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wm: sort windows by z index
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,8 +1,120 @@ | ||
| #include <stdlib.h> | ||
|
|
||
| void qsort(void *base, size_t nmemb, size_t size, | ||
| int (*compar)(const void *, const void *)) { | ||
| // TODO | ||
| abort(); | ||
| return; | ||
| /* This implementation is taken from Paul Edward's PDPCLIB. | ||
| Original code is credited to Raymond Gardner, Englewood CO. | ||
| Minor mods are credited to Paul Edwards. | ||
| Some reformatting and simplification done by Martin Baute. | ||
| All code is still Public Domain. | ||
| */ | ||
|
|
||
| static inline void memswp(char *i, char *j, size_t size) { | ||
| char tmp; | ||
| do { | ||
| tmp = *i; | ||
| *i++ = *j; | ||
| *j++ = tmp; | ||
| } while (--size); | ||
| } | ||
|
|
||
| /* For small sets, insertion sort is faster than quicksort. | ||
| T is the threshold below which insertion sort will be used. | ||
| Must be 3 or larger. | ||
| */ | ||
| #define T 7 | ||
|
|
||
| /* Macros for handling the QSort stack */ | ||
| #define PREPARE_STACK char * stack[STACKSIZE]; char * * stackptr = stack | ||
| #define PUSH( base, limit ) stackptr[0] = base; stackptr[1] = limit; stackptr += 2 | ||
| #define POP( base, limit ) stackptr -= 2; base = stackptr[0]; limit = stackptr[1] | ||
| /* TODO: Stack usage is log2( nmemb ) (minus what T shaves off the worst case). | ||
| Worst-case nmemb is platform dependent and should probably be | ||
| configured through _PDCLIB_config.h. | ||
| */ | ||
| #define STACKSIZE 64 | ||
|
|
||
| void qsort( void * base, size_t nmemb, size_t size, int (*compar)( const void *, const void * ) ) | ||
| { | ||
| char * i; | ||
| char * j; | ||
| size_t thresh = T * size; | ||
| char * base_ = (char *)base; | ||
| char * limit = base_ + nmemb * size; | ||
| PREPARE_STACK; | ||
|
|
||
| for ( ;; ) | ||
| { | ||
| if ( (size_t)( limit - base_ ) > thresh ) /* QSort for more than T elements. */ | ||
| { | ||
| /* We work from second to last - first will be pivot element. */ | ||
| i = base_ + size; | ||
| j = limit - size; | ||
| /* We swap first with middle element, then sort that with second | ||
| and last element so that eventually first element is the median | ||
| of the three - avoiding pathological pivots. | ||
| TODO: Instead of middle element, chose one randomly. | ||
| */ | ||
| memswp( ( ( ( (size_t)( limit - base_ ) ) / size ) / 2 ) * size + base_, base_, size ); | ||
| if ( compar( i, j ) > 0 ) memswp( i, j, size ); | ||
| if ( compar( base_, j ) > 0 ) memswp( base_, j, size ); | ||
| if ( compar( i, base_ ) > 0 ) memswp( i, base_, size ); | ||
| /* Now we have the median for pivot element, entering main Quicksort. */ | ||
| for ( ;; ) | ||
| { | ||
| do | ||
| { | ||
| /* move i right until *i >= pivot */ | ||
| i += size; | ||
| } while ( compar( i, base_ ) < 0 ); | ||
| do | ||
| { | ||
| /* move j left until *j <= pivot */ | ||
| j -= size; | ||
| } while ( compar( j, base_ ) > 0 ); | ||
| if ( i > j ) | ||
| { | ||
| /* break loop if pointers crossed */ | ||
| break; | ||
| } | ||
| /* else swap elements, keep scanning */ | ||
| memswp( i, j, size ); | ||
| } | ||
| /* move pivot into correct place */ | ||
| memswp( base_, j, size ); | ||
| /* larger subfile base / limit to stack, sort smaller */ | ||
| if ( j - base_ > limit - i ) | ||
| { | ||
| /* left is larger */ | ||
| PUSH( base_, j ); | ||
| base_ = i; | ||
| } | ||
| else | ||
| { | ||
| /* right is larger */ | ||
| PUSH( i, limit ); | ||
| limit = j; | ||
| } | ||
| } | ||
| else /* insertion sort for less than T elements */ | ||
| { | ||
| for ( j = base_, i = j + size; i < limit; j = i, i += size ) | ||
| { | ||
| for ( ; compar( j, j + size ) > 0; j -= size ) | ||
| { | ||
| memswp( j, j + size, size ); | ||
| if ( j == base_ ) | ||
| { | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| if ( stackptr != stack ) /* if any entries on stack */ | ||
| { | ||
| POP( base_, limit ); | ||
| } | ||
| else /* else stack empty, done */ | ||
| { | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| } |