summaryrefslogtreecommitdiff
path: root/deps/icu-small/source/common/uarrsort.cpp
blob: 60905821649db910b08e243426594485f9aee4fa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
// © 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 "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(max_align_t) - 1) / sizeof(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<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<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==NULL || U_FAILURE(*pErrorCode)) {
        return;
    }
    if((length>0 && array==NULL) || length<0 || itemSize<=0 || cmp==NULL) {
        *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);
    }
}