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authorgit perforce import user <a@b>2016-10-25 12:29:14 -0600
committerSheikh Dawood Abdul Ajees <Sheikh Dawood Abdul Ajees>2016-10-25 18:56:37 -0500
commit3dfe2108cfab31ba3ee5527e217d0d8e99a51162 (patch)
treefa6485c169e50d7415a651bf838f5bcd0fd3bfbd /KaplaDemo/samples/sampleViewer3/IJGWin32/jchuff.cpp
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Initial commit:
PhysX 3.4.0 Update @ 21294896 APEX 1.4.0 Update @ 21275617 [CL 21300167]
Diffstat (limited to 'KaplaDemo/samples/sampleViewer3/IJGWin32/jchuff.cpp')
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+/*
+ * jchuff.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 which are shared
+ * by the sequential, progressive and lossless decoders.
+ */
+#include "stdafx.h"
+
+#define JPEG_INTERNALS
+//#include "jinclude.h"
+//#include "jpeglib.h"
+//#include "jchuff.h" /* Declarations shared with jc*huff.c */
+
+
+/*
+ * Compute the derived values for a Huffman table.
+ * This routine also performs some validation checks on the table.
+ */
+
+GLOBAL(void)
+jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno,
+ c_derived_tbl ** pdtbl)
+{
+ JHUFF_TBL *htbl;
+ c_derived_tbl *dtbl;
+ int p, i, l, lastp, si, maxsymbol;
+ 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 = (c_derived_tbl *)
+ (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ SIZEOF(c_derived_tbl));
+ dtbl = *pdtbl;
+
+ /* 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;
+ lastp = 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 C.3: generate encoding tables */
+ /* These are code and size indexed by symbol value */
+
+ /* Set all codeless symbols to have code length 0;
+ * this lets us detect duplicate VAL entries here, and later
+ * allows emit_bits to detect any attempt to emit such symbols.
+ */
+ MEMZERO(dtbl->ehufsi, SIZEOF(dtbl->ehufsi));
+
+ /* This is also a convenient place to check for out-of-range
+ * and duplicated VAL entries. We allow 0..255 for AC symbols
+ * but only 0..16 for DC. (We could constrain them further
+ * based on data depth and mode, but this seems enough.)
+ */
+ maxsymbol = isDC ? 16 : 255;
+
+ for (p = 0; p < lastp; p++) {
+ i = htbl->huffval[p];
+ if (i < 0 || i > maxsymbol || dtbl->ehufsi[i])
+ ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
+ dtbl->ehufco[i] = huffcode[p];
+ dtbl->ehufsi[i] = huffsize[p];
+ }
+}
+
+
+/*
+ * Generate the best Huffman code table for the given counts, fill htbl.
+ *
+ * The JPEG standard requires that no symbol be assigned a codeword of all
+ * one bits (so that padding bits added at the end of a compressed segment
+ * can't look like a valid code). Because of the canonical ordering of
+ * codewords, this just means that there must be an unused slot in the
+ * longest codeword length category. Section K.2 of the JPEG spec suggests
+ * reserving such a slot by pretending that symbol 256 is a valid symbol
+ * with count 1. In theory that's not optimal; giving it count zero but
+ * including it in the symbol set anyway should give a better Huffman code.
+ * But the theoretically better code actually seems to come out worse in
+ * practice, because it produces more all-ones bytes (which incur stuffed
+ * zero bytes in the final file). In any case the difference is tiny.
+ *
+ * The JPEG standard requires Huffman codes to be no more than 16 bits long.
+ * If some symbols have a very small but nonzero probability, the Huffman tree
+ * must be adjusted to meet the code length restriction. We currently use
+ * the adjustment method suggested in JPEG section K.2. This method is *not*
+ * optimal; it may not choose the best possible limited-length code. But
+ * typically only very-low-frequency symbols will be given less-than-optimal
+ * lengths, so the code is almost optimal. Experimental comparisons against
+ * an optimal limited-length-code algorithm indicate that the difference is
+ * microscopic --- usually less than a hundredth of a percent of total size.
+ * So the extra complexity of an optimal algorithm doesn't seem worthwhile.
+ */
+
+GLOBAL(void)
+jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])
+{
+#define MAX_CLEN 32 /* assumed maximum initial code length */
+ UINT8 bits[MAX_CLEN+1]; /* bits[k] = # of symbols with code length k */
+ int codesize[257]; /* codesize[k] = code length of symbol k */
+ int others[257]; /* next symbol in current branch of tree */
+ int c1, c2;
+ int p, i, j;
+ long v;
+
+ /* This algorithm is explained in section K.2 of the JPEG standard */
+
+ MEMZERO(bits, SIZEOF(bits));
+ MEMZERO(codesize, SIZEOF(codesize));
+ for (i = 0; i < 257; i++)
+ others[i] = -1; /* init links to empty */
+
+ freq[256] = 1; /* make sure 256 has a nonzero count */
+ /* Including the pseudo-symbol 256 in the Huffman procedure guarantees
+ * that no real symbol is given code-value of all ones, because 256
+ * will be placed last in the largest codeword category.
+ */
+
+ /* Huffman's basic algorithm to assign optimal code lengths to symbols */
+
+ for (;;) {
+ /* Find the smallest nonzero frequency, set c1 = its symbol */
+ /* In case of ties, take the larger symbol number */
+ c1 = -1;
+ v = 1000000000L;
+ for (i = 0; i <= 256; i++) {
+ if (freq[i] && freq[i] <= v) {
+ v = freq[i];
+ c1 = i;
+ }
+ }
+
+ /* Find the next smallest nonzero frequency, set c2 = its symbol */
+ /* In case of ties, take the larger symbol number */
+ c2 = -1;
+ v = 1000000000L;
+ for (i = 0; i <= 256; i++) {
+ if (freq[i] && freq[i] <= v && i != c1) {
+ v = freq[i];
+ c2 = i;
+ }
+ }
+
+ /* Done if we've merged everything into one frequency */
+ if (c2 < 0)
+ break;
+
+ /* Else merge the two counts/trees */
+ freq[c1] += freq[c2];
+ freq[c2] = 0;
+
+ /* Increment the codesize of everything in c1's tree branch */
+ codesize[c1]++;
+ while (others[c1] >= 0) {
+ c1 = others[c1];
+ codesize[c1]++;
+ }
+
+ others[c1] = c2; /* chain c2 onto c1's tree branch */
+
+ /* Increment the codesize of everything in c2's tree branch */
+ codesize[c2]++;
+ while (others[c2] >= 0) {
+ c2 = others[c2];
+ codesize[c2]++;
+ }
+ }
+
+ /* Now count the number of symbols of each code length */
+ for (i = 0; i <= 256; i++) {
+ if (codesize[i]) {
+ /* The JPEG standard seems to think that this can't happen, */
+ /* but I'm paranoid... */
+ if (codesize[i] > MAX_CLEN)
+ ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
+
+ bits[codesize[i]]++;
+ }
+ }
+
+ /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
+ * Huffman procedure assigned any such lengths, we must adjust the coding.
+ * Here is what the JPEG spec says about how this next bit works:
+ * Since symbols are paired for the longest Huffman code, the symbols are
+ * removed from this length category two at a time. The prefix for the pair
+ * (which is one bit shorter) is allocated to one of the pair; then,
+ * skipping the BITS entry for that prefix length, a code word from the next
+ * shortest nonzero BITS entry is converted into a prefix for two code words
+ * one bit longer.
+ */
+
+ for (i = MAX_CLEN; i > 16; i--) {
+ while (bits[i] > 0) {
+ j = i - 2; /* find length of new prefix to be used */
+ while (bits[j] == 0)
+ j--;
+
+ bits[i] -= 2; /* remove two symbols */
+ bits[i-1]++; /* one goes in this length */
+ bits[j+1] += 2; /* two new symbols in this length */
+ bits[j]--; /* symbol of this length is now a prefix */
+ }
+ }
+
+ /* Remove the count for the pseudo-symbol 256 from the largest codelength */
+ while (bits[i] == 0) /* find largest codelength still in use */
+ i--;
+ bits[i]--;
+
+ /* Return final symbol counts (only for lengths 0..16) */
+ MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits));
+
+ /* Return a list of the symbols sorted by code length */
+ /* It's not real clear to me why we don't need to consider the codelength
+ * changes made above, but the JPEG spec seems to think this works.
+ */
+ p = 0;
+ for (i = 1; i <= MAX_CLEN; i++) {
+ for (j = 0; j <= 255; j++) {
+ if (codesize[j] == i) {
+ htbl->huffval[p] = (UINT8) j;
+ p++;
+ }
+ }
+ }
+
+ /* Set sent_table FALSE so updated table will be written to JPEG file. */
+ htbl->sent_table = FALSE;
+}