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49 lines
1.2 KiB
49 lines
1.2 KiB
2 years ago
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// Copyright 2013 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Helper function for bit twiddling
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#ifndef WOFF2_PORT_H_
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#define WOFF2_PORT_H_
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#include <assert.h>
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namespace woff2 {
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typedef unsigned int uint32;
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inline int Log2Floor(uint32 n) {
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#if defined(__GNUC__)
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return n == 0 ? -1 : 31 ^ __builtin_clz(n);
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#else
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if (n == 0)
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return -1;
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int log = 0;
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uint32 value = n;
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for (int i = 4; i >= 0; --i) {
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int shift = (1 << i);
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uint32 x = value >> shift;
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if (x != 0) {
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value = x;
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log += shift;
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}
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}
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assert(value == 1);
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return log;
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#endif
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}
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} // namespace woff2
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#endif // WOFF2_PORT_H_
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