--- /dev/null
+/*
+ * jdlhuff.c
+ *
+ * Copyright (C) 1991-1998, 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 lossless 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 "jlossls.h" /* Private declarations for lossless codec */
+#include "jdhuff.h" /* Declarations shared with jd*huff.c */
+
+
+#ifdef D_LOSSLESS_SUPPORTED
+
+typedef struct {
+ int ci, yoffset, MCU_width;
+} lhd_output_ptr_info;
+
+/*
+ * Private entropy decoder object for lossless Huffman decoding.
+ */
+
+typedef struct {
+ huffd_common_fields; /* Fields shared with other entropy decoders */
+
+ /* Pointers to derived tables (these workspaces have image lifespan) */
+ d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
+
+ /* Precalculated info set up by start_pass for use in decode_mcus: */
+
+ /* Pointers to derived tables to be used for each data unit within an MCU */
+ d_derived_tbl * cur_tbls[D_MAX_DATA_UNITS_IN_MCU];
+
+ /* Pointers to the proper output difference row for each group of data units
+ * within an MCU. For each component, there are Vi groups of Hi data units.
+ */
+ JDIFFROW output_ptr[D_MAX_DATA_UNITS_IN_MCU];
+
+ /* Number of output pointers in use for the current MCU. This is the sum
+ * of all Vi in the MCU.
+ */
+ int num_output_ptrs;
+
+ /* Information used for positioning the output pointers within the output
+ * difference rows.
+ */
+ lhd_output_ptr_info output_ptr_info[D_MAX_DATA_UNITS_IN_MCU];
+
+ /* Index of the proper output pointer for each data unit within an MCU */
+ int output_ptr_index[D_MAX_DATA_UNITS_IN_MCU];
+
+} lhuff_entropy_decoder;
+
+typedef lhuff_entropy_decoder * lhuff_entropy_ptr;
+
+
+/*
+ * Initialize for a Huffman-compressed scan.
+ */
+
+METHODDEF(void)
+start_pass_lhuff_decoder (j_decompress_ptr cinfo)
+{
+ j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
+ lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsd->entropy_private;
+ int ci, dctbl, sampn, ptrn, yoffset, xoffset;
+ jpeg_component_info * compptr;
+
+ for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
+ compptr = cinfo->cur_comp_info[ci];
+ dctbl = compptr->dc_tbl_no;
+ /* Make sure requested tables are present */
+ if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS ||
+ cinfo->dc_huff_tbl_ptrs[dctbl] == NULL)
+ ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);
+ /* 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->derived_tbls[dctbl]);
+ }
+
+ /* Precalculate decoding info for each sample in an MCU of this scan */
+ for (sampn = 0, ptrn = 0; sampn < cinfo->data_units_in_MCU;) {
+ compptr = cinfo->cur_comp_info[cinfo->MCU_membership[sampn]];
+ ci = compptr->component_index;
+ for (yoffset = 0; yoffset < compptr->MCU_height; yoffset++, ptrn++) {
+ /* Precalculate the setup info for each output pointer */
+ entropy->output_ptr_info[ptrn].ci = ci;
+ entropy->output_ptr_info[ptrn].yoffset = yoffset;
+ entropy->output_ptr_info[ptrn].MCU_width = compptr->MCU_width;
+ for (xoffset = 0; xoffset < compptr->MCU_width; xoffset++, sampn++) {
+ /* Precalculate the output pointer index for each sample */
+ entropy->output_ptr_index[sampn] = ptrn;
+ /* Precalculate which table to use for each sample */
+ entropy->cur_tbls[sampn] = entropy->derived_tbls[compptr->dc_tbl_no];
+ }
+ }
+ }
+ entropy->num_output_ptrs = ptrn;
+
+ /* Initialize bitread state variables */
+ entropy->bitstate.bits_left = 0;
+ entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
+ entropy->insufficient_data = FALSE;
+}
+
+
+/*
+ * 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.
+ */
+
+METHODDEF(boolean)
+process_restart (j_decompress_ptr cinfo)
+{
+ j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
+ lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsd->entropy_private;
+ /* 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;
+
+ /* 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->insufficient_data = FALSE;
+
+ return TRUE;
+}
+
+
+/*
+ * Decode and return nMCU's worth of Huffman-compressed differences.
+ * Each MCU is also disassembled and placed accordingly in diff_buf.
+ *
+ * MCU_col_num specifies the column of the first MCU being requested within
+ * the MCU-row. This tells us where to position the output row pointers in
+ * diff_buf.
+ *
+ * Returns the number of MCUs decoded. This may be less than nMCU if data
+ * source requested suspension. In that case no changes have been made to
+ * permanent state. (Exception: some output differences may already have
+ * been assigned. This is harmless for this module, since we'll just
+ * re-assign them on the next call.)
+ */
+
+METHODDEF(JDIMENSION)
+decode_mcus (j_decompress_ptr cinfo, JDIFFIMAGE diff_buf,
+ JDIMENSION MCU_row_num, JDIMENSION MCU_col_num, JDIMENSION nMCU)
+{
+ j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
+ lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsd->entropy_private;
+ unsigned int mcu_num;
+ int sampn, ci, yoffset, MCU_width, ptrn;
+ BITREAD_STATE_VARS;
+
+ /* Set output pointer locations based on MCU_col_num */
+ for (ptrn = 0; ptrn < entropy->num_output_ptrs; ptrn++) {
+ ci = entropy->output_ptr_info[ptrn].ci;
+ yoffset = entropy->output_ptr_info[ptrn].yoffset;
+ MCU_width = entropy->output_ptr_info[ptrn].MCU_width;
+ entropy->output_ptr[ptrn] =
+ diff_buf[ci][MCU_row_num + yoffset] + (MCU_col_num * MCU_width);
+ }
+
+ /*
+ * If we've run out of data, zero out the buffers and return.
+ * By resetting the undifferencer, the output samples will be CENTERJSAMPLE.
+ *
+ * NB: We should find a way to do this without interacting with the
+ * undifferencer module directly.
+ */
+ if (entropy->insufficient_data) {
+ for (ptrn = 0; ptrn < entropy->num_output_ptrs; ptrn++)
+ jzero_far((void FAR *) entropy->output_ptr[ptrn],
+ nMCU * entropy->output_ptr_info[ptrn].MCU_width * SIZEOF(JDIFF));
+
+ (*losslsd->predict_process_restart) (cinfo);
+ }
+
+ else {
+
+ /* Load up working state */
+ BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
+
+ /* Outer loop handles the number of MCU requested */
+
+ for (mcu_num = 0; mcu_num < nMCU; mcu_num++) {
+
+ /* Inner loop handles the samples in the MCU */
+ for (sampn = 0; sampn < cinfo->data_units_in_MCU; sampn++) {
+ d_derived_tbl * dctbl = entropy->cur_tbls[sampn];
+ register int s, r;
+
+ /* Section H.2.2: decode the sample difference */
+ HUFF_DECODE(s, br_state, dctbl, return mcu_num, label1);
+ if (s) {
+ if (s == 16) /* special case: always output 32768 */
+ s = 32768;
+ else { /* normal case: fetch subsequent bits */
+ CHECK_BIT_BUFFER(br_state, s, return mcu_num);
+ r = GET_BITS(s);
+ s = HUFF_EXTEND(r, s);
+ }
+ }
+
+ /* Output the sample difference */
+ *entropy->output_ptr[entropy->output_ptr_index[sampn]]++ = (JDIFF) s;
+ }
+
+ /* Completed MCU, so update state */
+ BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
+ }
+ }
+
+ return nMCU;
+}
+
+
+/*
+ * Module initialization routine for lossless Huffman entropy decoding.
+ */
+
+GLOBAL(void)
+jinit_lhuff_decoder (j_decompress_ptr cinfo)
+{
+ j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
+ lhuff_entropy_ptr entropy;
+ int i;
+
+ entropy = (lhuff_entropy_ptr)
+ (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ SIZEOF(lhuff_entropy_decoder));
+ losslsd->entropy_private = (void *) entropy;
+ losslsd->entropy_start_pass = start_pass_lhuff_decoder;
+ losslsd->entropy_process_restart = process_restart;
+ losslsd->entropy_decode_mcus = decode_mcus;
+
+ /* Mark tables unallocated */
+ for (i = 0; i < NUM_HUFF_TBLS; i++) {
+ entropy->derived_tbls[i] = NULL;
+ }
+}
+
+#endif /* D_LOSSLESS_SUPPORTED */
git://git.creatis.insa-lyon.fr / gdcm.git / blobdiff