From 8efca839fc616573bbc5d05ce6e6d8b87991ae93 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@kth.se>
Date: Sat, 20 Feb 2016 22:24:08 +0100
Subject: add bsearch
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Signed-off-by: Mattias Andrée <maandree@kth.se>
---
src/stdlib/bsearch.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
create mode 100644 src/stdlib/bsearch.c
(limited to 'src/stdlib')
diff --git a/src/stdlib/bsearch.c b/src/stdlib/bsearch.c
new file mode 100644
index 0000000..c459ea4
--- /dev/null
+++ b/src/stdlib/bsearch.c
@@ -0,0 +1,70 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015, 2016 Mattias Andrée (maandree@member.fsf.org)
+ *
+ * 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 <stdlib.h>
+
+
+# pragma GCC diagnostic ignored "-Wdiscarded-qualifiers"
+
+
+
+/**
+ * Search for an item in a sorted list of comparable
+ * elements. The list must be sorted in ascending order.
+ * The function usually implements binary search,
+ * as is done in this implementation.
+ *
+ * @etymology (B)inary (search).
+ *
+ * @param sought The sought item.
+ * @param list The beginning of the list to search.
+ * @param n The number of elements in the list.
+ * @param width The width, in bytes, of each element in the list.
+ * @param compar A function that shall compare two items, and return
+ * a value less than, equal to, or greater than zero
+ * if the first argument is less than, equal to, or
+ * greater than the second argument, respectively.
+ * @return The address of an arbritrart element in `list` that
+ * is equal to `sought`, or `NULL` if no such element
+ * can be found (does not exist, or because `list`
+ * is not properly sorted.)
+ *
+ * @since Always.
+ */
+void* (bsearch)(const void* sought, const void* list, size_t n, size_t width,
+ int (*compar)(const void*, const void*))
+{
+ int cmp, i;
+ char* test;
+ if (n == 0)
+ return NULL;
+ for (;;)
+ {
+ i = n >> 1;
+ test = (char*)list + i * width;
+ cmp = compar(sought, test);
+ if (!i)
+ return cmp ? NULL : test;
+ else if (cmp < 0)
+ n = i;
+ else if (cmp > 0)
+ n -= i, list = test;
+ else
+ return test;
+ }
+}
+
--
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