EVOLUTION-MANAGER

Edit File: jdhuff.c

/* * jdhuff.c * * Copyright (C) 1991-1997, 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]; /* 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; 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) { 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 (((INT32) code) >= (((INT32) 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] = (INT32) p - (INT32) 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->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++; } } } /* 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) { cinfo->src->next_input_byte = next_input_byte; cinfo->src->bytes_in_buffer = bytes_in_buffer; 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 = GETJOCTET(*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) { cinfo->src->next_input_byte = next_input_byte; cinfo->src->bytes_in_buffer = bytes_in_buffer; 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 = 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. * 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; } /* * 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[ (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. */ #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, -3, -7, -15, -31, -63, -127, -255, -511, -1023, -2047, -4095, -8191, -16383, -32767 }; #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; } /* * 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; int blkn; BITREAD_STATE_VARS; savable_state state; /* 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++) { JBLOCKROW block = MCU_data[blkn]; 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]; 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; } if (entropy->ac_needed[blkn]) { /* 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); 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; } }