initial import

1 files changed, 243 insertions, 0 deletions

diff --git a/stdlib/qsort.c b/stdlib/qsort.c
new file mode 100644
index 0000000000..bc8d171b79
--- /dev/null
+++ b/stdlib/qsort.c
@@ -0,0 +1,243 @@
+/* Copyright (C) 1991, 1992 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 Library General Public License as
+published by the Free Software Foundation; either version 2 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
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <ansidecl.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* 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 4 #defines implement a very fast in-line stack abstraction. */
+#define STACK_SIZE	(8 * sizeof(unsigned long int))
+#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 MAX_INT is allocated on the 
+      stack.  Assuming a 32-bit integer, this needs only 32 * 
+      sizeof(stack_node) == 136 bits.  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 segements.
+
+   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 (n)
+      stack size is needed (actually O(1) in this case)!  */
+
+void
+DEFUN(_quicksort, (pbase, total_elems, size, cmp),
+      PTR CONST pbase AND size_t total_elems AND size_t size AND
+      int EXFUN((*cmp), (CONST PTR, CONST PTR)))
+{
+  register char *base_ptr = (char *) pbase;
+
+  /* Allocating SIZE bytes for a pivot buffer facilitates a better
+     algorithm below since we can do comparisons directly on the pivot. */
+  char *pivot_buffer = (char *) __alloca (size);
+  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)];
+      /* Largest size needed for 32-bit int!!! */
+      stack_node stack[STACK_SIZE];
+      stack_node *top = stack + 1;
+
+      while (STACK_NOT_EMPTY)
+        {
+          char *left_ptr;
+          char *right_ptr;
+
+	  char *pivot = pivot_buffer;
+
+	  /* 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. */
+
+	  char *mid = lo + size * ((hi - lo) / size >> 1);
+
+	  if ((*cmp)((PTR) mid, (PTR) lo) < 0)
+	    SWAP(mid, lo, size);
+	  if ((*cmp)((PTR) hi, (PTR) mid) < 0)
+	    SWAP(mid, hi, size);
+	  else 
+	    goto jump_over;
+	  if ((*cmp)((PTR) mid, (PTR) lo) < 0)
+	    SWAP(mid, lo, size);
+	jump_over:;
+	  memcpy(pivot, mid, size);
+	  pivot = pivot_buffer;
+
+	  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)((PTR) left_ptr, (PTR) pivot) < 0)
+		left_ptr += size;
+
+	      while ((*cmp)((PTR) pivot, (PTR) right_ptr) < 0)
+		right_ptr -= size;
+
+	      if (left_ptr < right_ptr) 
+		{
+		  SWAP(left_ptr, right_ptr, size);
+		  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!). */
+
+#define min(x, y) ((x) < (y) ? (x) : (y))
+
+  {
+    char *CONST 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)((PTR) run_ptr, (PTR) 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)((PTR) run_ptr, (PTR) 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;
+              }
+          }
+      }
+  }
+}
+