diff options
Diffstat (limited to 'extern/draco/dracoenc/src/draco/core/hash_utils.cc')
-rw-r--r-- | extern/draco/dracoenc/src/draco/core/hash_utils.cc | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/extern/draco/dracoenc/src/draco/core/hash_utils.cc b/extern/draco/dracoenc/src/draco/core/hash_utils.cc new file mode 100644 index 00000000000..9a78c2cfafd --- /dev/null +++ b/extern/draco/dracoenc/src/draco/core/hash_utils.cc @@ -0,0 +1,57 @@ +// Copyright 2016 The Draco Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +#include "draco/core/hash_utils.h" + +#include <cstddef> +#include <functional> +#include <limits> + +namespace draco { + +// Will never return 1 or 0. +uint64_t FingerprintString(const char *s, size_t len) { + const uint64_t seed = 0x87654321; + const int hash_loop_count = static_cast<int>(len / 8) + 1; + uint64_t hash = seed; + + for (int i = 0; i < hash_loop_count; ++i) { + const int off = i * 8; + const int num_chars_left = static_cast<int>(len) - off; + uint64_t new_hash = seed; + + if (num_chars_left > 7) { + const int off2 = i * 8; + new_hash = static_cast<uint64_t>(s[off2]) << 56 | + static_cast<uint64_t>(s[off2 + 1]) << 48 | + static_cast<uint64_t>(s[off2 + 2]) << 40 | + static_cast<uint64_t>(s[off2 + 3]) << 32 | + static_cast<uint64_t>(s[off2 + 4]) << 24 | + static_cast<uint64_t>(s[off2 + 5]) << 16 | + static_cast<uint64_t>(s[off2 + 6]) << 8 | s[off2 + 7]; + } else { + for (int j = 0; j < num_chars_left; ++j) { + new_hash |= static_cast<uint64_t>(s[off + j]) + << (64 - ((num_chars_left - j) * 8)); + } + } + + hash = HashCombine(new_hash, hash); + } + + if (hash < std::numeric_limits<uint64_t>::max() - 1) + hash += 2; + return hash; +} +} // namespace draco |