GNU Compatibility: Implement qsort_r

This is a version of the qsort function allowing you to pass a "cookie" to the function.

Change-Id: I60c645213b9c9590e38b112634fcac1d7969b6d9
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2449
Reviewed-by: Adrien Destugues <[email protected]>

headers/compatibility/gnu/stdlib.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2020 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Isaac Turner, [email protected]
+ *		Jacob Secunda, [email protected]
+ */
+#ifndef _GNU_STDLIB_H_
+#define _GNU_STDLIB_H_
+
+
+#include_next <stdlib.h>
+
+
+#ifdef _GNU_SOURCE
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef int (*_compare_function_qsort_r)(const void*, const void*, void*);
+
+extern void qsort_r(void* base, size_t numElements, size_t sizeOfElement,
+	_compare_function_qsort_r, void* cookie);
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* _GNU_SOURCE */
+
+
+#endif /* _GNU_STDLIB_H_ */

src/libs/gnu/Jamfile

@@ -11,6 +11,7 @@ for architectureObject in [ MultiArchSubDirSetup ] {
 	on $(architectureObject) {
 		SharedLibrary [ MultiArchDefaultGristFiles libgnu.so ] :
 			memmem.c
+			qsort.c
 			xattr.cpp
 			;
 	}

src/libs/gnu/qsort.c

@@ -0,0 +1,210 @@
+/*
+ * Copyright 2020 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Isaac Turner, [email protected]
+ *		Jacob Secunda, [email protected]
+ */
+
+
+#include <stdlib.h>
+#include <string.h>
+
+
+#define SORT_R_SWAP(a, b, tmp) ((tmp) = (a), (a) = (b), (b) = (tmp))
+
+
+/* swap itemA and itemB */
+/* itemA and itemB must not be equal! */
+static inline void
+sort_r_swap(char* __restrict itemA, char* __restrict itemB,
+	size_t sizeOfElement)
+{
+	char tmp;
+	char* end = itemA + sizeOfElement;
+	for (; itemA < end; itemA++, itemB++)
+		SORT_R_SWAP(* itemA, * itemB, tmp);
+}
+
+
+/* swap itemA and itemB if itemA > itemB */
+/* itemA and itemB must not be equal! */
+static inline int
+sort_r_cmpswap(char* __restrict itemA, char* __restrict itemB,
+	size_t sizeOfElement, _compare_function_qsort_r cmpFunc, void* cookie)
+{
+	if (cmpFunc(itemA, itemB, cookie) > 0) {
+		sort_r_swap(itemA, itemB, sizeOfElement);
+		return 1;
+	}
+
+	return 0;
+}
+
+
+/*
+	Swap consecutive blocks of bytes of size na and nb starting at memory addr
+	ptr, with the smallest swap so that the blocks are in the opposite order.
+	Blocks may be internally re-ordered e.g.
+
+	  12345ab  ->   ab34512
+	  123abc   ->   abc123
+	  12abcde  ->   deabc12
+*/
+static inline void
+sort_r_swap_blocks(char* ptr, size_t numBytesA, size_t numBytesB)
+{
+	if (numBytesA > 0 && numBytesB > 0) {
+		if (numBytesA > numBytesB)
+			sort_r_swap(ptr, ptr + numBytesA, numBytesB);
+		else
+			sort_r_swap(ptr, ptr + numBytesB, numBytesA);
+	}
+}
+
+
+/* Note: quicksort is not stable, equivalent values may be swapped */
+static inline void
+sort_r_simple(char* base, size_t numElements, size_t sizeOfElement,
+	_compare_function_qsort_r cmpFunc, void* cookie)
+{
+	char* end = base + (numElements * sizeOfElement);
+
+	if (numElements < 10) {
+		// Insertion sort for arbitrarily small inputs
+
+		char* pivIndexA;
+		char* pivIndexB;
+		for (pivIndexA = base + sizeOfElement; pivIndexA < end;
+			pivIndexA += sizeOfElement) {
+			pivIndexB = pivIndexA;
+			while (pivIndexB > base
+				&& sort_r_cmpswap(pivIndexB - sizeOfElement , pivIndexB,
+						sizeOfElement, cmpFunc, cookie)) {
+				pivIndexB -= sizeOfElement;
+			}
+		}
+	} else {
+		// Quicksort when numElements >= 10
+
+		int cmp;
+		char* nextPivCmpItem;	// pl
+		char* nextPivEqualsPos;	// ple
+		char* lastPivCmpItem;	// pr
+		char* lastPivEqualsPos;	// pre
+		char* pivot;
+		char* last = base + sizeOfElement * (numElements - 1);
+		char* tmp;
+
+		// Use median of second, middle and second-last items as pivot.
+		// First and last may have been swapped with pivot and therefore be
+		// extreme.
+		char* pivList[3];
+		pivList[0] = base + sizeOfElement;
+		pivList[1] = base + sizeOfElement * (numElements / 2);
+		pivList[2] = last - sizeOfElement;
+
+		if (cmpFunc(pivList[0], pivList[1], cookie) > 0)
+			SORT_R_SWAP(pivList[0], pivList[1], tmp);
+		if (cmpFunc(pivList[1], pivList[2], cookie) > 0) {
+			SORT_R_SWAP(pivList[1], pivList[2], tmp);
+			if (cmpFunc(pivList[0], pivList[1], cookie) > 0)
+				SORT_R_SWAP(pivList[0], pivList[1], tmp);
+		}
+
+		// Swap mid value (pivList[1]), and last element to put pivot as last
+		// element.
+		if (pivList[1] != last)
+			sort_r_swap(pivList[1], last, sizeOfElement);
+
+		//									   v- end (beyond the array)
+		//  EEEEEELLLLLLLLuuuuuuuuGGGGGGGEEEEEEEE.
+		//  ^- base  ^- ple  ^- pl   ^- pr  ^- pre ^- last (where the pivot is)
+
+		// Pivot comparison key:
+		//   E = equal, L = less than, u = unknown, G = greater than, E = equal
+		pivot = last;
+		nextPivEqualsPos = nextPivCmpItem = base;
+		lastPivEqualsPos = lastPivCmpItem = last;
+
+		// Strategy:
+		//	Loop into the list from the left and right at the same time to find:
+		//		- an item on the left that is greater than the pivot
+		//		- an item on the right that is less than the pivot
+		//	Once found, they are swapped and the loop continues.
+		//	Meanwhile items that are equal to the pivot are moved to the edges
+		//	of the array.
+		while (nextPivCmpItem < lastPivCmpItem) {
+			// Move left hand items which are equal to the pivot to the far
+			// left. Break when we find an item that is greater than the pivot.
+			for (; nextPivCmpItem < lastPivCmpItem;
+				nextPivCmpItem += sizeOfElement) {
+				cmp = cmpFunc(nextPivCmpItem, pivot, cookie);
+				if (cmp > 0)
+					break;
+				else if (cmp == 0) {
+					if (nextPivEqualsPos < nextPivCmpItem) {
+						sort_r_swap(nextPivEqualsPos, nextPivCmpItem,
+							sizeOfElement);
+					}
+					nextPivEqualsPos += sizeOfElement;
+				}
+			}
+
+			// break if last batch of left hand items were equal to pivot
+			if (nextPivCmpItem >= lastPivCmpItem)
+				break;
+
+			// Move right hand items which are equal to the pivot to the far
+			// right. Break when we find an item that is less than the pivot.
+			for (; nextPivCmpItem < lastPivCmpItem;) {
+				lastPivCmpItem -= sizeOfElement;
+					// Move right pointer onto an unprocessed item
+				cmp = cmpFunc(lastPivCmpItem, pivot, cookie);
+				if (cmp == 0) {
+					lastPivEqualsPos -= sizeOfElement;
+					if (lastPivCmpItem < lastPivEqualsPos) {
+						sort_r_swap(lastPivCmpItem, lastPivEqualsPos,
+							sizeOfElement);
+					}
+				} else if (cmp < 0) {
+					if (nextPivCmpItem < lastPivCmpItem) {
+						sort_r_swap(nextPivCmpItem, lastPivCmpItem,
+							sizeOfElement);
+					}
+					nextPivCmpItem += sizeOfElement;
+					break;
+				}
+			}
+		}
+
+		nextPivCmpItem = lastPivCmpItem;
+			// lastPivCmpItem may have gone below nextPivCmpItem
+
+		// Now we need to go from: EEELLLGGGGEEEE
+		//					 to: LLLEEEEEEEGGGG
+
+		// Pivot comparison key:
+		// E = equal, L = less than, u = unknown, G = greater than, E = equal
+		sort_r_swap_blocks(base, nextPivEqualsPos - base,
+			nextPivCmpItem - nextPivEqualsPos);
+		sort_r_swap_blocks(lastPivCmpItem, lastPivEqualsPos - lastPivCmpItem,
+			end - lastPivEqualsPos);
+
+		sort_r_simple(base, (nextPivCmpItem - nextPivEqualsPos) / sizeOfElement,
+			sizeOfElement, cmpFunc, cookie);
+		sort_r_simple(end - (lastPivEqualsPos - lastPivCmpItem),
+			(lastPivEqualsPos - lastPivCmpItem) / sizeOfElement, sizeOfElement,
+			cmpFunc, cookie);
+	}
+}
+
+
+inline void
+qsort_r(void* base, size_t numElements, size_t sizeOfElement,
+	_compare_function_qsort_r cmpFunc, void* cookie)
+{
+	sort_r_simple((char*)base, numElements, sizeOfElement,
+		cmpFunc, cookie);
+}