72 lines
2.7 KiB
C++
72 lines
2.7 KiB
C++
/*
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* Copyright (C) 2013 The Android Open Source Project
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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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#include "dictionary/utils/format_utils.h"
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#include "dictionary/utils/byte_array_utils.h"
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namespace latinime {
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const uint32_t FormatUtils::MAGIC_NUMBER = 0x9BC13AFE;
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// Magic number (4 bytes), version (2 bytes), flags (2 bytes), header size (4 bytes) = 12
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const size_t FormatUtils::DICTIONARY_MINIMUM_SIZE = 12;
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/* static */ FormatUtils::FORMAT_VERSION FormatUtils::getFormatVersion(const int formatVersion) {
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switch (formatVersion) {
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case VERSION_2:
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case VERSION_201:
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AKLOGE("Dictionary versions 2 and 201 are incompatible with this version");
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return UNKNOWN_VERSION;
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case VERSION_202:
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return VERSION_202;
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case VERSION_4_ONLY_FOR_TESTING:
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return VERSION_4_ONLY_FOR_TESTING;
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case VERSION_402:
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return VERSION_402;
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case VERSION_403:
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return VERSION_403;
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default:
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return UNKNOWN_VERSION;
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}
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}
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/* static */ FormatUtils::FORMAT_VERSION FormatUtils::detectFormatVersion(
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const ReadOnlyByteArrayView dictBuffer) {
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// The magic number is stored big-endian.
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// If the dictionary is less than 4 bytes, we can't even read the magic number, so we don't
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// understand this format.
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if (dictBuffer.size() < DICTIONARY_MINIMUM_SIZE) {
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return UNKNOWN_VERSION;
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}
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const uint32_t magicNumber = ByteArrayUtils::readUint32(dictBuffer.data(), 0);
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switch (magicNumber) {
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case MAGIC_NUMBER:
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// The layout of the header is as follows:
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// Magic number (4 bytes) 0x9B 0xC1 0x3A 0xFE
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// Dictionary format version number (2 bytes)
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// Options (2 bytes)
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// Header size (4 bytes) : integer, big endian
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// Conceptually this converts the hardcoded value of the bytes in the file into
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// the symbolic value we use in the code. But we want the constants to be the
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// same so we use them for both here.
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return getFormatVersion(ByteArrayUtils::readUint16(dictBuffer.data(), 4));
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default:
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return UNKNOWN_VERSION;
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}
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}
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} // namespace latinime
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