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diff --git a/intl/icu/source/common/uarrsort.cpp b/intl/icu/source/common/uarrsort.cpp
new file mode 100644
index 0000000000..f9daa4b30f
--- /dev/null
+++ b/intl/icu/source/common/uarrsort.cpp
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+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+*******************************************************************************
+*
+*   Copyright (C) 2003-2013, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  uarrsort.c
+*   encoding:   UTF-8
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2003aug04
+*   created by: Markus W. Scherer
+*
+*   Internal function for sorting arrays.
+*/
+
+#include <cstddef>
+
+#include "unicode/utypes.h"
+#include "cmemory.h"
+#include "uarrsort.h"
+
+enum {
+    /**
+     * "from Knuth"
+     *
+     * A binary search over 8 items performs 4 comparisons:
+     * log2(8)=3 to subdivide, +1 to check for equality.
+     * A linear search over 8 items on average also performs 4 comparisons.
+     */
+    MIN_QSORT=9,
+    STACK_ITEM_SIZE=200
+};
+
+static constexpr int32_t sizeInMaxAlignTs(int32_t sizeInBytes) {
+    return (sizeInBytes + sizeof(std::max_align_t) - 1) / sizeof(std::max_align_t);
+}
+
+/* UComparator convenience implementations ---------------------------------- */
+
+U_CAPI int32_t U_EXPORT2
+uprv_uint16Comparator(const void *context, const void *left, const void *right) {
+    (void)context;
+    return (int32_t)*(const uint16_t *)left - (int32_t)*(const uint16_t *)right;
+}
+
+U_CAPI int32_t U_EXPORT2
+uprv_int32Comparator(const void *context, const void *left, const void *right) {
+    (void)context;
+    return *(const int32_t *)left - *(const int32_t *)right;
+}
+
+U_CAPI int32_t U_EXPORT2
+uprv_uint32Comparator(const void *context, const void *left, const void *right) {
+    (void)context;
+    uint32_t l=*(const uint32_t *)left, r=*(const uint32_t *)right;
+
+    /* compare directly because (l-r) would overflow the int32_t result */
+    if(l<r) {
+        return -1;
+    } else if(l==r) {
+        return 0;
+    } else /* l>r */ {
+        return 1;
+    }
+}
+
+/* Insertion sort using binary search --------------------------------------- */
+
+U_CAPI int32_t U_EXPORT2
+uprv_stableBinarySearch(char *array, int32_t limit, void *item, int32_t itemSize,
+                        UComparator *cmp, const void *context) {
+    int32_t start=0;
+    UBool found=false;
+
+    /* Binary search until we get down to a tiny sub-array. */
+    while((limit-start)>=MIN_QSORT) {
+        int32_t i=(start+limit)/2;
+        int32_t diff=cmp(context, item, array+i*itemSize);
+        if(diff==0) {
+            /*
+             * Found the item. We look for the *last* occurrence of such
+             * an item, for stable sorting.
+             * If we knew that there will be only few equal items,
+             * we could break now and enter the linear search.
+             * However, if there are many equal items, then it should be
+             * faster to continue with the binary search.
+             * It seems likely that we either have all unique items
+             * (where found will never become true in the insertion sort)
+             * or potentially many duplicates.
+             */
+            found=true;
+            start=i+1;
+        } else if(diff<0) {
+            limit=i;
+        } else {
+            start=i;
+        }
+    }
+
+    /* Linear search over the remaining tiny sub-array. */
+    while(start<limit) {
+        int32_t diff=cmp(context, item, array+start*itemSize);
+        if(diff==0) {
+            found=true;
+        } else if(diff<0) {
+            break;
+        }
+        ++start;
+    }
+    return found ? (start-1) : ~start;
+}
+
+static void
+doInsertionSort(char *array, int32_t length, int32_t itemSize,
+                UComparator *cmp, const void *context, void *pv) {
+    int32_t j;
+
+    for(j=1; j<length; ++j) {
+        char *item=array+j*itemSize;
+        int32_t insertionPoint=uprv_stableBinarySearch(array, j, item, itemSize, cmp, context);
+        if(insertionPoint<0) {
+            insertionPoint=~insertionPoint;
+        } else {
+            ++insertionPoint;  /* one past the last equal item */
+        }
+        if(insertionPoint<j) {
+            char *dest=array+insertionPoint*itemSize;
+            uprv_memcpy(pv, item, itemSize);  /* v=array[j] */
+            uprv_memmove(dest+itemSize, dest, (j-insertionPoint)*(size_t)itemSize);
+            uprv_memcpy(dest, pv, itemSize);  /* array[insertionPoint]=v */
+        }
+    }
+}
+
+static void
+insertionSort(char *array, int32_t length, int32_t itemSize,
+              UComparator *cmp, const void *context, UErrorCode *pErrorCode) {
+
+    icu::MaybeStackArray<std::max_align_t, sizeInMaxAlignTs(STACK_ITEM_SIZE)> v;
+    if (sizeInMaxAlignTs(itemSize) > v.getCapacity() &&
+            v.resize(sizeInMaxAlignTs(itemSize)) == nullptr) {
+        *pErrorCode = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+
+    doInsertionSort(array, length, itemSize, cmp, context, v.getAlias());
+}
+
+/* QuickSort ---------------------------------------------------------------- */
+
+/*
+ * This implementation is semi-recursive:
+ * It recurses for the smaller sub-array to shorten the recursion depth,
+ * and loops for the larger sub-array.
+ *
+ * Loosely after QuickSort algorithms in
+ * Niklaus Wirth
+ * Algorithmen und Datenstrukturen mit Modula-2
+ * B.G. Teubner Stuttgart
+ * 4. Auflage 1986
+ * ISBN 3-519-02260-5
+ */
+static void
+subQuickSort(char *array, int32_t start, int32_t limit, int32_t itemSize,
+             UComparator *cmp, const void *context,
+             void *px, void *pw) {
+    int32_t left, right;
+
+    /* start and left are inclusive, limit and right are exclusive */
+    do {
+        if((start+MIN_QSORT)>=limit) {
+            doInsertionSort(array+start*itemSize, limit-start, itemSize, cmp, context, px);
+            break;
+        }
+
+        left=start;
+        right=limit;
+
+        /* x=array[middle] */
+        uprv_memcpy(px, array+(size_t)((start+limit)/2)*itemSize, itemSize);
+
+        do {
+            while(/* array[left]<x */
+                  cmp(context, array+left*itemSize, px)<0
+            ) {
+                ++left;
+            }
+            while(/* x<array[right-1] */
+                  cmp(context, px, array+(right-1)*itemSize)<0
+            ) {
+                --right;
+            }
+
+            /* swap array[left] and array[right-1] via w; ++left; --right */
+            if(left<right) {
+                --right;
+
+                if(left<right) {
+                    uprv_memcpy(pw, array+(size_t)left*itemSize, itemSize);
+                    uprv_memcpy(array+(size_t)left*itemSize, array+(size_t)right*itemSize, itemSize);
+                    uprv_memcpy(array+(size_t)right*itemSize, pw, itemSize);
+                }
+
+                ++left;
+            }
+        } while(left<right);
+
+        /* sort sub-arrays */
+        if((right-start)<(limit-left)) {
+            /* sort [start..right[ */
+            if(start<(right-1)) {
+                subQuickSort(array, start, right, itemSize, cmp, context, px, pw);
+            }
+
+            /* sort [left..limit[ */
+            start=left;
+        } else {
+            /* sort [left..limit[ */
+            if(left<(limit-1)) {
+                subQuickSort(array, left, limit, itemSize, cmp, context, px, pw);
+            }
+
+            /* sort [start..right[ */
+            limit=right;
+        }
+    } while(start<(limit-1));
+}
+
+static void
+quickSort(char *array, int32_t length, int32_t itemSize,
+            UComparator *cmp, const void *context, UErrorCode *pErrorCode) {
+    /* allocate two intermediate item variables (x and w) */
+    icu::MaybeStackArray<std::max_align_t, sizeInMaxAlignTs(STACK_ITEM_SIZE) * 2> xw;
+    if(sizeInMaxAlignTs(itemSize)*2 > xw.getCapacity() &&
+            xw.resize(sizeInMaxAlignTs(itemSize) * 2) == nullptr) {
+        *pErrorCode=U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+
+    subQuickSort(array, 0, length, itemSize, cmp, context,
+                 xw.getAlias(), xw.getAlias() + sizeInMaxAlignTs(itemSize));
+}
+
+/* uprv_sortArray() API ----------------------------------------------------- */
+
+/*
+ * Check arguments, select an appropriate implementation,
+ * cast the array to char * so that array+i*itemSize works.
+ */
+U_CAPI void U_EXPORT2
+uprv_sortArray(void *array, int32_t length, int32_t itemSize,
+               UComparator *cmp, const void *context,
+               UBool sortStable, UErrorCode *pErrorCode) {
+    if(pErrorCode==nullptr || U_FAILURE(*pErrorCode)) {
+        return;
+    }
+    if((length>0 && array==nullptr) || length<0 || itemSize<=0 || cmp==nullptr) {
+        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
+        return;
+    }
+
+    if(length<=1) {
+        return;
+    } else if(length<MIN_QSORT || sortStable) {
+        insertionSort((char *)array, length, itemSize, cmp, context, pErrorCode);
+    } else {
+        quickSort((char *)array, length, itemSize, cmp, context, pErrorCode);
+    }
+}