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      1 /*
      2  * Copyright (C) 2013 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "suggest/policyimpl/dictionary/structure/pt_common/bigram/bigram_list_read_write_utils.h"
     18 
     19 #include "suggest/policyimpl/dictionary/utils/byte_array_utils.h"
     20 #include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
     21 
     22 namespace latinime {
     23 
     24 const BigramListReadWriteUtils::BigramFlags BigramListReadWriteUtils::MASK_ATTRIBUTE_ADDRESS_TYPE =
     25         0x30;
     26 const BigramListReadWriteUtils::BigramFlags
     27         BigramListReadWriteUtils::FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE = 0x10;
     28 const BigramListReadWriteUtils::BigramFlags
     29         BigramListReadWriteUtils::FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES = 0x20;
     30 const BigramListReadWriteUtils::BigramFlags
     31         BigramListReadWriteUtils::FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES = 0x30;
     32 const BigramListReadWriteUtils::BigramFlags
     33         BigramListReadWriteUtils::FLAG_ATTRIBUTE_OFFSET_NEGATIVE = 0x40;
     34 // Flag for presence of more attributes
     35 const BigramListReadWriteUtils::BigramFlags BigramListReadWriteUtils::FLAG_ATTRIBUTE_HAS_NEXT =
     36         0x80;
     37 // Mask for attribute probability, stored on 4 bits inside the flags byte.
     38 const BigramListReadWriteUtils::BigramFlags
     39         BigramListReadWriteUtils::MASK_ATTRIBUTE_PROBABILITY = 0x0F;
     40 
     41 /* static */ bool BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(
     42         const uint8_t *const bigramsBuf, const int bufSize, BigramFlags *const outBigramFlags,
     43         int *const outTargetPtNodePos, int *const bigramEntryPos) {
     44     if (bufSize <= *bigramEntryPos) {
     45         AKLOGE("Read invalid pos in getBigramEntryPropertiesAndAdvancePosition(). bufSize: %d, "
     46                 "bigramEntryPos: %d.", bufSize, *bigramEntryPos);
     47         return false;
     48     }
     49     const BigramFlags bigramFlags = ByteArrayUtils::readUint8AndAdvancePosition(bigramsBuf,
     50             bigramEntryPos);
     51     if (outBigramFlags) {
     52         *outBigramFlags = bigramFlags;
     53     }
     54     const int targetPos = getBigramAddressAndAdvancePosition(bigramsBuf, bigramFlags,
     55             bigramEntryPos);
     56     if (outTargetPtNodePos) {
     57         *outTargetPtNodePos = targetPos;
     58     }
     59     return true;
     60 }
     61 
     62 /* static */ bool BigramListReadWriteUtils::skipExistingBigrams(const uint8_t *const bigramsBuf,
     63         const int bufSize, int *const bigramListPos) {
     64     BigramFlags flags;
     65     do {
     66         if (!getBigramEntryPropertiesAndAdvancePosition(bigramsBuf, bufSize, &flags,
     67                 0 /* outTargetPtNodePos */, bigramListPos)) {
     68             return false;
     69         }
     70     } while(hasNext(flags));
     71     return true;
     72 }
     73 
     74 /* static */ int BigramListReadWriteUtils::getBigramAddressAndAdvancePosition(
     75         const uint8_t *const bigramsBuf, const BigramFlags flags, int *const pos) {
     76     int offset = 0;
     77     const int origin = *pos;
     78     switch (MASK_ATTRIBUTE_ADDRESS_TYPE & flags) {
     79         case FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE:
     80             offset = ByteArrayUtils::readUint8AndAdvancePosition(bigramsBuf, pos);
     81             break;
     82         case FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES:
     83             offset = ByteArrayUtils::readUint16AndAdvancePosition(bigramsBuf, pos);
     84             break;
     85         case FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES:
     86             offset = ByteArrayUtils::readUint24AndAdvancePosition(bigramsBuf, pos);
     87             break;
     88     }
     89     if (isOffsetNegative(flags)) {
     90         return origin - offset;
     91     } else {
     92         return origin + offset;
     93     }
     94 }
     95 
     96 } // namespace latinime
     97