/* $NetBSD: blocksort.c,v 1.6 1999/08/30 05:12:58 simonb Exp $ */ /*-------------------------------------------------------------*/ /*--- Block sorting machinery ---*/ /*--- blocksort.c ---*/ /*-------------------------------------------------------------*/ /*-- This file is a part of bzip2 and/or libbzip2, a program and library for lossless, block-sorting data compression. Copyright (C) 1996-1998 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, Guildford, Surrey, UK. jseward@acm.org bzip2/libbzip2 version 0.9.0 of 28 June 1998 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 "bzlib_private.h" /*---------------------------------------------*/ /*-- Compare two strings in block. We assume (see discussion above) that i1 and i2 have a max offset of 10 on entry, and that the first bytes of both block and quadrant have been copied into the "overshoot area", ie into the subscript range [nblock .. nblock+NUM_OVERSHOOT_BYTES-1]. --*/ static __inline__ Bool fullGtU ( UChar* block, UInt16* quadrant, UInt32 nblock, Int32* workDone, Int32 i1, Int32 i2 ) { Int32 k; UChar c1, c2; UInt16 s1, s2; AssertD ( i1 != i2, "fullGtU(1)" ); c1 = block[i1]; c2 = block[i2]; if (c1 != c2) return (c1 > c2); i1++; i2++; c1 = block[i1]; c2 = block[i2]; if (c1 != c2) return (c1 > c2); i1++; i2++; c1 = block[i1]; c2 = block[i2]; if (c1 != c2) return (c1 > c2); i1++; i2++; c1 = block[i1]; c2 = block[i2]; if (c1 != c2) return (c1 > c2); i1++; i2++; c1 = block[i1]; c2 = block[i2]; if (c1 != c2) return (c1 > c2); i1++; i2++; c1 = block[i1]; c2 = block[i2]; if (c1 != c2) return (c1 > c2); i1++; i2++; k = nblock; do { 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++; 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++; 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++; 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 -= 4; (*workDone)++; } 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 simpleSort ( EState* s, Int32 lo, Int32 hi, Int32 d ) { Int32 i, j, h, bigN, hp; Int32 v; UChar* block = s->block; UInt32* zptr = s->zptr; UInt16* quadrant = s->quadrant; Int32* workDone = &(s->workDone); Int32 nblock = s->nblock; Int32 workLimit = s->workLimit; Bool firstAttempt = s->firstAttempt; 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 = zptr[i]; j = i; while ( fullGtU ( block, quadrant, nblock, workDone, zptr[j-h]+d, v+d ) ) { zptr[j] = zptr[j-h]; j = j - h; if (j <= (lo + h - 1)) break; } zptr[j] = v; i++; /*-- copy 2 --*/ if (i > hi) break; v = zptr[i]; j = i; while ( fullGtU ( block, quadrant, nblock, workDone, zptr[j-h]+d, v+d ) ) { zptr[j] = zptr[j-h]; j = j - h; if (j <= (lo + h - 1)) break; } zptr[j] = v; i++; /*-- copy 3 --*/ if (i > hi) break; v = zptr[i]; j = i; while ( fullGtU ( block, quadrant, nblock, workDone, zptr[j-h]+d, v+d ) ) { zptr[j] = zptr[j-h]; j = j - h; if (j <= (lo + h - 1)) break; } zptr[j] = v; i++; if (*workDone > workLimit && firstAttempt) 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 swap(lv1, lv2) \ { Int32 tmp = lv1; lv1 = lv2; lv2 = tmp; } static void vswap ( UInt32* zptr, Int32 p1, Int32 p2, Int32 n ) { while (n > 0) { swap(zptr[p1], zptr[p2]); p1++; p2++; n--; } } static UChar med3 ( UChar a, UChar b, UChar c ) { UChar t; if (a > b) { t = a; a = b; b = t; }; if (b > c) { t = b; b = c; c = t; }; if (a > b) b = a; return b; } #define min(a,b) ((a) < (b)) ? (a) : (b) typedef struct { Int32 ll; Int32 hh; Int32 dd; } StackElem; #define push(lz,hz,dz) { stack[sp].ll = lz; \ stack[sp].hh = hz; \ stack[sp].dd = dz; \ sp++; } #define pop(lz,hz,dz) { sp--; \ lz = stack[sp].ll; \ hz = stack[sp].hh; \ dz = stack[sp].dd; } #define SMALL_THRESH 20 #define DEPTH_THRESH 10 /*-- If you are ever unlucky/improbable enough to get a stack overflow whilst sorting, increase the following constant and try again. In practice I have never seen the stack go above 27 elems, so the following limit seems very generous. --*/ #define QSORT_STACK_SIZE 1000 static void qSort3 ( EState* s, Int32 loSt, Int32 hiSt, Int32 dSt ) { Int32 unLo, unHi, ltLo, gtHi, med, n, m; Int32 sp, lo, hi, d; StackElem stack[QSORT_STACK_SIZE]; UChar* block = s->block; UInt32* zptr = s->zptr; Int32* workDone = &(s->workDone); Int32 workLimit = s->workLimit; Bool firstAttempt = s->firstAttempt; sp = 0; push ( loSt, hiSt, dSt ); while (sp > 0) { AssertH ( sp < QSORT_STACK_SIZE, 1001 ); pop ( lo, hi, d ); if (hi - lo < SMALL_THRESH || d > DEPTH_THRESH) { simpleSort ( s, lo, hi, d ); if (*workDone > workLimit && firstAttempt) return; continue; } med = med3 ( block[zptr[ lo ]+d], block[zptr[ hi ]+d], block[zptr[ (lo+hi)>>1 ]+d] ); unLo = ltLo = lo; unHi = gtHi = hi; while (True) { while (True) { if (unLo > unHi) break; n = ((Int32)block[zptr[unLo]+d]) - med; if (n == 0) { swap(zptr[unLo], zptr[ltLo]); ltLo++; unLo++; continue; }; if (n > 0) break; unLo++; } while (True) { if (unLo > unHi) break; n = ((Int32)block[zptr[unHi]+d]) - med; if (n == 0) { swap(zptr[unHi], zptr[gtHi]); gtHi--; unHi--; continue; }; if (n < 0) break; unHi--; } if (unLo > unHi) break; swap(zptr[unLo], zptr[unHi]); unLo++; unHi--; } AssertD ( unHi == unLo-1, "bad termination in qSort3" ); if (gtHi < ltLo) { push(lo, hi, d+1 ); continue; } n = min(ltLo-lo, unLo-ltLo); vswap(zptr, lo, unLo-n, n); m = min(hi-gtHi, gtHi-unHi); vswap(zptr, unLo, hi-m+1, m); n = lo + unLo - ltLo - 1; m = hi - (gtHi - unHi) + 1; push ( lo, n, d ); push ( n+1, m-1, d+1 ); push ( m, hi, d ); } } /*---------------------------------------------*/ #define BIGFREQ(b) (ftab[((b)+1) << 8] - ftab[(b) << 8]) #define SETMASK (1 << 21) #define CLEARMASK (~(SETMASK)) static void sortMain ( EState* s ) { Int32 i, j, k, ss, sb; Int32 runningOrder[256]; Int32 copy[256]; Bool bigDone[256]; UChar c1, c2; Int32 numQSorted; UChar* block = s->block; UInt32* zptr = s->zptr; UInt16* quadrant = s->quadrant; Int32* ftab = s->ftab; Int32* workDone = &(s->workDone); Int32 nblock = s->nblock; Int32 workLimit = s->workLimit; Bool firstAttempt = s->firstAttempt; /*-- In the various block-sized structures, live data runs from 0 to last+NUM_OVERSHOOT_BYTES inclusive. First, set up the overshoot area for block. --*/ if (s->verbosity >= 4) VPrintf0( " sort initialise ...\n" ); for (i = 0; i < BZ_NUM_OVERSHOOT_BYTES; i++) block[nblock+i] = block[i % nblock]; for (i = 0; i < nblock+BZ_NUM_OVERSHOOT_BYTES; i++) quadrant[i] = 0; if (nblock <= 4000) { /*-- Use simpleSort(), since the full sorting mechanism has quite a large constant overhead. --*/ if (s->verbosity >= 4) VPrintf0( " simpleSort ...\n" ); for (i = 0; i < nblock; i++) zptr[i] = i; firstAttempt = False; *workDone = workLimit = 0; simpleSort ( s, 0, nblock-1, 0 ); if (s->verbosity >= 4) VPrintf0( " simpleSort done.\n" ); } else { numQSorted = 0; for (i = 0; i <= 255; i++) bigDone[i] = False; if (s->verbosity >= 4) VPrintf0( " bucket sorting ...\n" ); for (i = 0; i <= 65536; i++) ftab[i] = 0; c1 = block[nblock-1]; for (i = 0; i < nblock; i++) { c2 = block[i]; ftab[(c1 << 8) + c2]++; c1 = c2; } for (i = 1; i <= 65536; i++) ftab[i] += ftab[i-1]; c1 = block[0]; for (i = 0; i < nblock-1; i++) { c2 = block[i+1]; j = (c1 << 8) + c2; c1 = c2; ftab[j]--; zptr[ftab[j]] = i; } j = (block[nblock-1] << 8) + block[0]; ftab[j]--; zptr[ftab[j]] = nblock-1; /*-- 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++) 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. --*/ for (i = 0; i <= 255; i++) { /*-- Process big buckets, starting with the least full. Basically this is a 4-step process in which we call qSort3 to sort the small buckets [ss, j], but also make a big effort to avoid the calls if we can. --*/ ss = runningOrder[i]; /*-- Step 1: Complete the big bucket [ss] by quicksorting any unsorted small buckets [ss, j], for j != ss. Hopefully previous pointer-scanning phases have already completed many of the small buckets [ss, j], so we don't have to sort them at all. --*/ for (j = 0; j <= 255; j++) { if (j != ss) { sb = (ss << 8) + j; if ( ! (ftab[sb] & SETMASK) ) { Int32 lo = ftab[sb] & CLEARMASK; Int32 hi = (ftab[sb+1] & CLEARMASK) - 1; if (hi > lo) { if (s->verbosity >= 4) VPrintf4( " qsort [0x%x, 0x%x] done %d this %d\n", ss, j, numQSorted, hi - lo + 1 ); qSort3 ( s, lo, hi, 2 ); numQSorted += ( hi - lo + 1 ); if (*workDone > workLimit && firstAttempt) return; } } ftab[sb] |= SETMASK; } } /*-- Step 2: Deal specially with case [ss, ss]. This establishes the sorted order for [ss, ss] without any comparisons. A clever trick, cryptically described as steps Q6b and Q6c in SRC-124 (aka BW94). This makes it entirely practical to not use a preliminary run-length coder, but unfortunately we are now stuck with the .bz2 file format. --*/ { Int32 put0, get0, put1, get1; Int32 sbn = (ss << 8) + ss; Int32 lo = ftab[sbn] & CLEARMASK; Int32 hi = (ftab[sbn+1] & CLEARMASK) - 1; UChar ssc = (UChar)ss; put0 = lo; get0 = ftab[ss << 8] & CLEARMASK; put1 = hi; get1 = (ftab[(ss+1) << 8] & CLEARMASK) - 1; while (get0 < put0) { j = zptr[get0]-1; if (j < 0) j += nblock; c1 = block[j]; if (c1 == ssc) { zptr[put0] = j; put0++; }; get0++; } while (get1 > put1) { j = zptr[get1]-1; if (j < 0) j += nblock; c1 = block[j]; if (c1 == ssc) { zptr[put1] = j; put1--; }; get1--; } ftab[sbn] |= SETMASK; } /*-- Step 3: The [ss] big bucket is now done. Record this fact, and update the quadrant descriptors. Remember to update quadrants in the overshoot area too, if necessary. The "if (i < 255)" test merely skips this updating for the last bucket processed, since updating for the last bucket is pointless. The quadrant array provides a way to incrementally cache sort orderings, as they appear, so as to make subsequent comparisons in fullGtU() complete faster. For repetitive blocks this makes a big difference (but not big enough to be able to avoid randomisation for very repetitive data.) The precise meaning is: at all times: for 0 <= i < nblock and 0 <= j <= nblock if block[i] != block[j], then the relative values of quadrant[i] and quadrant[j] are meaningless. else { if quadrant[i] < quadrant[j] then the string starting at i lexicographically precedes the string starting at j else if quadrant[i] > quadrant[j] then the string starting at j lexicographically precedes the string starting at i else the relative ordering of the strings starting at i and j has not yet been determined. } --*/ bigDone[ss] = True; if (i < 255) { Int32 bbStart = ftab[ss << 8] & CLEARMASK; Int32 bbSize = (ftab[(ss+1) << 8] & CLEARMASK) - bbStart; Int32 shifts = 0; while ((bbSize >> shifts) > 65534) shifts++; for (j = 0; j < bbSize; j++) { Int32 a2update = zptr[bbStart + j]; UInt16 qVal = (UInt16)(j >> shifts); quadrant[a2update] = qVal; if (a2update < BZ_NUM_OVERSHOOT_BYTES) quadrant[a2update + nblock] = qVal; } AssertH ( ( ((bbSize-1) >> shifts) <= 65535 ), 1002 ); } /*-- Step 4: Now scan this big bucket [ss] so as to synthesise the sorted order for small buckets [t, ss] for all t != ss. This will avoid doing Real Work in subsequent Step 1's. --*/ for (j = 0; j <= 255; j++) copy[j] = ftab[(j << 8) + ss] & CLEARMASK; for (j = ftab[ss << 8] & CLEARMASK; j < (ftab[(ss+1) << 8] & CLEARMASK); j++) { k = zptr[j]-1; if (k < 0) k += nblock; c1 = block[k]; if ( ! bigDone[c1] ) { zptr[copy[c1]] = k; copy[c1] ++; } } for (j = 0; j <= 255; j++) ftab[(j << 8) + ss] |= SETMASK; } if (s->verbosity >= 4) VPrintf3( " %d pointers, %d sorted, %d scanned\n", nblock, numQSorted, nblock - numQSorted ); } } /*---------------------------------------------*/ static void randomiseBlock ( EState* s ) { Int32 i; BZ_RAND_INIT_MASK; for (i = 0; i < 256; i++) s->inUse[i] = False; for (i = 0; i < s->nblock; i++) { BZ_RAND_UPD_MASK; s->block[i] ^= BZ_RAND_MASK; s->inUse[s->block[i]] = True; } } /*---------------------------------------------*/ void _BZblockSort ( EState* s ) { Int32 i; s->workLimit = s->workFactor * (s->nblock - 1); s->workDone = 0; s->blockRandomised = False; s->firstAttempt = True; sortMain ( s ); if (s->verbosity >= 3) VPrintf3( " %d work, %d block, ratio %5.2f\n", s->workDone, s->nblock-1, (float)(s->workDone) / (float)(s->nblock-1) ); if (s->workDone > s->workLimit && s->firstAttempt) { if (s->verbosity >= 2) VPrintf0( " sorting aborted; randomising block\n" ); randomiseBlock ( s ); s->workLimit = s->workDone = 0; s->blockRandomised = True; s->firstAttempt = False; sortMain ( s ); if (s->verbosity >= 3) VPrintf3( " %d work, %d block, ratio %f\n", s->workDone, s->nblock-1, (float)(s->workDone) / (float)(s->nblock-1) ); } s->origPtr = -1; for (i = 0; i < s->nblock; i++) if (s->zptr[i] == 0) { s->origPtr = i; break; }; AssertH( s->origPtr != -1, 1003 ); } /*-------------------------------------------------------------*/ /*--- end blocksort.c ---*/ /*-------------------------------------------------------------*/