Add generic perfect string hashes, use for directives

Add a generic facility for generating perfect string hashes, where all
that is needed is an enum and a string table.  The existing mechanism
using a custom Perl script wrapped around a module continues to be
available for any use case where this particular approach isn't
sophisticated enough.

Much of this patch comes from renaming "enum directives" to "enum
directive" as a result of the string hash generator expecting a set of
uniform naming conventions.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/nasmlib/perfhash.c b/nasmlib/perfhash.c
new file mode 100644
index 00000000..5cd6714e
--- /dev/null
+++ b/nasmlib/perfhash.c
@@ -0,0 +1,55 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2017 The NASM Authors - All Rights Reserved
+ *   See the file AUTHORS included with the NASM distribution for
+ *   the specific copyright holders.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following
+ *   conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *   * 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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 "perfhash.h"
+#include "hashtbl.h"            /* For crc64i() */
+
+int perfhash_find(const struct perfect_hash *hash, const char *str)
+{
+    uint32_t k1, k2;
+    uint64_t crc;
+    uint16_t ix;
+
+    crc = crc64i(hash->crcinit, str);
+    k1 = (uint32_t)crc & hash->hashmask;
+    k2 = (uint32_t)(crc >> 32) & hash->hashmask;
+
+    ix = hash->hashvals[k1] + hash->hashvals[k2 + hash->hashmask + 1];
+
+    if (ix >= hash->tbllen ||
+        !hash->strings[ix] ||
+        nasm_stricmp(str, hash->strings[ix]))
+        return hash->errval;
+
+    return hash->tbloffs + ix;
+}