1 files changed, 150 insertions, 0 deletions
diff --git a/lib/libc/stdlib/hsearch_r.c b/lib/libc/stdlib/hsearch_r.c
new file mode 100644
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--- /dev/null
+++ b/lib/libc/stdlib/hsearch_r.c
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+/*-
+ * Copyright (c) 2015 Nuxi, https://nuxi.nl/
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <errno.h>
+#include <limits.h>
+#include <search.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "hsearch.h"
+
+/*
+ * Look up an unused entry in the hash table for a given hash. For this
+ * implementation we use quadratic probing. Quadratic probing has the
+ * advantage of preventing primary clustering.
+ */
+static ENTRY *
+hsearch_lookup_free(struct __hsearch *hsearch, size_t hash)
+{
+	size_t index, i;
+
+	for (index = hash, i = 0;; index += ++i) {
+		ENTRY *entry = &hsearch->entries[index & hsearch->index_mask];
+		if (entry->key == NULL)
+			return (entry);
+	}
+}
+
+/*
+ * Computes an FNV-1a hash of the key. Depending on the pointer size, this
+ * either uses the 32- or 64-bit FNV prime.
+ */
+static size_t
+hsearch_hash(size_t offset_basis, const char *str)
+{
+	size_t hash;
+
+	hash = offset_basis;
+	while (*str != '\0') {
+		hash ^= (uint8_t)*str++;
+		if (sizeof(size_t) * CHAR_BIT <= 32)
+			hash *= UINT32_C(16777619);
+		else
+			hash *= UINT64_C(1099511628211);
+	}
+	return (hash);
+}
+
+int
+hsearch_r(ENTRY item, ACTION action, ENTRY **retval, struct hsearch_data *htab)
+{
+	struct __hsearch *hsearch;
+	ENTRY *entry, *old_entries, *new_entries;
+	size_t hash, index, i, old_hash, old_count, new_count;
+
+	hsearch = htab->__hsearch;
+	hash = hsearch_hash(hsearch->offset_basis, item.key);
+
+	/*
+	 * Search the hash table for an existing entry for this key.
+	 * Stop searching if we run into an unused hash table entry.
+	 */
+	for (index = hash, i = 0;; index += ++i) {
+		entry = &hsearch->entries[index & hsearch->index_mask];
+		if (entry->key == NULL)
+			break;
+		if (strcmp(entry->key, item.key) == 0) {
+			*retval = entry;
+			return (1);
+		}
+	}
+
+	/* Only perform the insertion if action is set to ENTER. */
+	if (action == FIND) {
+		errno = ESRCH;
+		return (0);
+	}
+
+	if (hsearch->entries_used * 2 >= hsearch->index_mask) {
+		/* Preserve the old hash table entries. */
+		old_count = hsearch->index_mask + 1;
+		old_entries = hsearch->entries;
+
+		/*
+		 * Allocate and install a new table if insertion would
+		 * yield a hash table that is more than 50% used. By
+		 * using 50% as a threshold, a lookup will only take up
+		 * to two steps on average.
+		 */
+		new_count = (hsearch->index_mask + 1) * 2;
+		new_entries = calloc(new_count, sizeof(ENTRY));
+		if (new_entries == NULL)
+			return (0);
+		hsearch->entries = new_entries;
+		hsearch->index_mask = new_count - 1;
+
+		/* Copy over the entries from the old table to the new table. */
+		for (i = 0; i < old_count; ++i) {
+			entry = &old_entries[i];
+			if (entry->key != NULL) {
+				old_hash = hsearch_hash(hsearch->offset_basis,
+				    entry->key);
+				*hsearch_lookup_free(hsearch, old_hash) =
+				    *entry;
+			}
+		}
+
+		/* Destroy the old hash table entries. */
+		free(old_entries);
+
+		/*
+		 * Perform a new lookup for a free table entry, so that
+		 * we insert the entry into the new hash table.
+		 */
+		hsearch = htab->__hsearch;
+		entry = hsearch_lookup_free(hsearch, hash);
+	}
+
+	/* Insert the new entry into the hash table. */
+	*entry = item;
+	++hsearch->entries_used;
+	*retval = entry;
+	return (1);
+}