-/*--------------------------------------------------------------------*
- | whereami is given a filename f in the form: whereami(argv[0])
- | It returns the directory in which the executable file (containing
- | this code [main.c] ) may be found. A dot will be returned to indicate
- | the current directory.
- *--------------------------------------------------------------------*/
-
-static void
-whereami(name)
- char *name;
-{
- register char *cutoff = NULL; /* stifle -Wall */
- register char *s;
- register char *t;
- int cc;
- char ebuf[4096];
-
- /*
- * See if the file is accessible either through the current directory
- * or through an absolute path.
- */
-
- if (access(name, R_OK) == 0) {
-
- /*-------------------------------------------------------------*
- * The file was accessible without any other work. But the current
- * working directory might change on us, so if it was accessible
- * through the cwd, then we should get it for later accesses.
- *-------------------------------------------------------------*/
-
- t = imagedir;
- if (!absolute_pathname(name)) {
-#if defined(DOS) || defined(__WIN32__)
- int drive;
- char *newrbuf;
-
- newrbuf = imagedir;
-#ifndef __DJGPP__
- if (*(name + 1) == ':') {
- if (*name >= 'a' && *name <= 'z')
- drive = (int) (*name - 'a' + 1);
- else
- drive = (int) (*name - 'A' + 1);
- *newrbuf++ = *name;
- *newrbuf++ = *(name + 1);
- *newrbuf++ = DIR_SEPARATOR;
+
+/* 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 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)! */
+
+void wxQsort(void *const pbase, size_t total_elems,
+ size_t size, CMPFUNCDATA cmp, const void* user_data)
+{
+ 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;
+
+ PUSH (NULL, NULL);
+
+ 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. */
+
+ char *mid = lo + size * ((hi - lo) / size >> 1);
+
+ if ((*cmp) ((void *) mid, (void *) lo, user_data) < 0)
+ SWAP (mid, lo, size);
+ if ((*cmp) ((void *) hi, (void *) mid, user_data) < 0)
+ SWAP (mid, hi, size);
+ else
+ goto jump_over;
+ if ((*cmp) ((void *) mid, (void *) lo, user_data) < 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, user_data) < 0)
+ left_ptr += size;
+
+ while ((*cmp) ((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;
+ }
+ else if (left_ptr == right_ptr)
+ {
+ left_ptr += size;
+ right_ptr -= size;
+ break;
+ }
projects / wxWidgets.git / blobdiff