util: added binsearch.h for binary array searches

This was moved from the schema_query code. It will now be used in more
than one place, so best to make it a library macro. I think there are
quite a few places that could benefit from this.

diff --git a/lib/util/binsearch.h b/lib/util/binsearch.h
new file mode 100644 (file)
index 0000000..ac83990
--- /dev/null
+++ b/lib/util/binsearch.h
@@ -0,0 +1,68 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   a generic binary search macro
+
+   Copyright (C) Andrew Tridgell 2009
+
+   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/>.
+*/
+
+#ifndef _BINSEARCH_H
+#define _BINSEARCH_H
+
+/* a binary array search, where the array is an array of pointers to structures,
+   and we want to find a match for 'target' on 'field' in those structures.
+
+   Inputs:
+      array:          base pointer to an array of structures
+      arrray_size:    number of elements in the array
+      field:          the name of the field in the structure we are keying off
+      target:         the field value we are looking for
+      comparison_fn:  the comparison function
+      result:         where the result of the search is put
+
+   if the element is found, then 'result' is set to point to the found array element. If not,
+   then 'result' is set to NULL.
+
+   The array is assumed to be sorted by the same comparison_fn as the
+   search (with, for example, qsort)
+ */
+#define BINARY_ARRAY_SEARCH_P(array, array_size, field, target, comparison_fn, result) do { \
+       int32_t _b, _e; \
+       (result) = NULL; \
+       if (array_size) { for (_b = 0, _e = (array_size)-1; _b <= _e; ) { \
+               int32_t _i = (_b+_e)/2; \
+               int _r = comparison_fn(target, array[_i]->field); \
+               if (_r == 0) { (result) = array[_i]; break; } \
+               if (_r < 0) _e = _i - 1; else _b = _i + 1; \
+       }} } while (0)
+
+/*
+  like BINARY_ARRAY_SEARCH_P, but assumes that the array is an array
+  of structures, rather than pointers to structures
+
+  result points to the found structure, or NULL
+ */
+#define BINARY_ARRAY_SEARCH(array, array_size, field, target, comparison_fn, result) do { \
+       int32_t _b, _e; \
+       (result) = NULL; \
+       if (array_size) { for (_b = 0, _e = (array_size)-1; _b <= _e; ) {       \
+               int32_t _i = (_b+_e)/2; \
+               int _r = comparison_fn(target, array[_i].field); \
+               if (_r == 0) { (result) = &array[_i]; break; } \
+               if (_r < 0) _e = _i - 1; else _b = _i + 1; \
+       }} } while (0)
+
+#endif