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228 lines
7.4 KiB
228 lines
7.4 KiB
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/*-------------------------------------------------------------*/ |
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/*--- Huffman coding low-level stuff ---*/ |
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/*--- huffman.c ---*/ |
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/*-------------------------------------------------------------*/ |
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/*-- |
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This file is a part of bzip2 and/or libbzip2, a program and |
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library for lossless, block-sorting data compression. |
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Copyright (C) 1996-2002 Julian R Seward. All rights reserved. |
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Redistribution and use in source and binary forms, with or without |
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modification, are permitted provided that the following conditions |
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are met: |
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1. Redistributions of source code must retain the above copyright |
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notice, this list of conditions and the following disclaimer. |
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2. The origin of this software must not be misrepresented; you must |
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not claim that you wrote the original software. If you use this |
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software in a product, an acknowledgment in the product |
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documentation would be appreciated but is not required. |
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3. Altered source versions must be plainly marked as such, and must |
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not be misrepresented as being the original software. |
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4. The name of the author may not be used to endorse or promote |
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products derived from this software without specific prior written |
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permission. |
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS |
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OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
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DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE |
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GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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Julian Seward, Cambridge, UK. |
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jseward@acm.org |
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bzip2/libbzip2 version 1.0 of 21 March 2000 |
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This program is based on (at least) the work of: |
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Mike Burrows |
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David Wheeler |
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Peter Fenwick |
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Alistair Moffat |
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Radford Neal |
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Ian H. Witten |
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Robert Sedgewick |
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Jon L. Bentley |
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For more information on these sources, see the manual. |
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--*/ |
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#include "bzlib_private.h" |
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/*---------------------------------------------------*/ |
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#define WEIGHTOF(zz0) ((zz0) & 0xffffff00) |
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#define DEPTHOF(zz1) ((zz1) & 0x000000ff) |
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#define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3)) |
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#define ADDWEIGHTS(zw1,zw2) \ |
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(WEIGHTOF(zw1)+WEIGHTOF(zw2)) | \ |
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(1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2))) |
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#define UPHEAP(z) \ |
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{ \ |
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Int32 zz, tmp; \ |
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zz = z; tmp = heap[zz]; \ |
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while (weight[tmp] < weight[heap[zz >> 1]]) { \ |
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heap[zz] = heap[zz >> 1]; \ |
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zz >>= 1; \ |
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} \ |
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heap[zz] = tmp; \ |
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} |
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#define DOWNHEAP(z) \ |
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{ \ |
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Int32 zz, yy, tmp; \ |
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zz = z; tmp = heap[zz]; \ |
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while (True) { \ |
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yy = zz << 1; \ |
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if (yy > nHeap) break; \ |
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if (yy < nHeap && \ |
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weight[heap[yy+1]] < weight[heap[yy]]) \ |
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yy++; \ |
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if (weight[tmp] < weight[heap[yy]]) break; \ |
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heap[zz] = heap[yy]; \ |
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zz = yy; \ |
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} \ |
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heap[zz] = tmp; \ |
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} |
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/*---------------------------------------------------*/ |
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void BZ2_hbMakeCodeLengths ( UChar *len, |
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Int32 *freq, |
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Int32 alphaSize, |
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Int32 maxLen ) |
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{ |
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/*-- |
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Nodes and heap entries run from 1. Entry 0 |
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for both the heap and nodes is a sentinel. |
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--*/ |
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Int32 nNodes, nHeap, n1, n2, i, j, k; |
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Bool tooLong; |
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Int32 heap [ BZ_MAX_ALPHA_SIZE + 2 ]; |
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Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ]; |
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Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ]; |
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for (i = 0; i < alphaSize; i++) |
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weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8; |
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while (True) { |
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nNodes = alphaSize; |
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nHeap = 0; |
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heap[0] = 0; |
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weight[0] = 0; |
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parent[0] = -2; |
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for (i = 1; i <= alphaSize; i++) { |
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parent[i] = -1; |
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nHeap++; |
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heap[nHeap] = i; |
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UPHEAP(nHeap); |
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} |
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AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 ); |
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while (nHeap > 1) { |
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n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); |
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n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); |
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nNodes++; |
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parent[n1] = parent[n2] = nNodes; |
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weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]); |
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parent[nNodes] = -1; |
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nHeap++; |
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heap[nHeap] = nNodes; |
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UPHEAP(nHeap); |
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} |
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AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 ); |
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tooLong = False; |
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for (i = 1; i <= alphaSize; i++) { |
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j = 0; |
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k = i; |
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while (parent[k] >= 0) { k = parent[k]; j++; } |
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len[i-1] = j; |
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if (j > maxLen) tooLong = True; |
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} |
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if (! tooLong) break; |
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for (i = 1; i < alphaSize; i++) { |
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j = weight[i] >> 8; |
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j = 1 + (j / 2); |
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weight[i] = j << 8; |
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} |
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} |
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} |
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/*---------------------------------------------------*/ |
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void BZ2_hbAssignCodes ( Int32 *code, |
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UChar *length, |
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Int32 minLen, |
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Int32 maxLen, |
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Int32 alphaSize ) |
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{ |
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Int32 n, vec, i; |
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vec = 0; |
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for (n = minLen; n <= maxLen; n++) { |
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for (i = 0; i < alphaSize; i++) |
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if (length[i] == n) { code[i] = vec; vec++; }; |
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vec <<= 1; |
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} |
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} |
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/*---------------------------------------------------*/ |
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void BZ2_hbCreateDecodeTables ( Int32 *limit, |
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Int32 *base, |
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Int32 *perm, |
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UChar *length, |
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Int32 minLen, |
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Int32 maxLen, |
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Int32 alphaSize ) |
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{ |
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Int32 pp, i, j, vec; |
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pp = 0; |
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for (i = minLen; i <= maxLen; i++) |
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for (j = 0; j < alphaSize; j++) |
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if (length[j] == i) { perm[pp] = j; pp++; }; |
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for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0; |
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for (i = 0; i < alphaSize; i++) base[length[i]+1]++; |
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for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1]; |
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for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0; |
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vec = 0; |
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for (i = minLen; i <= maxLen; i++) { |
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vec += (base[i+1] - base[i]); |
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limit[i] = vec-1; |
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vec <<= 1; |
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} |
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for (i = minLen + 1; i <= maxLen; i++) |
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base[i] = ((limit[i-1] + 1) << 1) - base[i]; |
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} |
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/*-------------------------------------------------------------*/ |
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/*--- end huffman.c ---*/ |
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/*-------------------------------------------------------------*/
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