FB: Add range iteration support.

This commit is contained in:
David Goldblatt 2020-07-27 12:26:06 -07:00 committed by David Goldblatt
parent ceee823519
commit ddb8dc4ad0
2 changed files with 298 additions and 1 deletions

View File

@ -219,4 +219,69 @@ fb_fls(fb_group_t *fb, size_t nbits, size_t max_bit) {
/* forward */ false);
}
/* Returns whether or not we found a range. */
JEMALLOC_ALWAYS_INLINE bool
fb_iter_range_impl(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
size_t *r_len, bool val, bool forward) {
assert(start < nbits);
ssize_t next_range_begin = fb_find_impl(fb, nbits, start, val, forward);
if ((forward && next_range_begin == (ssize_t)nbits)
|| (!forward && next_range_begin == (ssize_t)-1)) {
return false;
}
/* Half open range; the set bits are [begin, end). */
ssize_t next_range_end = fb_find_impl(fb, nbits, next_range_begin, !val,
forward);
if (forward) {
*r_begin = next_range_begin;
*r_len = next_range_end - next_range_begin;
} else {
*r_begin = next_range_end + 1;
*r_len = next_range_begin - next_range_end;
}
return true;
}
/*
* Used to iterate through ranges of set bits.
*
* Tries to find the next contiguous sequence of set bits with a first index >=
* start. If one exists, puts the earliest bit of the range in *r_begin, its
* length in *r_len, and returns true. Otherwise, returns false (without
* touching *r_begin or *r_end).
*/
static inline bool
fb_srange_iter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
size_t *r_len) {
return fb_iter_range_impl(fb, nbits, start, r_begin, r_len,
/* val */ true, /* forward */ true);
}
/*
* The same as fb_srange_iter, but searches backwards from start rather than
* forwards. (The position returned is still the earliest bit in the range).
*/
static inline bool
fb_srange_riter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
size_t *r_len) {
return fb_iter_range_impl(fb, nbits, start, r_begin, r_len,
/* val */ true, /* forward */ false);
}
/* Similar to fb_srange_iter, but searches for unset bits. */
static inline bool
fb_urange_iter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
size_t *r_len) {
return fb_iter_range_impl(fb, nbits, start, r_begin, r_len,
/* val */ false, /* forward */ true);
}
/* Similar to fb_srange_riter, but searches for unset bits. */
static inline bool
fb_urange_riter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
size_t *r_len) {
return fb_iter_range_impl(fb, nbits, start, r_begin, r_len,
/* val */ false, /* forward */ false);
}
#endif /* JEMALLOC_INTERNAL_FB_H */

View File

@ -301,6 +301,236 @@ TEST_BEGIN(test_empty_full) {
}
TEST_END
TEST_BEGIN(test_iter_range_simple) {
size_t set_limit = 30;
size_t nbits = 100;
fb_group_t fb[FB_NGROUPS(100)];
fb_init(fb, nbits);
/*
* Failing to initialize these can lead to build failures with -Wall;
* the compiler can't prove that they're set.
*/
size_t begin = (size_t)-1;
size_t len = (size_t)-1;
bool result;
/* A set of checks with only the first set_limit bits *set*. */
fb_set_range(fb, nbits, 0, set_limit);
for (size_t i = 0; i < set_limit; i++) {
result = fb_srange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(i, begin, "Incorrect begin at %zu", i);
expect_zu_eq(set_limit - i, len, "Incorrect len at %zu", i);
result = fb_urange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i);
expect_zu_eq(nbits - set_limit, len, "Incorrect len at %zu", i);
result = fb_srange_riter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(0, begin, "Incorrect begin at %zu", i);
expect_zu_eq(i + 1, len, "Incorrect len at %zu", i);
result = fb_urange_riter(fb, nbits, i, &begin, &len);
expect_false(result, "Should not have found a range at %zu", i);
}
for (size_t i = set_limit; i < nbits; i++) {
result = fb_srange_iter(fb, nbits, i, &begin, &len);
expect_false(result, "Should not have found a range at %zu", i);
result = fb_urange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(i, begin, "Incorrect begin at %zu", i);
expect_zu_eq(nbits - i, len, "Incorrect len at %zu", i);
result = fb_srange_riter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(0, begin, "Incorrect begin at %zu", i);
expect_zu_eq(set_limit, len, "Incorrect len at %zu", i);
result = fb_urange_riter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i);
expect_zu_eq(i - set_limit + 1, len, "Incorrect len at %zu", i);
}
/* A set of checks with only the first set_limit bits *unset*. */
fb_unset_range(fb, nbits, 0, set_limit);
fb_set_range(fb, nbits, set_limit, nbits - set_limit);
for (size_t i = 0; i < set_limit; i++) {
result = fb_srange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i);
expect_zu_eq(nbits - set_limit, len, "Incorrect len at %zu", i);
result = fb_urange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(i, begin, "Incorrect begin at %zu", i);
expect_zu_eq(set_limit - i, len, "Incorrect len at %zu", i);
result = fb_srange_riter(fb, nbits, i, &begin, &len);
expect_false(result, "Should not have found a range at %zu", i);
result = fb_urange_riter(fb, nbits, i, &begin, &len);
expect_true(result, "Should not have found a range at %zu", i);
expect_zu_eq(0, begin, "Incorrect begin at %zu", i);
expect_zu_eq(i + 1, len, "Incorrect len at %zu", i);
}
for (size_t i = set_limit; i < nbits; i++) {
result = fb_srange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(i, begin, "Incorrect begin at %zu", i);
expect_zu_eq(nbits - i, len, "Incorrect len at %zu", i);
result = fb_urange_iter(fb, nbits, i, &begin, &len);
expect_false(result, "Should not have found a range at %zu", i);
result = fb_srange_riter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i);
expect_zu_eq(i - set_limit + 1, len, "Incorrect len at %zu", i);
result = fb_urange_riter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
expect_zu_eq(0, begin, "Incorrect begin at %zu", i);
expect_zu_eq(set_limit, len, "Incorrect len at %zu", i);
}
}
TEST_END
/*
* Doing this bit-by-bit is too slow for a real implementation, but for testing
* code, it's easy to get right. In the exhaustive tests, we'll compare the
* (fast but tricky) real implementation against the (slow but simple) testing
* one.
*/
static bool
fb_iter_simple(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
size_t *r_len, bool val, bool forward) {
ssize_t stride = (forward ? (ssize_t)1 : (ssize_t)-1);
ssize_t range_begin = (ssize_t)start;
for (; range_begin != (ssize_t)nbits && range_begin != -1;
range_begin += stride) {
if (fb_get(fb, nbits, range_begin) == val) {
ssize_t range_end = range_begin;
for (; range_end != (ssize_t)nbits && range_end != -1;
range_end += stride) {
if (fb_get(fb, nbits, range_end) != val) {
break;
}
}
if (forward) {
*r_begin = range_begin;
*r_len = range_end - range_begin;
} else {
*r_begin = range_end + 1;
*r_len = range_begin - range_end;
}
return true;
}
}
return false;
}
static void
expect_iter_results_at(fb_group_t *fb, size_t nbits, size_t pos,
bool val, bool forward) {
bool iter_res;
size_t iter_begin;
size_t iter_len;
if (val) {
if (forward) {
iter_res = fb_srange_iter(fb, nbits, pos,
&iter_begin, &iter_len);
} else {
iter_res = fb_srange_riter(fb, nbits, pos,
&iter_begin, &iter_len);
}
} else {
if (forward) {
iter_res = fb_urange_iter(fb, nbits, pos,
&iter_begin, &iter_len);
} else {
iter_res = fb_urange_riter(fb, nbits, pos,
&iter_begin, &iter_len);
}
}
bool simple_iter_res;
size_t simple_iter_begin;
size_t simple_iter_len;
simple_iter_res = fb_iter_simple(fb, nbits, pos, &simple_iter_begin,
&simple_iter_len, val, forward);
expect_b_eq(iter_res, simple_iter_res, "Result mismatch at %zu", pos);
if (iter_res && simple_iter_res) {
assert_zu_eq(iter_begin, simple_iter_begin,
"Begin mismatch at %zu", pos);
expect_zu_eq(iter_len, simple_iter_len,
"Length mismatch at %zu", pos);
}
}
static void
expect_iter_results(fb_group_t *fb, size_t nbits) {
for (size_t i = 0; i < nbits; i++) {
expect_iter_results_at(fb, nbits, i, false, false);
expect_iter_results_at(fb, nbits, i, false, true);
expect_iter_results_at(fb, nbits, i, true, false);
expect_iter_results_at(fb, nbits, i, true, true);
}
}
static void
set_pattern_3(fb_group_t *fb, size_t nbits, bool zero_val) {
for (size_t i = 0; i < nbits; i++) {
if ((i % 6 < 3 && zero_val) || (i % 6 >= 3 && !zero_val)) {
fb_set(fb, nbits, i);
} else {
fb_unset(fb, nbits, i);
}
}
}
static void
do_test_iter_range_exhaustive(size_t nbits) {
/* This test is also pretty slow. */
if (nbits > 1000) {
return;
}
size_t sz = FB_NGROUPS(nbits) * sizeof(fb_group_t);
fb_group_t *fb = malloc(sz);
fb_init(fb, nbits);
set_pattern_3(fb, nbits, /* zero_val */ true);
expect_iter_results(fb, nbits);
set_pattern_3(fb, nbits, /* zero_val */ false);
expect_iter_results(fb, nbits);
fb_set_range(fb, nbits, 0, nbits);
fb_unset_range(fb, nbits, 0, nbits / 2 == 0 ? 1 : nbits / 2);
expect_iter_results(fb, nbits);
fb_unset_range(fb, nbits, 0, nbits);
fb_set_range(fb, nbits, 0, nbits / 2 == 0 ? 1: nbits / 2);
expect_iter_results(fb, nbits);
free(fb);
}
TEST_BEGIN(test_iter_range_exhaustive) {
#define NB(nbits) \
do_test_iter_range_exhaustive(nbits);
NBITS_TAB
#undef NB
}
TEST_END
int
main(void) {
return test_no_reentrancy(
@ -309,5 +539,7 @@ main(void) {
test_search_simple,
test_search_exhaustive,
test_range_simple,
test_empty_full);
test_empty_full,
test_iter_range_simple,
test_iter_range_exhaustive);
}