js8call/jsc.cpp

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/**
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* This file is part of JS8Call.
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*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
* (C) 2018 Jordan Sherer <kn4crd@gmail.com> - All Rights Reserved
*
**/
#include "jsc.h"
#include "varicode.h"
#include <cmath>
Codeword JSC::codeword(quint32 index, bool separate, quint32 bytesize, quint32 s, quint32 c){
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QList<Codeword> out;
quint32 v = ((index % s) << 1) + (quint32)separate;
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out.prepend(Varicode::intToBits(v, bytesize + 1));
quint32 x = index / s;
while(x > 0){
x -= 1;
out.prepend(Varicode::intToBits((x % c) + s, bytesize));
x /= c;
}
Codeword word;
foreach(auto w, out){
word.append(w);
}
return word;
}
QList<CodewordPair> JSC::compress(QString text){
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QList<CodewordPair> out;
const quint32 b = 4;
const quint32 s = 7;
const quint32 c = pow(2, 4) - s;
foreach(QString w, text.split(" ", QString::SkipEmptyParts)){
bool ok = false;
auto index = lookup(w, &ok);
if(ok){
// cool, we found the word...
out.append({ codeword(index, true, b, s, c), (quint32)w.length() + 1 /* for the space that follows */ });
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} else {
// hmm. no dice. let's go for a prefix match
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while(!w.isEmpty()){
bool hasPrefix = false;
auto d = w.toLatin1().data();
for(quint32 i = 0; i < JSC::size; i++){
quint32 len = JSC::list[i].size;
if(strncmp(d, JSC::list[i].str, len) == 0){
w = QString(w.mid(len));
auto index = JSC::list[i].index;
bool isLast = w.isEmpty();
out.append({ codeword(index, isLast, b, s, c), len + (isLast ? 1 : 0) /* for the space that follows */});
hasPrefix = true;
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break;
}
}
if(!hasPrefix){
// no match...SOL
break;
}
}
}
}
return out;
}
QString JSC::decompress(Codeword const& bitvec){
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const quint32 b = 4;
const quint32 s = 7;
const quint32 c = pow(2, b) - s;
QStringList out;
quint32 base[8];
base[0] = 0;
base[1] = s;
base[2] = base[1] + s*c;
base[3] = base[2] + s*c*c;
base[4] = base[3] + s*c*c*c;
base[5] = base[4] + s*c*c*c*c;
base[6] = base[5] + s*c*c*c*c*c;
base[7] = base[6] + s*c*c*c*c*c*c;
QList<quint64> bytes;
QList<int> separators;
auto iter = bitvec.begin();
while(iter != bitvec.end()){
quint64 byte = Varicode::bitsToInt(iter, 4);
iter += 4;
bytes.append(byte);
if(byte < s){
if(*iter){
separators.append(bytes.length()-1);
}
iter += 1;
}
}
int start = 0;
while(start < bytes.length()){
int k = 0;
int j = 0;
while(start + k < bytes.length() && bytes[start + k] >= s){
j = j*c + (bytes[start + k] - s);
k++;
}
j = j*s + bytes[start + k] + base[k];
out.append(QString(JSC::map[j].str));
if(!separators.isEmpty() && separators.first() == start + k){
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out.append(" ");
separators.removeFirst();
}
start = start + (k + 1);
}
return out.join("");
}
quint32 JSC::lookup(QString w, bool * ok){
return lookup(w.toLatin1().data(), ok);
}
quint32 JSC::lookup(char const* b, bool *ok){
for(quint32 i = 0; i < JSC::size; i++){
if(strcmp(b, JSC::map[i].str) == 0){
if(ok) *ok = true;
return i;
}
}
if(ok) *ok = false;
return 0;
}