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

/*--- Block sorting machinery                               ---*/

/*---                                           blocksort.c ---*/

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

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

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

   lossless, block-sorting data compression.

   bzip2/libbzip2 version 1.0.8 of 13 July 2019

   Copyright (C) 1996-2019 Julian Seward <jseward@acm.org>

   Please read the WARNING, DISCLAIMER and PATENTS sections in the 

   README file.

   This program is released under the terms of the license contained

   in the file LICENSE.

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

#include "bzlib_private.h"

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

/*--- Fallback O(N log(N)^2) sorting        ---*/

/*--- algorithm, for repetitive blocks      ---*/

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

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

static 

__inline__

void fallbackSimpleSort ( UInt32* fmap, 

                          UInt32* eclass, 

                          Int32   lo, 

                          Int32   hi )

{

   Int32 i, j, tmp;

   UInt32 ec_tmp;

   if (lo == hi) return;

   if (hi - lo > 3) {

      for ( i = hi-4; i >= lo; i-- ) {

         tmp = fmap[i];

         ec_tmp = eclass[tmp];

         for ( j = i+4; j <= hi && ec_tmp > eclass[fmap[j]]; j += 4 )

            fmap[j-4] = fmap[j];

         fmap[j-4] = tmp;

      }

   }

   for ( i = hi-1; i >= lo; i-- ) {

      tmp = fmap[i];

      ec_tmp = eclass[tmp];

      for ( j = i+1; j <= hi && ec_tmp > eclass[fmap[j]]; j++ )

         fmap[j-1] = fmap[j];

      fmap[j-1] = tmp;

   }

}

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

#define fswap(zz1, zz2) \

   { Int32 zztmp = zz1; zz1 = zz2; zz2 = zztmp; }

#define fvswap(zzp1, zzp2, zzn)       \

{                                     \

   Int32 yyp1 = (zzp1);               \

   Int32 yyp2 = (zzp2);               \

   Int32 yyn  = (zzn);                \

   while (yyn > 0) {                  \

      fswap(fmap[yyp1], fmap[yyp2]);  \

      yyp1++; yyp2++; yyn--;          \

   }                                  \

}

#define fmin(a,b) ((a) < (b)) ? (a) : (b)

#define fpush(lz,hz) { stackLo[sp] = lz; \

                       stackHi[sp] = hz; \

                       sp++; }

#define fpop(lz,hz) { sp--;              \

                      lz = stackLo[sp];  \

                      hz = stackHi[sp]; }

#define FALLBACK_QSORT_SMALL_THRESH 10

#define FALLBACK_QSORT_STACK_SIZE   100

static

void fallbackQSort3 ( UInt32* fmap, 

                      UInt32* eclass,

                      Int32   loSt, 

                      Int32   hiSt )

{

   Int32 unLo, unHi, ltLo, gtHi, n, m;

   Int32 sp, lo, hi;

   UInt32 med, r, r3;

   Int32 stackLo[FALLBACK_QSORT_STACK_SIZE];

   Int32 stackHi[FALLBACK_QSORT_STACK_SIZE];

   r = 0;

   sp = 0;

   fpush ( loSt, hiSt );

   while (sp > 0) {

      AssertH ( sp < FALLBACK_QSORT_STACK_SIZE - 1, 1004 );

      fpop ( lo, hi );

      if (hi - lo < FALLBACK_QSORT_SMALL_THRESH) {

         fallbackSimpleSort ( fmap, eclass, lo, hi );

         continue;

      }

      /* Random partitioning.  Median of 3 sometimes fails to

         avoid bad cases.  Median of 9 seems to help but 

         looks rather expensive.  This too seems to work but

         is cheaper.  Guidance for the magic constants 

         7621 and 32768 is taken from Sedgewick's algorithms

         book, chapter 35.

      */

      r = ((r * 7621) + 1) % 32768;

      r3 = r % 3;

      if (r3 == 0) med = eclass[fmap[lo]]; else

      if (r3 == 1) med = eclass[fmap[(lo+hi)>>1]]; else

                   med = eclass[fmap[hi]];

      unLo = ltLo = lo;

      unHi = gtHi = hi;

      while (1) {

         while (1) {

            if (unLo > unHi) break;

            n = (Int32)eclass[fmap[unLo]] - (Int32)med;

            if (n == 0) { 

               fswap(fmap[unLo], fmap[ltLo]); 

               ltLo++; unLo++; 

               continue; 

            };

            if (n > 0) break;

            unLo++;

         }

         while (1) {

            if (unLo > unHi) break;

            n = (Int32)eclass[fmap[unHi]] - (Int32)med;

            if (n == 0) { 

               fswap(fmap[unHi], fmap[gtHi]); 

               gtHi--; unHi--; 

               continue; 

            };

            if (n < 0) break;

            unHi--;

         }

         if (unLo > unHi) break;

         fswap(fmap[unLo], fmap[unHi]); unLo++; unHi--;

      }

      AssertD ( unHi == unLo-1, "fallbackQSort3(2)" );

      if (gtHi < ltLo) continue;

      n = fmin(ltLo-lo, unLo-ltLo); fvswap(lo, unLo-n, n);

      m = fmin(hi-gtHi, gtHi-unHi); fvswap(unLo, hi-m+1, m);

      n = lo + unLo - ltLo - 1;

      m = hi - (gtHi - unHi) + 1;

      if (n - lo > hi - m) {

         fpush ( lo, n );

         fpush ( m, hi );

      } else {

         fpush ( m, hi );

         fpush ( lo, n );

      }

   }

}

#undef fmin

#undef fpush

#undef fpop

#undef fswap

#undef fvswap

#undef FALLBACK_QSORT_SMALL_THRESH

#undef FALLBACK_QSORT_STACK_SIZE

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

/* Pre:

      nblock > 0

      eclass exists for [0 .. nblock-1]

      ((UChar*)eclass) [0 .. nblock-1] holds block

      ptr exists for [0 .. nblock-1]

   Post:

      ((UChar*)eclass) [0 .. nblock-1] holds block

      All other areas of eclass destroyed

      fmap [0 .. nblock-1] holds sorted order

      bhtab [ 0 .. 2+(nblock/32) ] destroyed

*/

#define       SET_BH(zz)  bhtab[(zz) >> 5] |= ((UInt32)1 << ((zz) & 31))

#define     CLEAR_BH(zz)  bhtab[(zz) >> 5] &= ~((UInt32)1 << ((zz) & 31))

#define     ISSET_BH(zz)  (bhtab[(zz) >> 5] & ((UInt32)1 << ((zz) & 31)))

#define      WORD_BH(zz)  bhtab[(zz) >> 5]

#define UNALIGNED_BH(zz)  ((zz) & 0x01f)

static

void fallbackSort ( UInt32* fmap, 

                    UInt32* eclass, 

                    UInt32* bhtab,

                    Int32   nblock,

                    Int32   verb )

{

   Int32 ftab[257];

   Int32 ftabCopy[256];

   Int32 H, i, j, k, l, r, cc, cc1;

   Int32 nNotDone;

   Int32 nBhtab;

   UChar* eclass8 = (UChar*)eclass;

   /*--

      Initial 1-char radix sort to generate

      initial fmap and initial BH bits.

   --*/

   if (verb >= 4)

      VPrintf0 ( "        bucket sorting ...\n" );

   for (i = 0; i < 257;    i++) ftab[i] = 0;

   for (i = 0; i < nblock; i++) ftab[eclass8[i]]++;

   for (i = 0; i < 256;    i++) ftabCopy[i] = ftab[i];

   for (i = 1; i < 257;    i++) ftab[i] += ftab[i-1];

   for (i = 0; i < nblock; i++) {

      j = eclass8[i];

      k = ftab[j] - 1;

      ftab[j] = k;

      fmap[k] = i;

   }

   nBhtab = 2 + (nblock / 32);

   for (i = 0; i < nBhtab; i++) bhtab[i] = 0;

   for (i = 0; i < 256; i++) SET_BH(ftab[i]);

   /*--

      Inductively refine the buckets.  Kind-of an

      "exponential radix sort" (!), inspired by the

      Manber-Myers suffix array construction algorithm.

   --*/

   /*-- set sentinel bits for block-end detection --*/

   for (i = 0; i < 32; i++) { 

      SET_BH(nblock + 2*i);

      CLEAR_BH(nblock + 2*i + 1);

   }

   /*-- the log(N) loop --*/

   H = 1;

   while (1) {

      if (verb >= 4) 

         VPrintf1 ( "        depth %6d has ", H );

      j = 0;

      for (i = 0; i < nblock; i++) {

         if (ISSET_BH(i)) j = i;

         k = fmap[i] - H; if (k < 0) k += nblock;

         eclass[k] = j;

      }

      nNotDone = 0;

      r = -1;

      while (1) {

   /*-- find the next non-singleton bucket --*/

         k = r + 1;

         while (ISSET_BH(k) && UNALIGNED_BH(k)) k++;

         if (ISSET_BH(k)) {

            while (WORD_BH(k) == 0xffffffff) k += 32;

            while (ISSET_BH(k)) k++;

         }

         l = k - 1;

         if (l >= nblock) break;

         while (!ISSET_BH(k) && UNALIGNED_BH(k)) k++;

         if (!ISSET_BH(k)) {

            while (WORD_BH(k) == 0x00000000) k += 32;

            while (!ISSET_BH(k)) k++;

         }

         r = k - 1;

         if (r >= nblock) break;

         /*-- now [l, r] bracket current bucket --*/

         if (r > l) {

            nNotDone += (r - l + 1);

            fallbackQSort3 ( fmap, eclass, l, r );

            /*-- scan bucket and generate header bits-- */

            cc = -1;

            for (i = l; i <= r; i++) {

               cc1 = eclass[fmap[i]];

               if (cc != cc1) { SET_BH(i); cc = cc1; };

            }

         }

      }

      if (verb >= 4) 

         VPrintf1 ( "%6d unresolved strings\n", nNotDone );

      H *= 2;

      if (H > nblock || nNotDone == 0) break;

   }

   /*-- 

      Reconstruct the original block in

      eclass8 [0 .. nblock-1], since the

      previous phase destroyed it.

   --*/

   if (verb >= 4)

      VPrintf0 ( "        reconstructing block ...\n" );

   j = 0;

   for (i = 0; i < nblock; i++) {

      while (ftabCopy[j] == 0) j++;

      ftabCopy[j]--;

      eclass8[fmap[i]] = (UChar)j;

   }

   AssertH ( j < 256, 1005 );

}

#undef       SET_BH

#undef     CLEAR_BH

#undef     ISSET_BH

#undef      WORD_BH

#undef UNALIGNED_BH

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

/*--- The main, O(N^2 log(N)) sorting       ---*/

/*--- algorithm.  Faster for "normal"       ---*/

/*--- non-repetitive blocks.                ---*/

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

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

static

__inline__

Bool mainGtU ( UInt32  i1, 

               UInt32  i2,

               UChar*  block, 

               UInt16* quadrant,

               UInt32  nblock,

               Int32*  budget )

{

   Int32  k;

   UChar  c1, c2;

   UInt16 s1, s2;

   AssertD ( i1 != i2, "mainGtU" );

   /* 1 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 2 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 3 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 4 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 5 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 6 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 7 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 8 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 9 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 10 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 11 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   /* 12 */

   c1 = block[i1]; c2 = block[i2];

   if (c1 != c2) return (c1 > c2);

   i1++; i2++;

   k = nblock + 8;

   do {

      /* 1 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      /* 2 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      /* 3 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      /* 4 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      /* 5 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      /* 6 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      /* 7 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      /* 8 */

      c1 = block[i1]; c2 = block[i2];

      if (c1 != c2) return (c1 > c2);

      s1 = quadrant[i1]; s2 = quadrant[i2];

      if (s1 != s2) return (s1 > s2);

      i1++; i2++;

      if (i1 >= nblock) i1 -= nblock;

      if (i2 >= nblock) i2 -= nblock;

      k -= 8;

      (*budget)--;

   }

      while (k >= 0);

   return False;

}

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

/*--

   Knuth's increments seem to work better

   than Incerpi-Sedgewick here.  Possibly

   because the number of elems to sort is

   usually small, typically <= 20.

--*/

static

Int32 incs[14] = { 1, 4, 13, 40, 121, 364, 1093, 3280,

                   9841, 29524, 88573, 265720,

                   797161, 2391484 };

static

void mainSimpleSort ( UInt32* ptr,

                      UChar*  block,

                      UInt16* quadrant,

                      Int32   nblock,

                      Int32   lo, 

                      Int32   hi, 

                      Int32   d,

                      Int32*  budget )

{

   Int32 i, j, h, bigN, hp;

   UInt32 v;

   bigN = hi - lo + 1;

   if (bigN < 2) return;

   hp = 0;

   while (incs[hp] < bigN) hp++;

   hp--;

   for (; hp >= 0; hp--) {

      h = incs[hp];

      i = lo + h;

      while (True) {

         /*-- copy 1 --*/

         if (i > hi) break;

         v = ptr[i];

         j = i;

         while ( mainGtU ( 

                    ptr[j-h]+d, v+d, block, quadrant, nblock, budget 

                 ) ) {

            ptr[j] = ptr[j-h];

            j = j - h;

            if (j <= (lo + h - 1)) break;

         }

         ptr[j] = v;

         i++;

         /*-- copy 2 --*/

         if (i > hi) break;

         v = ptr[i];

         j = i;

         while ( mainGtU ( 

                    ptr[j-h]+d, v+d, block, quadrant, nblock, budget 

                 ) ) {

            ptr[j] = ptr[j-h];

            j = j - h;

            if (j <= (lo + h - 1)) break;

         }

         ptr[j] = v;

         i++;

         /*-- copy 3 --*/

         if (i > hi) break;

         v = ptr[i];

         j = i;

         while ( mainGtU ( 

                    ptr[j-h]+d, v+d, block, quadrant, nblock, budget 

                 ) ) {

            ptr[j] = ptr[j-h];

            j = j - h;

            if (j <= (lo + h - 1)) break;

         }

         ptr[j] = v;

         i++;

         if (*budget < 0) return;

      }

   }

}

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

/*--

   The following is an implementation of

   an elegant 3-way quicksort for strings,

   described in a paper "Fast Algorithms for

   Sorting and Searching Strings", by Robert

   Sedgewick and Jon L. Bentley.

--*/

#define mswap(zz1, zz2) \

   { Int32 zztmp = zz1; zz1 = zz2; zz2 = zztmp; }

#define mvswap(zzp1, zzp2, zzn)       \

{                                     \

   Int32 yyp1 = (zzp1);               \

   Int32 yyp2 = (zzp2);               \

   Int32 yyn  = (zzn);                \

   while (yyn > 0) {                  \

      mswap(ptr[yyp1], ptr[yyp2]);    \

      yyp1++; yyp2++; yyn--;          \

   }                                  \

}

static 

__inline__

UChar mmed3 ( UChar a, UChar b, UChar c )

{

   UChar t;

   if (a > b) { t = a; a = b; b = t; };

   if (b > c) { 

      b = c;

      if (a > b) b = a;

   }

   return b;

}

#define mmin(a,b) ((a) < (b)) ? (a) : (b)

#define mpush(lz,hz,dz) { stackLo[sp] = lz; \

                          stackHi[sp] = hz; \

                          stackD [sp] = dz; \

                          sp++; }

#define mpop(lz,hz,dz) { sp--;             \

                         lz = stackLo[sp]; \

                         hz = stackHi[sp]; \

                         dz = stackD [sp]; }

#define mnextsize(az) (nextHi[az]-nextLo[az])

#define mnextswap(az,bz)                                        \

   { Int32 tz;                                                  \

     tz = nextLo[az]; nextLo[az] = nextLo[bz]; nextLo[bz] = tz; \

     tz = nextHi[az]; nextHi[az] = nextHi[bz]; nextHi[bz] = tz; \

     tz = nextD [az]; nextD [az] = nextD [bz]; nextD [bz] = tz; }

#define MAIN_QSORT_SMALL_THRESH 20

#define MAIN_QSORT_DEPTH_THRESH (BZ_N_RADIX + BZ_N_QSORT)

#define MAIN_QSORT_STACK_SIZE 100

static

void mainQSort3 ( UInt32* ptr,

                  UChar*  block,

                  UInt16* quadrant,

                  Int32   nblock,

                  Int32   loSt, 

                  Int32   hiSt, 

                  Int32   dSt,

                  Int32*  budget )

{

   Int32 unLo, unHi, ltLo, gtHi, n, m, med;

   Int32 sp, lo, hi, d;

   Int32 stackLo[MAIN_QSORT_STACK_SIZE];

   Int32 stackHi[MAIN_QSORT_STACK_SIZE];

   Int32 stackD [MAIN_QSORT_STACK_SIZE];

   Int32 nextLo[3];

   Int32 nextHi[3];

   Int32 nextD [3];

   sp = 0;

   mpush ( loSt, hiSt, dSt );

   while (sp > 0) {

      AssertH ( sp < MAIN_QSORT_STACK_SIZE - 2, 1001 );

      mpop ( lo, hi, d );

      if (hi - lo < MAIN_QSORT_SMALL_THRESH || 

          d > MAIN_QSORT_DEPTH_THRESH) {

         mainSimpleSort ( ptr, block, quadrant, nblock, lo, hi, d, budget );

         if (*budget < 0) return;

         continue;

      }

      med = (Int32) 

            mmed3 ( block[ptr[ lo         ]+d],

                    block[ptr[ hi         ]+d],

                    block[ptr[ (lo+hi)>>1 ]+d] );

      unLo = ltLo = lo;

      unHi = gtHi = hi;

      while (True) {

         while (True) {

            if (unLo > unHi) break;

            n = ((Int32)block[ptr[unLo]+d]) - med;

            if (n == 0) { 

               mswap(ptr[unLo], ptr[ltLo]); 

               ltLo++; unLo++; continue; 

            };

            if (n >  0) break;

            unLo++;

         }

         while (True) {

            if (unLo > unHi) break;

            n = ((Int32)block[ptr[unHi]+d]) - med;

            if (n == 0) { 

               mswap(ptr[unHi], ptr[gtHi]); 

               gtHi--; unHi--; continue; 

            };

            if (n <  0) break;

            unHi--;

         }

         if (unLo > unHi) break;

         mswap(ptr[unLo], ptr[unHi]); unLo++; unHi--;

      }

      AssertD ( unHi == unLo-1, "mainQSort3(2)" );

      if (gtHi < ltLo) {

         mpush(lo, hi, d+1 );

         continue;

      }

      n = mmin(ltLo-lo, unLo-ltLo); mvswap(lo, unLo-n, n);

      m = mmin(hi-gtHi, gtHi-unHi); mvswap(unLo, hi-m+1, m);

      n = lo + unLo - ltLo - 1;

      m = hi - (gtHi - unHi) + 1;

      nextLo[0] = lo;  nextHi[0] = n;   nextD[0] = d;

      nextLo[1] = m;   nextHi[1] = hi;  nextD[1] = d;

      nextLo[2] = n+1; nextHi[2] = m-1; nextD[2] = d+1;

      if (mnextsize(0) < mnextsize(1)) mnextswap(0,1);

      if (mnextsize(1) < mnextsize(2)) mnextswap(1,2);

      if (mnextsize(0) < mnextsize(1)) mnextswap(0,1);

      AssertD (mnextsize(0) >= mnextsize(1), "mainQSort3(8)" );

      AssertD (mnextsize(1) >= mnextsize(2), "mainQSort3(9)" );

      mpush (nextLo[0], nextHi[0], nextD[0]);

      mpush (nextLo[1], nextHi[1], nextD[1]);

      mpush (nextLo[2], nextHi[2], nextD[2]);

   }

}

#undef mswap

#undef mvswap

#undef mpush

#undef mpop

#undef mmin

#undef mnextsize

#undef mnextswap

#undef MAIN_QSORT_SMALL_THRESH

#undef MAIN_QSORT_DEPTH_THRESH

#undef MAIN_QSORT_STACK_SIZE

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

/* Pre:

      nblock > N_OVERSHOOT

      block32 exists for [0 .. nblock-1 +N_OVERSHOOT]

      ((UChar*)block32) [0 .. nblock-1] holds block

      ptr exists for [0 .. nblock-1]

   Post:

      ((UChar*)block32) [0 .. nblock-1] holds block

      All other areas of block32 destroyed

      ftab [0 .. 65536 ] destroyed

      ptr [0 .. nblock-1] holds sorted order

      if (*budget < 0), sorting was abandoned

*/

#define BIGFREQ(b) (ftab[((b)+1) << 8] - ftab[(b) << 8])

#define SETMASK (1 << 21)

#define CLEARMASK (~(SETMASK))

static

void mainSort ( UInt32* ptr, 

                UChar*  block,

                UInt16* quadrant, 

                UInt32* ftab,

                Int32   nblock,

                Int32   verb,

                Int32*  budget )

{

   Int32  i, j, k, ss, sb;

   Int32  runningOrder[256];

   Bool   bigDone[256];

   Int32  copyStart[256];

   Int32  copyEnd  [256];

   UChar  c1;

   Int32  numQSorted;

   UInt16 s;

   if (verb >= 4) VPrintf0 ( "        main sort initialise ...\n" );

   /*-- set up the 2-byte frequency table --*/

   for (i = 65536; i >= 0; i--) ftab[i] = 0;

   j = block[0] << 8;

   i = nblock-1;

   for (; i >= 3; i -= 4) {

      quadrant[i] = 0;

      j = (j >> 8) | ( ((UInt16)block[i]) << 8);

      ftab[j]++;

      quadrant[i-1] = 0;

      j = (j >> 8) | ( ((UInt16)block[i-1]) << 8);

      ftab[j]++;

      quadrant[i-2] = 0;

      j = (j >> 8) | ( ((UInt16)block[i-2]) << 8);

      ftab[j]++;

      quadrant[i-3] = 0;

      j = (j >> 8) | ( ((UInt16)block[i-3]) << 8);

      ftab[j]++;

   }

   for (; i >= 0; i--) {

      quadrant[i] = 0;

      j = (j >> 8) | ( ((UInt16)block[i]) << 8);

      ftab[j]++;

   }

   /*-- (emphasises close relationship of block & quadrant) --*/

   for (i = 0; i < BZ_N_OVERSHOOT; i++) {

      block   [nblock+i] = block[i];

      quadrant[nblock+i] = 0;

   }

   if (verb >= 4) VPrintf0 ( "        bucket sorting ...\n" );

   /*-- Complete the initial radix sort --*/

   for (i = 1; i <= 65536; i++) ftab[i] += ftab[i-1];

   s = block[0] << 8;

   i = nblock-1;

   for (; i >= 3; i -= 4) {

      s = (s >> 8) | (block[i] << 8);

      j = ftab[s] -1;

      ftab[s] = j;

      ptr[j] = i;

      s = (s >> 8) | (block[i-1] << 8);

      j = ftab[s] -1;

      ftab[s] = j;

      ptr[j] = i-1;

      s = (s >> 8) | (block[i-2] << 8);

      j = ftab[s] -1;

      ftab[s] = j;

      ptr[j] = i-2;

      s = (s >> 8) | (block[i-3] << 8);

      j = ftab[s] -1;

      ftab[s] = j;

      ptr[j] = i-3;

   }

   for (; i >= 0; i--) {

      s = (s >> 8) | (block[i] << 8);

      j = ftab[s] -1;

      ftab[s] = j;

      ptr[j] = i;

   }

   /*--

      Now ftab contains the first loc of every small bucket.

      Calculate the running order, from smallest to largest

      big bucket.

   --*/

   for (i = 0; i <= 255; i++) {

      bigDone     [i] = False;

      runningOrder[i] = i;

   }

   {

      Int32 vv;

      Int32 h = 1;

      do h = 3 * h + 1; while (h <= 256);

      do {

         h = h / 3;

         for (i = h; i <= 255; i++) {

            vv = runningOrder[i];

            j = i;

            while ( BIGFREQ(runningOrder[j-h]) > BIGFREQ(vv) ) {

               runningOrder[j] = runningOrder[j-h];

               j = j - h;

               if (j <= (h - 1)) goto zero;

            }

            zero:

            runningOrder[j] = vv;

         }

      } while (h != 1);

   }

   /*--

      The main sorting loop.

   --*/

   numQSorted = 0;

   for (i = 0; i <= 255; i++) {

      /*--

         Process big buckets, starting with the least full.

         Basically this is a 3-step process in which we call