561 lines
27 KiB
C++
561 lines
27 KiB
C++
/*
|
|
* Copyright (C) 2011 The Android Open Source Project
|
|
*
|
|
* 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.
|
|
*/
|
|
|
|
#ifndef LATINIME_BINARY_FORMAT_H
|
|
#define LATINIME_BINARY_FORMAT_H
|
|
|
|
#include <limits>
|
|
#include "bloom_filter.h"
|
|
#include "unigram_dictionary.h"
|
|
|
|
namespace latinime {
|
|
|
|
class BinaryFormat {
|
|
private:
|
|
const static int32_t MINIMAL_ONE_BYTE_CHARACTER_VALUE = 0x20;
|
|
const static int32_t CHARACTER_ARRAY_TERMINATOR = 0x1F;
|
|
const static int MULTIPLE_BYTE_CHARACTER_ADDITIONAL_SIZE = 2;
|
|
|
|
public:
|
|
const static int UNKNOWN_FORMAT = -1;
|
|
// Originally, format version 1 had a 16-bit magic number, then the version number `01'
|
|
// then options that must be 0. Hence the first 32-bits of the format are always as follow
|
|
// and it's okay to consider them a magic number as a whole.
|
|
const static uint32_t FORMAT_VERSION_1_MAGIC_NUMBER = 0x78B10100;
|
|
const static unsigned int FORMAT_VERSION_1_HEADER_SIZE = 5;
|
|
// The versions of Latin IME that only handle format version 1 only test for the magic
|
|
// number, so we had to change it so that version 2 files would be rejected by older
|
|
// implementations. On this occasion, we made the magic number 32 bits long.
|
|
const static uint32_t FORMAT_VERSION_2_MAGIC_NUMBER = 0x9BC13AFE;
|
|
|
|
const static int CHARACTER_ARRAY_TERMINATOR_SIZE = 1;
|
|
const static int SHORTCUT_LIST_SIZE_SIZE = 2;
|
|
|
|
static int detectFormat(const uint8_t* const dict);
|
|
static unsigned int getHeaderSize(const uint8_t* const dict);
|
|
static unsigned int getFlags(const uint8_t* const dict);
|
|
static int getGroupCountAndForwardPointer(const uint8_t* const dict, int* pos);
|
|
static uint8_t getFlagsAndForwardPointer(const uint8_t* const dict, int* pos);
|
|
static int32_t getCharCodeAndForwardPointer(const uint8_t* const dict, int* pos);
|
|
static int readFrequencyWithoutMovingPointer(const uint8_t* const dict, const int pos);
|
|
static int skipOtherCharacters(const uint8_t* const dict, const int pos);
|
|
static int skipChildrenPosition(const uint8_t flags, const int pos);
|
|
static int skipFrequency(const uint8_t flags, const int pos);
|
|
static int skipShortcuts(const uint8_t* const dict, const uint8_t flags, const int pos);
|
|
static int skipBigrams(const uint8_t* const dict, const uint8_t flags, const int pos);
|
|
static int skipAllAttributes(const uint8_t* const dict, const uint8_t flags, const int pos);
|
|
static int skipChildrenPosAndAttributes(const uint8_t* const dict, const uint8_t flags,
|
|
const int pos);
|
|
static int readChildrenPosition(const uint8_t* const dict, const uint8_t flags, const int pos);
|
|
static bool hasChildrenInFlags(const uint8_t flags);
|
|
static int getAttributeAddressAndForwardPointer(const uint8_t* const dict, const uint8_t flags,
|
|
int *pos);
|
|
static int getTerminalPosition(const uint8_t* const root, const int32_t* const inWord,
|
|
const int length);
|
|
static int getWordAtAddress(const uint8_t* const root, const int address, const int maxDepth,
|
|
uint16_t* outWord, int* outUnigramFrequency);
|
|
static int computeFrequencyForBigram(const int unigramFreq, const int bigramFreq);
|
|
static int getProbability(const int position, const std::map<int, int> *bigramMap,
|
|
const uint8_t *bigramFilter, const int unigramFreq);
|
|
|
|
// Flags for special processing
|
|
// Those *must* match the flags in makedict (BinaryDictInputOutput#*_PROCESSING_FLAG) or
|
|
// something very bad (like, the apocalypse) will happen. Please update both at the same time.
|
|
enum {
|
|
REQUIRES_GERMAN_UMLAUT_PROCESSING = 0x1,
|
|
REQUIRES_FRENCH_LIGATURES_PROCESSING = 0x4
|
|
};
|
|
const static unsigned int NO_FLAGS = 0;
|
|
};
|
|
|
|
inline int BinaryFormat::detectFormat(const uint8_t* const dict) {
|
|
// The magic number is stored big-endian.
|
|
const uint32_t magicNumber = (dict[0] << 24) + (dict[1] << 16) + (dict[2] << 8) + dict[3];
|
|
switch (magicNumber) {
|
|
case FORMAT_VERSION_1_MAGIC_NUMBER:
|
|
// Format 1 header is exactly 5 bytes long and looks like:
|
|
// Magic number (2 bytes) 0x78 0xB1
|
|
// Version number (1 byte) 0x01
|
|
// Options (2 bytes) must be 0x00 0x00
|
|
return 1;
|
|
case FORMAT_VERSION_2_MAGIC_NUMBER:
|
|
// Format 2 header is as follows:
|
|
// Magic number (4 bytes) 0x9B 0xC1 0x3A 0xFE
|
|
// Version number (2 bytes) 0x00 0x02
|
|
// Options (2 bytes)
|
|
// Header size (4 bytes) : integer, big endian
|
|
return (dict[4] << 8) + dict[5];
|
|
default:
|
|
return UNKNOWN_FORMAT;
|
|
}
|
|
}
|
|
|
|
inline unsigned int BinaryFormat::getFlags(const uint8_t* const dict) {
|
|
switch (detectFormat(dict)) {
|
|
case 1:
|
|
return NO_FLAGS;
|
|
default:
|
|
return (dict[6] << 8) + dict[7];
|
|
}
|
|
}
|
|
|
|
inline unsigned int BinaryFormat::getHeaderSize(const uint8_t* const dict) {
|
|
switch (detectFormat(dict)) {
|
|
case 1:
|
|
return FORMAT_VERSION_1_HEADER_SIZE;
|
|
case 2:
|
|
// See the format of the header in the comment in detectFormat() above
|
|
return (dict[8] << 24) + (dict[9] << 16) + (dict[10] << 8) + dict[11];
|
|
default:
|
|
return std::numeric_limits<unsigned int>::max();
|
|
}
|
|
}
|
|
|
|
inline int BinaryFormat::getGroupCountAndForwardPointer(const uint8_t* const dict, int* pos) {
|
|
const int msb = dict[(*pos)++];
|
|
if (msb < 0x80) return msb;
|
|
return ((msb & 0x7F) << 8) | dict[(*pos)++];
|
|
}
|
|
|
|
inline uint8_t BinaryFormat::getFlagsAndForwardPointer(const uint8_t* const dict, int* pos) {
|
|
return dict[(*pos)++];
|
|
}
|
|
|
|
inline int32_t BinaryFormat::getCharCodeAndForwardPointer(const uint8_t* const dict, int* pos) {
|
|
const int origin = *pos;
|
|
const int32_t character = dict[origin];
|
|
if (character < MINIMAL_ONE_BYTE_CHARACTER_VALUE) {
|
|
if (character == CHARACTER_ARRAY_TERMINATOR) {
|
|
*pos = origin + 1;
|
|
return NOT_A_CHARACTER;
|
|
} else {
|
|
*pos = origin + 3;
|
|
const int32_t char_1 = character << 16;
|
|
const int32_t char_2 = char_1 + (dict[origin + 1] << 8);
|
|
return char_2 + dict[origin + 2];
|
|
}
|
|
} else {
|
|
*pos = origin + 1;
|
|
return character;
|
|
}
|
|
}
|
|
|
|
inline int BinaryFormat::readFrequencyWithoutMovingPointer(const uint8_t* const dict,
|
|
const int pos) {
|
|
return dict[pos];
|
|
}
|
|
|
|
inline int BinaryFormat::skipOtherCharacters(const uint8_t* const dict, const int pos) {
|
|
int currentPos = pos;
|
|
int32_t character = dict[currentPos++];
|
|
while (CHARACTER_ARRAY_TERMINATOR != character) {
|
|
if (character < MINIMAL_ONE_BYTE_CHARACTER_VALUE) {
|
|
currentPos += MULTIPLE_BYTE_CHARACTER_ADDITIONAL_SIZE;
|
|
}
|
|
character = dict[currentPos++];
|
|
}
|
|
return currentPos;
|
|
}
|
|
|
|
static inline int attributeAddressSize(const uint8_t flags) {
|
|
static const int ATTRIBUTE_ADDRESS_SHIFT = 4;
|
|
return (flags & UnigramDictionary::MASK_ATTRIBUTE_ADDRESS_TYPE) >> ATTRIBUTE_ADDRESS_SHIFT;
|
|
/* Note: this is a value-dependant optimization of what may probably be
|
|
more readably written this way:
|
|
switch (flags * UnigramDictionary::MASK_ATTRIBUTE_ADDRESS_TYPE) {
|
|
case UnigramDictionary::FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE: return 1;
|
|
case UnigramDictionary::FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES: return 2;
|
|
case UnigramDictionary::FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTE: return 3;
|
|
default: return 0;
|
|
}
|
|
*/
|
|
}
|
|
|
|
static inline int skipExistingBigrams(const uint8_t* const dict, const int pos) {
|
|
int currentPos = pos;
|
|
uint8_t flags = BinaryFormat::getFlagsAndForwardPointer(dict, ¤tPos);
|
|
while (flags & UnigramDictionary::FLAG_ATTRIBUTE_HAS_NEXT) {
|
|
currentPos += attributeAddressSize(flags);
|
|
flags = BinaryFormat::getFlagsAndForwardPointer(dict, ¤tPos);
|
|
}
|
|
currentPos += attributeAddressSize(flags);
|
|
return currentPos;
|
|
}
|
|
|
|
static inline int childrenAddressSize(const uint8_t flags) {
|
|
static const int CHILDREN_ADDRESS_SHIFT = 6;
|
|
return (UnigramDictionary::MASK_GROUP_ADDRESS_TYPE & flags) >> CHILDREN_ADDRESS_SHIFT;
|
|
/* See the note in attributeAddressSize. The same applies here */
|
|
}
|
|
|
|
static inline int shortcutByteSize(const uint8_t* const dict, const int pos) {
|
|
return ((int)(dict[pos] << 8)) + (dict[pos + 1]);
|
|
}
|
|
|
|
inline int BinaryFormat::skipChildrenPosition(const uint8_t flags, const int pos) {
|
|
return pos + childrenAddressSize(flags);
|
|
}
|
|
|
|
inline int BinaryFormat::skipFrequency(const uint8_t flags, const int pos) {
|
|
return UnigramDictionary::FLAG_IS_TERMINAL & flags ? pos + 1 : pos;
|
|
}
|
|
|
|
inline int BinaryFormat::skipShortcuts(const uint8_t* const dict, const uint8_t flags,
|
|
const int pos) {
|
|
if (UnigramDictionary::FLAG_HAS_SHORTCUT_TARGETS & flags) {
|
|
return pos + shortcutByteSize(dict, pos);
|
|
} else {
|
|
return pos;
|
|
}
|
|
}
|
|
|
|
inline int BinaryFormat::skipBigrams(const uint8_t* const dict, const uint8_t flags,
|
|
const int pos) {
|
|
if (UnigramDictionary::FLAG_HAS_BIGRAMS & flags) {
|
|
return skipExistingBigrams(dict, pos);
|
|
} else {
|
|
return pos;
|
|
}
|
|
}
|
|
|
|
inline int BinaryFormat::skipAllAttributes(const uint8_t* const dict, const uint8_t flags,
|
|
const int pos) {
|
|
// This function skips all attributes: shortcuts and bigrams.
|
|
int newPos = pos;
|
|
newPos = skipShortcuts(dict, flags, newPos);
|
|
newPos = skipBigrams(dict, flags, newPos);
|
|
return newPos;
|
|
}
|
|
|
|
inline int BinaryFormat::skipChildrenPosAndAttributes(const uint8_t* const dict,
|
|
const uint8_t flags, const int pos) {
|
|
int currentPos = pos;
|
|
currentPos = skipChildrenPosition(flags, currentPos);
|
|
currentPos = skipAllAttributes(dict, flags, currentPos);
|
|
return currentPos;
|
|
}
|
|
|
|
inline int BinaryFormat::readChildrenPosition(const uint8_t* const dict, const uint8_t flags,
|
|
const int pos) {
|
|
int offset = 0;
|
|
switch (UnigramDictionary::MASK_GROUP_ADDRESS_TYPE & flags) {
|
|
case UnigramDictionary::FLAG_GROUP_ADDRESS_TYPE_ONEBYTE:
|
|
offset = dict[pos];
|
|
break;
|
|
case UnigramDictionary::FLAG_GROUP_ADDRESS_TYPE_TWOBYTES:
|
|
offset = dict[pos] << 8;
|
|
offset += dict[pos + 1];
|
|
break;
|
|
case UnigramDictionary::FLAG_GROUP_ADDRESS_TYPE_THREEBYTES:
|
|
offset = dict[pos] << 16;
|
|
offset += dict[pos + 1] << 8;
|
|
offset += dict[pos + 2];
|
|
break;
|
|
default:
|
|
// If we come here, it means we asked for the children of a word with
|
|
// no children.
|
|
return -1;
|
|
}
|
|
return pos + offset;
|
|
}
|
|
|
|
inline bool BinaryFormat::hasChildrenInFlags(const uint8_t flags) {
|
|
return (UnigramDictionary::FLAG_GROUP_ADDRESS_TYPE_NOADDRESS
|
|
!= (UnigramDictionary::MASK_GROUP_ADDRESS_TYPE & flags));
|
|
}
|
|
|
|
inline int BinaryFormat::getAttributeAddressAndForwardPointer(const uint8_t* const dict,
|
|
const uint8_t flags, int *pos) {
|
|
int offset = 0;
|
|
const int origin = *pos;
|
|
switch (UnigramDictionary::MASK_ATTRIBUTE_ADDRESS_TYPE & flags) {
|
|
case UnigramDictionary::FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE:
|
|
offset = dict[origin];
|
|
*pos = origin + 1;
|
|
break;
|
|
case UnigramDictionary::FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES:
|
|
offset = dict[origin] << 8;
|
|
offset += dict[origin + 1];
|
|
*pos = origin + 2;
|
|
break;
|
|
case UnigramDictionary::FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES:
|
|
offset = dict[origin] << 16;
|
|
offset += dict[origin + 1] << 8;
|
|
offset += dict[origin + 2];
|
|
*pos = origin + 3;
|
|
break;
|
|
}
|
|
if (UnigramDictionary::FLAG_ATTRIBUTE_OFFSET_NEGATIVE & flags) {
|
|
return origin - offset;
|
|
} else {
|
|
return origin + offset;
|
|
}
|
|
}
|
|
|
|
// This function gets the byte position of the last chargroup of the exact matching word in the
|
|
// dictionary. If no match is found, it returns NOT_VALID_WORD.
|
|
inline int BinaryFormat::getTerminalPosition(const uint8_t* const root,
|
|
const int32_t* const inWord, const int length) {
|
|
int pos = 0;
|
|
int wordPos = 0;
|
|
|
|
while (true) {
|
|
// If we already traversed the tree further than the word is long, there means
|
|
// there was no match (or we would have found it).
|
|
if (wordPos > length) return NOT_VALID_WORD;
|
|
int charGroupCount = BinaryFormat::getGroupCountAndForwardPointer(root, &pos);
|
|
const int32_t wChar = inWord[wordPos];
|
|
while (true) {
|
|
// If there are no more character groups in this node, it means we could not
|
|
// find a matching character for this depth, therefore there is no match.
|
|
if (0 >= charGroupCount) return NOT_VALID_WORD;
|
|
const int charGroupPos = pos;
|
|
const uint8_t flags = BinaryFormat::getFlagsAndForwardPointer(root, &pos);
|
|
int32_t character = BinaryFormat::getCharCodeAndForwardPointer(root, &pos);
|
|
if (character == wChar) {
|
|
// This is the correct node. Only one character group may start with the same
|
|
// char within a node, so either we found our match in this node, or there is
|
|
// no match and we can return NOT_VALID_WORD. So we will check all the characters
|
|
// in this character group indeed does match.
|
|
if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & flags) {
|
|
character = BinaryFormat::getCharCodeAndForwardPointer(root, &pos);
|
|
while (NOT_A_CHARACTER != character) {
|
|
++wordPos;
|
|
// If we shoot the length of the word we search for, or if we find a single
|
|
// character that does not match, as explained above, it means the word is
|
|
// not in the dictionary (by virtue of this chargroup being the only one to
|
|
// match the word on the first character, but not matching the whole word).
|
|
if (wordPos > length) return NOT_VALID_WORD;
|
|
if (inWord[wordPos] != character) return NOT_VALID_WORD;
|
|
character = BinaryFormat::getCharCodeAndForwardPointer(root, &pos);
|
|
}
|
|
}
|
|
// If we come here we know that so far, we do match. Either we are on a terminal
|
|
// and we match the length, in which case we found it, or we traverse children.
|
|
// If we don't match the length AND don't have children, then a word in the
|
|
// dictionary fully matches a prefix of the searched word but not the full word.
|
|
++wordPos;
|
|
if (UnigramDictionary::FLAG_IS_TERMINAL & flags) {
|
|
if (wordPos == length) {
|
|
return charGroupPos;
|
|
}
|
|
pos = BinaryFormat::skipFrequency(UnigramDictionary::FLAG_IS_TERMINAL, pos);
|
|
}
|
|
if (UnigramDictionary::FLAG_GROUP_ADDRESS_TYPE_NOADDRESS
|
|
== (UnigramDictionary::MASK_GROUP_ADDRESS_TYPE & flags)) {
|
|
return NOT_VALID_WORD;
|
|
}
|
|
// We have children and we are still shorter than the word we are searching for, so
|
|
// we need to traverse children. Put the pointer on the children position, and
|
|
// break
|
|
pos = BinaryFormat::readChildrenPosition(root, flags, pos);
|
|
break;
|
|
} else {
|
|
// This chargroup does not match, so skip the remaining part and go to the next.
|
|
if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & flags) {
|
|
pos = BinaryFormat::skipOtherCharacters(root, pos);
|
|
}
|
|
pos = BinaryFormat::skipFrequency(flags, pos);
|
|
pos = BinaryFormat::skipChildrenPosAndAttributes(root, flags, pos);
|
|
}
|
|
--charGroupCount;
|
|
}
|
|
}
|
|
}
|
|
|
|
// This function searches for a terminal in the dictionary by its address.
|
|
// Due to the fact that words are ordered in the dictionary in a strict breadth-first order,
|
|
// it is possible to check for this with advantageous complexity. For each node, we search
|
|
// for groups with children and compare the children address with the address we look for.
|
|
// When we shoot the address we look for, it means the word we look for is in the children
|
|
// of the previous group. The only tricky part is the fact that if we arrive at the end of a
|
|
// node with the last group's children address still less than what we are searching for, we
|
|
// must descend the last group's children (for example, if the word we are searching for starts
|
|
// with a z, it's the last group of the root node, so all children addresses will be smaller
|
|
// than the address we look for, and we have to descend the z node).
|
|
/* Parameters :
|
|
* root: the dictionary buffer
|
|
* address: the byte position of the last chargroup of the word we are searching for (this is
|
|
* what is stored as the "bigram address" in each bigram)
|
|
* outword: an array to write the found word, with MAX_WORD_LENGTH size.
|
|
* outUnigramFrequency: a pointer to an int to write the frequency into.
|
|
* Return value : the length of the word, of 0 if the word was not found.
|
|
*/
|
|
inline int BinaryFormat::getWordAtAddress(const uint8_t* const root, const int address,
|
|
const int maxDepth, uint16_t* outWord, int* outUnigramFrequency) {
|
|
int pos = 0;
|
|
int wordPos = 0;
|
|
|
|
// One iteration of the outer loop iterates through nodes. As stated above, we will only
|
|
// traverse nodes that are actually a part of the terminal we are searching, so each time
|
|
// we enter this loop we are one depth level further than last time.
|
|
// The only reason we count nodes is because we want to reduce the probability of infinite
|
|
// looping in case there is a bug. Since we know there is an upper bound to the depth we are
|
|
// supposed to traverse, it does not hurt to count iterations.
|
|
for (int loopCount = maxDepth; loopCount > 0; --loopCount) {
|
|
int lastCandidateGroupPos = 0;
|
|
// Let's loop through char groups in this node searching for either the terminal
|
|
// or one of its ascendants.
|
|
for (int charGroupCount = getGroupCountAndForwardPointer(root, &pos); charGroupCount > 0;
|
|
--charGroupCount) {
|
|
const int startPos = pos;
|
|
const uint8_t flags = getFlagsAndForwardPointer(root, &pos);
|
|
const int32_t character = getCharCodeAndForwardPointer(root, &pos);
|
|
if (address == startPos) {
|
|
// We found the address. Copy the rest of the word in the buffer and return
|
|
// the length.
|
|
outWord[wordPos] = character;
|
|
if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & flags) {
|
|
int32_t nextChar = getCharCodeAndForwardPointer(root, &pos);
|
|
// We count chars in order to avoid infinite loops if the file is broken or
|
|
// if there is some other bug
|
|
int charCount = maxDepth;
|
|
while (NOT_A_CHARACTER != nextChar && --charCount > 0) {
|
|
outWord[++wordPos] = nextChar;
|
|
nextChar = getCharCodeAndForwardPointer(root, &pos);
|
|
}
|
|
}
|
|
*outUnigramFrequency = readFrequencyWithoutMovingPointer(root, pos);
|
|
return ++wordPos;
|
|
}
|
|
// We need to skip past this char group, so skip any remaining chars after the
|
|
// first and possibly the frequency.
|
|
if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & flags) {
|
|
pos = skipOtherCharacters(root, pos);
|
|
}
|
|
pos = skipFrequency(flags, pos);
|
|
|
|
// The fact that this group has children is very important. Since we already know
|
|
// that this group does not match, if it has no children we know it is irrelevant
|
|
// to what we are searching for.
|
|
const bool hasChildren = (UnigramDictionary::FLAG_GROUP_ADDRESS_TYPE_NOADDRESS !=
|
|
(UnigramDictionary::MASK_GROUP_ADDRESS_TYPE & flags));
|
|
// We will write in `found' whether we have passed the children address we are
|
|
// searching for. For example if we search for "beer", the children of b are less
|
|
// than the address we are searching for and the children of c are greater. When we
|
|
// come here for c, we realize this is too big, and that we should descend b.
|
|
bool found;
|
|
if (hasChildren) {
|
|
// Here comes the tricky part. First, read the children position.
|
|
const int childrenPos = readChildrenPosition(root, flags, pos);
|
|
if (childrenPos > address) {
|
|
// If the children pos is greater than address, it means the previous chargroup,
|
|
// which address is stored in lastCandidateGroupPos, was the right one.
|
|
found = true;
|
|
} else if (1 >= charGroupCount) {
|
|
// However if we are on the LAST group of this node, and we have NOT shot the
|
|
// address we should descend THIS node. So we trick the lastCandidateGroupPos
|
|
// so that we will descend this node, not the previous one.
|
|
lastCandidateGroupPos = startPos;
|
|
found = true;
|
|
} else {
|
|
// Else, we should continue looking.
|
|
found = false;
|
|
}
|
|
} else {
|
|
// Even if we don't have children here, we could still be on the last group of this
|
|
// node. If this is the case, we should descend the last group that had children,
|
|
// and their address is already in lastCandidateGroup.
|
|
found = (1 >= charGroupCount);
|
|
}
|
|
|
|
if (found) {
|
|
// Okay, we found the group we should descend. Its address is in
|
|
// the lastCandidateGroupPos variable, so we just re-read it.
|
|
if (0 != lastCandidateGroupPos) {
|
|
const uint8_t lastFlags =
|
|
getFlagsAndForwardPointer(root, &lastCandidateGroupPos);
|
|
const int32_t lastChar =
|
|
getCharCodeAndForwardPointer(root, &lastCandidateGroupPos);
|
|
// We copy all the characters in this group to the buffer
|
|
outWord[wordPos] = lastChar;
|
|
if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & lastFlags) {
|
|
int32_t nextChar =
|
|
getCharCodeAndForwardPointer(root, &lastCandidateGroupPos);
|
|
int charCount = maxDepth;
|
|
while (-1 != nextChar && --charCount > 0) {
|
|
outWord[++wordPos] = nextChar;
|
|
nextChar = getCharCodeAndForwardPointer(root, &lastCandidateGroupPos);
|
|
}
|
|
}
|
|
++wordPos;
|
|
// Now we only need to branch to the children address. Skip the frequency if
|
|
// it's there, read pos, and break to resume the search at pos.
|
|
lastCandidateGroupPos = skipFrequency(lastFlags, lastCandidateGroupPos);
|
|
pos = readChildrenPosition(root, lastFlags, lastCandidateGroupPos);
|
|
break;
|
|
} else {
|
|
// Here is a little tricky part: we come here if we found out that all children
|
|
// addresses in this group are bigger than the address we are searching for.
|
|
// Should we conclude the word is not in the dictionary? No! It could still be
|
|
// one of the remaining chargroups in this node, so we have to keep looking in
|
|
// this node until we find it (or we realize it's not there either, in which
|
|
// case it's actually not in the dictionary). Pass the end of this group, ready
|
|
// to start the next one.
|
|
pos = skipChildrenPosAndAttributes(root, flags, pos);
|
|
}
|
|
} else {
|
|
// If we did not find it, we should record the last children address for the next
|
|
// iteration.
|
|
if (hasChildren) lastCandidateGroupPos = startPos;
|
|
// Now skip the end of this group (children pos and the attributes if any) so that
|
|
// our pos is after the end of this char group, at the start of the next one.
|
|
pos = skipChildrenPosAndAttributes(root, flags, pos);
|
|
}
|
|
|
|
}
|
|
}
|
|
// If we have looked through all the chargroups and found no match, the address is
|
|
// not the address of a terminal in this dictionary.
|
|
return 0;
|
|
}
|
|
|
|
static inline int backoff(const int unigramFreq) {
|
|
return unigramFreq;
|
|
// For some reason, applying the backoff weight gives bad results in tests. To apply the
|
|
// backoff weight, we divide the probability by 2, which in our storing format means
|
|
// decreasing the score by 8.
|
|
// TODO: figure out what's wrong with this.
|
|
// return unigramFreq > 8 ? unigramFreq - 8 : (0 == unigramFreq ? 0 : 8);
|
|
}
|
|
|
|
inline int BinaryFormat::computeFrequencyForBigram(const int unigramFreq, const int bigramFreq) {
|
|
// We divide the range [unigramFreq..255] in 16.5 steps - in other words, we want the
|
|
// unigram frequency to be the median value of the 17th step from the top. A value of
|
|
// 0 for the bigram frequency represents the middle of the 16th step from the top,
|
|
// while a value of 15 represents the middle of the top step.
|
|
// See makedict.BinaryDictInputOutput for details.
|
|
const float stepSize = ((float)MAX_FREQ - unigramFreq) / (1.5f + MAX_BIGRAM_FREQ);
|
|
return (int)(unigramFreq + (bigramFreq + 1) * stepSize);
|
|
}
|
|
|
|
// This returns a probability in log space.
|
|
inline int BinaryFormat::getProbability(const int position, const std::map<int, int> *bigramMap,
|
|
const uint8_t *bigramFilter, const int unigramFreq) {
|
|
if (!bigramMap || !bigramFilter) return backoff(unigramFreq);
|
|
if (!isInFilter(bigramFilter, position)) return backoff(unigramFreq);
|
|
const std::map<int, int>::const_iterator bigramFreqIt = bigramMap->find(position);
|
|
if (bigramFreqIt != bigramMap->end()) {
|
|
const int bigramFreq = bigramFreqIt->second;
|
|
return computeFrequencyForBigram(unigramFreq, bigramFreq);
|
|
} else {
|
|
return backoff(unigramFreq);
|
|
}
|
|
}
|
|
|
|
} // namespace latinime
|
|
|
|
#endif // LATINIME_BINARY_FORMAT_H
|