/* GLIB - Library of useful routines for C programming
- * Copyright (C) 1991, 1992, 1996, 1997 Free Software Foundation, Inc.
+ * Copyright (C) 1991, 1992, 1996, 1997,1999,2004 Free Software Foundation, Inc.
* Copyright (C) 2000 Eazel, Inc.
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
#include "config.h"
+#include <alloca.h>
+#include <limits.h>
+#include <stdlib.h>
#include <string.h>
#include "galias.h"
#include "glib.h"
-
/* Byte-wise swap two items of size SIZE. */
#define SWAP(a, b, size) \
do \
/* Stack node declarations used to store unfulfilled partition obligations. */
typedef struct
-{
- char *lo;
- char *hi;
-}
-stack_node;
+ {
+ 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))
+/* 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 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 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
- * 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 (n) stack size is needed (actually O(1)
- * in this case)!
- */
+ 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)! */
/**
* g_qsort_with_data:
{
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 *) g_alloca (size);
const size_t max_thresh = MAX_THRESH * size;
g_return_if_fail (total_elems >= 0);
g_return_if_fail (compare_func != NULL);
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;
+ stack_node *top = stack;
- while (STACK_NOT_EMPTY)
- {
- char *left_ptr;
- char *right_ptr;
+ PUSH (NULL, NULL);
- char *pivot = pivot_buffer;
+ 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. */
+ 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 ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
SWAP (mid, lo, size);
jump_over:;
- memcpy (pivot, mid, size);
- pivot = pivot_buffer;
- left_ptr = lo + size;
+ 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. */
+ Gotta like those tight inner loops! They are the main reason
+ that this algorithm runs much faster than others. */
do
{
- while ((*compare_func)
- ((void *) left_ptr, (void *) pivot,
- user_data) < 0)
+ while ((*compare_func) ((void *) left_ptr, (void *) mid, user_data) < 0)
left_ptr += size;
- while ((*compare_func)
- ((void *) pivot, (void *) right_ptr,
- user_data) < 0)
+ while ((*compare_func) ((void *) mid, (void *) right_ptr, user_data) < 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;
}
}
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. */
+ /* 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)
+ if ((size_t) (right_ptr - lo) <= max_thresh)
+ {
+ if ((size_t) (hi - left_ptr) <= max_thresh)
/* Ignore both small partitions. */
- POP (lo, hi);
- else
+ 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;
- }
- }
+ 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!). */
+ 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);
+ 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. */
+ 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 ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr,
- user_data) < 0)
- tmp_ptr = run_ptr;
+ for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size)
+ if ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 0)
+ tmp_ptr = run_ptr;
if (tmp_ptr != base_ptr)
SWAP (tmp_ptr, base_ptr, size);
while ((run_ptr += size) <= end_ptr)
{
tmp_ptr = run_ptr - size;
- while ((*compare_func)
- ((void *) run_ptr, (void *) tmp_ptr,
- user_data) < 0)
+ while ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 0)
tmp_ptr -= size;
tmp_ptr += size;
- if (tmp_ptr != run_ptr)
- {
- char *trav;
+ 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;
- }
- }
+ {
+ char c = *trav;
+ char *hi, *lo;
+
+ for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)
+ *hi = *lo;
+ *hi = c;
+ }
+ }
}
}
}
projects / platform / upstream / glib.git / commitdiff