summaryrefslogtreecommitdiffstats
path: root/libnetdata/string/string.c
blob: d2db8aab43a790f74f142ea5f99a65d7017555a3 (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
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
// SPDX-License-Identifier: GPL-3.0-or-later

#include "../libnetdata.h"
#include <Judy.h>

typedef int32_t REFCOUNT;

// ----------------------------------------------------------------------------
// STRING implementation - dedup all STRING

struct netdata_string {
    uint32_t length;    // the string length including the terminating '\0'

    REFCOUNT refcount;  // how many times this string is used
                        // We use a signed number to be able to detect duplicate frees of a string.
                        // If at any point this goes below zero, we have a duplicate free.

    const char str[];   // the string itself, is appended to this structure
};

static struct string_hashtable {
    Pvoid_t JudyHSArray;        // the Judy array - hashtable
    netdata_rwlock_t rwlock;    // the R/W lock to protect the Judy array

    long int entries;           // the number of entries in the index
    long int active_references; // the number of active references alive
    long int memory;            // the memory used, without the JudyHS index

    size_t inserts;             // the number of successful inserts to the index
    size_t deletes;             // the number of successful deleted from the index
    size_t searches;            // the number of successful searches in the index
    size_t duplications;        // when a string is referenced
    size_t releases;            // when a string is unreferenced

#ifdef NETDATA_INTERNAL_CHECKS
    // internal statistics
    size_t found_deleted_on_search;
    size_t found_available_on_search;
    size_t found_deleted_on_insert;
    size_t found_available_on_insert;
    size_t spins;
#endif

} string_base = {
    .JudyHSArray = NULL,
    .rwlock = NETDATA_RWLOCK_INITIALIZER,
};

#ifdef NETDATA_INTERNAL_CHECKS
#define string_internal_stats_add(var, val) __atomic_add_fetch(&string_base.var, val, __ATOMIC_RELAXED)
#else
#define string_internal_stats_add(var, val) do {;} while(0)
#endif

#define string_stats_atomic_increment(var) __atomic_add_fetch(&string_base.var, 1, __ATOMIC_RELAXED)
#define string_stats_atomic_decrement(var) __atomic_sub_fetch(&string_base.var, 1, __ATOMIC_RELAXED)

void string_statistics(size_t *inserts, size_t *deletes, size_t *searches, size_t *entries, size_t *references, size_t *memory, size_t *duplications, size_t *releases) {
    *inserts = string_base.inserts;
    *deletes = string_base.deletes;
    *searches = string_base.searches;
    *entries = (size_t)string_base.entries;
    *references = (size_t)string_base.active_references;
    *memory = (size_t)string_base.memory;
    *duplications = string_base.duplications;
    *releases = string_base.releases;
}

#define string_entry_acquire(se) __atomic_add_fetch(&((se)->refcount), 1, __ATOMIC_SEQ_CST);
#define string_entry_release(se) __atomic_sub_fetch(&((se)->refcount), 1, __ATOMIC_SEQ_CST);

static inline bool string_entry_check_and_acquire(STRING *se) {
    REFCOUNT expected, desired, count = 0;

    expected = __atomic_load_n(&se->refcount, __ATOMIC_SEQ_CST);

    do {
        count++;

        if(expected <= 0) {
            // We cannot use this.
            // The reference counter reached value zero,
            // so another thread is deleting this.
            string_internal_stats_add(spins, count - 1);
            return false;
        }

        desired = expected + 1;

    } while(!__atomic_compare_exchange_n(&se->refcount, &expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST));

    string_internal_stats_add(spins, count - 1);

    // statistics
    // string_base.active_references is altered at the in string_strdupz() and string_freez()
    string_stats_atomic_increment(duplications);

    return true;
}

STRING *string_dup(STRING *string) {
    if(unlikely(!string)) return NULL;

#ifdef NETDATA_INTERNAL_CHECKS
    if(unlikely(__atomic_load_n(&string->refcount, __ATOMIC_SEQ_CST) <= 0))
        fatal("STRING: tried to %s() a string that is freed (it has %d references).", __FUNCTION__, string->refcount);
#endif

    string_entry_acquire(string);

    // statistics
    string_stats_atomic_increment(active_references);
    string_stats_atomic_increment(duplications);

    return string;
}

// Search the index and return an ACQUIRED string entry, or NULL
static inline STRING *string_index_search(const char *str, size_t length) {
    STRING *string;

    // Find the string in the index
    // With a read-lock so that multiple readers can use the index concurrently.

    netdata_rwlock_rdlock(&string_base.rwlock);

    Pvoid_t *Rc;
    Rc = JudyHSGet(string_base.JudyHSArray, (void *)str, length);
    if(likely(Rc)) {
        // found in the hash table
        string = *Rc;

        if(string_entry_check_and_acquire(string)) {
            // we can use this entry
            string_internal_stats_add(found_available_on_search, 1);
        }
        else {
            // this entry is about to be deleted by another thread
            // do not touch it, let it go...
            string = NULL;
            string_internal_stats_add(found_deleted_on_search, 1);
        }
    }
    else {
        // not found in the hash table
        string = NULL;
    }

    string_stats_atomic_increment(searches);
    netdata_rwlock_unlock(&string_base.rwlock);

    return string;
}

// Insert a string to the index and return an ACQUIRED string entry,
// or NULL if the call needs to be retried (a deleted entry with the same key is still in the index)
// The returned entry is ACQUIRED, and it can either be:
//   1. a new item inserted, or
//   2. an item found in the index that is not currently deleted
static inline STRING *string_index_insert(const char *str, size_t length) {
    STRING *string;

    netdata_rwlock_wrlock(&string_base.rwlock);

    STRING **ptr;
    {
        JError_t J_Error;
        Pvoid_t *Rc = JudyHSIns(&string_base.JudyHSArray, (void *)str, length, &J_Error);
        if (unlikely(Rc == PJERR)) {
            fatal(
                "STRING: Cannot insert entry with name '%s' to JudyHS, JU_ERRNO_* == %u, ID == %d",
                str,
                JU_ERRNO(&J_Error),
                JU_ERRID(&J_Error));
        }
        ptr = (STRING **)Rc;
    }

    if (likely(*ptr == 0)) {
        // a new item added to the index
        size_t mem_size = sizeof(STRING) + length;
        string = mallocz(mem_size);
        strcpy((char *)string->str, str);
        string->length = length;
        string->refcount = 1;
        *ptr = string;
        string_base.inserts++;
        string_base.entries++;
        string_base.memory += (long)mem_size;
    }
    else {
        // the item is already in the index
        string = *ptr;

        if(string_entry_check_and_acquire(string)) {
            // we can use this entry
            string_internal_stats_add(found_available_on_insert, 1);
        }
        else {
            // this entry is about to be deleted by another thread
            // do not touch it, let it go...
            string = NULL;
            string_internal_stats_add(found_deleted_on_insert, 1);
        }

        string_stats_atomic_increment(searches);
    }

    netdata_rwlock_unlock(&string_base.rwlock);
    return string;
}

// delete an entry from the index
static inline void string_index_delete(STRING *string) {
    netdata_rwlock_wrlock(&string_base.rwlock);

#ifdef NETDATA_INTERNAL_CHECKS
    if(unlikely(__atomic_load_n(&string->refcount, __ATOMIC_SEQ_CST) != 0))
        fatal("STRING: tried to delete a string at %s() that is already freed (it has %d references).", __FUNCTION__, string->refcount);
#endif

    bool deleted = false;

    if (likely(string_base.JudyHSArray)) {
        JError_t J_Error;
        int ret = JudyHSDel(&string_base.JudyHSArray, (void *)string->str, string->length, &J_Error);
        if (unlikely(ret == JERR)) {
            error(
                "STRING: Cannot delete entry with name '%s' from JudyHS, JU_ERRNO_* == %u, ID == %d",
                string->str,
                JU_ERRNO(&J_Error),
                JU_ERRID(&J_Error));
        } else
            deleted = true;
    }

    if (unlikely(!deleted))
        error("STRING: tried to delete '%s' that is not in the index. Ignoring it.", string->str);
    else {
        size_t mem_size = sizeof(STRING) + string->length;
        string_base.deletes++;
        string_base.entries--;
        string_base.memory -= (long)mem_size;
        freez(string);
    }

    netdata_rwlock_unlock(&string_base.rwlock);
}

STRING *string_strdupz(const char *str) {
    if(unlikely(!str || !*str)) return NULL;

    size_t length = strlen(str) + 1;
    STRING *string = string_index_search(str, length);

    while(!string) {
        // The search above did not find anything,
        // We loop here, because during insert we may find an entry that is being deleted by another thread.
        // So, we have to let it go and retry to insert it again.

        string = string_index_insert(str, length);
    }

    // statistics
    string_stats_atomic_increment(active_references);

    return string;
}

void string_freez(STRING *string) {
    if(unlikely(!string)) return;

    REFCOUNT refcount = string_entry_release(string);

#ifdef NETDATA_INTERNAL_CHECKS
    if(unlikely(refcount < 0))
        fatal("STRING: tried to %s() a string that is already freed (it has %d references).", __FUNCTION__, string->refcount);
#endif

    if(unlikely(refcount == 0))
        string_index_delete(string);

    // statistics
    string_stats_atomic_decrement(active_references);
    string_stats_atomic_increment(releases);
}

size_t string_strlen(STRING *string) {
    if(unlikely(!string)) return 0;
    return string->length - 1;
}

const char *string2str(STRING *string) {
    if(unlikely(!string)) return "";
    return string->str;
}

STRING *string_2way_merge(STRING *a, STRING *b) {
    static STRING *X = NULL;

    if(unlikely(!X)) {
        X = string_strdupz("[x]");
    }

    if(unlikely(a == b)) return string_dup(a);
    if(unlikely(a == X)) return string_dup(a);
    if(unlikely(b == X)) return string_dup(b);
    if(unlikely(!a)) return string_dup(X);
    if(unlikely(!b)) return string_dup(X);

    size_t alen = string_strlen(a);
    size_t blen = string_strlen(b);
    size_t length = alen + blen + string_strlen(X) + 1;
    char buf1[length + 1], buf2[length + 1], *dst1;
    const char *s1, *s2;

    s1 = string2str(a);
    s2 = string2str(b);
    dst1 = buf1;
    for( ; *s1 && *s2 && *s1 == *s2 ;s1++, s2++)
        *dst1++ = *s1;

    *dst1 = '\0';

    if(*s1 != '\0' || *s2 != '\0') {
        *dst1++ = '[';
        *dst1++ = 'x';
        *dst1++ = ']';

        s1 = &(string2str(a))[alen - 1];
        s2 = &(string2str(b))[blen - 1];
        char *dst2 = &buf2[length];
        *dst2 = '\0';
        for (; *s1 && *s2 && *s1 == *s2; s1--, s2--)
            *(--dst2) = *s1;

        strcpy(dst1, dst2);
    }

    return string_strdupz(buf1);
}

// ----------------------------------------------------------------------------
// STRING unit test

struct thread_unittest {
    int join;
    int dups;
};

static void *string_thread(void *arg) {
    struct thread_unittest *tu = arg;

    for(; 1 ;) {
        if(__atomic_load_n(&tu->join, __ATOMIC_RELAXED))
            break;

        STRING *s = string_strdupz("string thread checking 1234567890");

        for(int i = 0; i < tu->dups ; i++)
            string_dup(s);

        for(int i = 0; i < tu->dups ; i++)
            string_freez(s);

        string_freez(s);
    }

    return arg;
}

static char **string_unittest_generate_names(size_t entries) {
    char **names = mallocz(sizeof(char *) * entries);
    for(size_t i = 0; i < entries ;i++) {
        char buf[25 + 1] = "";
        snprintfz(buf, 25, "name.%zu.0123456789.%zu \t !@#$%%^&*(),./[]{}\\|~`", i, entries / 2 + i);
        names[i] = strdupz(buf);
    }
    return names;
}

static void string_unittest_free_char_pp(char **pp, size_t entries) {
    for(size_t i = 0; i < entries ;i++)
        freez(pp[i]);

    freez(pp);
}

int string_unittest(size_t entries) {
    size_t errors = 0;

    fprintf(stderr, "Generating %zu names and values...\n", entries);
    char **names = string_unittest_generate_names(entries);

    // check string
    {
        long int string_entries_starting = string_base.entries;

        fprintf(stderr, "\nChecking strings...\n");

        STRING *s1 = string_strdupz("hello unittest");
        STRING *s2 = string_strdupz("hello unittest");
        if(s1 != s2) {
            errors++;
            fprintf(stderr, "ERROR: duplicating strings are not deduplicated\n");
        }
        else
            fprintf(stderr, "OK: duplicating string are deduplicated\n");

        STRING *s3 = string_dup(s1);
        if(s3 != s1) {
            errors++;
            fprintf(stderr, "ERROR: cloning strings are not deduplicated\n");
        }
        else
            fprintf(stderr, "OK: cloning string are deduplicated\n");

        if(s1->refcount != 3) {
            errors++;
            fprintf(stderr, "ERROR: string refcount is not 3\n");
        }
        else
            fprintf(stderr, "OK: string refcount is 3\n");

        STRING *s4 = string_strdupz("world unittest");
        if(s4 == s1) {
            errors++;
            fprintf(stderr, "ERROR: string is sharing pointers on different strings\n");
        }
        else
            fprintf(stderr, "OK: string is properly handling different strings\n");

        usec_t start_ut, end_ut;
        STRING **strings = mallocz(entries * sizeof(STRING *));

        start_ut = now_realtime_usec();
        for(size_t i = 0; i < entries ;i++) {
            strings[i] = string_strdupz(names[i]);
        }
        end_ut = now_realtime_usec();
        fprintf(stderr, "Created %zu strings in %llu usecs\n", entries, end_ut - start_ut);

        start_ut = now_realtime_usec();
        for(size_t i = 0; i < entries ;i++) {
            strings[i] = string_dup(strings[i]);
        }
        end_ut = now_realtime_usec();
        fprintf(stderr, "Cloned %zu strings in %llu usecs\n", entries, end_ut - start_ut);

        start_ut = now_realtime_usec();
        for(size_t i = 0; i < entries ;i++) {
            strings[i] = string_strdupz(string2str(strings[i]));
        }
        end_ut = now_realtime_usec();
        fprintf(stderr, "Found %zu existing strings in %llu usecs\n", entries, end_ut - start_ut);

        start_ut = now_realtime_usec();
        for(size_t i = 0; i < entries ;i++) {
            string_freez(strings[i]);
        }
        end_ut = now_realtime_usec();
        fprintf(stderr, "Released %zu referenced strings in %llu usecs\n", entries, end_ut - start_ut);

        start_ut = now_realtime_usec();
        for(size_t i = 0; i < entries ;i++) {
            string_freez(strings[i]);
        }
        end_ut = now_realtime_usec();
        fprintf(stderr, "Released (again) %zu referenced strings in %llu usecs\n", entries, end_ut - start_ut);

        start_ut = now_realtime_usec();
        for(size_t i = 0; i < entries ;i++) {
            string_freez(strings[i]);
        }
        end_ut = now_realtime_usec();
        fprintf(stderr, "Freed %zu strings in %llu usecs\n", entries, end_ut - start_ut);

        freez(strings);

        if(string_base.entries != string_entries_starting + 2) {
            errors++;
            fprintf(stderr, "ERROR: strings dictionary should have %ld items but it has %ld\n", string_entries_starting + 2, string_base.entries);
        }
        else
            fprintf(stderr, "OK: strings dictionary has 2 items\n");
    }

    // check 2-way merge
    {
        struct testcase {
            char *src1; char *src2; char *expected;
        } tests[] = {
            { "", "", ""},
            { "a", "", "[x]"},
            { "", "a", "[x]"},
            { "a", "a", "a"},
            { "abcd", "abcd", "abcd"},
            { "foo_cs", "bar_cs", "[x]_cs"},
            { "cp_UNIQUE_INFIX_cs", "cp_unique_infix_cs", "cp_[x]_cs"},
            { "cp_UNIQUE_INFIX_ci_unique_infix_cs", "cp_unique_infix_ci_UNIQUE_INFIX_cs", "cp_[x]_cs"},
            { "foo[1234]", "foo[4321]", "foo[[x]]"},
            { NULL, NULL, NULL },
        };

        for (struct testcase *tc = &tests[0]; tc->expected != NULL; tc++) {
            STRING *src1 = string_strdupz(tc->src1);
            STRING *src2 = string_strdupz(tc->src2);
            STRING *expected = string_strdupz(tc->expected);

            STRING *result = string_2way_merge(src1, src2);
            if (string_cmp(result, expected) != 0) {
                fprintf(stderr, "string_2way_merge(\"%s\", \"%s\") -> \"%s\" (expected=\"%s\")\n",
                        string2str(src1),
                        string2str(src2),
                        string2str(result),
                        string2str(expected));
                errors++;
            }

            string_freez(src1);
            string_freez(src2);
            string_freez(expected);
            string_freez(result);
        }
    }

    // threads testing of string
    {
        struct thread_unittest tu = {
            .dups = 1,
            .join = 0,
        };

#ifdef NETDATA_INTERNAL_CHECKS
        size_t ofound_deleted_on_search = string_base.found_deleted_on_search,
               ofound_available_on_search = string_base.found_available_on_search,
               ofound_deleted_on_insert = string_base.found_deleted_on_insert,
               ofound_available_on_insert = string_base.found_available_on_insert,
               ospins = string_base.spins;
#endif

        size_t oinserts, odeletes, osearches, oentries, oreferences, omemory, oduplications, oreleases;
        string_statistics(&oinserts, &odeletes, &osearches, &oentries, &oreferences, &omemory, &oduplications, &oreleases);

        time_t seconds_to_run = 5;
        int threads_to_create = 2;
        fprintf(
            stderr,
            "Checking string concurrency with %d threads for %lld seconds...\n",
            threads_to_create,
            (long long)seconds_to_run);
        // check string concurrency
        netdata_thread_t threads[threads_to_create];
        tu.join = 0;
        for (int i = 0; i < threads_to_create; i++) {
            char buf[100 + 1];
            snprintf(buf, 100, "string%d", i);
            netdata_thread_create(
                &threads[i], buf, NETDATA_THREAD_OPTION_DONT_LOG | NETDATA_THREAD_OPTION_JOINABLE, string_thread, &tu);
        }
        sleep_usec(seconds_to_run * USEC_PER_SEC);

        __atomic_store_n(&tu.join, 1, __ATOMIC_RELAXED);
        for (int i = 0; i < threads_to_create; i++) {
            void *retval;
            netdata_thread_join(threads[i], &retval);
        }

        size_t inserts, deletes, searches, sentries, references, memory, duplications, releases;
        string_statistics(&inserts, &deletes, &searches, &sentries, &references, &memory, &duplications, &releases);

        fprintf(stderr, "inserts %zu, deletes %zu, searches %zu, entries %zu, references %zu, memory %zu, duplications %zu, releases %zu\n",
                inserts - oinserts, deletes - odeletes, searches - osearches, sentries - oentries, references - oreferences, memory - omemory, duplications - oduplications, releases - oreleases);

#ifdef NETDATA_INTERNAL_CHECKS
        size_t found_deleted_on_search = string_base.found_deleted_on_search,
               found_available_on_search = string_base.found_available_on_search,
               found_deleted_on_insert = string_base.found_deleted_on_insert,
               found_available_on_insert = string_base.found_available_on_insert,
               spins = string_base.spins;

        fprintf(stderr, "on insert: %zu ok + %zu deleted\non search: %zu ok + %zu deleted\nspins: %zu\n",
                found_available_on_insert - ofound_available_on_insert,
                found_deleted_on_insert - ofound_deleted_on_insert,
                found_available_on_search - ofound_available_on_search,
                found_deleted_on_search - ofound_deleted_on_search,
                spins - ospins
        );
#endif
    }

    string_unittest_free_char_pp(names, entries);

    fprintf(stderr, "\n%zu errors found\n", errors);
    return  errors ? 1 : 0;
}