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compression of polylines is now a lot faster

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This commit is contained in:
Dennis Luxen 2011-08-06 17:48:10 +00:00
parent 3bcd262099
commit c8b0f96251
1 changed files with 38 additions and 44 deletions
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54
DataStructures/PolylineCompressor.h
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@ -27,53 +27,47 @@ or see http://www.gnu.org/licenses/agpl.txt.
class PolylineCompressor { class PolylineCompressor {
private: private:
inline string encodeSignedNumber(const int number) const { inline void encodeVectorSignedNumber(vector<int> & numbers, string & output) {
int signedNumber = number << 1; for(unsigned i = 0; i < numbers.size(); ++i) {
if (number < 0) { numbers[i] <<= 1;
signedNumber = ~(signedNumber); if (numbers[i] < 0) {
numbers[i] = ~(numbers[i]);
}
}
for(unsigned i = 0; i < numbers.size(); ++i) {
encodeNumber(numbers[i], output);
} }
return (encodeNumber(signedNumber));
} }
inline string encodeNumber(int numberToEncode) const { inline void encodeNumber(int numberToEncode, string & output) {
string encodeString;
while (numberToEncode >= 0x20) { while (numberToEncode >= 0x20) {
int nextValue = (0x20 | (numberToEncode & 0x1f)) + 63; int nextValue = (0x20 | (numberToEncode & 0x1f)) + 63;
encodeString += (static_cast<char> (nextValue)); output += (static_cast<char> (nextValue));
if(92 == nextValue)
output += (static_cast<char> (nextValue));
numberToEncode >>= 5; numberToEncode >>= 5;
} }
numberToEncode += 63; numberToEncode += 63;
encodeString += (static_cast<char> (numberToEncode)); output += (static_cast<char> (numberToEncode));
if(92 == numberToEncode)
return encodeString; output += (static_cast<char> (numberToEncode));
}
inline void replaceBackslash(string & str) {
size_t found = 0;
do {
found = str.find("\\", found);
if(found ==string::npos)
break;
str.insert(found, "\\");
found+=2;
} while(true);
} }
public: public:
inline void printEncodedString(vector<_Coordinate>& polyline, string &output) { inline void printEncodedString(const vector<_Coordinate>& polyline, string &output) {
vector<int> deltaNumbers(2*polyline.size());
output += "\""; output += "\"";
if(!polyline.empty()) { if(!polyline.empty()) {
output += encodeSignedNumber(polyline[0].lat); deltaNumbers[0] = polyline[0].lat;
output += encodeSignedNumber(polyline[0].lon); deltaNumbers[1] = polyline[0].lon;
for(unsigned i = 1; i < polyline.size(); ++i) {
deltaNumbers[(2*i)] = (polyline[i].lat - polyline[i-1].lat);
deltaNumbers[(2*i)+1] = (polyline[i].lon - polyline[i-1].lon);
} }
for(unsigned i = 1; i < polyline.size(); i++) { encodeVectorSignedNumber(deltaNumbers, output);
output += encodeSignedNumber(polyline[i].lat - polyline[i-1].lat);
output += encodeSignedNumber(polyline[i].lon - polyline[i-1].lon);
} }
output += "\""; output += "\"";
replaceBackslash(output);
} }
inline void printUnencodedString(vector<_Coordinate> & polyline, string & output) { inline void printUnencodedString(vector<_Coordinate> & polyline, string & output) {