LibELF: Move ELF hash functions to their own file (and make constexpr)

Userland/Libraries/LibELF/Hashes.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2019-2020, Andrew Kaster <andrewdkaster@gmail.com>
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * 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 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 HOLDER 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.
+ */
+
+#pragma once
+
+#include <AK/StringView.h>
+
+namespace ELF {
+
+constexpr u32 compute_sysv_hash(const StringView& name)
+{
+    // SYSV ELF hash algorithm
+    // Note that the GNU HASH algorithm has less collisions
+
+    u32 hash = 0;
+
+    for (auto ch : name) {
+        hash = hash << 4;
+        hash += ch;
+
+        const u32 top_nibble_of_hash = hash & 0xf0000000u;
+        hash ^= top_nibble_of_hash >> 24;
+        hash &= ~top_nibble_of_hash;
+    }
+
+    return hash;
+}
+
+constexpr u32 compute_gnu_hash(const StringView& name)
+{
+    // GNU ELF hash algorithm
+    u32 hash = 5381;
+
+    for (auto ch : name)
+        hash = hash * 33 + ch;
+
+    return hash;
+}
+
+}