Initial revision.

diff --git a/src/CacheDigest.cc b/src/CacheDigest.cc
new file mode 100644 (file)
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--- /dev/null
+++ b/src/CacheDigest.cc
@@ -0,0 +1,113 @@
+
+/*
+ * $Id: CacheDigest.cc,v 1.1 1998/03/30 21:03:33 rousskov Exp $
+ *
+ * DEBUG: section ??    Cache Digest
+ * AUTHOR: Alex Rousskov
+ *
+ * SQUID Internet Object Cache  http://squid.nlanr.net/Squid/
+ * --------------------------------------------------------
+ *
+ *  Squid is the result of efforts by numerous individuals from the
+ *  Internet community.  Development is led by Duane Wessels of the
+ *  National Laboratory for Applied Network Research and funded by
+ *  the National Science Foundation.
+ *
+ *  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 2 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, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *  
+ */
+
+#include "squid.h"
+
+static const int BitsPerEntry = 4;
+
+/* static array used by cacheDigestHashKey for optimization purposes */
+static u_num32 hashed_keys[4];
+
+/* local functions */
+static void cacheDigestHashKey(int bit_count, const char *key);
+
+
+CacheDigest *
+cacheDigestCreate(int capacity)
+{
+    CacheDigest *cd = xcalloc(1, sizeof(CacheDigest));
+    assert(MD5_DIGEST_CHARS == 16); /* our hash functions rely on 16 byte keys */
+    assert(capacity > 0);
+    cd->capacity = capacity;
+    cd->mask_size = (size_t) (capacity * BitsPerEntry + 7)/ 8;
+    cd->mask = xcalloc(cd->mask_size, 1);
+    return cd;
+}
+
+void
+cacheDigestDestroy(CacheDigest *cd)
+{
+    assert(cd);
+    xfree(cd->mask);
+    xfree(cd);
+}
+
+void
+cacheDigestAdd(CacheDigest *cd, const cache_key *key)
+{
+    assert(cd && key);
+    /* hash */
+    cacheDigestHashKey(cd->capacity * BitsPerEntry, key);
+    /* turn on corresponding bits */
+    CBIT_SET(cd->mask, hashed_keys[0]);
+    CBIT_SET(cd->mask, hashed_keys[1]);
+    CBIT_SET(cd->mask, hashed_keys[2]);
+    CBIT_SET(cd->mask, hashed_keys[3]);
+    cd->count++;
+}
+
+/* returns true if the key belongs to the digest */
+int
+cacheDigestTest(const CacheDigest *cd, const cache_key *key)
+{
+    assert(cd && key);
+    /* hash */
+    cacheDigestHashKey(cd->capacity * BitsPerEntry, key);
+    /* test corresponding bits */
+    return 
+       CBIT_TEST(cd->mask, hashed_keys[0]) &&
+       CBIT_TEST(cd->mask, hashed_keys[1]) &&
+       CBIT_TEST(cd->mask, hashed_keys[2]) &&
+       CBIT_TEST(cd->mask, hashed_keys[3]);
+}
+
+void
+cacheDigestDel(CacheDigest *cd, const cache_key *key)
+{
+    assert(cd && key);
+    cd->del_count++;
+    /* we do not support deletions from the digest */
+}
+
+
+static void
+cacheDigestHashKey(int bit_count, const char *key)
+{
+    /* get four hashed values */
+    memcpy(hashed_keys, key, sizeof(hashed_keys));
+    /* wrap */
+    hashed_keys[0] %= bit_count;
+    hashed_keys[1] %= bit_count;
+    hashed_keys[2] %= bit_count;
+    hashed_keys[3] %= bit_count;
+}
+
+