| /* |
| * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code 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 |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #ifndef SHARE_RUNTIME_FLAGS_JVMFLAGLOOKUP_HPP |
| #define SHARE_RUNTIME_FLAGS_JVMFLAGLOOKUP_HPP |
| |
| #include "runtime/globals_extension.hpp" |
| #include "runtime/flags/jvmFlag.hpp" |
| |
| // This is a hashtable that maps from (const char*) to (JVMFlag*) to speed up |
| // the processing of JVM command-line arguments at runtime. |
| // |
| // With constexpr, this table is generated at C++ compile time so there's |
| // no set up cost at runtime. |
| class JVMFlagLookup { |
| static constexpr int NUM_BUCKETS = 277; |
| short _buckets[NUM_BUCKETS]; |
| short _table[NUM_JVMFlagsEnum]; |
| u2 _hashes[NUM_JVMFlagsEnum]; |
| |
| // Cannot use strlen() -- it's not constexpr. |
| static constexpr size_t string_len(const char* s) { |
| size_t len = 0; |
| while (*s != 0) { |
| len++; |
| s++; |
| } |
| return len; |
| } |
| |
| // This is executed at build-time only, so it doesn't matter if we walk |
| // the string twice. |
| static constexpr unsigned int hash_code(const char* s) { |
| return hash_code(s, string_len(s)); |
| } |
| |
| static constexpr unsigned int hash_code(const char* s, size_t len) { |
| unsigned int h = 0; |
| while (len -- > 0) { |
| h = 31*h + (unsigned int) *s; |
| s++; |
| } |
| return h; |
| } |
| |
| JVMFlag* find_impl(const char* flag_name, size_t length) const; |
| |
| public: |
| constexpr JVMFlagLookup(); |
| static JVMFlag* find(const char* flag_name, size_t length); |
| }; |
| |
| #endif // SHARE_RUNTIME_FLAGS_JVMFLAGLOOKUP_HPP |