[blkn] && block) { |
| |
| for (k = 1; k < DCTSIZE2; k++) { |
| HUFF_DECODE_FAST(s, l, actbl); |
| r = s >> 4; |
| s &= 15; |
| |
| if (s) { |
| k += r; |
| FILL_BIT_BUFFER_FAST |
| r = GET_BITS(s); |
| s = HUFF_EXTEND(r, s); |
| (*block)[jpeg_natural_order[k]] = (JCOEF)s; |
| } else { |
| if (r != 15) break; |
| k += 15; |
| } |
| } |
| |
| } else { |
| |
| for (k = 1; k < DCTSIZE2; k++) { |
| HUFF_DECODE_FAST(s, l, actbl); |
| r = s >> 4; |
| s &= 15; |
| |
| if (s) { |
| k += r; |
| FILL_BIT_BUFFER_FAST |
| DROP_BITS(s); |
| } else { |
| if (r != 15) break; |
| k += 15; |
| } |
| } |
| } |
| } |
| |
| if (cinfo->unread_marker != 0) { |
| cinfo->unread_marker = 0; |
| return FALSE; |
| } |
| |
| br_state.bytes_in_buffer -= (buffer - br_state.next_input_byte); |
| br_state.next_input_byte = buffer; |
| BITREAD_SAVE_STATE(cinfo, entropy->bitstate); |
| entropy->saved = state; |
| 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.) |
| */ |
| |
| #define BUFSIZE (DCTSIZE2 * 8) |
| |
| METHODDEF(boolean) |
| decode_mcu(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
| { |
| huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy; |
| int usefast = 1; |
| |
| /* 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; |
| usefast = 0; |
| } |
| |
| if (cinfo->src->bytes_in_buffer < BUFSIZE * (size_t)cinfo->blocks_in_MCU || |
| cinfo->unread_marker != 0) |
| usefast = 0; |
| |
| /* 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) { |
| |
| if (usefast) { |
| if (!decode_mcu_fast(cinfo, MCU_data)) goto use_slow; |
| } else { |
| use_slow: |
| if (!decode_mcu_slow(cinfo, MCU_data)) return FALSE; |
| } |
| |
| } |
| |
| /* 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; |
| |
| /* Motion JPEG frames typically do not include the Huffman tables if they |
| are the default tables. Thus, if the tables are not set by the time |
| the Huffman decoder is initialized (usually within the body of |
| jpeg_start_decompress()), we set them to default values. */ |
| std_huff_tables((j_common_ptr)cinfo); |
| |
| 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; |
| } |
| } |