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LZ-String encoding for Java; cross-platform to desktop, GWT, and Android at the minimum.
The newest version!
/*
* LZString4Java By Rufus Huang
* https://github.com/rufushuang/lz-string4java
* MIT License
*
* Port from original JavaScript version by pieroxy
* https://github.com/pieroxy/lz-string
*/
package blazing.chain;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
public final class LZSEncoding {
private LZSEncoding() {}
private static final char[] keyStrBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray(),
keyStrUriSafe = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-$".toCharArray(),
valStrBase64 = new char[]{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
62, 0, 0, 0, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 64, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
0, 0, 0, 0, 0, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51},
valStrUriSafe = new char[]{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 0, 0, 0, 62, 0, 63, 0, 0,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
0, 0, 0, 0, 0, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51};
/**
* Compress a String using LZ-String encoding but only using Base64 characters ('A'-'Z', 'a'-'z', '0'-'9', '+', '/',
* and '=' for Base64 validity).
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compressToBase64(String uncompressed) {
if (uncompressed == null)
return null;
String res = _compress(uncompressed, 6, keyStrBase64);
switch (res.length() & 3) { // To produce valid Base64
case 1:
return res + "===";
case 2:
return res + "==";
case 3:
return res + "=";
case 0:
default: // When could this happen ?
return res;
}
}
/**
* Decompresses a String that had been compressed with {@link #compressToBase64(String)}.
* @param compressed a Base64-encoded, compressed String
* @return the original uncompressed version of the String
*/
public static String decompressFromBase64(String compressed) {
if (compressed == null)
return null;
if (compressed.length() == 0)
return "";
return _decompress(compressed.length(), compressed, valStrBase64);
}
/**
* Compresses a String using the properties of UTF-16 encoding to store approximately 15 bits of LZW-compressed text
* in each 2-byte Unicode character, which does particularly well with ASCII text and can be smaller than UTF-8 in
* some cases, especially where each char must be stored as UTF-16, e.g. Java Strings or browser-based LocalStorage.
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compressToUTF16(String uncompressed) {
if (uncompressed == null)
return null;
return _compress(uncompressed, 15, 32) + " ";
}
/**
* Decompresses a String that had been compressed with {@link #compressToUTF16(String)}.
* @param compressed a UTF16-encoded (as by {@link #compressToUTF16(String)}), compressed String
* @return the original uncompressed version of the String
*/
public static String decompressFromUTF16(String compressed) {
if (compressed == null)
return null;
if (compressed.length() == 0)
return "";
return _decompress(compressed.length(), 16384, compressed, -32);
}
/**
* Compress a String using LZ-String encoding but only using valid URI component characters ('A'-'Z', 'a'-'z',
* '0'-'9', '+', '-', and possibly '$').
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compressToEncodedURIComponent(String uncompressed) {
if (uncompressed == null)
return null;
String res = _compress(uncompressed, 6, keyStrUriSafe);
switch (res.length() & 3) { // To produce valid URI-encoding
case 1:
return res + "$$$";
case 2:
return res + "$$";
case 3:
return res + "$";
case 0:
default: // When could this happen ?
return res;
}
}
/**
* Decompresses a String that had been compressed with {@link #compressToEncodedURIComponent(String)}.
* @param compressed a URI-encoded, compressed String
* @return the original uncompressed version of the String
*/
public static String decompressFromEncodedURIComponent(String compressed) {
if (compressed == null) return null;
if (compressed.length() == 0) return "";
return _decompress(compressed.length(), compressed, valStrUriSafe);
}
/**
* Compresses a String as tightly as possible by using 16 bits of each 16-bit character, which can infrequently
* result in invalid UTF-16 codepoints, but that may not matter for all applications.
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compress(String uncompressed) {
return _compress(uncompressed, 16, 0);
}
private static String _compress(String uncompressedStr, int bitsPerChar, char[] getCharFromInt) {
if (uncompressedStr == null) return null;
if (uncompressedStr.isEmpty()) return "";
int i, value;
HashMap context_dictionary = new HashMap<>(256, 0.5f);
HashSet context_dictionaryToCreate = new HashSet<>(256, 0.5f);
String context_c;
String context_wc;
String context_w = "";
int context_enlargeIn = 2; // Compensate for the first entry which should not count
int context_dictSize = 3;
int context_numBits = 2;
StringBuilder context_data = new StringBuilder(uncompressedStr.length() >>> 1);
int context_data_val = 0;
int context_data_position = 0;
int ii;
int uncompressedLength = uncompressedStr.length();
for (ii = 0; ii < uncompressedLength; ii++) {
context_c = String.valueOf(uncompressedStr.charAt(ii));
if (!context_dictionary.containsKey(context_c)) {
context_dictionary.put(context_c, context_dictSize++);
context_dictionaryToCreate.add(context_c);
}
context_wc = context_w + context_c;
if (context_dictionary.containsKey(context_wc)) {
context_w = context_wc;
} else {
if (context_dictionaryToCreate.contains(context_w)) {
if ((value = context_w.charAt(0)) < 256) {
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
}
for (i = 0; i < 8; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
} else {
value = 1;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | value;
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value = 0;
}
value = context_w.charAt(0);
for (i = 0; i < 16; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_enlargeIn--;
if (context_enlargeIn == 0) {
context_enlargeIn = 1 << context_numBits++;
}
context_dictionaryToCreate.remove(context_w);
} else {
value = context_dictionary.get(context_w);
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_enlargeIn--;
if (context_enlargeIn == 0) {
context_enlargeIn = 1 << context_numBits++;
}
// Add wc to the dictionary.
context_dictionary.put(context_wc, context_dictSize++);
context_w = context_c;
}
}
// Output the code for w.
if (!context_w.isEmpty()) {
if (context_dictionaryToCreate.contains(context_w)) {
if (context_w.charAt(0) < 256) {
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
}
value = context_w.charAt(0);
for (i = 0; i < 8; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
} else {
value = 1;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | value;
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value = 0;
}
value = context_w.charAt(0);
for (i = 0; i < 16; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_dictionaryToCreate.remove(context_w);
} else {
value = context_dictionary.get(context_w);
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
}
// Mark the end of the stream
value = 2;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append(getCharFromInt[context_data_val]);
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
// Flush the last char
while (true) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data.append(getCharFromInt[context_data_val]);
break;
} else
context_data_position++;
}
return context_data.toString();
}
private static String _compress(String uncompressedStr, int bitsPerChar, int offset) {
if (uncompressedStr == null) return null;
if (uncompressedStr.isEmpty()) return "";
int i, value;
HashMap context_dictionary = new HashMap<>(256, 0.5f);
HashSet context_dictionaryToCreate = new HashSet<>(256, 0.5f);
String context_c;
String context_wc;
String context_w = "";
int context_enlargeIn = 2; // Compensate for the first entry which should not count
int context_dictSize = 3;
int context_numBits = 2;
StringBuilder context_data = new StringBuilder(uncompressedStr.length() >>> 1);
int context_data_val = 0;
int context_data_position = 0;
int ii;
int uncompressedLength = uncompressedStr.length();
for (ii = 0; ii < uncompressedLength; ii++) {
context_c = String.valueOf(uncompressedStr.charAt(ii));
if (!context_dictionary.containsKey(context_c)) {
context_dictionary.put(context_c, context_dictSize++);
context_dictionaryToCreate.add(context_c);
}
context_wc = context_w + context_c;
if (context_dictionary.containsKey(context_wc)) {
context_w = context_wc;
} else {
if (context_dictionaryToCreate.contains(context_w)) {
if ((value = context_w.charAt(0)) < 256) {
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
}
for (i = 0; i < 8; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
} else {
value = 1;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | value;
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value = 0;
}
value = context_w.charAt(0);
for (i = 0; i < 16; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_enlargeIn--;
if (context_enlargeIn == 0) {
context_enlargeIn = 1 << context_numBits++;
}
context_dictionaryToCreate.remove(context_w);
} else {
value = context_dictionary.get(context_w);
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_enlargeIn--;
if (context_enlargeIn == 0) {
context_enlargeIn = 1 << context_numBits++;
}
// Add wc to the dictionary.
context_dictionary.put(context_wc, context_dictSize++);
context_w = context_c;
}
}
// Output the code for w.
if (!context_w.isEmpty()) {
if (context_dictionaryToCreate.contains(context_w)) {
if (context_w.charAt(0) < 256) {
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
}
value = context_w.charAt(0);
for (i = 0; i < 8; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
} else {
value = 1;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | value;
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value = 0;
}
value = context_w.charAt(0);
for (i = 0; i < 16; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_dictionaryToCreate.remove(context_w);
} else {
value = context_dictionary.get(context_w);
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
}
// Mark the end of the stream
value = 2;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (context_data_val + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
// Flush the last char
while (true) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data.append((char) (context_data_val + offset));
break;
} else
context_data_position++;
}
return context_data.toString();
}
/**
* Decompresses a String that had been compressed with {@link #compress(String)}.
* @param compressed a compressed String using the default encoding from {@link #compress(String)}
* @return the original uncompressed version of the String
*/
public static String decompress(final String compressed) {
if (compressed == null)
return null;
if (compressed.length() == 0)
return "";
return _decompress(compressed.length(), 32768, compressed, 0);
}
private static String _decompress(int length, String getNextValue, char[] modify) {
if(getNextValue == null)
return null;
if(getNextValue.length() == 0)
return "";
ArrayList dictionary = new ArrayList<>();
int enlargeIn = 4, dictSize = 4, numBits = 3, position = 32, index = 1, resb, maxpower, power;
String entry, w, c;
StringBuilder sb = new StringBuilder(getNextValue.length());
char bits, val = modify[getNextValue.charAt(0)];
for (char i = 0; i < 3; i++) {
dictionary.add(i, String.valueOf(i));
}
bits = 0;
maxpower = 2;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = 32;
val = modify[getNextValue.charAt(index++)];
}
bits |= ((-resb) >>> 31) << power++;
}
switch (bits) {
case 0:
maxpower = 8;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = 32;
val = modify[getNextValue.charAt(index++)];
}
bits |= ((-resb) >>> 31) << power++;
}
c = String.valueOf(bits);
break;
case 1:
bits = 0;
maxpower = 16;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = 32;
val = modify[getNextValue.charAt(index++)];
}
bits |= ((-resb) >>> 31) << power++;
}
c = String.valueOf(bits);
break;
default:
return "";
}
dictionary.add(c);
w = c;
sb.append(w);
while (true) {
if (index > length) {
return "";
}
int cc = 0;
maxpower = numBits;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = 32;
val = modify[getNextValue.charAt(index++)];
}
cc |= ((-resb) >>> 31) << power++;
}
switch (cc) {
case 0:
bits = 0;
maxpower = 8;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = 32;
val = modify[getNextValue.charAt(index++)];
}
bits |= ((-resb) >>> 31) << power++;
}
dictionary.add(String.valueOf(bits));
cc = dictSize++;
enlargeIn--;
break;
case 1:
bits = 0;
maxpower = 16;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = 32;
val = modify[getNextValue.charAt(index++)];
}
bits |= ((-resb) >>> 31) << power++;
}
dictionary.add(String.valueOf(bits));
cc = dictSize++;
enlargeIn--;
break;
case 2:
return sb.toString();
}
if (enlargeIn == 0) {
enlargeIn = 1 << numBits;
numBits++;
}
if (cc < dictionary.size() && dictionary.get(cc) != null) {
entry = dictionary.get(cc);
} else {
if (cc == dictSize) {
entry = w + w.charAt(0);
} else {
return "";
}
}
sb.append(entry);
// Add w+entry[0] to the dictionary.
dictionary.add(w + entry.charAt(0));
dictSize++;
enlargeIn--;
w = entry;
if (enlargeIn == 0) {
enlargeIn = 1 << numBits;
numBits++;
}
}
}
private static String _decompress(int length, int resetValue, String getNextValue, int offset) {
if(getNextValue == null)
return null;
if(getNextValue.length() == 0)
return "";
ArrayList dictionary = new ArrayList<>();
int enlargeIn = 4, dictSize = 4, numBits = 3, position = resetValue, index = 1, resb, maxpower, power;
String entry, w, c;
StringBuilder sb = new StringBuilder(getNextValue.length());
char bits, val = (char) (getNextValue.charAt(0) + offset);
for (char i = 0; i < 3; i++) {
dictionary.add(i, String.valueOf(i));
}
bits = 0;
maxpower = 2;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (char) (getNextValue.charAt(index++) + offset);
}
bits |= ((-resb) >>> 31) << power++;
}
switch (bits) {
case 0:
maxpower = 8;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (char) (getNextValue.charAt(index++) + offset);
}
bits |= ((-resb) >>> 31) << power++;
}
c = String.valueOf(bits);
break;
case 1:
bits = 0;
maxpower = 16;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (char) (getNextValue.charAt(index++) + offset);
}
bits |= ((-resb) >>> 31) << power++;
}
c = String.valueOf(bits);
break;
default:
return "";
}
dictionary.add(c);
w = c;
sb.append(w);
while (true) {
if (index > length) {
return "";
}
int cc = 0;
maxpower = numBits;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (char) (getNextValue.charAt(index++) + offset);
}
cc |= ((-resb) >>> 31) << power++;
}
switch (cc) {
case 0:
bits = 0;
maxpower = 8;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (char) (getNextValue.charAt(index++) + offset);
}
bits |= ((-resb) >>> 31) << power++;
}
dictionary.add(String.valueOf(bits));
cc = dictSize++;
enlargeIn--;
break;
case 1:
bits = 0;
maxpower = 16;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (char) (getNextValue.charAt(index++) + offset);
}
bits |= ((-resb) >>> 31) << power++;
}
dictionary.add(String.valueOf(bits));
cc = dictSize++;
enlargeIn--;
break;
case 2:
return sb.toString();
}
if (enlargeIn == 0) {
enlargeIn = 1 << numBits;
numBits++;
}
if (cc < dictionary.size() && dictionary.get(cc) != null) {
entry = dictionary.get(cc);
} else {
if (cc == dictSize) {
entry = w + w.charAt(0);
} else {
return "";
}
}
sb.append(entry);
// Add w+entry[0] to the dictionary.
dictionary.add(w + entry.charAt(0));
dictSize++;
enlargeIn--;
w = entry;
if (enlargeIn == 0) {
enlargeIn = 1 << numBits;
numBits++;
}
}
}
}
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