[PATCH 4/8] lib/sort: Kill qsort()

[Matt Mackall <mpm@selenic.com>]

Remove qsort() before anyone gets too attached to it.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: mm2/lib/qsort.c
===================================================================
--- mm2.orig/lib/qsort.c	2005-01-30 20:33:19.000000000 -0800
+++ /dev/null	1970-01-01 00:00:00.000000000 +0000
@@ -1,249 +0,0 @@
-/* Copyright (C) 1991, 1992, 1996, 1997, 1999 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Written by Douglas C. Schmidt (schmidt@ics.uci.edu).
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, write to the Free
-   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
-   02111-1307 USA.  */
-
-/* If you consider tuning this algorithm, you should consult first:
-   Engineering a sort function; Jon Bentley and M. Douglas McIlroy;
-   Software - Practice and Experience; Vol. 23 (11), 1249-1265, 1993.  */
-
-# include <linux/module.h>
-# include <linux/slab.h>
-# include <linux/string.h>
-
-MODULE_LICENSE("GPL");
-
-/* Byte-wise swap two items of size SIZE. */
-#define SWAP(a, b, size)						      \
-  do									      \
-    {									      \
-      register size_t __size = (size);					      \
-      register char *__a = (a), *__b = (b);				      \
-      do								      \
-	{								      \
-	  char __tmp = *__a;						      \
-	  *__a++ = *__b;						      \
-	  *__b++ = __tmp;						      \
-	} while (--__size > 0);						      \
-    } while (0)
-
-/* Discontinue quicksort algorithm when partition gets below this size.
-   This particular magic number was chosen to work best on a Sun 4/260. */
-#define MAX_THRESH 4
-
-/* Stack node declarations used to store unfulfilled partition obligations. */
-typedef struct
-  {
-    char *lo;
-    char *hi;
-  } stack_node;
-
-/* The next 5 #defines implement a very fast in-line stack abstraction. */
-/* The stack needs log (total_elements) entries (we could even subtract
-   log(MAX_THRESH)).  Since total_elements has type size_t, we get as
-   upper bound for log (total_elements):
-   bits per byte (CHAR_BIT) * sizeof(size_t).  */
-#define CHAR_BIT 8
-#define STACK_SIZE	(CHAR_BIT * sizeof(size_t))
-#define PUSH(low, high)	((void) ((top->lo = (low)), (top->hi = (high)), ++top))
-#define	POP(low, high)	((void) (--top, (low = top->lo), (high = top->hi)))
-#define	STACK_NOT_EMPTY	(stack < top)
-
-
-/* Order size using quicksort.  This implementation incorporates
-   four optimizations discussed in Sedgewick:
-
-   1. Non-recursive, using an explicit stack of pointer that store the
-      next array partition to sort.  To save time, this maximum amount
-      of space required to store an array of SIZE_MAX is allocated on the
-      stack.  Assuming a 32-bit (64 bit) integer for size_t, this needs
-      only 32 * sizeof(stack_node) == 256 bytes (for 64 bit: 1024 bytes).
-      Pretty cheap, actually.
-
-   2. Chose the pivot element using a median-of-three decision tree.
-      This reduces the probability of selecting a bad pivot value and
-      eliminates certain extraneous comparisons.
-
-   3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving
-      insertion sort to order the MAX_THRESH items within each partition.
-      This is a big win, since insertion sort is faster for small, mostly
-      sorted array segments.
-
-   4. The larger of the two sub-partitions is always pushed onto the
-      stack first, with the algorithm then concentrating on the
-      smaller partition.  This *guarantees* no more than log (total_elems)
-      stack size is needed (actually O(1) in this case)!  */
-
-void
-qsort(void *const pbase, size_t total_elems, size_t size,
-      int(*cmp)(const void *,const void *))
-{
-  register char *base_ptr = (char *) pbase;
-
-  const size_t max_thresh = MAX_THRESH * size;
-
-  if (total_elems == 0)
-    /* Avoid lossage with unsigned arithmetic below.  */
-    return;
-
-  if (total_elems > MAX_THRESH)
-    {
-      char *lo = base_ptr;
-      char *hi = &lo[size * (total_elems - 1)];
-      stack_node stack[STACK_SIZE];
-      stack_node *top = stack + 1;
-
-      while (STACK_NOT_EMPTY)
-        {
-          char *left_ptr;
-          char *right_ptr;
-
-	  /* Select median value from among LO, MID, and HI. Rearrange
-	     LO and HI so the three values are sorted. This lowers the
-	     probability of picking a pathological pivot value and
-	     skips a comparison for both the LEFT_PTR and RIGHT_PTR in
-	     the while loops. */
-
-	  char *mid = lo + size * ((hi - lo) / size >> 1);
-
-	  if ((*cmp) ((void *) mid, (void *) lo) < 0)
-	    SWAP (mid, lo, size);
-	  if ((*cmp) ((void *) hi, (void *) mid) < 0)
-	    SWAP (mid, hi, size);
-	  else
-	    goto jump_over;
-	  if ((*cmp) ((void *) mid, (void *) lo) < 0)
-	    SWAP (mid, lo, size);
-	jump_over:;
-
-	  left_ptr  = lo + size;
-	  right_ptr = hi - size;
-
-	  /* Here's the famous ``collapse the walls'' section of quicksort.
-	     Gotta like those tight inner loops!  They are the main reason
-	     that this algorithm runs much faster than others. */
-	  do
-	    {
-	      while ((*cmp) ((void *) left_ptr, (void *) mid) < 0)
-		left_ptr += size;
-
-	      while ((*cmp) ((void *) mid, (void *) right_ptr) < 0)
-		right_ptr -= size;
-
-	      if (left_ptr < right_ptr)
-		{
-		  SWAP (left_ptr, right_ptr, size);
-		  if (mid == left_ptr)
-		    mid = right_ptr;
-		  else if (mid == right_ptr)
-		    mid = left_ptr;
-		  left_ptr += size;
-		  right_ptr -= size;
-		}
-	      else if (left_ptr == right_ptr)
-		{
-		  left_ptr += size;
-		  right_ptr -= size;
-		  break;
-		}
-	    }
-	  while (left_ptr <= right_ptr);
-
-          /* Set up pointers for next iteration.  First determine whether
-             left and right partitions are below the threshold size.  If so,
-             ignore one or both.  Otherwise, push the larger partition's
-             bounds on the stack and continue sorting the smaller one. */
-
-          if ((size_t) (right_ptr - lo) <= max_thresh)
-            {
-              if ((size_t) (hi - left_ptr) <= max_thresh)
-		/* Ignore both small partitions. */
-                POP (lo, hi);
-              else
-		/* Ignore small left partition. */
-                lo = left_ptr;
-            }
-          else if ((size_t) (hi - left_ptr) <= max_thresh)
-	    /* Ignore small right partition. */
-            hi = right_ptr;
-          else if ((right_ptr - lo) > (hi - left_ptr))
-            {
-	      /* Push larger left partition indices. */
-              PUSH (lo, right_ptr);
-              lo = left_ptr;
-            }
-          else
-            {
-	      /* Push larger right partition indices. */
-              PUSH (left_ptr, hi);
-              hi = right_ptr;
-            }
-        }
-    }
-
-  /* Once the BASE_PTR array is partially sorted by quicksort the rest
-     is completely sorted using insertion sort, since this is efficient
-     for partitions below MAX_THRESH size. BASE_PTR points to the beginning
-     of the array to sort, and END_PTR points at the very last element in
-     the array (*not* one beyond it!). */
-
-  {
-    char *end_ptr = &base_ptr[size * (total_elems - 1)];
-    char *tmp_ptr = base_ptr;
-    char *thresh = min(end_ptr, base_ptr + max_thresh);
-    register char *run_ptr;
-
-    /* Find smallest element in first threshold and place it at the
-       array's beginning.  This is the smallest array element,
-       and the operation speeds up insertion sort's inner loop. */
-
-    for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size)
-      if ((*cmp) ((void *) run_ptr, (void *) tmp_ptr) < 0)
-        tmp_ptr = run_ptr;
-
-    if (tmp_ptr != base_ptr)
-      SWAP (tmp_ptr, base_ptr, size);
-
-    /* Insertion sort, running from left-hand-side up to right-hand-side.  */
-
-    run_ptr = base_ptr + size;
-    while ((run_ptr += size) <= end_ptr)
-      {
-	tmp_ptr = run_ptr - size;
-	while ((*cmp) ((void *) run_ptr, (void *) tmp_ptr) < 0)
-	  tmp_ptr -= size;
-
-	tmp_ptr += size;
-        if (tmp_ptr != run_ptr)
-          {
-            char *trav;
-
-	    trav = run_ptr + size;
-	    while (--trav >= run_ptr)
-              {
-                char c = *trav;
-                char *hi, *lo;
-
-                for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)
-                  *hi = *lo;
-                *hi = c;
-              }
-          }
-      }
-  }
-}
-EXPORT_SYMBOL(qsort);
Index: mm2/lib/Kconfig
===================================================================
--- mm2.orig/lib/Kconfig	2005-01-30 20:33:19.000000000 -0800
+++ mm2/lib/Kconfig	2005-01-30 20:36:12.000000000 -0800
@@ -30,9 +30,6 @@
 	  require M here.  See Castagnoli93.
 	  Module will be libcrc32c.
 
-config QSORT
-	bool "Quick Sort"
-
 #
 # compression support is select'ed if needed
 #
Index: mm2/lib/Makefile
===================================================================
--- mm2.orig/lib/Makefile	2005-01-30 20:33:19.000000000 -0800
+++ mm2/lib/Makefile	2005-01-30 20:36:12.000000000 -0800
@@ -26,7 +26,6 @@
 obj-$(CONFIG_CRC32)	+= crc32.o
 obj-$(CONFIG_LIBCRC32C)	+= libcrc32c.o
 obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
-obj-$(CONFIG_QSORT)	+= qsort.o
 
 obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/
 obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/