libavutil: add a merge sort.

compared to qsort this is slower but its stable and doesnt have a O(n^2) worst case

Michael Niedermayer committed 14 years ago

Commit f87dacb1 parent 096db651 file · +25 −0Browse files

Unified · Split

@@ -90,3 +90,28 @@ · 89 unmodified lines
90	90	}\
91	91	}\
92	92	}
	93	+
	94	+/**
	95	+ * Merge sort, this sort requires a temporary buffer and is stable, its worst
	96	+ * case time is O(n log n)
	97	+ * @param p must be a lvalue pointer, this function may exchange it with tmp
	98	+ * @param tmp must be a lvalue pointer, this function may exchange it with p
	99	+ */
	100	+#define AV_MSORT(p, tmp, num, type, cmp) {\
	101	+ unsigned i, j, step;\
	102	+ for(step=1; step<(num); step+=step){\
	103	+ for(i=0; i<(num); i+=2*step){\
	104	+ unsigned a[2] = {i, i+step};\
	105	+ unsigned end = FFMIN(i+2*step, (num));\
	106	+ for(j=i; a[0]<i+step && a[1]<end; j++){\
	107	+ int idx= cmp(p+a[0], p+a[1]) < 0;\
	108	+ tmp[j] = p[ a[idx]++ ];\
	109	+ }\
	110	+ if(a[0]>=i+step) a[0] = a[1];\
	111	+ for(; j<end; j++){\
	112	+ tmp[j] = p[ a[0]++ ];\
	113	+ }\
	114	+ }\
	115	+ FFSWAP(type*, p, tmp);\
	116	+ }\
	117	+}

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