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48 lines
1.2 KiB
48 lines
1.2 KiB
// 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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