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util/binsearch: macro for greater than or equal search

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Sometimes you want to find the place where an item would be in a
sorted list, whether or not it is actually there.

The BINARY_ARRAY_SEARCH_GTE macro takes an extra 'next' pointer
argument over the other binsearch macros. This will end up pointing to
the next element in the case where there is not an exact match, or
NULL when there is. That is, searching the list

     { 2, 3, 4, 4, 9}

with a standard integer compare should give the following results:

search term    *result    *next
         1      -          2
         3      3          -
         4      4 [1]      -
         7      -          9
         9      9          -
        10      -          - [2]

Notes
[1] There are two fours, but you will always get the first one.
[2] The both NULL case means the search term is beyond the last list
item.

You can safely use the same pointer for both 'result' and 'next', if
you don't care to distinguish between the 'greater-than' and 'equals'
cases.

There is a torture test for this.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
This commit is contained in:
Douglas Bagnall 2016-01-29 17:53:20 +13:00 committed by Andrew Bartlett
parent 42fe66fa73
commit 5235f1facf
4 changed files with 179 additions and 1 deletions
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33
lib/util/binsearch.h
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@ -81,4 +81,37 @@
if (_r < 0) _e = _i - 1; else _b = _i + 1; \
}} } while (0)
/*
like BINARY_ARRAY_SEARCH_V, but if an exact result is not found, the 'next'
argument will point to the element after the place where the exact result
would have been. If an exact result is found, 'next' will be NULL. If the
target is beyond the end of the list, both 'result' and 'next' will be NULL.
Unlike other binsearch macros, where there are several elements that compare
the same, the result will always point to the first one.
If you don't care to distinguish between the 'greater than' and 'equals'
cases, you can use the same pointer for both 'result' and 'next'.
As with all the binsearch macros, the comparison function is always called
with the search term first.
*/
#define BINARY_ARRAY_SEARCH_GTE(array, array_size, target, comparison_fn, \
result, next) do { \
int32_t _b, _e; \
(result) = NULL; (next) = NULL; \
if ((array_size) > 0) { \
for (_b = 0, _e = (array_size)-1; _b <= _e; ) { \
int32_t _i = (_b + _e) / 2; \
int _r = comparison_fn(target, array[_i]); \
if (_r == 0) { \
(result) = &array[_i]; \
_e = _i - 1; \
} else if (_r < 0) { _e = _i - 1; \
} else { _b = _i + 1; } \
} \
if ((result) == NULL &&_b < (array_size)) { \
(next) = &array[_b]; \
} } } while (0)
#endif

144
lib/util/tests/binsearch.c Normal file
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@ -0,0 +1,144 @@
/*
Unix SMB/CIFS implementation.
Tests for binsearch.h macros.
Copyright Catalyst IT 2016.
Written by Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
#include "lib/util/binsearch.h"
#include "torture/torture.h"
#include "torture/local/proto.h"
static int int_cmp(int a, int b)
{
return a - b;
}
static bool test_binsearch_gte(struct torture_context *tctx)
{
int array[] = { -11, -7, -7, -7, -1, 0, 0, 1, 723, 723, 723,
724, 724, 10000};
size_t a_len = ARRAY_SIZE(array);
int targets[] = { -121, -8, -7, -6, 17, -10, 10, -1, 723,
724, 725, 10002, 10000, 0, -11, 1, 11};
int i, j, target;
int *result = NULL, *next = NULL;
for (i = 0; i < ARRAY_SIZE(targets); i++) {
target = targets[i];
torture_comment(tctx, "looking for targets[%d] %d\n",
i, target);
BINARY_ARRAY_SEARCH_GTE(array, a_len, target,
int_cmp, result, next);
if (result == NULL) {
/* we think there is no exact match */
for (j = 0; j < a_len; j++) {
if (target == array[j]) {
torture_comment(tctx,
"failed to find %d\n",
targets[i]);
torture_fail(tctx,
"result is wrongly NULL");
}
}
if (next != NULL) {
torture_assert(tctx, (next >= array &&
next < array + a_len),
"next is out of bounds");
torture_assert(tctx, *next > target,
"next <= target");
if (target <= array[0]) {
torture_assert(tctx, next == array,
"search before start failed");
}
if (next != array) {
torture_assert(tctx, next[-1] < target,
"next[-1] >= target");
}
}
else {
torture_assert(tctx, array[a_len - 1] < target,
"next was not found\n");
}
} else {
/* we think we found an exact match */
torture_assert(tctx, *result == target,
"result has wrong value");
torture_assert(tctx, (result >= array &&
result < array + a_len),
"result is out of bounds!");
torture_assert(tctx, next == NULL,
"next should be NULL on exact match\n");
if (result != array) {
torture_assert(tctx, result[-1] != target,
"didn't find first target\n");
}
}
if (target >= array[a_len - 1]) {
torture_assert(tctx, next == NULL,
"next is not NULL at array end\n");
}
}
/* try again, with result and next the same pointer */
for (i = 0; i < ARRAY_SIZE(targets); i++) {
target = targets[i];
torture_comment(tctx, "looking for targets[%d] %d\n",
i, target);
BINARY_ARRAY_SEARCH_GTE(array, a_len, target,
int_cmp, result, result);
if (result == NULL) {
/* we think the target is greater than all elements */
torture_assert(tctx, array[a_len - 1] < target,
"element >= target not found\n");
} else {
/* we think an element is >= target */
torture_assert(tctx, *result >= target,
"result has wrong value");
torture_assert(tctx, (result >= array &&
result < array + a_len),
"result is out of bounds!");
if (result != array) {
torture_assert(tctx, result[-1] < target,
"didn't find first target\n");
}
}
}
return true;
}
struct torture_suite *torture_local_util_binsearch(TALLOC_CTX *mem_ctx)
{
struct torture_suite *suite = torture_suite_create(mem_ctx, "binsearch");
torture_suite_add_simple_test(suite, "binsearch_v", test_binsearch_v);
torture_suite_add_simple_test(suite, "binsearch_gte", test_binsearch_gte);
return suite;
}

1
source4/torture/local/local.c
View File

@ -39,6 +39,7 @@
torture_local_util_str,
torture_local_util_time,
torture_local_util_data_blob,
torture_local_util_binsearch,
torture_local_util_asn1,
torture_local_util_anonymous_shared,
torture_local_util_strv,

2
source4/torture/local/wscript_build
View File

@ -5,7 +5,7 @@ TORTURE_LOCAL_SOURCE = '''../../../lib/util/charset/tests/iconv.c
../../lib/messaging/tests/irpc.c ../../librpc/tests/binding_string.c
../../../lib/util/tests/idtree.c ../../../lib/util/tests/dlinklist.c
../../lib/socket/testsuite.c ../../libcli/resolve/testsuite.c
../../../lib/util/tests/strlist.c
../../../lib/util/tests/strlist.c ../../../lib/util/tests/binsearch.c
../../../lib/util/tests/str.c ../../../lib/util/tests/time.c
../../../lib/util/tests/asn1_tests.c ../../../lib/util/tests/data_blob.c
../../../lib/util/tests/file.c ../../../lib/util/tests/genrand.c