You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
300 lines
9.7 KiB
300 lines
9.7 KiB
//+----------------------------------------------------------------------------
|
|
//
|
|
// File: qsort.cpp
|
|
//
|
|
// Module: CMPBK32.DLL
|
|
//
|
|
// Synopsis: Quick Sort Implementation (taken from libc)
|
|
//
|
|
// Copyright (c) 1997-1998 Microsoft Corporation
|
|
//
|
|
// Author: quintinb created header 08/17/99
|
|
//
|
|
//+----------------------------------------------------------------------------
|
|
#include "cmmaster.h"
|
|
|
|
/* prototypes for local routines */
|
|
static void __cdecl shortsort(char *lo, char *hi, unsigned width,
|
|
int (__cdecl *comp)(const void *, const void *));
|
|
static void __cdecl swap(char *p, char *q, unsigned int width);
|
|
|
|
/* this parameter defines the cutoff between using quick sort and
|
|
insertion sort for arrays; arrays with lengths shorter or equal to the
|
|
below value use insertion sort */
|
|
|
|
#define CUTOFF 8 /* testing shows that this is good value */
|
|
|
|
|
|
/***
|
|
*qsort(base, num, wid, comp) - quicksort function for sorting arrays
|
|
*
|
|
*Purpose:
|
|
* quicksort the array of elements
|
|
* side effects: sorts in place
|
|
*
|
|
*Entry:
|
|
* char *base = pointer to base of array
|
|
* unsigned num = number of elements in the array
|
|
* unsigned width = width in bytes of each array element
|
|
* int (*comp)() = pointer to function returning analog of strcmp for
|
|
* strings, but supplied by user for comparing the array elements.
|
|
* it accepts 2 pointers to elements and returns neg if 1<2, 0 if
|
|
* 1=2, pos if 1>2.
|
|
*
|
|
*Exit:
|
|
* returns void
|
|
*
|
|
*Exceptions:
|
|
*
|
|
*******************************************************************************/
|
|
|
|
/* sort the array between lo and hi (inclusive) */
|
|
|
|
void __cdecl CmQSort (
|
|
void *base,
|
|
unsigned num,
|
|
unsigned width,
|
|
int (__cdecl *comp)(const void *, const void *)
|
|
)
|
|
{
|
|
char *lo, *hi; /* ends of sub-array currently sorting */
|
|
char *mid; /* points to middle of subarray */
|
|
char *loguy, *higuy; /* traveling pointers for partition step */
|
|
unsigned size; /* size of the sub-array */
|
|
char *lostk[30], *histk[30];
|
|
int stkptr; /* stack for saving sub-array to be processed */
|
|
|
|
/* Note: the number of stack entries required is no more than
|
|
1 + log2(size), so 30 is sufficient for any array */
|
|
|
|
if (num < 2 || width == 0)
|
|
return; /* nothing to do */
|
|
|
|
stkptr = 0; /* initialize stack */
|
|
|
|
lo = (char *)base;
|
|
hi = (char *)base + width * (num-1); /* initialize limits */
|
|
|
|
/* this entry point is for pseudo-recursion calling: setting
|
|
lo and hi and jumping to here is like recursion, but stkptr is
|
|
prserved, locals aren't, so we preserve stuff on the stack */
|
|
recurse:
|
|
|
|
size = PtrToUlong((PVOID)(hi - lo)) / width + 1; /* number of el's to sort */
|
|
|
|
/* below a certain size, it is faster to use a O(n^2) sorting method */
|
|
if (size <= CUTOFF) {
|
|
shortsort(lo, hi, width, comp);
|
|
}
|
|
else {
|
|
/* First we pick a partititioning element. The efficiency of the
|
|
algorithm demands that we find one that is approximately the
|
|
median of the values, but also that we select one fast. Using
|
|
the first one produces bad performace if the array is already
|
|
sorted, so we use the middle one, which would require a very
|
|
wierdly arranged array for worst case performance. Testing shows
|
|
that a median-of-three algorithm does not, in general, increase
|
|
performance. */
|
|
|
|
mid = lo + (size / 2) * width; /* find middle element */
|
|
swap(mid, lo, width); /* swap it to beginning of array */
|
|
|
|
/* We now wish to partition the array into three pieces, one
|
|
consisiting of elements <= partition element, one of elements
|
|
equal to the parition element, and one of element >= to it. This
|
|
is done below; comments indicate conditions established at every
|
|
step. */
|
|
|
|
loguy = lo;
|
|
higuy = hi + width;
|
|
|
|
/* Note that higuy decreases and loguy increases on every iteration,
|
|
so loop must terminate. */
|
|
for (;;) {
|
|
/* lo <= loguy < hi, lo < higuy <= hi + 1,
|
|
A[i] <= A[lo] for lo <= i <= loguy,
|
|
A[i] >= A[lo] for higuy <= i <= hi */
|
|
|
|
do {
|
|
loguy += width;
|
|
} while (loguy <= hi && comp(loguy, lo) <= 0);
|
|
|
|
/* lo < loguy <= hi+1, A[i] <= A[lo] for lo <= i < loguy,
|
|
either loguy > hi or A[loguy] > A[lo] */
|
|
|
|
do {
|
|
higuy -= width;
|
|
} while (higuy > lo && comp(higuy, lo) >= 0);
|
|
|
|
/* lo-1 <= higuy <= hi, A[i] >= A[lo] for higuy < i <= hi,
|
|
either higuy <= lo or A[higuy] < A[lo] */
|
|
|
|
if (higuy < loguy)
|
|
break;
|
|
|
|
/* if loguy > hi or higuy <= lo, then we would have exited, so
|
|
A[loguy] > A[lo], A[higuy] < A[lo],
|
|
loguy < hi, highy > lo */
|
|
|
|
swap(loguy, higuy, width);
|
|
|
|
/* A[loguy] < A[lo], A[higuy] > A[lo]; so condition at top
|
|
of loop is re-established */
|
|
}
|
|
|
|
/* A[i] >= A[lo] for higuy < i <= hi,
|
|
A[i] <= A[lo] for lo <= i < loguy,
|
|
higuy < loguy, lo <= higuy <= hi
|
|
implying:
|
|
A[i] >= A[lo] for loguy <= i <= hi,
|
|
A[i] <= A[lo] for lo <= i <= higuy,
|
|
A[i] = A[lo] for higuy < i < loguy */
|
|
|
|
swap(lo, higuy, width); /* put partition element in place */
|
|
|
|
/* OK, now we have the following:
|
|
A[i] >= A[higuy] for loguy <= i <= hi,
|
|
A[i] <= A[higuy] for lo <= i < higuy
|
|
A[i] = A[lo] for higuy <= i < loguy */
|
|
|
|
/* We've finished the partition, now we want to sort the subarrays
|
|
[lo, higuy-1] and [loguy, hi].
|
|
We do the smaller one first to minimize stack usage.
|
|
We only sort arrays of length 2 or more.*/
|
|
|
|
if ( higuy - 1 - lo >= hi - loguy ) {
|
|
if (lo + width < higuy) {
|
|
lostk[stkptr] = lo;
|
|
histk[stkptr] = higuy - width;
|
|
++stkptr;
|
|
} /* save big recursion for later */
|
|
|
|
if (loguy < hi) {
|
|
lo = loguy;
|
|
goto recurse; /* do small recursion */
|
|
}
|
|
}
|
|
else {
|
|
if (loguy < hi) {
|
|
lostk[stkptr] = loguy;
|
|
histk[stkptr] = hi;
|
|
++stkptr; /* save big recursion for later */
|
|
}
|
|
|
|
if (lo + width < higuy) {
|
|
hi = higuy - width;
|
|
goto recurse; /* do small recursion */
|
|
}
|
|
}
|
|
}
|
|
|
|
/* We have sorted the array, except for any pending sorts on the stack.
|
|
Check if there are any, and do them. */
|
|
|
|
--stkptr;
|
|
if (stkptr >= 0) {
|
|
lo = lostk[stkptr];
|
|
hi = histk[stkptr];
|
|
goto recurse; /* pop subarray from stack */
|
|
}
|
|
else
|
|
return; /* all subarrays done */
|
|
}
|
|
|
|
|
|
/***
|
|
*shortsort(hi, lo, width, comp) - insertion sort for sorting short arrays
|
|
*
|
|
*Purpose:
|
|
* sorts the sub-array of elements between lo and hi (inclusive)
|
|
* side effects: sorts in place
|
|
* assumes that lo < hi
|
|
*
|
|
*Entry:
|
|
* char *lo = pointer to low element to sort
|
|
* char *hi = pointer to high element to sort
|
|
* unsigned width = width in bytes of each array element
|
|
* int (*comp)() = pointer to function returning analog of strcmp for
|
|
* strings, but supplied by user for comparing the array elements.
|
|
* it accepts 2 pointers to elements and returns neg if 1<2, 0 if
|
|
* 1=2, pos if 1>2.
|
|
*
|
|
*Exit:
|
|
* returns void
|
|
*
|
|
*Exceptions:
|
|
*
|
|
*******************************************************************************/
|
|
|
|
static void __cdecl shortsort (
|
|
char *lo,
|
|
char *hi,
|
|
unsigned width,
|
|
int (__cdecl *comp)(const void *, const void *)
|
|
)
|
|
{
|
|
char *p, *max;
|
|
|
|
/* Note: in assertions below, i and j are alway inside original bound of
|
|
array to sort. */
|
|
|
|
while (hi > lo) {
|
|
/* A[i] <= A[j] for i <= j, j > hi */
|
|
max = lo;
|
|
for (p = lo+width; p <= hi; p += width) {
|
|
/* A[i] <= A[max] for lo <= i < p */
|
|
if (comp(p, max) > 0) {
|
|
max = p;
|
|
}
|
|
/* A[i] <= A[max] for lo <= i <= p */
|
|
}
|
|
|
|
/* A[i] <= A[max] for lo <= i <= hi */
|
|
|
|
swap(max, hi, width);
|
|
|
|
/* A[i] <= A[hi] for i <= hi, so A[i] <= A[j] for i <= j, j >= hi */
|
|
|
|
hi -= width;
|
|
|
|
/* A[i] <= A[j] for i <= j, j > hi, loop top condition established */
|
|
}
|
|
/* A[i] <= A[j] for i <= j, j > lo, which implies A[i] <= A[j] for i < j,
|
|
so array is sorted */
|
|
}
|
|
|
|
|
|
/***
|
|
*swap(a, b, width) - swap two elements
|
|
*
|
|
*Purpose:
|
|
* swaps the two array elements of size width
|
|
*
|
|
*Entry:
|
|
* char *a, *b = pointer to two elements to swap
|
|
* unsigned width = width in bytes of each array element
|
|
*
|
|
*Exit:
|
|
* returns void
|
|
*
|
|
*Exceptions:
|
|
*
|
|
*******************************************************************************/
|
|
|
|
static void __cdecl swap (
|
|
char *a,
|
|
char *b,
|
|
unsigned width
|
|
)
|
|
{
|
|
char tmp;
|
|
|
|
if ( a != b )
|
|
/* Do the swap one character at a time to avoid potential alignment
|
|
problems. */
|
|
while ( width-- ) {
|
|
tmp = *a;
|
|
*a++ = *b;
|
|
*b++ = tmp;
|
|
}
|
|
}
|