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authorJörg Frings-Fürst <debian@jff.email>2024-03-24 08:54:48 +0100
committerJörg Frings-Fürst <debian@jff.email>2024-03-24 08:54:48 +0100
commit163a663518f33bab48b28431972e580b366b4d49 (patch)
treef518ffabaca4a0b93f0103d617e803792d3b0b43 /lib/struniq.h
parent1b3a8d5ad2ea2f099d514d9dd51ebf926a628076 (diff)
parentdd0000f7e25abe6c28d4329d324fd7fcab54094f (diff)
Merge branch 'release/debian/1.2-1'HEADdebian/1.2-1master
Diffstat (limited to 'lib/struniq.h')
-rw-r--r--lib/struniq.h119
1 files changed, 119 insertions, 0 deletions
diff --git a/lib/struniq.h b/lib/struniq.h
new file mode 100644
index 00000000..e67ea0fe
--- /dev/null
+++ b/lib/struniq.h
@@ -0,0 +1,119 @@
+/* Define a file-local string uniquification function.
+ Copyright (C) 2009-2024 Free Software Foundation, Inc.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file 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 Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2009. */
+
+
+/* This file needs the following includes:
+
+ #include <limits.h>
+ #include <stdlib.h>
+ #include <string.h>
+ #include "flexmember.h"
+ #include "glthread/lock.h"
+ #include "thread-optim.h"
+
+ and the following gnulib modules as dependencies:
+
+ flexmember
+ lock
+ stdbool
+ thread-optim
+ */
+
+
+/* Simple hash set of strings. We don't want to drag in lots of hash table
+ code here. */
+
+#define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
+
+/* A hash function for NUL-terminated char* strings using
+ the method described by Bruno Haible.
+ See https://www.haible.de/bruno/hashfunc.html. */
+static size_t _GL_ATTRIBUTE_PURE
+string_hash (const void *x)
+{
+ const char *s = (const char *) x;
+ size_t h = 0;
+
+ for (; *s; s++)
+ h = *s + ((h << 9) | (h >> (SIZE_BITS - 9)));
+
+ return h;
+}
+
+/* A hash table of fixed size. Multiple threads can access it read-only
+ simultaneously, but only one thread can insert into it at the same time. */
+
+/* A node in a hash bucket collision list. */
+struct struniq_hash_node
+ {
+ struct struniq_hash_node * volatile next;
+ char contents[FLEXIBLE_ARRAY_MEMBER];
+ };
+
+#define STRUNIQ_HASH_TABLE_SIZE 257
+static struct struniq_hash_node * volatile struniq_hash_table[STRUNIQ_HASH_TABLE_SIZE]
+ /* = { NULL, ..., NULL } */;
+
+/* This lock protects the struniq_hash_table against multiple simultaneous
+ insertions. */
+gl_lock_define_initialized(static, struniq_lock)
+
+/* Store a copy of the given string in a string pool with indefinite extent.
+ Return a pointer to this copy. */
+static const char *
+struniq (const char *string)
+{
+ size_t hashcode = string_hash (string);
+ size_t slot = hashcode % STRUNIQ_HASH_TABLE_SIZE;
+ size_t size;
+ struct struniq_hash_node *new_node;
+ struct struniq_hash_node *p;
+ for (p = struniq_hash_table[slot]; p != NULL; p = p->next)
+ if (strcmp (p->contents, string) == 0)
+ return p->contents;
+ size = strlen (string) + 1;
+ new_node =
+ (struct struniq_hash_node *)
+ malloc (FLEXSIZEOF (struct struniq_hash_node, contents, size));
+ if (new_node == NULL)
+ /* Out of memory. Return a statically allocated string. */
+ return "C";
+ memcpy (new_node->contents, string, size);
+ {
+ bool mt = gl_multithreaded ();
+ /* Lock while inserting new_node. */
+ if (mt) gl_lock_lock (struniq_lock);
+ /* Check whether another thread already added the string while we were
+ waiting on the lock. */
+ for (p = struniq_hash_table[slot]; p != NULL; p = p->next)
+ if (strcmp (p->contents, string) == 0)
+ {
+ free (new_node);
+ new_node = p;
+ goto done;
+ }
+ /* Really insert new_node into the hash table. Fill new_node entirely
+ first, because other threads may be iterating over the linked list. */
+ new_node->next = struniq_hash_table[slot];
+ struniq_hash_table[slot] = new_node;
+ done:
+ /* Unlock after new_node is inserted. */
+ if (mt) gl_lock_unlock (struniq_lock);
+ }
+ return new_node->contents;
+}