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![Jeff Hostetler](/assets/img/avatar_default.png)
This is to address concerns raised by ThreadSanitizer on the mailing list
about threaded unprotected R/W access to map.size with my previous "disallow
rehash" change (0607e10009
).
See:
https://public-inbox.org/git/adb37b70139fd1e2bac18bfd22c8b96683ae18eb.1502780344.git.martin.agren@gmail.com/
Add API to hashmap to disable item counting and thus automatic rehashing.
Also include API to later re-enable them.
When item counting is disabled, the map.size field is invalid. So to
prevent accidents, the field has been renamed and an accessor function
hashmap_get_size() has been added. All direct references to this
field have been been updated. And the name of the field changed
to map.private_size to communicate this.
Here is the relevant output from ThreadSanitizer showing the problem:
WARNING: ThreadSanitizer: data race (pid=10554)
Read of size 4 at 0x00000082d488 by thread T2 (mutexes: write M16):
#0 hashmap_add hashmap.c:209
#1 hash_dir_entry_with_parent_and_prefix name-hash.c:302
#2 handle_range_dir name-hash.c:347
#3 handle_range_1 name-hash.c:415
#4 lazy_dir_thread_proc name-hash.c:471
#5 <null> <null>
Previous write of size 4 at 0x00000082d488 by thread T1 (mutexes: write M31):
#0 hashmap_add hashmap.c:209
#1 hash_dir_entry_with_parent_and_prefix name-hash.c:302
#2 handle_range_dir name-hash.c:347
#3 handle_range_1 name-hash.c:415
#4 handle_range_dir name-hash.c:380
#5 handle_range_1 name-hash.c:415
#6 lazy_dir_thread_proc name-hash.c:471
#7 <null> <null>
Martin gives instructions for running TSan on test t3008 in this post:
https://public-inbox.org/git/CAN0heSoJDL9pWELD6ciLTmWf-a=oyxe4EXXOmCKvsG5MSuzxsA@mail.gmail.com/
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
269 lines
6.2 KiB
C
269 lines
6.2 KiB
C
#include "git-compat-util.h"
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#include "hashmap.h"
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struct test_entry
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{
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struct hashmap_entry ent;
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/* key and value as two \0-terminated strings */
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char key[FLEX_ARRAY];
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};
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static const char *get_value(const struct test_entry *e)
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{
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return e->key + strlen(e->key) + 1;
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}
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static int test_entry_cmp(const void *cmp_data,
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const void *entry,
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const void *entry_or_key,
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const void *keydata)
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{
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const int ignore_case = cmp_data ? *((int *)cmp_data) : 0;
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const struct test_entry *e1 = entry;
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const struct test_entry *e2 = entry_or_key;
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const char *key = keydata;
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if (ignore_case)
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return strcasecmp(e1->key, key ? key : e2->key);
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else
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return strcmp(e1->key, key ? key : e2->key);
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}
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static struct test_entry *alloc_test_entry(int hash, char *key, int klen,
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char *value, int vlen)
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{
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struct test_entry *entry = malloc(sizeof(struct test_entry) + klen
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+ vlen + 2);
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hashmap_entry_init(entry, hash);
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memcpy(entry->key, key, klen + 1);
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memcpy(entry->key + klen + 1, value, vlen + 1);
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return entry;
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}
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#define HASH_METHOD_FNV 0
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#define HASH_METHOD_I 1
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#define HASH_METHOD_IDIV10 2
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#define HASH_METHOD_0 3
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#define HASH_METHOD_X2 4
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#define TEST_SPARSE 8
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#define TEST_ADD 16
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#define TEST_SIZE 100000
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static unsigned int hash(unsigned int method, unsigned int i, const char *key)
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{
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unsigned int hash = 0;
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switch (method & 3)
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{
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case HASH_METHOD_FNV:
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hash = strhash(key);
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break;
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case HASH_METHOD_I:
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hash = i;
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break;
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case HASH_METHOD_IDIV10:
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hash = i / 10;
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break;
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case HASH_METHOD_0:
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hash = 0;
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break;
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}
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if (method & HASH_METHOD_X2)
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hash = 2 * hash;
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return hash;
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}
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/*
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* Test performance of hashmap.[ch]
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* Usage: time echo "perfhashmap method rounds" | test-hashmap
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*/
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static void perf_hashmap(unsigned int method, unsigned int rounds)
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{
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struct hashmap map;
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char buf[16];
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struct test_entry **entries;
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unsigned int *hashes;
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unsigned int i, j;
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entries = malloc(TEST_SIZE * sizeof(struct test_entry *));
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hashes = malloc(TEST_SIZE * sizeof(int));
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for (i = 0; i < TEST_SIZE; i++) {
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snprintf(buf, sizeof(buf), "%i", i);
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entries[i] = alloc_test_entry(0, buf, strlen(buf), "", 0);
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hashes[i] = hash(method, i, entries[i]->key);
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}
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if (method & TEST_ADD) {
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/* test adding to the map */
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for (j = 0; j < rounds; j++) {
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hashmap_init(&map, test_entry_cmp, NULL, 0);
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/* add entries */
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for (i = 0; i < TEST_SIZE; i++) {
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hashmap_entry_init(entries[i], hashes[i]);
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hashmap_add(&map, entries[i]);
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}
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hashmap_free(&map, 0);
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}
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} else {
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/* test map lookups */
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hashmap_init(&map, test_entry_cmp, NULL, 0);
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/* fill the map (sparsely if specified) */
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j = (method & TEST_SPARSE) ? TEST_SIZE / 10 : TEST_SIZE;
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for (i = 0; i < j; i++) {
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hashmap_entry_init(entries[i], hashes[i]);
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hashmap_add(&map, entries[i]);
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}
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for (j = 0; j < rounds; j++) {
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for (i = 0; i < TEST_SIZE; i++) {
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hashmap_get_from_hash(&map, hashes[i],
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entries[i]->key);
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}
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}
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hashmap_free(&map, 0);
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}
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}
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#define DELIM " \t\r\n"
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/*
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* Read stdin line by line and print result of commands to stdout:
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*
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* hash key -> strhash(key) memhash(key) strihash(key) memihash(key)
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* put key value -> NULL / old value
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* get key -> NULL / value
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* remove key -> NULL / old value
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* iterate -> key1 value1\nkey2 value2\n...
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* size -> tablesize numentries
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*
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* perfhashmap method rounds -> test hashmap.[ch] performance
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*/
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int cmd_main(int argc, const char **argv)
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{
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char line[1024];
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struct hashmap map;
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int icase;
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/* init hash map */
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icase = argc > 1 && !strcmp("ignorecase", argv[1]);
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hashmap_init(&map, test_entry_cmp, &icase, 0);
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/* process commands from stdin */
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while (fgets(line, sizeof(line), stdin)) {
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char *cmd, *p1 = NULL, *p2 = NULL;
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int l1 = 0, l2 = 0, hash = 0;
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struct test_entry *entry;
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/* break line into command and up to two parameters */
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cmd = strtok(line, DELIM);
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/* ignore empty lines */
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if (!cmd || *cmd == '#')
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continue;
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p1 = strtok(NULL, DELIM);
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if (p1) {
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l1 = strlen(p1);
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hash = icase ? strihash(p1) : strhash(p1);
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p2 = strtok(NULL, DELIM);
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if (p2)
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l2 = strlen(p2);
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}
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if (!strcmp("hash", cmd) && l1) {
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/* print results of different hash functions */
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printf("%u %u %u %u\n", strhash(p1), memhash(p1, l1),
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strihash(p1), memihash(p1, l1));
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} else if (!strcmp("add", cmd) && l1 && l2) {
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/* create entry with key = p1, value = p2 */
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entry = alloc_test_entry(hash, p1, l1, p2, l2);
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/* add to hashmap */
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hashmap_add(&map, entry);
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} else if (!strcmp("put", cmd) && l1 && l2) {
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/* create entry with key = p1, value = p2 */
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entry = alloc_test_entry(hash, p1, l1, p2, l2);
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/* add / replace entry */
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entry = hashmap_put(&map, entry);
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/* print and free replaced entry, if any */
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puts(entry ? get_value(entry) : "NULL");
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free(entry);
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} else if (!strcmp("get", cmd) && l1) {
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/* lookup entry in hashmap */
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entry = hashmap_get_from_hash(&map, hash, p1);
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/* print result */
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if (!entry)
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puts("NULL");
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while (entry) {
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puts(get_value(entry));
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entry = hashmap_get_next(&map, entry);
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}
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} else if (!strcmp("remove", cmd) && l1) {
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/* setup static key */
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struct hashmap_entry key;
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hashmap_entry_init(&key, hash);
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/* remove entry from hashmap */
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entry = hashmap_remove(&map, &key, p1);
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/* print result and free entry*/
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puts(entry ? get_value(entry) : "NULL");
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free(entry);
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} else if (!strcmp("iterate", cmd)) {
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struct hashmap_iter iter;
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hashmap_iter_init(&map, &iter);
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while ((entry = hashmap_iter_next(&iter)))
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printf("%s %s\n", entry->key, get_value(entry));
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} else if (!strcmp("size", cmd)) {
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/* print table sizes */
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printf("%u %u\n", map.tablesize,
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hashmap_get_size(&map));
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} else if (!strcmp("intern", cmd) && l1) {
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/* test that strintern works */
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const char *i1 = strintern(p1);
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const char *i2 = strintern(p1);
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if (strcmp(i1, p1))
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printf("strintern(%s) returns %s\n", p1, i1);
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else if (i1 == p1)
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printf("strintern(%s) returns input pointer\n", p1);
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else if (i1 != i2)
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printf("strintern(%s) != strintern(%s)", i1, i2);
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else
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printf("%s\n", i1);
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} else if (!strcmp("perfhashmap", cmd) && l1 && l2) {
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perf_hashmap(atoi(p1), atoi(p2));
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} else {
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printf("Unknown command %s\n", cmd);
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}
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}
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hashmap_free(&map, 1);
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return 0;
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}
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