Subversion Repositories planix.SVN

/*-------------------------------------------------------------*/

/*--- Huffman coding low-level stuff                        ---*/

/*---                                             huffman.c ---*/

/*-------------------------------------------------------------*/

/*--

  This file is a part of bzip2 and/or libbzip2, a program and

  library for lossless, block-sorting data compression.

  Copyright (C) 1996-2000 Julian R Seward.  All rights reserved.

  Redistribution and use in source and binary forms, with or without

  modification, are permitted provided that the following conditions

  are met:

  1. Redistributions of source code must retain the above copyright

     notice, this list of conditions and the following disclaimer.

  2. The origin of this software must not be misrepresented; you must 

     not claim that you wrote the original software.  If you use this 

     software in a product, an acknowledgment in the product 

     documentation would be appreciated but is not required.

  3. Altered source versions must be plainly marked as such, and must

     not be misrepresented as being the original software.

  4. The name of the author may not be used to endorse or promote 

     products derived from this software without specific prior written 

     permission.

  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS

  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY

  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE

  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  Julian Seward, Cambridge, UK.

  jseward@acm.org

  bzip2/libbzip2 version 1.0 of 21 March 2000

  This program is based on (at least) the work of:

     Mike Burrows

     David Wheeler

     Peter Fenwick

     Alistair Moffat

     Radford Neal

     Ian H. Witten

     Robert Sedgewick

     Jon L. Bentley

  For more information on these sources, see the manual.

--*/

#include "os.h"

#include "bzlib.h"

#include "bzlib_private.h"

/*---------------------------------------------------*/

#define WEIGHTOF(zz0)  ((zz0) & 0xffffff00)

#define DEPTHOF(zz1)   ((zz1) & 0x000000ff)

#define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3))

#define ADDWEIGHTS(zw1,zw2)                           \

   (WEIGHTOF(zw1)+WEIGHTOF(zw2)) |                    \

   (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2)))

#define UPHEAP(z)                                     \

{                                                     \

   Int32 zz, tmp;                                     \

   zz = z; tmp = heap[zz];                            \

   while (weight[tmp] < weight[heap[zz >> 1]]) {      \

      heap[zz] = heap[zz >> 1];                       \

      zz >>= 1;                                       \

   }                                                  \

   heap[zz] = tmp;                                    \

}

#define DOWNHEAP(z)                                   \

{                                                     \

   Int32 zz, yy, tmp;                                 \

   zz = z; tmp = heap[zz];                            \

   while (True) {                                     \

      yy = zz << 1;                                   \

      if (yy > nHeap) break;                          \

      if (yy < nHeap &&                               \

          weight[heap[yy+1]] < weight[heap[yy]])      \

         yy++;                                        \

      if (weight[tmp] < weight[heap[yy]]) break;      \

      heap[zz] = heap[yy];                            \

      zz = yy;                                        \

   }                                                  \

   heap[zz] = tmp;                                    \

}

/*---------------------------------------------------*/

void BZ2_hbMakeCodeLengths ( UChar *len, 

                             Int32 *freq,

                             Int32 alphaSize,

                             Int32 maxLen )

{

   /*--

      Nodes and heap entries run from 1.  Entry 0

      for both the heap and nodes is a sentinel.

   --*/

   Int32 nNodes, nHeap, n1, n2, i, j, k;

   Bool  tooLong;

   Int32 heap   [ BZ_MAX_ALPHA_SIZE + 2 ];

   Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ];

   Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ]; 

   for (i = 0; i < alphaSize; i++)

      weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8;

   while (True) {

      nNodes = alphaSize;

      nHeap = 0;

      heap[0] = 0;

      weight[0] = 0;

      parent[0] = -2;

      for (i = 1; i <= alphaSize; i++) {

         parent[i] = -1;

         nHeap++;

         heap[nHeap] = i;

         UPHEAP(nHeap);

      }

      AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 );

      while (nHeap > 1) {

         n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1);

         n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1);

         nNodes++;

         parent[n1] = parent[n2] = nNodes;

         weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]);

         parent[nNodes] = -1;

         nHeap++;

         heap[nHeap] = nNodes;

         UPHEAP(nHeap);

      }

      AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 );

      tooLong = False;

      for (i = 1; i <= alphaSize; i++) {

         j = 0;

         k = i;

         while (parent[k] >= 0) { k = parent[k]; j++; }

         len[i-1] = j;

         if (j > maxLen) tooLong = True;

      }

      if (! tooLong) break;

      for (i = 1; i < alphaSize; i++) {

         j = weight[i] >> 8;

         j = 1 + (j / 2);

         weight[i] = j << 8;

      }

   }

}

/*---------------------------------------------------*/

void BZ2_hbAssignCodes ( Int32 *code,

                         UChar *length,

                         Int32 minLen,

                         Int32 maxLen,

                         Int32 alphaSize )

{

   Int32 n, vec, i;

   vec = 0;

   for (n = minLen; n <= maxLen; n++) {

      for (i = 0; i < alphaSize; i++)

         if (length[i] == n) { code[i] = vec; vec++; };

      vec <<= 1;

   }

}

/*---------------------------------------------------*/

void BZ2_hbCreateDecodeTables ( Int32 *limit,

                                Int32 *base,

                                Int32 *perm,

                                UChar *length,

                                Int32 minLen,

                                Int32 maxLen,

                                Int32 alphaSize )

{

   Int32 pp, i, j, vec;

   pp = 0;

   for (i = minLen; i <= maxLen; i++)

      for (j = 0; j < alphaSize; j++)

         if (length[j] == i) { perm[pp] = j; pp++; };

   for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0;

   for (i = 0; i < alphaSize; i++) base[length[i]+1]++;

   for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1];

   for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0;

   vec = 0;

   for (i = minLen; i <= maxLen; i++) {

      vec += (base[i+1] - base[i]);

      limit[i] = vec-1;

      vec <<= 1;

   }

   for (i = minLen + 1; i <= maxLen; i++)

      base[i] = ((limit[i-1] + 1) << 1) - base[i];

}

/*-------------------------------------------------------------*/

/*--- end                                         huffman.c ---*/

/*-------------------------------------------------------------*/